A filler gauge with flexible measurement is disclosed in the invention. The invention provides a filler gauge that is easy to be manufactured and able to lower cost as well as increase scope of measurement. In addition, each single unit of the filler gauge is made of plastic material that is flexible, bendable, and able to be trimmed so that various objects to be measured can be measured by suitable single units. Moreover, a ruler area and an angle-measuring area are further provided on each single unit so that a filler gauge capable of doing thickness, depth, and angle measurements is completed.

The invention relates to a filler gauge with flexible measurement and, more particularly, to a filler gauge that performs thickness measurement for an object to be measured.
Among all kinds of measuring tools such as block gauge, internal gauge, radius gauge, passimeter, filler gauge, height gauge, hardness gauge, leveling block, micrometer, and so on that are commonly used in electronic products or mechanical products, filler gauge is widely used in electronic components because of its small volume and capability of precision control such as measuring thickness of assembly and doing gap adjustment. The conventional filler gauges are composed of tens of metal sheets with different thickness and thickness dimensions (e.g. inch or mm) marked on them. However, when in use, a conventional filler gauge always encounters some irresolvable problems since the gauge is made of metal materials. To illustrate the problems, a bus slot that is assembled to a motherboard will be regarded as an object to be measured in order to illustrate the encountered problems.
1. If an object to be measured is a hard material and a lead angle is formed in the measured area of the object due to a shift, then the filler gauge cannot enter the object in parallel. Therefore, despite that the metal sheets are bendable thin metal sheets or unbendable thicker ones, they will rub the object to be measured and cause damage to the measured object when the metal sheets enter the area for measurement. Besides, if the measured object contains electronic lines or has the same metal materials as the metal sheets, then static or radiation interference will be resulted in because the filler gauge is made of metal sheets. Owing to that, the measured object might generate second-time defects, and such problem can really bother a user.
2. If the size of entrance for measuring an object is smaller than that of the measuring terminal of the filler gauge, the measuring terminal of the metal sheet in use has to be trimmed smaller. However, because the metal sheet is not easy to be trimmed, a prick will be formed at the place being trimmed, and the prick will damage the measured object.
3. In addition to thickness, the other dimensions required being measured usually also include depth or lead angle of the object""s perimeter, etc. However, a conventional filler gauge only has a single function of measuring thickness. If the other kinds of measurement are required, other tools such as the above-mentioned tools will have to be applied, but changing tools can be very inconvenient to a user.
4. After a period of time of use, the thickness display area of a metal sheet may become hard to be read because the area will be abraded, and the abrasion may be irritating to a user.
To solve the foregoing problems, the invention provides a filler gauge that each single unit of the gauge is made of plastic material, which is flexible, bendable, and allowed to be trimmed. The following descriptions are to illustrate the functions of the invention that can solve the problems of conventional filler gauge.
1. A single unit of filler gauge that is made of plastic material does not have conductivity; therefore, no static or radiation interference will be brought in to the object to be measured.
2. A single unit of filler gauge can apply its flexibility and bend appropriately in accordance with the angle it enters for measuring to prevent the measured object from abrasion so that second time defects can be avoided.
3. The measuring terminal of the single unit can be trimmed according to the size of entrance for measurement. Therefore, even though a prick may be generated, the object to be measured will not be damaged by the prick because the measuring terminal is made of soft plastic.
4. A ruler area and an angle-measuring area are provided on each single unit so that the filler gauge is capable of measuring thickness, depth, and angle of the object altogether. Therefore, the user can save time to change tools for measurements other than thickness measurement because the filler gauge of the invention can handle other measurements as well. Hence, the economic value of the filler gauge can be enhanced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


Compositions and methods for selectively binding specific metal ions, such as Ca2+ and Cd2+, contained in a source solution are disclosed and described. This is accomplished by the use of a composition comprised of an EGTA ligand covalently bonded to a membrane support. The composition formula of the present invention is Mxe2x80x94Bxe2x80x94L where M is a membrane having a hydrophilic, partially hydrophilic or a composite membrane with a hydrophilic surface, B is a covalent linkage, and L is an EGTA ligand. The separation is accomplished by passing a source solution containing the ions to be separated through a device containing the membrane-ligand composition, causing the selected ions to be complexed to the EGTA ligands and subsequently removing the selected ions from the device by passing an aqueous receiving solution through the device and quantitatively stripping the selected ions from the EGTA ligand.

Effective methods for the recovery and/or separation of particular divalent metal ions, such as (a) Ca2+ from source solutions containing Mg2+ and/or other ions and (b) Cd2+ from source solutions containing Zn2+ and/or other ions, are of great importance in modern technology. It is particularly difficult to remove these particular metal ions in the presence of moderate to strong acids and soluble complexing or chelating agents, such as the halide ions, which have a high affinity for the desired metal ions. It is also difficult to remove the aforementioned divalent metal ions when they are present at low concentrations in solutions containing other metal ions at much greater concentrations. Hence, there is a real need for a process to selectively concentrate certain divalent metal ions when present at low concentrations and particularly when in the presence of acid solutions and other complexing agents.
Some methods for the recovery of divalent metal cations from solution are known in the art. However, the removal and/or separation of specific divalent metal cations is often complicated by a myriad of conditions including the presence of other divalent cations, the presence of other cations in very high concentrations, and the presence of other chelating agents. It is also known that ligands present as solutes in a solvent have the ability to selectively form strong bonds with particular ions or groups of ions present as solutes in the same solvent according to size, donor atom-related properties and other known selectivity characteristics.
Ethyleneglycol-bis-(xcex2-aminoethyl ether)-N,N,N,Nxe2x80x2-tetraacetic acid and (ethylenediamine)tetraacetic acid, commonly referred to as EGTA and EDTA respectively, are both ligands that may be used as solutes to complex divalent ions. However, EGTA has a greater selective preference for larger divalent metal ions than EDTA. See Critical Stability Constants, Volume 1: Amino Acids, A. E. Martell and P. M. Smith, Plenum Press, N.Y. and London, 1974. Therefore, EGTA is an important ligand for use in complexing larger divalent metal ions.
This being the case, researchers have not previously been able to incorporate EGTA into phase separation systems. This is significant because EGTA present in solution as a solute simply acts to complex selected ions, but does not provide a means for their separation. Specifically, never before has EGTA been successfully covalently bonded to a membrane support. As such, EGTA bonded membranes have not been used in phase separation processes for removing, separating and concentrating larger ionic radii or desired divalent ions from solutions, particularly where such desired ions are present in solutions with smaller and/or similar ions present at a much higher concentration.
As such, it would be useful to provide a composition and method for removing, separating, and/or concentrating certain desired divalent metal ions in solution from other ions, such as (a) Ca2+ from Mg2+ and/or (b) Cd2+ from Zn2+, even when the desired ion is present at a low concentration.
The present invention is drawn to a novel composition comprising an EGTA ligand covalently bonded to a membrane. The invention is also drawn to methods for removing, separating and/or concentrating certain desired divalent metal ions including (a) Ca2+ from source solutions containing Mg2+ and/or other ions and (b) Cd2+ from source solutions containing Zn2+ and/or other ions. In fact, the removal of these ions (Ca3+ and/or Cd2+) may occur when they are present at from very low to very high concentrations, i.e., from ppb to g/l levels of Cd2+ and/or Ca2+.
The concentration of the desired ions is accomplished by forming a complex of the desired ions with an EGTA ligand bound membrane. The separation is effected in a separation device, such as a membrane cartridge, through which the source solution is flowed. This process enables the desired ions to complex with the EGTA ligand attached to the membrane. The metal ion and the EGTA ligand are then decoupled by flowing a receiving liquid through the separation device (in much smaller volume than the volume of source solution passed through the column) to remove and concentrate the desired ions in the receiving liquid solution. The receiving liquid or recovery solution forms a stronger complex with the desired ions than does the EGTA, or alternatively, temporarily forms a stronger interaction with the EGTA ligand than do the desired metal ions, and thus, the desired metal ions are quantitatively stripped from the ligand in a concentrated form in the receiving solution. The recovery of desired ions from the receiving liquid may be accomplished by various methods commonly known in the art.
The present invention provides a composition and method for the removal and/or separation of particular divalent metal ions including Ca2+ and/or Cd2+ present in low concentrations from a solution utilizing an EGTA ligand attached to a membrane. The present invention is particularly adaptable to the removal of (a) Ca2+ from source solutions containing Mg2+ and/or other ions, and (b) Cd2+ from source solutions containing Zn2+ and/or other ions. The invention may also be carried out in moderately acidic solutions, e.g., solutions with a pH greater than about 3.0. Furthermore, the desired selectivity and interaction strength is unexpectedly high despite the fact that one of the four carboxylic acid groups of the ligand is used to attach the ligand to the membrane support.
The present invention requires that the ligand be covalently bonded to a membrane which acts as a support to the EGTA ligand. Specifically, the composition of the present invention comprises an EGTA ligand that is covalently bonded to a membrane as represented Ad Formula 1, as follows:
Mxe2x80x94Bxe2x80x94L xe2x80x83xe2x80x83Formula 1
where M is any membrane or composite membrane derivatized to have a hydrophilic surface and which contains polar functional groups, L is an EGTA ligand and B is the covalent linkage joining the ligand (L) to the membrane (M) surface. Typically, the EGTA ligand (L) is joined to the membrane surface by the reaction of ligand precursor XL where X is a functional group which reacts with an activated polar group on the membrane surface, thereby forming covalent linkage B. Representative of B linkages are members selected from the group consisting of amide (xe2x80x94NHC(O)xe2x80x94, ester (xe2x80x94C(O)Cxe2x80x94), thioester (xe2x80x94C(O)Sxe2x80x94), carbonyl (xe2x80x94C(O)xe2x80x94), ether (xe2x80x94Oxe2x80x94), thioether (xe2x80x94Sxe2x80x94), sulfonate (xe2x80x94S(O)2Oxe2x80x94) and sulfonamide (xe2x80x94SO2NHxe2x80x94), though amide bonds are often preferred.
More specifically, the membrane (M) may be inherently hydrophilic, partially hydrophilic or a composite comprising a porous polymer membrane substrate having an insoluble cross-linked hydrophilic coating deposited thereon. Membranes that are inherently hydrophilic or partially hydrophilic and contain moieties appropriate for forming covalent bonds with the ligand (L) have particular utility. Such membranes include polyamides such as nylon, and cellulosic materials such as cellulose, regenerated cellulose, cellulose acetate and nitrocellulose. If the membrane used does not contain reactive groups, it may be modified or derivatized appropriately.
Composite membranes are also preferred. A composite membrane comprises a porous polymer or copolymer membrane core and an insoluble coating deposited thereon. The substrate and the coating may be joined by crosslinking, grafting or by other known procedures. Representative suitable polymers forming the membrane core substrate include fluorinated polymers including poly (tetrafluoroethylene) (xe2x80x9cTEFLONxe2x80x9d), polyvinylidene fluoride (PVDF), and the like; polyolefins such as polyethylene, ultra-high molecular weight polyethylene (UPE), polypropylene, polymethylpentene, and the like; polystyrene or substituted polystyrenes; polysulfones such as polysulfone, polyethersulfone, and the like; polyesters including polyethylene terephthalate, polybutylene terephthalate, and the like; polyacrylates and polycarbonates; polyethers such as perfluorinated polyethers; and vinyl polymers such as polyvinyl chloride and polyacrylonitriles. Copolymers can also be used for forming the polymer membrane, such as copolymers of butadiene and styrene, fluorinated ethylene-propylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and the like. The preferred membrane is a hydrophilic ultrahigh molecular weight polyethylene (UPE) containing carboxylic groups, such as those described in U.S. Pat. Nos. 4,618,533, 5,618,433 and 5,547,760.
The membrane is selected to yield both selected bulk properties and selected surface properties. For naturally hydrophilic membranes, the selected bulk and surface properties will be provided by the polymer of which the membrane is formed. For composite membranes, the selected bulk properties will be provided by the membrane substrate and the selected surface properties will be provided by the coating.
A composite membrane is formed by depositing a monomer directly on the surface of the substrate, including the inner surfaces of the pores, by in situ deposition of the cross-linked monomer. The desired deposition of the cross-linked monomer onto the porous substrate is effected as a direct coating and does not require or utilize an intermediate binding chemical moiety. Any monomer for the coating polymer can be used so long as it is capable of being polymerized by free radical polymerization and can be crosslinked. The only requirements of the polymerized monomer is that it is capable of coating the entire surface of the porous membrane, that it provide the surface with ligand-reactive functional groups and that it be sufficiently hydrophilic to allow for efficient use of the ligand to be attached. Generally, the porous substrate has an average pore size between about 0.001 and 10 xcexcm and more usually, between about 0.1 and 5.0 xcexcm. The composite membrane is formed by any suitable method, such as is disclosed in U.S. Pat. No. 4,618,533, which is hereby incorporated by reference in their entirety. Briefly, this procedure involves washing the porous membrane substrate with a suitable solvent for wetting the entire surface of the substrate. The substrate is then bathed in a mixture of the free radical polymerizable monomer, a polymerization initiator, and a cross-linking agent in a solvent under conditions to effect free radical polymerization of the monomer and coating of the porous substrate with the cross-linked polymer. The surface of the coated polymer membrane contains hydrophilic or polar-substituents that can be activated to react with and covalently bond the ligands to the membrane surface.
The composite membranes prepared according to U.S. Pat. No. 4,618,533 can contain carboxylic acid moieties on the surface. Other suitable moieties could include hydroxyl, sulfonic acid, epoxy, primary amine and derivatized benzyl groups such as polymers referenced above.
Preparation of a composite membrane by a precipitated crystal technique involves, briefly, washing the porous membrane substrate with a suitable solvent for wetting the entire surface of the substrate. The substrate is then bathed in a solution containing the compound which is to be precipitated. This solution is then removed and the membrane substrate is treated with a compound that precipitates and fixes the crystals to the substrate. The membrane is washed and dried before use.
With composite membranes, the core membrane material is not thought to affect that performance of the derivatized membrane and it is limited in composition only by its ability to be coated, or have deposited on its surface, an insoluble polymer layer that contains the appropriate reactive group. This provides a hydrophilic layer which interacts well with water or other aqueous solutions. The end result is that when the ligand is attached to the surface of either a hydrophilic membrane or a composite membrane having a hydrophilic surface, the basic characteristics of any given ligand molecule are not changed by the process of attaching it to the surface or by the nature of the surface itself.
Formulas similar to the Mxe2x80x94Bxe2x80x94 portion of Formula 1 have been previously described in U.S. Pat. No. 5,547,760 and U.S. Pat. No. 5,618,433, which are incorporated herein by reference. These membranes and attachment mechanisms are instructive to one skilled in the art in practicing the present invention. However it is to be emphasized that the present invention does not reside in the discovery of the Mxe2x80x94Bxe2x80x94 portion of Formula 1. Rather, it is the discovery of the advantageous ion binding capabilities of the EGTA ligand (L) when attached to a membrane (M) via a covalent linkage (B).
EGTA ligands covalently bonded to membranes as shown in Formula 1 are characterized by high selectivity for and removal and separation of desired divalent metal ions, such as Ca2+ and/or Cd2+, present at from very low to very high concentrations in various source solutions, including source solutions that contain other divalent ions. The source solutions for which the present invention is particularly useful would contain the desired ions and other ions present in greater concentrations which one does not desire to remove. Such other ions can include H+, Mg2+ and Zn2+.
The present invention also provides methods for removing desired divalent metal ions from solutions that can contain other metal ions present in much higher concentrations by the use of such EGTA ligand bonded membranes disclosed herein. These methods may be carried out in any manner that provides for bringing the ions to be removed from a solution into contact with the EGTA ligands affixed to the membrane. Contact is preferably made in a contacting device comprising a housing, e.g., cartridge, containing the composition of matter of the invention by causing solution containing desired ions to flow through the cartridge and thus come in contact with the composition of the invention. Preferably the membrane configuration is a pleated membrane, although other membrane configurations, such as flat sheet, stacked disk or hollow fibers may be used. However, various contact apparatus may be used instead of a cartridge such as but not limited to a cassette, syringe, unit, canister, multi-well plate or filter holder. The process of selectively removing and concentrating the desired ions is characterized by the ability to quantitatively complex from a larger volume of solution the desired ions, even when they are present at very low concentrations.
The desired ions are recovered from the ligands bound to the membranes by flowing through a small volume of a receiving phase which contains a solubilizing reagent. The solubilizing reagent need not be selective, but merely be capable of forming a stronger complex with the desired divalent metal ion than does the EGTA ligand. Alternatively, the solubilizing reagent may contain ions that temporarily form a stronger interaction with the EGTA ligand than does the desired metal ions. This causes the desired metal ion to be quantitatively stripped from the ligand bound membranes in concentrated form and transferred to the receiving solution. The recovery of the desired metal ion from such a receiving solution is readily accomplished by evaporation, precipitation, or by other known methods.
There are several applications for which one may wish to remove/separate the aforementioned divalent metal ions from solution. An example of such an application is the separation of ppb levels of Cd2+ or other divalent metals from concentrated Cu, Ni, Zn, Ag, Pb and/or Hg contained in process streams and industrial effluents. This is true both because of the unsatisfactory technologies presently available or because a more economical method is desired. For example, Cd2+ is often present at low concentrations in solutions containing other divalent ions at much greater concentrations. Therefore, the removal of Cd2+ from such solutions would be important environmentally because of impurity concerns. Additionally, quantitation and/or removal of Cd2+ or Ca2+ ions from other non-desirable ions may also be employed. Specifically, this removal process may be implemented when the desired ions (Cd2+ and/or Ca2+) are present at from very low levels (ppb) to very high levels (g/l), even in the presence of concentrated Cu, Ni, Zn, Ag, Pb and/or Hg process streams.
All of these functions and others may be accomplished by use of the compositions and methods of the present invention. The invention will now be illustrated by the following examples which are not intended to be limiting in any way. All references cited are incorporated herein by reference in their entirety.

Polymeric membranes functionalized with EGTA ligands, and process of separating ions


A client stores a first set of workspace data, and is coupled via a computer network to a global server. The client may be configured to synchronize portions of the first set of workspace data with the global server, which stores independently modifiable copies of the portions. The global server may also store workspace data which is not downloaded from the client, and thus stores a second set of workspace data. The global server may be configured to identify and authenticate a user seeking global server access from a remote terminal, and is configured to provide access to the first set or to the second set. Further, services may be stored anywhere in the computer network. The global server may be configured to provide the user with access to the services. The system may further include a synchronization-start module at the client site (which may be protected by a firewall) that initiates interconnection and synchronization with the global server when predetermined criteria have been satisfied.

1. Field of the Invention
This invention relates generally to computer networks, and more particularly provides a system and method for globally and securely accessing unified information in a computer network.
2. Description of the Background Art
The internet currently interconnects about 100,000 computer networks and several million computers. Each of these computers stores numerous application programs for providing numerous services, such as generating, sending and receiving e-mail, accessing World Wide Web sites, generating and receiving facsimile documents, storing and retrieving data, etc.
A roaming user, i.e., a user who travels and accesses a workstation remotely, is faced with several problems. Program designers have developed communication techniques for enabling the roaming user to establish a communications link and to download needed information and needed service application programs from the remote workstation to a local computer. Using these techniques, the roaming user can manipulate the data on the remote workstation and, when finished, can upload the manipulated data back from the remote workstation to the local computer. However, slow computers and slow communication channels make downloading large files and programs a time-consuming process. Further, downloading files and programs across insecure channels severely threatens the integrity and confidentiality of the downloaded data.
Data consistency is also a significant concern for the roaming user. For example, when maintaining multiple independently modifiable copies of a document, a user risks using an outdated version. By the time the user notices an inconsistency, interparty miscommunication or data loss may have already resulted. The user must then spend more time attempting to reconcile the inconsistent versions and addressing any miscommunications.
The problem of data inconsistency is exacerbated when multiple copies of a document are maintained at different network locations. For example, due to network security systems such as conventional firewall technology, a user may have access only to a particular one of these network locations. Without access to the other sites, the user cannot confirm that the version on the accessible site is the most recent draft.
Data consistency problems may also arise when using application programs from different vendors. For example, the Netscape Navigator(trademark) web engine and the Internet Explorer(trademark) web engine each store bookmarks for quick reference to interesting web sites. However, since each web engine uses different formats and stores bookmarks in different files, the bookmarks are not interchangeable. In addition, one web engine may store a needed bookmark, and the other may not. A user who, for example, runs the Internet Explorer(trademark) web engine at home and runs the Netscape Navigator(trademark) web engine at work risks having inconsistent bookmarks at each location.
Therefore, a system and method are needed to enable multiple users to access computer services remotely without consuming excessive user time, without severely threatening the integrity and confidentiality of the data, and without compromising data consistency.
The present invention provides a system and methods for providing global and secure access to services and to unified (synchronized) workspace elements in a computer network. A user can gain access to a global server using any terminal, which is connected via a computer network such as the Internet to the global server and which is enabled with a web engine.
A client stores a first set of workspace data, and is coupled via a computer network to a global server. The client is configured to synchronize selected portions of the first set of workspace data (comprising workspace elements) with the global server, which stores independently modifiable copies of the selected portions. The global server may also store workspace data not received from the client, such as e-mail sent directly to the global server. Accordingly, the global server stores a second set of workspace data. The global server is configured to identify and authenticate a user attempting to access it from a remote terminal, and is configured to provide access based on the client configuration either to the first set of workspace data stored on the client or to the second set of workspace data stored on the global server. It will be appreciated that the global server can manage multiple clients and can synchronize workspace data between clients.
Service engines for managing services such as e-mail management, accessing bookmarks, calendaring, network access, etc. may be stored anywhere in the computer network, including on the client, on the global server or on any other computer. The global server is configured to provide the user with access to services, which based on level of authentication management or user preferences may include only a subset of available services. Upon receiving a service request from the client, the global server sends configuration information to enable access to the service.
Each client includes a base system and the global server includes a synchronization agent. The base system and synchronization agent automatically establish a secure connection therebetween and synchronize the selected portions of the first set of workspace data stored on the client and the second set of workspace data stored on the global server. The base system operates on the client and examines the selected portions to determine whether any workspace elements have been modified since last synchronization. The synchronization agent operates on the global server and informs the base system whether any of the workspace elements in the second set have been modified. Modified version may then be exchanged so that an updated set of workspace elements may be stored at both locations, and so that the remote user can access an updated database. If a conflict exists between two versions, the base system then performs a responsive action such as examining content and generating a preferred version, which may be stored at both locations. The system may further include a synchronization-start module at the client site (which may be protected by a firewall) that initiates interconnection and synchronization when predetermined criteria have been satisfied.
A method of the present invention includes establishing a communications link between the client and the global server. The method includes establishing a communications link between the client and a service based upon user requests. The method receives configuration data and uses the configuration data to configure the client components such as the operating system, the web engine and other components. Configuring client components enables the client to communicate with the service and provides a user-and-service-specific user interface on the client. Establishing a communications link may also include confirming access privileges.
Another method uses a global translator to synchronize workspace elements. The method includes the steps of selecting workspace elements for synchronization, establishing a communications link between a client and a global server, examining version information for each of the workspace elements on the client and on the global server to determine workspace elements which have been modified since last synchronization. The method continues by comparing the corresponding versions and performing a responsive action. Responsive actions may include storing the preferred version at both stores or reconciling the versions using content-based analysis.
The system and methods of the present invention advantageously provide a secure globally accessible third party, i.e. the global server. The system and methods provide a secure technique for enabling a user to access the global server and thus workspace data remotely and securely. Because of the global firewall and the identification and security services performed by the global server, corporations can store relatively secret information on the global server for use by authorized clients. Yet, the present invention also enables corporations to maintain only a portion of their secret information on the global server, so that there would be only limited loss should the global server be compromised. Further, the global server may advantageously act as a client proxy for controlling access to services, logging use of keys and logging access of resources.
A client user who maintains a work site, a home site, an off-site and the global server site can securely synchronize the workspace data or portions thereof among all four sites. Further, the predetermined criteria (which control when the synchronization-start module initiates synchronization) may be set so that the general synchronization module synchronizes the workspace data upon user request, at predetermined times during the day such as while the user is commuting, or after a predetermined user action such as user log-off or user log-on. Because the system and method operate over the Internet, the system is accessible using any connected terminal having a web engine such as an intemet-enabled smart phone, television settop (e.g., web TV), etc. and is accessible over any distance. Since the system and method include format translation, merging of workspace elements between different application programs and different platforms is possible. Further, because synchronization is initiated from within the firewall, the typical firewall, which prevents in-bound communications and only some protocols of out-bound communications, does not act as an impediment to workspace element synchronization.
Further, a roaming user may be enabled to access workspace data from the global server or may be enabled to access a service for accessing workspace data from a client. For example, a user may prefer not to store personal information on the global server but may prefer to have remote access to the information. Further, the user may prefer to store highly confidential workspace elements on the client at work as added security should the global server be compromised.
The present invention may further benefit the roaming user who needs emergency access to information. The roaming user may request a Management Information Systems (MIS) director controlling the client to provide the global server with the proper keys to enable access to the information on the client. If only temporary access is desired, the keys can then be later destroyed either automatically or upon request. Alternatively, the MIS director may select the needed information as workspace elements to be synchronized and may request immediate synchronization with the global server. Accordingly, the global server and the client can synchronize the needed information, and the user can access the information from the global server after it has completed synchronization.
The present invention also enables the system and methods to synchronize keys, available services and corresponding service addresses to update accessibility of workspace data and services. For example, if the user of a client accesses a site on the Internet which requires a digital certificate and the user obtains the certificate, the system and methods of the present invention may synchronize this newly obtained certificate with the keys stored on the global server. Thus, the user need not contact the global server to provide it with the information. The synchronization means will synchronize the information automatically.

System and method for globally and securely accessing unified information in a computer network


The present invention concerns a method of producing flow rates of a transport liquid of about 1 to 1000 nl/min. The method provides a pump having a housing defining a space and including a channel and a wettable membrane positioned in the housing, the membrane including a first side facing toward the channel and a second side facing the space. The method further includes at least partially filling the channel with the transport liquid, contacting the wettable membrane with the transport liquid to generate an underpressure in the channel,evaporating the transport liquid at the wettable membrane to remove the transport liquid from the channel and to create an underpressure in the channel, and maintaining a generally constant vapor pressure of the transport liquid in the space.

The present invention concerns a pump for flow rates in the range from about 1 to 1000 nl/min. The pumps according to the invention are particularly suitable for applications in the field of medical diagnostics such as microdialysis or ultrafiltration.
A pump is claimed for low flow rates which having channel which is at least partially filled with a transport liquid and a membrane that can be wetted by the transport liquid which closes one opening of the channel and through which evaporation can take place. There is a space on the opposite side of the membrane to the transport liquid which has an essentially constant vapour pressure of the transport liquid. The invention also encompasses microdialysis and ultrafiltration systems containing such a pump.
Miniaturized pumps are known in the prior art e.g. peristaltic pumps which can achieve flow rates as low as about 100 nl/min. The focus of miniaturized pump development is usually to achieve the highest possible delivery rate with a minimum pump volume. Furthermore it has turned out that such pumps do not operate reliably enough in the low pumping range when used for long-term applications and in particular it is difficult to avoid large variations in the flow rates. Other arrangements are known in the field of ultrafiltration and microdialysis in which a negative pressure reservoir (for example a drawn syringe) is connected to a fluid system via a constricted capillary path. However, this has the disadvantage that the pressure time course is non-linear. A further arrangement for achieving low flow rates is known from the document WO 95/10221.
In this arrangement a liquid located in a channel is directly contacted with a sorbent. Typical flow rates for such a system are in the range of a few μl/min. The long-term constancy (measured over several days) of this pump is quite low.
The object of the present invention was to provide a pump for very low flow rates which operates reliably and has a sufficiently constant flow rate over a long time period (e.g. several days). A further object of the present invention was to propose a pump for such low flow rates which is very simple and cost-effective to manufacture. The pump should also be mechanically simple to manufacture and be compatible with integrated microfluidic systems based on planar technologies (e.g. microtechnology).
With a pump according to the invention a transport liquid is located in a channel which has an opening which is closed by a membrane that can be wetted by the transport liquid. Transport liquid penetrates the membrane due to capillary effects and is led away via capillary channels through the membrane into a gas space having an essentially constant vapour pressure of the transport liquid or it is physically or chemically bound (taken up) by a suitable sorbent such that further unhindered evaporation through the membrane can occur. The constant vapour pressure conditions in the gas space result in a constant flow rate.
Within the scope of the invention it is possible to generally use transport liquids which can penetrate into a membrane and evaporate through it. Aqueous transport liquids are preferred within the scope of the present invention. In addition to the water component, aqueous transport liquids can contain substances or mixtures which influence the surface tension and/or the viscosity in order to adjust the permeation properties of the transport liquid into the membrane to a desired value. However, the transport liquids preferably contain no substances that cannot evaporate at room temperature, e.g. salts, since these could lead to a blockage of the membrane. Suitable embodiments are described further below for cases in which it is intended to transport liquids containing substances that cannot evaporate.
The channel of the pump according to the invention preferably has an area in the range 1 to 105 μm2 and a length of 1-1000 mm. The lateral dimension of the cross section is preferably greatly enlarged (1 to 1000 mm2) in the area of the wettable membrane in order to provide an adequately large exchange area with the adjoining gas space. The evaporation process at the membrane removes transport liquid from the fluid channel and thus generates an underpressure which causes the desired pump action. The pump can be used to transport the transport liquid itself when for example this liquid is used as a perfusion liquid for a microdialysis. In another inventive embodiment the fluid channel contains a working fluid which for example is used as a perfusate or for other purposes and is segmented from the transport liquid. In another application of the pump such as ultrafiltration, evaporation of the transport liquid generates an underpressure in the channel which conveys a fluid from the surroundings into the fluid channel. In the field of ultrafiltration this would be an external fluid (interstitial fluid) which enters the channel through an ultrafiltration membrane.
The term membrane in the sense of the present invention is intended to generally encompass structures through which liquid is sucked from the fluid channel by capillary forces and evaporated. In addition to the bodies that are referred to as membranes in everyday usage which have a plurality of usually disordered capillary channels, the term membrane is also intended to encompass arrays of (possibly only a few) capillary channels. Such an embodiment is described in more detail in conjunction with the figures. Such capillary arrays can be manufactured by microtechnical methods in which very small and constant cross-sections are achievable. Very low flow rates can be achieved with such capillary-active membranes that can be adjusted by the manufacturing process via the number and cross-section of the capillary channels.
The evaporation rate can be additionally controlled by sealing with a hydrophobic, non-wettable membrane (e.g. Teflon).
In cases were either a direct contact of the liquid to be transported with the evaporator membrane has to be avoided e.g. when transporting liquids containing salts where direct evaporation on the membrane would lead to the formation of a solid salt residue with a concomitant damaging effect on the constancy of the evaporation rate, or when for example a suitable sorbent is not available for the liquid to be transported, the indirect approach of using an additional transport liquid (for example degassed and deionized water) can ensure the pump operation.
In the case of immiscible liquids (e.g. toluene as the liquid (working fluid) to be transported, water as the evaporating transport liquid), it is possible for the two liquids to be present directly in the system with a common phase boundary without the liquid to be transported coming into contact with the membrane during pump operation over a long period (e.g. for several days). This can be achieved by using a stock of transport liquid in an intermediate buffer which is preferably larger than the total volume of transport liquid (working fluid) to be conveyed.
In the case of miscible liquids the two liquids (e.g. Ringer's solution and pure water) can be segmented from one another by an impermeable membrane. In this case a diffusion barrier can also be preferably used such that in the above case the Ringer's solution displaces a water volume located in one or several connected reservoirs (e.g. a dilution cascade) and the concomitant dilution ensures that the salt concentration at the evaporation membrane is reduced to an adequate extent. This can prevent or at least reduce salting-out on the membrane which would otherwise alter the pump rate. The advantages of this solution are that it avoids moving parts (e.g. a bending membrane), and is simple to manufacture and integrate into the pump body.
A further advantage of this solution is that, depending on the geometric design of the transport path, the reservoirs can act wholly or partially as bubble traps for gases that may be present in the liquid to be transported or which may be released during transport and thus can help to prevent direct contact of gas bubbles with the evaporation membrane.
Another simple method for segmenting the liquid to be transported and the transport liquid is to introduce a gas bubble which permanently separates the t0o liquids. The volume of this gas bubble must be large enough to guarantee segmentation over all changes in the cross-section of the transport path and optionally also in the container which serves as a storage medium for the transport liquid.
An advantage of the solution employing one or several reservoirs to dilute the liquid to be transported compared to a gas bubble for segmentation is that the function is still ensured even after strong shaking movements which in the case of gas bubble segmentation could lead to a mixing of the liquids. The fact that the gas bubble may dissolve in the liquid shows that it also has the disadvantage that the flow rate additionally depends on temperature due to the temperature-dependent expansion/contraction of the gas buffer.
An important aspect of the present invention is the membrane that can be wetted by the transport liquid. The pump effect of the membrane is based on the fact that a liquid can be sucked by surface forces into capillaries or pores of the membrane. The capillary pressure that is generated by this means is directly proportional to the surface tension of the liquid and to the cosine of the angle of contact between the liquid and the membrane material and is inversely proportional to the radius of the capillaries or pores. Hence membranes are suitable for the present invention which have a contact angle with regard to the transport liquid between 0 and 90 degrees. This stated relationship also shows that the capillary pressure increases when the diameter of the capillaries or pores decreases. Typical pore diameters of capillaries in the membrane are in the range from 10 nm to 100 μm. It is important for the present invention that the transport liquid is in direct contact with the membrane such that a capillary effect occurs. Consequently it is necessary to ensure that there is no interruption in the liquid contact between the transport liquid and membrane which may occur when the pore diameter of the membrane becomes too large with a concomitant decrease in capillary pressure or it may also be caused by a defect (hole) in the membrane which would lead to a pressure equilibration by the return flow of gas.
Furthermore it is advantageous to use membrane systems within the scope of the invention which, apart from a wettable membrane, have an additional membrane which is located on the side of the first membrane which faces away from the transport liquid. Membranes which cannot be penetrated by liquids with a high surface tension can be used for this second membrane such as membranes made of PTFE, Cuprophan® or Gambran®. The evaporation rate of the transport liquid can be modulated by means of the properties of this second membrane. Furthermore it is also possible to use membranes which have different regions of which one region facing the transport liquid is wettable and a region facing away is not wettable.
It is also possible to integrate the manufacture of the pump body and membrane (monolithic) or to use tailor-made membranes of a defined pore size and pore distribution in a hybrid approach. The integrated manufacture of such membranes based on silicon is described for example in T. A. Desai et al., Biomedical Microdevices 2 (1999), 11-41. Another method is to use a microporous Si membrane having a statistical distribution of pore sizes (R. W. Tjerkstra et al., Micro Total Analysor Systems 1998, Kluwer 1998, p. 133-136). Such membranes can for example be manufactured in polymer substrates using laser ablation, hot-stamping etc.
The pump action of the membrane used is maintained until the partial pressure of the liquid to be pumped on the side of the membrane facing away from the liquid (gas side) is less than the saturation vapour pressure at the respective working temperature. In order to maintain a constant vapour pressure (and to minimize possible environmental influences) it is proposed that a gas space be provided which contains a sorbent which is not in direct contact with the wettable membrane. The continuous sorption of the evaporating liquid maintains a constant difference of the vapour pressure over the liquid in the pores and the saturation vapour pressure.
The term sorbent encompasses adsorbents as well as absorbents. Suitable sorbents are for example silica gels, molecular sieves, aluminium oxides, zeolites, clays, active charcoal, sodium sulfate, phosphorous pentoxide etc.
It is important for the desired pump function that there is no direct contact between the sorbent and the capillaries/pores of the wettable membrane to prevent direct transfer of liquid by this means. On the contrary, in order to achieve low flow rates that remain constant over long periods it is necessary that firstly evaporation of transport liquid occurs and that the evaporated transport liquid is taken up from the gas phase by the sorbent. This can be achieved by spacing apart the wettable membrane and the sorbent such that there is no direct fluid contact. Furthermore it is possible to use one (or also several) non-wettable membrane(s) which are preferably located directly next to the wettable membrane. With such a membrane the sorbent can also be in direct contact without generating a fluid short circuit. Such an arrangement also enables the use of a liquid sorbent such as a highly concentrated or saturated salt solution. Another method is to modify a region of the wettable membrane that faces away from the transport liquids or faces the sorbent in such a manner that the membrane cannot be wetted and thus adopts the function of a second non-wettable membrane. Such a modification of the membrane can for example be achieved by a plasma reaction. With embodiments containing membranes which have a wettable region and a non-wettable region, the sorbent can directly contact the non-wettable region without making a fluid short-circuit.
In order to be effective the sorbent should be located in a vessel (container) which seals it from the outer space and in particular largely prevents penetration of moisture from the external space. The vessel has an opening which is closed by the wettable membrane or the non-wettable membrane. As a result evaporated transport fluid enters the vessel through the membrane and is taken up there by the sorbent. The sorbent should be selected such that the equilibrium vapour pressure of the transport liquid which is less than the saturation vapour pressure of the fluid in the gas phase remains constant for a long period as a result of the sorbent. This is important in order to set a defined evaporation rate of the transport liquid which increases the constancy of the flow rate.
It was surprisingly found that embodiments of the vessel containing the sorbent having flexible walls did not have an adverse effect on the pump action but on the contrary variations in the flow caused by pressure changes in the external space or by temperature changes were considerably reduced. Foils such as 3E composite aluminium foils of low density and low buckling strength are especially suitable as flexible walls. Elastic plastics such as silicons can also be used.
It was surprisingly found that another simplified embodiment which does not need any sorbent also results in very constant transport rates. In this embodiment a space is enclosed by walls to form a housing above the side of the membrane or of the membrane sandwich which faces away from the transport liquid, the walls having openings which comprise between 0.001% and 100% of the surface of the walls i.e. the housing is omitted in the extreme case. The transport rate of liquid vapour into the surrounding gas phase can be adjusted over a wide range by the geometric dimensions and number of openings and by the choice of gas permeable membranes. Embodiments are also possible in which the space on the side of the membrane opposite to the transport liquid is not surrounded by a housing belonging to the pump. This is the case when the space per se has an essentially constant vapour pressure of the transport liquid which is the case for air-conditioned rooms. In □articular designs are also possible in which the pump according to the invention is used within an air-conditioned system for example an analyser.
The transport rate depends on a number of factors of which the viscosity of the liquid and the membrane properties have already been mentioned above. These influencing variables in turn depend on the temperature. Hence, for example the evaporation rate and also the diffusion rate in the gas phase increase with increasing temperature. In contrast a temperature increase has the opposite effect on the viscosity of the liquid, the surface tension of the liquid and the interfacial tension between the membrane and liquid. Hence there is a complex relationship between the transport rate and the temperature. However, a low temperature dependency can be ensured by suitable selection of the relevant materials such as the membrane(s) and the sorbent. The present invention is particularly suitable for applications under thermostatted conditions. On the one hand it is possible to have an active temperature control where for example the temperature in the region surrounding the membrane is adjusted to a preselected range using a peltier element. A pump according to the invention can be used particularly advantageously in close contact with the human body. In this case direct contact of the housing in which the pump is located with the body surface is advantageous. The temperature regulation can be additionally supported by thermally insulating the sides of the pump or microdialysis or ultrafiltration system that are not adjacent to the body. In addition it is also possible to integrate a temperature measuring unit into a system containing a pump according to the invention which reports deviations from a target temperature range or even takes into account the currently measured temperature when evaluating analytical measurements.
There is preferably no direct contact between the transport fluid and the wettable membrane when the pump according to the invention is delivered to avoid an unnecessary consumption of liquid. When the pump is put into operation by the user the contact can be made by applying a pressure pulse to a certain area.
The liquid pumps according to the invention enable the very advantageous construction of microdialysis and ultrafiltration systems. In the case of microdialysis the transport liquid can be used directly as the perfusate which is led through a microdialysis catheter in order to take up the analyte. Alternatively □t is also possible to have a liquid (e.g. Ringer's solution) which is different from the transport liquid which is fluidically coupled to the transport liquid.
In the case of ultrafiltration the consumption of transport liquid by the evaporation process can be used to generate an underpressure in the channel which draws in body fluid (interstitial fluid) into an ultrafiltration catheter. In the case of microdialysis as well as ultrafiltration a sensor may be provided downstream of the microdialysis membrane or ultrafiltration membrane for the detection of one or several analytes.


A 2T-2S SRAM cell exhibiting a complementary scheme, that includes two selector devices that exhibit negative differential resistance. Advantages include lower area and better performance than traditional SRAM cells, according to some embodiments. The term 1T-1S refers to a transistor in series with a selector device. Accordingly, the term 2T-2S refers to two such 1T-1S structures.

SRAM is a type of semiconductor memory that uses bistable latching circuitry (flip-flop) to store each bit. SRAM exhibits data remanence, but it is still volatile in the conventional sense that data is eventually lost when the memory is not powered. The term static differentiates SRAM from DRAM ("Dynamic Random-Access Memory"), which must be periodically refreshed. SRAM is faster and more expensive than DRAM; it is typically used for CPU cache while DRAM is used for a computer's main memory. Conventional SRAM devices may consume significant area on the front-end of a process limiting the potential for significant storage density.