Abstract: The disclosure provides an approach for formally verifying a state machine replication protocol (SMRP) based on a model SMRP, and deploying a distributed system, such as a blockchain, that runs using the formally verified SMRP. The approach provides a verifier that models the SMRP within a model distributed system. Modeling includes modeling actions by model components of the model distributed system so as to transition state of the model SMRP, and then verifying that applicable invariants hold true after the state transition. As long as the model and actual SMRPs are logically equivalent, then launching an actual SMRP based on the model SMRP should preserve formally verified byzantine fault tolerance within the actual SMRP of the distributed system.

Abstract: A distributed file system operating over a plurality of hosts is built on top of a tree structure having a root node, internal nodes, and leaf nodes. Each host maintains at least one node and non-leaf nodes are allocated buffers according to a workload of the distributed file system. A write operation is performed by inserting write data into one of the nodes of the tree structure having a buffer. A read operation is performed by traversing the tree structure down to a leaf node that stores read target data, collecting updates to the read target data, which are stored in buffers of the traversed nodes, applying the updates to the read target data, and returning the updated read target data as read data.

Abstract: Surgical systems and methods for robotically-assisted insertion of a stem implant into a cavity of a bone. A manipulator includes a robotic arm that supports an end effector which detachably receives the stem implant. A navigation system includes a localizer to track poses of the bone and the end effector. Controller(s) coupled to the manipulator and the navigation system obtain a surgical plan defining a planned relationship between the stem implant and the bone. Based on the tracked poses and the surgical plan, the controller(s) control the manipulator to enable movement of the end effector and the stem implant to facilitate insertion of the stem implant into the cavity.

Abstract: Surgical systems, methods and surgical planning programs to facilitate preparation of an anatomical cavity to receive a cup implant. The system includes a control system, a localizer and a robotic manipulator configured to move an energy applicator that is adapted to remove tissue. The control system obtains or generates a surgical plan that defines characteristics of cement holes to be formed within a wall of the anatomical cavity for receiving bone cement. The control system registers the surgical plan to the anatomical cavity with the localizer and controls the robotic manipulator to utilize the energy applicator to form the cement holes within the wall of the anatomical cavity according to the surgical plan.

Abstract: Surgical systems, methods and surgical planning programs to facilitate preparation of an anatomical cavity to receive a cup implant. The system includes a control system, a localizer and a robotic manipulator configured to move an energy applicator that is adapted to remove tissue. The control system obtains or generates a surgical plan that defines characteristics of cement holes to be formed within a wall of the anatomical cavity for receiving bone cement. The control system registers the surgical plan to the anatomical cavity with the localizer and controls the robotic manipulator to utilize the energy applicator to form the cement holes within the wall of the anatomical cavity according to the surgical plan.

Abstract: Methods and systems are provided for robotic assisted surgery. A robotic system includes a localizer, at least one controller, and a surgical robotic manipulator which separately and detachably receives an energy applicator and an implant insertion tool that detachably receives an implant specifically for knee, hip or shoulder replacement surgery. The at least one controller determines a location within a portion of a patient's anatomy in which to form a cavity for the implant. The surgical robotic manipulator is controlled to form the cavity with the energy applicator. The surgical robotic manipulator is then controlled to insert the implant into the cavity with the implant insertion tool.

Abstract: Methods and systems are provided for robotic assisted surgery. A robotic system includes a localizer, at least one controller, and a surgical robotic manipulator which separately and detachably receives an energy applicator and an implant insertion tool that detachably receives an implant specifically for knee, hip or shoulder replacement surgery. The at least one controller determines a location within a portion of a patient's anatomy in which to form a cavity for the implant. The surgical robotic manipulator is controlled to form the cavity with the energy applicator. The surgical robotic manipulator is then controlled to insert the implant into the cavity with the implant insertion tool.

Abstract: Methods and systems are provided for robotic assisted surgery. A robotic system includes a localizer, a surgical robotic manipulator, an end effector configured to be removably coupled to the manipulator, and a controller. The controller is configured to receive signals from the localizer, determine a final position of a cavity creation tool used to penetrate a portion of a patient's anatomy based on the signals received from the localizer, and determine an implant insertion path for an implant to be inserted into a final implant position within the portion of the patient's anatomy, wherein the final implant position corresponds to the final position of the cavity creation tool. The controller is also configured to move the end effector with the implant coupled thereto such that the implant moves along the implant insertion path, and terminate the movement of the end effector when the implant reaches the final implant position.

Abstract: Methods and systems are provided for robotic assisted surgery. A robotic system includes a localizer, a surgical robotic manipulator, an end effector configured to be removably coupled to the manipulator, and a controller. The controller is configured to receive signals from the localizer, determine a final position of a cavity creation tool used to penetrate a portion of a patient's anatomy based on the signals received from the localizer, and determine an implant insertion path for an implant to be inserted into a final implant position within the portion of the patient's anatomy, wherein the final implant position corresponds to the final position of the cavity creation tool. The controller is also configured to move the end effector with the implant coupled thereto such that the implant moves along the implant insertion path, and terminate the movement of the end effector when the implant reaches the final implant position.

Abstract: Disclosed is apparatus for distributing a solid, gel, powder or viscous test substance in an extraction fluid, the apparatus comprising a flow cell for holding the test substance and having an inlet and an outlet; an extraction chamber located between said inlet and outlet comprising a convergent nozzle; and a recirculating pump for driving extraction fluid: (i) into the flow cell via the inlet; (ii) through the extraction chamber; and (iii) back to the flow cell via the outlet, whereby a pressure differential is established across the extraction chamber such that the velocity of the extraction fluid is greater at the outlet than at the inlet; characterized in that the apparatus further comprises a tortuous path flow control valve (TPV) located at the outlet and configured to permit flow of extraction fluid and extracted test substance but to prevent or retard passage of said test substance through the outlet.

Abstract: A replicated state machine with N replica servers may be configured to tolerate a count of F faults. A first operation (of a first ordering type) executes when a first quorum of correctly functioning replicas is available. A second operation (also of the first operation type) executes when a second quorum of correctly functioning replicas is available. A third operation (of a second ordering type) executes when a third quorum of correctly functioning replicas are available. The operations are executed by the replicated state machine such that: (1) the replicated state machine does not guarantee operational ordering between the first operation and the second operation; (2) the replicated state machine guarantees ordering between the first operation and the third operation; and (3) the replicated state machine guarantees ordering between the second operation and the third operation.

Abstract: A replicated state machine with N replica servers may be configured to tolerate a count of F faults. A first operation (of a first ordering type) executes when a first quorum of correctly functioning replicas is available. A second operation (also of the first operation type) executes when a second quorum of correctly functioning replicas is available. A third operation (of a second ordering type) executes when a third quorum of correctly functioning replicas are available. The operations are executed by the replicated state machine such that: (1) the replicated state machine does not guarantee operational ordering between the first operation and the second operation; (2) the replicated state machine guarantees ordering between the first operation and the third operation; and (3) the replicated state machine guarantees ordering between the second operation and the third operation.

Abstract: A kit and a method for implanting a prosthetic acetabular cup in an acetabular has a prosthetic acetabular cup having an open end for receiving a head of a prosthetic femoral component. The cup has a flange extending outwardly from a surface thereof adjacent the open end. The flange is angled toward the acetabulum. The acetabulum is prepared to receive the prosthetic acetabular cup, the preparation includes forming a circumferential rim shaped seat in the bone around the acetabulum. The cup flange has a maximum diameter less than the outer diameter of the circumferential rim.

Abstract: Non-mutating tree-structured file identifiers are used to identify files stored in a file system. Each of multiple files in the file system has a corresponding non-mutating file identifier, and these file identifiers are assigned and maintained using a tree structure.

Abstract: A delta pager maintains a database with atomic, isolated transactions. When a transaction seeks to make changes to the database, the delta pager stores the changes in write buffers, and applies the changes when intervening transactions do not literally or substantively change the state of the database relied upon by the transaction. The delta pager applies the changes to commit the transaction by conjoining the write buffers with the current state of the database to form a new data structure representing the state of the database. The delta pager coalesces write buffers to maintain efficiency, subject to snapshots the delta pager respects to preserve selected states of the database. The delta pager makes selected sections of the database durable by moving selected data to a durable store. The delta pager also provides cache objects between the durable store and current transactions to promote efficient access to data.

Abstract: Scalable leases reduce latency and reduce the burden on a server in managing data leases. Instead of processing individual lease requests for clients seeking access to the same data, scalable leases provide for blanket leases that all of the clients can use to access the selected data. Leases may be encrypted or selectively distributed to restrict access to the data. Moreover, distributed data structures may be used to cache leases at identifiable nodes in a network to offload work from the server without all clients in the network having to cache all blanket leases issued. Thresholds for issuing blanket leases may be determined or adjusted by considerations such as demand for the selected data and server workload. Similarly, leases may be renewed on the basis of demand for selected data, conflicting lease requests, and other factors. Scalable leases may be issued for read leases and controlled write leases.

Abstract: The described implementations relate to efficient scheduling of transactions and tasks. A memory location, address, or variable previously accessed by a blocked entity is observed periodically to determine an appropriate time to wake and retry the blocked entity. If the previous accessed memory location, address or variable changes state, a scheduler wakes the blocked entity and the blocked entity retries processing. A doubly-indexed data structure of blocked entities and memory locations associated with the blocked entities may be used to efficiently determine when a retrying execution would be profitable.

Abstract: A virtual machine monitor (VMM) is configured to enforce deterministic execution of virtual machines in a multiprocessor machine. The VMM is configured to ensure that any communication by physical processors via shared memory is deterministic. When such VMMs are implemented in a distributed environment of multiprocessor machines coupled via a logical communication link, non-deterministic server applications running on virtual machines using the VMM may be replicated.

Abstract: Synchronized devices comprising a distributed system attempt to agree on a compatible sequence of commands to execute. Each device in the distributed system may act as a proposer, acceptor, or a learner. Each proposer proposes a command for each device to execute. The acceptors either accept or reject the proposed commands. The learners keep track of the proposed commands and determine, using a transactional substrate, whether the acceptors have a accepted sequences of commands that commute with respect to one another. Once the learners have determined that a quorum of acceptors have accepted sequences of commands that commute with respect to one another the accepted commands are executed by each device in the distributed system.

Abstract: A mechanism that enables a nondeterministic client-server application to be run as a replicated state machine without requiring the application to be modified. A replicated state machine substrate is utilized to coordinate the execution of multiple virtual machine monitors, each of which runs an identical copy of an operating system and server application. The virtual machine monitors each act as deterministic state machines, virtualizing state machine characteristics and behaviors.