Making Operation-based CRDTs Operation-based

Conflict-free Replicated Datatypes can simplify the design of predictable eventual consistency. They can be classified into state-based or operation-based. Operation-based approaches have the potential for allowing compact designs in both the sent message and the object state size, but cur- rent approaches are still far from this objective. Here we explore the design space for operation-based solutions, and we leverage the interaction with the middleware by offering a technique that delivers very compact solutions, while only broadcasting operation names and arguments.(undefined)(undefined

Anterior spinal artery as a collateral channel in cases of bilateral vertebral arterial steno-occlusive diseases

BACKGROUND AND PURPOSE: We report 6 cases of retrograde flow through the anterior spinal artery (ASA) from cervical vertebral artery (VA) to intracranial distal VA because the perfusion from bilateral vertebral arteries was tenuous. Its hemodynamic and clinical implications are discussed. METHODS: In association with bilateral steno-occlusive disease of vertebral arteries, 6 cases of retrograde flow through ASA were reviewed in terms of clinical and angiographic characteristics. All 6 patients presented with stroke in the posterior fossa and underwent conventional angiography as part of diagnostic evaluation and/or therapeutic intervention. RESULTS: On the angiography, 2 patients showed bilateral VA occlusion, and the other 4 patients showed VA occlusion on 1 side and severe stenosis in the other VA. Distal perfusion by ASA was prominent in 2, and not prominent in 4. Reversal or disappearance of the retrograde flow through ASA was observed after successful recanalization of the occluded VA in 4 patients. In 1 patient, increased perfusion through ASA was observed because the stenosed VA was completely occluded. CONCLUSION: When the vertebral arteries were occluded bilaterally or when a single VA was occluded and the other carried a severe stenosis and, as a result, the basilar arterial blood supply was tenuous, retrograde flow through ASA could be observed. This is a potentially important source of collateral supply to the posterior fossa neural contents. The degree and extent of perfusion via this collateral channel varied depending on presence of other collateral routes and patency of the vertebrobasilar junction