Accurately computing the electronic properties of a quantum ring.

A promising approach to study condensed-matter systems is to simulate them on an engineered quantum platform1-4. However, the accuracy needed to outperform classical methods has not been achieved so far. Here, using 18 superconducting qubits, we provide an experimental blueprint for an accurate condensed-matter simulator and demonstrate how to investigate fundamental electronic properties. We benchmark the underlying method by reconstructing the single-particle band structure of a one-dimensional wire. We demonstrate nearly complete mitigation of decoherence and readout errors, and measure the energy eigenvalues of this wire with an error of approximately 0.01 rad, whereas typical energy scales are of the order of 1 rad. Insight into the fidelity of this algorithm is gained by highlighting the robust properties of a Fourier transform, including the ability to resolve eigenenergies with a statistical uncertainty of 10-4 rad. We also synthesize magnetic flux and disordered local potentials, which are two key tenets of a condensed-matter system. When sweeping the magnetic flux we observe avoided level crossings in the spectrum, providing a detailed fingerprint of the spatial distribution of local disorder. By combining these methods we reconstruct electronic properties of the eigenstates, observing persistent currents and a strong suppression of conductance with added disorder. Our work describes an accurate method for quantum simulation5,6 and paves the way to study new quantum materials with superconducting qubits.

Demonstrating a Continuous Set of Two-Qubit Gates for Near-Term Quantum Algorithms.

Quantum algorithms offer a dramatic speedup for computational problems in material science and chemistry. However, any near-term realizations of these algorithms will need to be optimized to fit within the finite resources offered by existing noisy hardware. Here, taking advantage of the adjustable coupling of gmon qubits, we demonstrate a continuous two-qubit gate set that can provide a threefold reduction in circuit depth as compared to a standard decomposition. We implement two gate families: an imaginary swap-like (iSWAP-like) gate to attain an arbitrary swap angle, θ, and a controlled-phase gate that generates an arbitrary conditional phase, ϕ. Using one of each of these gates, we can perform an arbitrary two-qubit gate within the excitation-preserving subspace allowing for a complete implementation of the so-called Fermionic simulation (fSim) gate set. We benchmark the fidelity of the iSWAP-like and controlled-phase gate families as well as 525 other fSim gates spread evenly across the entire fSim(θ,ϕ) parameter space, achieving a purity-limited average two-qubit Pauli error of 3.8×10^{-3} per fSim gate.

Learning Curve for Flow Diversion of Posterior Circulation Aneurysms: A Long-Term International Multicenter Cohort Study.

BACKGROUND AND PURPOSE: Flow diversion has gradually become a standard treatment for intracranial aneurysms of the anterior circulation. Recently, the off-label use of the flow diverters to treat posterior circulation aneurysms has also increased despite initial concerns of rupture and the suboptimal results. This study aimed to explore the change in complication rates and treatment outcomes across time for posterior circulation aneurysms treated using flow diversion and to further evaluate the mechanisms and variables that could potentially explain the change and outcomes. MATERIALS AND METHODS: A retrospective review using a standardized data set at multiple international academic institutions was performed to identify patients with ruptured and unruptured posterior circulation aneurysms treated with flow diversion during a decade spanning January 2011 to January 2020. This period was then categorized into 4 intervals. RESULTS: A total of 378 procedures were performed during the study period. Across time, there was an increasing tendency to treat more vertebral artery and fewer large vertebrobasilar aneurysms (P = .05). Moreover, interventionalists have been increasingly using fewer overlapping flow diverters per aneurysm (P = .07). There was a trend toward a decrease in the rate of thromboembolic complications from 15.8% in 2011-13 to 8.9% in 2018-19 (P = .34). CONCLUSIONS: This multicenter experience revealed a trend toward treating fewer basilar aneurysms, smaller aneurysms, and increased usage of a single flow diverter, leading to a decrease in the rate of thromboembolic and hemorrhagic complications.

Noise-resilient edge modes on a chain of superconducting qubits.

Inherent symmetry of a quantum system may protect its otherwise fragile states. Leveraging such protection requires testing its robustness against uncontrolled environmental interactions. Using 47 superconducting qubits, we implement the one-dimensional kicked Ising model, which exhibits nonlocal Majorana edge modes (MEMs) with [Formula: see text] parity symmetry. We find that any multiqubit Pauli operator overlapping with the MEMs exhibits a uniform late-time decay rate comparable to single-qubit relaxation rates, irrespective of its size or composition. This characteristic allows us to accurately reconstruct the exponentially localized spatial profiles of the MEMs. Furthermore, the MEMs are found to be resilient against certain symmetry-breaking noise owing to a prethermalization mechanism. Our work elucidates the complex interplay between noise and symmetry-protected edge modes in a solid-state environment.

Realizing topologically ordered states on a quantum processor.

The discovery of topological order has revised the understanding of quantum matter and provided the theoretical foundation for many quantum error­correcting codes. Realizing topologically ordered states has proven to be challenging in both condensed matter and synthetic quantum systems. We prepared the ground state of the toric code Hamiltonian using an efficient quantum circuit on a superconducting quantum processor. We measured a topological entanglement entropy near the expected value of ­ln2 and simulated anyon interferometry to extract the braiding statistics of the emergent excitations. Furthermore, we investigated key aspects of the surface code, including logical state injection and the decay of the nonlocal order parameter. Our results demonstrate the potential for quantum processors to provide insights into topological quantum matter and quantum error correction.

Intraluminal septation of the basilar artery: incidence and potential clinical significance.

Variations in the cerebrovascular tree can increase surgical or interventional morbidity. To date, only scant comments are to be found in the literature regarding intraluminal variations of the basilar artery. To further elucidate such anatomy, a cadaveric study was performed. One hundred and fifty human brains were evaluated for the present study. The basilar artery was identified in each and sectioned longitudinally to observe for the presence of intraluminal septa. One specimen (0.67%) was identified that harbored an intraluminal septum of the basilar artery. This wall was within the proximal basilar artery and measured 3 mm by 1.5 mm. No specimen was found to have other anomalies of the basilar artery and in the single specimen with an intraluminal septum no signs of intracranial pathology were seen. Although seemingly rare, septation of the basilar artery can be found. Knowledge of such an intraluminal vascular variation may be important during invasive and minimally invasive procedures.

Risk of Branch Occlusion and Ischemic Complications with the Pipeline Embolization Device in the Treatment of Posterior Circulation Aneurysms.

BACKGROUND AND PURPOSE: Flow diversion with the Pipeline Embolization Device is increasingly used for endovascular treatment of intracranial aneurysms due to high reported obliteration rates and low associated morbidity. While obliteration of covered branches in the anterior circulation is generally asymptomatic, this has not been studied within the posterior circulation. The aim of this study was to evaluate the association between branch coverage and occlusion, as well as associated ischemic events in a cohort of patients with posterior circulation aneurysms treated with the Pipeline Embolization Device. MATERIALS AND METHODS: A retrospective review of prospectively maintained databases at 8 academic institutions from 2009 to 2016 was performed to identify patients with posterior circulation aneurysms treated with the Pipeline Embolization Device. Branch coverage following placement was evaluated, including the posterior inferior cerebellar artery, anterior inferior cerebellar artery, superior cerebellar artery, and posterior cerebral artery. If the Pipeline Embolization Device crossed the ostia of the contralateral vertebral artery, its long-term patency was assessed as well. RESULTS: A cohort of 129 consecutive patients underwent treatment of 131 posterior circulation aneurysms with the Pipeline Embolization Device. Adjunctive coiling was used in 40 (31.0%) procedures. One or more branches were covered in 103 (79.8%) procedures. At a median follow-up of 11 months, 11% were occluded, most frequently the vertebral artery (34.8%). Branch obliteration was most common among asymptomatic aneurysms (P < .001). Ischemic complications occurred in 29 (22.5%) procedures. On multivariable analysis, there was no significant difference in ischemic complications in cases in which a branch was covered (P = .24) or occluded (P = .16). CONCLUSIONS: There was a low occlusion incidence in end arteries following branch coverage at last follow-up. The incidence was higher in the posterior cerebral artery and vertebral artery where collateral supply is high. Branch occlusion was not associated with a significant increase in ischemic complications.

Isolation and characterization of glucocorticoid- and cyclic AMP-induced genes in T lymphocytes.

Glucocorticoids and cyclic AMP exert dramatic effects on the proliferation and viability of murine T lymphocytes through unknown mechanisms. To identify gene products which might be involved in glucocorticoid-induced responses in lymphoid cells, we constructed a lambda cDNA library prepared from murine thymoma WEHI-7TG cells treated for 5 h with glucocorticoids and forskolin. The library was screened with a subtracted cDNA probe enriched for sequences induced by the two drugs, and cDNA clones representing 11 different inducible genes were isolated. The pattern of expression in BALB/c mouse tissues was examined for each cDNA clone. We have identified two clones that hybridized to mRNAs detected exclusively in the thymus. Other clones were identified that demonstrated tissue-specific gene expression in heart, brain, brain and thymus, or lymphoid tissue (spleen and thymus). The kinetics of induction by dexamethasone and forskolin were examined for each gene. The majority of the cDNA clones hybridized to mRNAs that were regulated by glucocorticoids and forskolin, two were regulated only by glucocorticoids, and three hybridized to mRNAs that required both drugs for induction. Inhibition of protein synthesis by cycloheximide resulted in the induction of all mRNAs that were inducible by glucocorticoids. Preliminary sequence analysis of four of the 11 cDNAs suggests that two cDNAs represent previously undescribed genes while two others correspond to the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein.

Treatment of Tandem Internal Carotid Artery Aneurysms Using a Single Pipeline Embolization Device: Evaluation of Safety and Efficacy.

BACKGROUND AND PURPOSE: Tandem aneurysms are defined as multiple aneurysms located in close proximity on the same parent vessel. Endovascular treatment of these aneurysms has rarely been reported. Our aim was to evaluate the safety and efficacy of a single Pipeline Embolization Device for the treatment of tandem aneurysms of the internal carotid artery. MATERIALS AND METHODS: A retrospective analysis of consecutive aneurysms treated with the Pipeline Embolization Device between 2009 and 2016 at 3 institutions in the United States was performed. Cases included aneurysms of the ICA treated with a single Pipeline Embolization Device, and they were divided into tandem versus solitary. Angiographic and clinical outcomes were compared. RESULTS: The solitary group (median age, 58 years) underwent 184 Pipeline Embolization Device procedures for 184 aneurysms. The tandem group (median age, 50.5 years) underwent 34 procedures for 78 aneurysms. Aneurysms were primarily located along the paraophthalmic segment of the ICA in both the single and tandem groups (72.3% versus 78.2%, respectively, P = .53). The median maximal diameters in the solitary and tandem groups were 6.2 and 6.7 mm, respectively. Complete occlusion on the last angiographic follow-up was achieved in 75.1% of aneurysms in the single compared with 88.6%% in the tandem group (P = .06). Symptomatic thromboembolic complications were encountered in 2.7% and 8.8% of procedures in the single and tandem groups, respectively (P = .08). CONCLUSIONS: Tandem aneurysms of the ICA can be treated with a single Pipeline Embolization Device with high rates of complete occlusion. While there appeared to be a trend toward higher thromboembolic complication rates, this did not reach statistical significance.

Predictors of Incomplete Occlusion following Pipeline Embolization of Intracranial Aneurysms: Is It Less Effective in Older Patients?

BACKGROUND AND PURPOSE: Flow diversion with the Pipeline Embolization Device (PED) for the treatment of intracranial aneurysms is associated with a high rate of aneurysm occlusion. However, clinical and radiographic predictors of incomplete aneurysm occlusion are poorly defined. In this study, predictors of incomplete occlusion at last angiographic follow-up after PED treatment were assessed. MATERIALS AND METHODS: A retrospective analysis of consecutive aneurysms treated with the PED between 2009 and 2016, at 3 academic institutions in the United States, was performed. Cases with angiographic follow-up were selected to evaluate factors predictive of incomplete aneurysm occlusion at last follow-up. RESULTS: We identified 465 aneurysms treated with the PED; 380 (81.7%) aneurysms (329 procedures; median age, 58 years; female/male ratio, 4.8:1) had angiographic follow-up, and were included. Complete occlusion (100%) was achieved in 78.2% of aneurysms. Near-complete (90%-99%) and partial (<90%) occlusion were collectively achieved in 21.8% of aneurysms and defined as incomplete occlusion. Of aneurysms followed for at least 12 months (211 of 380), complete occlusion was achieved in 83.9%. Older age (older than 70 years), nonsmoking status, aneurysm location within the posterior communicating artery or posterior circulation, greater aneurysm maximal diameter (≥21 mm), and shorter follow-up time (<12 months) were significantly associated with incomplete aneurysm occlusion at last angiographic follow-up on univariable analysis. However, on multivariable logistic regression, only age, smoking status, and duration of follow-up were independently associated with occlusion status. CONCLUSIONS: Complete occlusion following PED treatment of intracranial aneurysms can be influenced by several factors related to the patient, aneurysm, and treatment. Of these factors, older age (older than 70 years) and nonsmoking status were independent predictors of incomplete occlusion. While the physiologic explanation for these findings remains unknown, identification of factors predictive of incomplete aneurysm occlusion following PED placement can assist in patient selection and counseling and might provide insight into the biologic factors affecting endothelialization.

Identification of a gene induced by glucocorticoids in murine T-cells: a potential G protein-coupled receptor.

Using cDNA cloning techniques we previously identified a set of genes induced by glucocorticoids and cAMP in murine T-lymphocytes. We report here the sequence of one of these cDNA clones (clone 4.2), renamed here as glucocorticoid-induced receptor (GIR), which encodes a potential new member of the family of receptors that couple to G-proteins. Several different forms of cDNA for this gene were isolated and shown to correspond to multiple mRNA species in lymphoid cells using an RNase protection assay. The cDNA clone corresponding to the most abundant form of GIR mRNA encodes a precursor protein of 423 amino acids, with a putative signal peptide of 17 amino acids. A hydropathy plot reveals the presence of seven hydrophobic regions, with significant similarities to other G-protein-coupled receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Genes newly identified as regulated by glucocorticoids in murine thymocytes.

Glucocorticoids induce dramatic biochemical and morphological changes in lymphocytes through an unknown process that requires RNA and protein synthesis. In order to identify genes involved in this response, we previously isolated 11 cDNA clones from the murine WEHI-7TG thymoma cell line that correspond to mRNAs induced by glucocorticoids. We now report the isolation of two new cDNA clones whose gene expression is regulated by glucocorticoids in WEHI-7TG cells. We further characterize the two new cDNA clones, as well as those described previously, by examining the response of each of the corresponding mRNAs to glucocorticoids in murine thymocytes. With the exception of two, all cDNAs correspond to genes that are induced by glucocorticoids in murine thymocytes within 4 h of treatment. We previously identified two of the cDNAs as the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein. We have now identified four additional cDNA clones that correspond to the genes for calmodulin, mitochondrial phosphate carrier protein, immunoglobulin (Ig)-related glycoprotein (GP-70), and the 70 kilodalton autoantigen for Lupus and Graves diseases. Two other cDNA clones represent previously undescribed genes: one shares a high similarity to known sequences for the family of G-protein-coupled receptors and the other to a human placental-specific protein, PP11. Another cDNA appears to contain sequences for an unknown gene and the remnants of a mouse transposon. ETn. The remaining clones represent new, unidentified genes induced by glucocorticoids in murine thymocytes and in the WEHI-7TG cell line.

Beta amyloid is neurotoxic in hippocampal slice cultures.

We examined the neurotoxicity of the 40 amino acid fragment of beta amyloid peptide (A beta 1-40) in cultured hippocampal slices. When injected into area CA3, A beta 1-40 produced widespread neuronal damage. Injection of the reverse sequence peptide, A beta 40-1, or vehicle alone produced little damage. The distribution A beta 1-40 was highly correlated with the area of neuronal damage. Thioflavine S and electron microscopic analysis confirmed that injected A beta 1-40 formed 7-9 nm AD type amyloid fibrils in the cultures. A beta 1-40 also altered the number of GFAP immunoreactive astrocytes and ED-1 immunoreactive microglia/macrophages within and around the A beta 1-40 deposit. The observed neurotoxicity of A beta 1-40 in hippocampal slice cultures provides evidence that this peptide may be responsible for the neurodegeneration observed in AD.

Effect of hematocrit on calculation of cerebral blood flow and lambda in xenon CT.

Knowledge of the patient's hematocrit is necessary for calculation of cerebral blood flow (CBF) with xenon CT, and is a potential source of error. This study quantifies the effect of hematocrit on the calculation of CBF and lambda, and determines if the magnitude of the effect is dependent on actual CBF or lambda. The effect of hematocrit was measured empirically using software employing the numerical calculation method. CBF and lambda were found to be inversely related to hematocrit. The percent error produced by an inaccurate hematocrit is greater for lower actual CBF values.

Indomethacin in the management of elevated intracranial pressure: a review.

Elevated intracranial pressure occurs frequently in patients with severe head injury. A number of studies in recent years suggest that indomethacin may be useful in the management of elevated intracranial pressure. Indomethacin acts primarily by reducing cerebral blood flow and decreasing cerebral edema following head injury. This review summarizes the basic and clinical studies of the effects of indomethacin on cerebral blood flow, brain edema, and intracranial pressure. The pharmacology of indomethacin, and issues for future investigation in the use of indomethacin in severe head injury, are discussed.

Cerebral salt wasting syndrome: a review.

Hyponatremia is frequently seen in neurosurgical patients and is often attributed to inappropriate secretion of antidiuretic hormone. A number of studies in recent years have shown that hyponatremia in many patients with intracranial disease may actually be caused by cerebral salt wasting, in which a renal loss of sodium leads to hyponatremia and a decrease in extracellular fluid volume. The appropriate treatment of cerebral salt wasting fluid and salt replacement, is opposite from the usual treatment of hyponatremia caused by inappropriate secretion of antidiuretic hormone. This review summarizes the evidence in favor of cerebral salt wasting in patients with intracranial disease, examines the possible mechanisms responsible for this phenomenon, and discusses methods for diagnosis and treatment.

Abducens nerve palsy after radiofrequency rhizolysis for trigeminal neuralgia: case report.

OBJECTIVE AND IMPORTANCE: Abducens nerve palsy is a rare and reversible complication associated with percutaneous radiofrequency trigeminal rhizolysis. CLINICAL PRESENTATION: An 86-year-old man developed an abducens nerve palsy immediately after undergoing percutaneous radiofrequency trigeminal rhizolysis for severe trigeminal neuralgia involving all three divisions of the trigeminal nerve. The palsy resolved spontaneously after 2 months. CONCLUSION: This case, in combination with previous reports, suggests that cases of transient sixth nerve palsy associated with percutaneous radiofrequency trigeminal rhizolysis for trigeminal neuralgia are more likely to occur in elderly patients with ophthalmic division involvement.

The evaluation of the National Long Term Care Demonstration. 9. The effect of channeling on mortality, functioning, and well-being.

A key component of the channeling evaluation was its focus on the life quality of program clients and their caregivers. In this article, life quality results in the areas of mortality, functioning, and client and caregiver well-being are presented for research treatment and control group members. Results show no significant differences in mortality, some beneficial program effects on client and caregiver well-being, and somewhat mixed effects on client functioning.

Community care demonstrations: what have we learned?

Based on a review of community care demonstrations, we conclude that expanding public financing of community services beyond what already exists is likely to increase costs. Small nursing home cost reductions are more than offset by the increased costs of providing services to those who would remain at home even without the expanded services. However, expanded community services appear to make people better off and not to cause substantial reductions in family caregiving. Policymakers should move beyond asking whether expanding community care will reduce costs to addressing how much community care society is willing to pay for, who should receive it, and how it can be delivered efficiently.

Cerebral salt wasting syndrome.

There is significant evidence to show that many patients with hyponatremia and intracranial disease who were previously diagnosed with SIADH actually have CSW. The critical difference between SIADH and CSW is that CSW involves renal salt loss leading to hyponatremia and volume loss, whereas SIADH is a euvolemic or hypervolemic condition. Attention to volume status in patients with hyponatremia is essential. The primary treatment for CSW is water and salt replacement. The mechanisms underlying CSW are not understood but may involve ANP or other natriuretic factors and direct neural influence on renal function. Future investigation is needed to better define the incidence of CSW in patients with intracranial disease, identify other disorders that can lead to CSW, and elucidate the mechanisms underlying this syndrome.