Dynamics of magnetization at infinite temperature in a Heisenberg spin chain.

Understanding universal aspects of quantum dynamics is an unresolved problem in statistical mechanics. In particular, the spin dynamics of the one-dimensional Heisenberg model were conjectured as to belong to the Kardar-Parisi-Zhang (KPZ) universality class based on the scaling of the infinite-temperature spin-spin correlation function. In a chain of 46 superconducting qubits, we studied the probability distribution of the magnetization transferred across the chain's center, [Formula: see text]. The first two moments of [Formula: see text] show superdiffusive behavior, a hallmark of KPZ universality. However, the third and fourth moments ruled out the KPZ conjecture and allow for evaluating other theories. Our results highlight the importance of studying higher moments in determining dynamic universality classes and provide insights into universal behavior in quantum systems.

Stable quantum-correlated many-body states through engineered dissipation.

Engineered dissipative reservoirs have the potential to steer many-body quantum systems toward correlated steady states useful for quantum simulation of high-temperature superconductivity or quantum magnetism. Using up to 49 superconducting qubits, we prepared low-energy states of the transverse-field Ising model through coupling to dissipative auxiliary qubits. In one dimension, we observed long-range quantum correlations and a ground-state fidelity of 0.86 for 18 qubits at the critical point. In two dimensions, we found mutual information that extends beyond nearest neighbors. Lastly, by coupling the system to auxiliaries emulating reservoirs with different chemical potentials, we explored transport in the quantum Heisenberg model. Our results establish engineered dissipation as a scalable alternative to unitary evolution for preparing entangled many-body states on noisy quantum processors.

Formation of robust bound states of interacting microwave photons.

Systems of correlated particles appear in many fields of modern science and represent some of the most intractable computational problems in nature. The computational challenge in these systems arises when interactions become comparable to other energy scales, which makes the state of each particle depend on all other particles1. The lack of general solutions for the three-body problem and acceptable theory for strongly correlated electrons shows that our understanding of correlated systems fades when the particle number or the interaction strength increases. One of the hallmarks of interacting systems is the formation of multiparticle bound states2-9. Here we develop a high-fidelity parameterizable fSim gate and implement the periodic quantum circuit of the spin-½ XXZ model in a ring of 24 superconducting qubits. We study the propagation of these excitations and observe their bound nature for up to five photons. We devise a phase-sensitive method for constructing the few-body spectrum of the bound states and extract their pseudo-charge by introducing a synthetic flux. By introducing interactions between the ring and additional qubits, we observe an unexpected resilience of the bound states to integrability breaking. This finding goes against the idea that bound states in non-integrable systems are unstable when their energies overlap with the continuum spectrum. Our work provides experimental evidence for bound states of interacting photons and discovers their stability beyond the integrability limit.

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.

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.

Perceived relevance mediates the relationship between professional identity and attitudes towards interprofessional education in first-year university students.

The strength of health science students' identification with their chosen profession is associated with their attitudes towards interprofessional education (IPE). However, little is known about the factors that might mediate this relationship. In this article, we examine the relationships between professional identification, communication and teamwork skills, perceived relevance of IPE, and positive and negative attitudes towards IPE. A sample of 444 first-year university students from 25 health science professions enrolled in a first-year interprofessional program participated in this research by completing a questionnaire. Data were analysed using path analysis. Positive IPE attitudes were more strongly endorsed than negative IPE attitudes. Perceived relevance of IPE to future careers was the strongest predictor of both positive and negative attitudes to IPE, and fully mediated the effect of professional identity. Self-reported communication and teamwork skills were a significant negative predictor of negative attitudes to IPE only, and the effect was not mediated by perceived relevance. These findings indicate that IPE may be particularly challenging for students who do not have confidence in their abilities to communicate and work effectively in teams. Building these skills through alternative communication technologies may decrease negative attitudes. In order to maintain or increase positive attitudes towards IPE in introductory programs that span professions, the curriculum needs to be designed to demonstrate relevance to the future careers of participating students.

The superficial musculoaponeurotic system of the face: a model explored.

Regional differences in the integument of the body are explained, at least in part, by differences in fascial arrangements. In the face, where the skin is more mobile due to the action of the underlying facial muscles, fascial organisation is important for support and separation of muscle groups. This study used bequeathed cadaver material to investigate a current model of the SMAS proposed by Macchi et al., the original boundaries of which were explored and extended using both histology and gross dissection. As a clearly identifiable structure spanning the lateral and midface, the SMAS in the specimen supported the model proposed by Macchi et al. The three main findings that support the model were the layered morphological appearance of the SMAS, its progression from fibrous to aponeurotic in a lateral to medial direction, and the enveloping of the zygomaticus musculature. Extension beyond the proposed model into the temporal region was observed, but nasal and forehead regions showed no evidence of SMAS, while its presence in the cervical platysma region remained inconclusive. Fascial and soft tissue variability was considerable within facial regions of the examined specimen, helping to explain the debate around the SMAS in the literature.

Artificial ionospheric layers during pump frequency stepping near the 4th gyroharmonic at HAARP.

We report on artificial descending plasma layers created in the ionosphere F region by high-power high-frequency (HF) radio waves from High-frequency Active Auroral Research Program at frequencies f(0) near the fourth electron gyroharmonic 4f(ce). The data come from concurrent measurements of the secondary escaping radiation from the HF-pumped ionosphere, also known as stimulated electromagnetic emission, reflected probing signals at f(0), and plasma line radar echoes. The artificial layers appeared only for injections along the magnetic field and f(0)>4f(ce) at the nominal HF interaction altitude in the background ionosphere. Their average downward speed ~0.5 km/s holds until the terminal altitude where the local fourth gyroharmonic matches f(0). The total descent increases with the nominal offset f(0)-4f(ce).

Curative resection for low rectal adenocarcinoma: abdomino-perineal vs anterior resection.

OBJECTIVE: Local recurrence after abdomino-perineal excision of the rectum for tumours has been reported to occur in up to a third of patients in contrast to 4% after restorative anterior resection. METHOD: Low rectal tumours were defined as tumours within 8 cm of the anal verge and were treated by either stapled low anterior resection (SLAR) or abdomino-perineal excision of the rectum (APER). One hundred and seventy-eight patients with tumours in the lower third of the rectum (30% of 591 rectal cancers) underwent surgical resection between 1980 and 2001. Data were collected prospectively; 68 (38%) had SLAR and 110 (62%) had APER with median follow up of approximately 12 years; 54 SLAR (79%) and 76 APER (69%) had curative procedures on clinical and pathological criteria. RESULTS: Local and distant recurrence occurred in seven (13%) and eight (15%) patients in the SLAR group and six (8%) and 14 (18%) patients in the APER group, respectively. Overall 5-year survival was 63% and 60% in the SLAR and APER groups, respectively CONCLUSION: For rectal cancers within 8 cm of the anal verge, both procedures achieved equivalent results measured by low local recurrence rates and overall survival.

Distinctive organization of genes for light-harvesting proteins in the cryptophyte alga Rhodomonas.

Cryptophyte algae contain two kinds of light-harvesting protein, phycobiliproteins and chlorophyll a,c-binding proteins. The beta subunit of the phycobiliprotein phycoerythrin (PE) is encoded in the chloroplast. Genes for the other PE polypeptides are located in the nucleus but little is known of their organization. We cloned and sequenced six cpeA genes encoding the phycoerythrin alpha subunit from a genomic library of the cryptophyte Rhodomonas CS24. Derived peptide sequences of the cpeA genes show that alpha subunits occur in at least two forms, a longer alpha1 form and a shorter alpha2 form. Remarkably, all six cpeA genes occur in divergent pairs encoding one alpha1 and one alpha2 subunit. Four cac genes encoding chlorophyll a,c-binding proteins were cloned and sequenced and also found to occur in divergent pairs comprising one cac1 and one cac2 gene. Inspection of the predicted targeting sequences of the alpha1 and alpha2 phycoerythrin polypeptides shows that only the alpha1 polypeptides have a thylakoid lumen targeting sequence, corresponding to the TAT pathway. Given the previously reported lack of a lumen-targeting sequence on the beta subunit, we propose a novel import mechanism in which the entire alpha1alpha2 betabeta phycoerythrin complex is assembled in the stroma and transported into the thylakoid under the direction of the single targeting sequence on the alpha1 protein. The FAP motif implicated in plastid targeting in diatoms appears to be conserved in this cryptophyte.

How can experiences of patients and carers influence the clinical care of large bowel cancer?

A qualitative project was designed to investigate the care of large bowel cancer from patients' and carers' perspectives using semi-structured interviews; tape-recorded, transcribed and analysed; to identify recurrent themes. Forty-nine patients treated surgically for bowel cancer from three hospital trusts in West Surrey were visited at home, and eight of their carers attended a focus group from a choice of three geographical locations. Five main themes identified: experience of symptoms; general practitioner (GP) management; impact of diagnosis; perceptions of clinical care and treatment; information needs. Results showed that patients and carers were ignorant of the symptoms and signs of large bowel cancer and wanted more information. They were satisfied when the GP took symptoms seriously and referred promptly. Three groups of patients were particularly vulnerable: those requiring stomas (25), those diagnosed with polyps initially (11) and patients admitted as an emergency (7). Specialist nurses were seen as the main source of written information and support, which was most needed at the time of diagnosis and discharge. The public needs more accessible information about the symptoms and signs of bowel cancer. Referral to multiprofessional bowel cancer teams is essential to provide appropriate support and clear information from the time of diagnosis throughout the care pathway. Recommended strategies for improving clinical care are outlined.

Effect of faecal occult blood testing on colorectal cancer mortality in the surveillance of subjects at moderate risk of colorectal neoplasia: a case-control study.

Colonoscopy is the established method of surveillance of subjects at high risk of developing colorectal neoplasia. Its role in the surveillance of a population at moderate risk is less clear, however, as the procedure is expensive, time consuming and occasionally hazardous. The aim of this study was to estimate by case-control methods the effect of faecal occult blood (FOB) screening on colorectal cancer (CRC) mortality in a population at moderate risk of developing CRC. Screening by FOB testing prior to diagnosis in patients over the age of 45 years who died of CRC diagnosed in 1989-1998 was compared with screening in controls matched with the case for age and sex. Information about episodes of FOB testing and potential confounders was obtained from the data collection system of the screening programme. Cases were less likely than controls to have ever been screened, with an odds ratio of 0.64 (95% confidence interval 0.34-1.15) for exposure to at least one FOB testing. There was no significant difference between the sub-groups according to gender, age at diagnosis or location of the cancer. The inverse association between screening for faecal occult blood and fatal colorectal cancer suggests that screening in a population at moderate risk of CRC can reduce mortality from CRC in this group.

Cloning and analysis of the spinosad biosynthetic gene cluster of Saccharopolyspora spinosa.

BACKGROUND: Spinosad is a mixture of novel macrolide secondary metabolites produced by Saccharopolyspora spinosa. It is used in agriculture as a potent insect control agent with exceptional safety to non-target organisms. The cloning of the spinosyn biosynthetic gene cluster provides the starting materials for the molecular genetic manipulation of spinosad yields, and for the production of novel derivatives containing alterations in the polyketide core or in the attached sugars. RESULTS: We cloned the spinosad biosynthetic genes by molecular probing, complementation of blocked mutants, and cosmid walking, and sequenced an 80 kb region. We carried out gene disruptions of some of the genes and analyzed the mutants for product formation and for the bioconversion of intermediates in the spinosyn pathway. The spinosyn gene cluster contains five large open reading frames that encode a multifunctional, multi-subunit type I polyketide synthase (PKS). The PKS cluster is flanked on one side by genes involved in the biosynthesis of the amino sugar forosamine, in O-methylations of rhamnose, in sugar attachment to the polyketide, and in polyketide cross-bridging. Genes involved in the early common steps in the biosynthesis of forosamine and rhamnose, and genes dedicated to rhamnose biosynthesis, were not located in the 80 kb cluster. CONCLUSIONS: Most of the S. spinosa genes involved in spinosyn biosynthesis are found in one 74 kb cluster, though it does not contain all of the genes required for the essential deoxysugars. Characterization of the clustered genes suggests that the spinosyns are synthesized largely by mechanisms similar to those used to assemble complex macrolides in other actinomycetes. However, there are several unusual genes in the spinosyn cluster that could encode enzymes that generate the most striking structural feature of these compounds, a tetracyclic polyketide aglycone nucleus.

Genes for the biosynthesis of spinosyns: applications for yield improvement in Saccharopolyspora spinosa.

Spinosyns A and D are the active ingredients in an insect control agent produced by fermentation of Saccharopolyspora spinosa. Spinosyns are macrolides with a 21-carbon, tetracyclic lactone backbone to which the deoxysugars forosamine and tri-O-methylrhamnose are attached. The spinosyn biosynthesis genes, except for the rhamnose genes, are located in a cluster that spans 74 kb of the S. spinosa genome. DNA sequence analysis, targeted gene disruptions and bioconversion studies identified five large genes encoding type I polyketide synthase subunits, and 14 genes involved in sugar biosynthesis, sugar attachment to the polyketide or cross-bridging of the polyketide. Four rhamnose biosynthetic genes, two of which are also necessary for forosamine biosynthesis, are located outside the spinosyn gene cluster. Duplication of the spinosyn genes linked to the polyketide synthase genes stimulated the final step in the biosynthesis--the conversion of the forosamine-less pseudoaglycones to endproducts. Duplication of genes involved in the early steps of deoxysugar biosynthesis increased spinosyn yield significantly.

A cluster of genes for the biosynthesis of spinosyns, novel macrolide insect control agents produced by Saccharopolyspora spinosa.

Spinosyns A and D are the active ingredients in a family of insect control agents produced by fermentation of Saccharopolyspora spinosa. Spinosyns are 21-carbon tetracyclic lactones to which are attached two deoxysugars. Most of the genes involved in spinosyn biosynthesis are clustered in an 74 kb region of the S. spinosa genome. This region has been characterized by DNA sequence analysis and by targeted gene disruptions. The spinosyn biosynthetic gene cluster contains five large genes encoding a type I polyketide synthase, and 14 genes involved in modification of the macrolactone, or in the synthesis, modification and attachment of the deoxysugars. Four genes required for rhamnose biosynthesis (two of which are also required for forosamine biosynthesis) are not present in the cluster. A pathway for the biosynthesis of spinosyns is proposed.

A 10-year prospective audit of outcome of surgical treatment for colorectal carcinoma.

The outcome of 555 patients who underwent surgery under the care of a surgeon with an interest in colorectal disease was examined prospectively over a 10-year period with no exclusions. There was a 4.7 percent incidence of clinical leaks (10 percent for anterior resection) and an overall corrected 10-year survival rate after curative surgery of 58, 59 and 48 percent for right colonic, left colonic and rectal tumours respectively. The incidence of isolated local recurrence was 8 percent after curative surgery for carcinoma of the rectum. Twenty-five percent of patients with rectal tumours required abdominoperineal excision. Patients who underwent curative abdominoperineal excision of the rectum had corrected 5- and 10-year survival rates of 48 and 36 percent, compared with 60 and 58 percent respectively for curative anterior resection. The perioperative mortality rate of those undergoing palliative surgery was 8 percent, and 75 percent died within 2 years from distant and not local disease. A policy of always attempting resection was validated by the fact that 99 percent of primary tumours were removed with a low perioperative mortality rate (4 percent overall), a high curative resection rate and a low morbidity rate.