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.

Estimating population lung cancer risk from radon using a resource efficient stratified population weighted sample survey protocol - Lessons and results from Ireland.

A 2018 estimate indicates that there were 226,057 radon-attributable lung cancer deaths in 66 countries that had representative radon surveys. This is a shocking figure, and as it comes from only 66 countries it underestimates the worldwide death toll. Any research that enables countries to conduct representative radon surveys and to understand better the risk to citizens from radon is surely welcome. We hope this paper provides a useful methodology for estimating population risk. The estimation of population weighted average indoor radon levels requires statistically valid sampling methodologies that use a representative sample of occupied homes throughout the country. A literature review indicates that in many population weighted surveys, the sampling methodology may not have been designed to do this. This paper describes a simple, resource efficient methodology which produces statistically valid and reliable estimates based on a small scale sample that is representative of the population distribution. The resource efficient design of this study enables it to be repeated at frequent intervals providing for a longitudinal analysis of the population risk from indoor radon. This survey was conducted in Ireland using 653 measurements and a representative sampling strategy to provide a baseline population weighted radon exposure for future comparisons. This study estimates the average population weighted indoor radon concentration in Ireland to be 97.83 Bq m-3 (95% Confidence Interval 90.69 Bq m-3 to 105.53 Bq m-3), and that there are an estimated 350 lung cancer cases and 255 deaths per year due to radon exposure. The mortality rate of 5.3 per 100,000 due to indoor radon, demonstrates that radon remains one of the highest preventable causes of death in Ireland.

Transcriptional induction of cholinesterase expression and protection against chemical warfare nerve agents.

We investigated whether transcriptional inducers could enhance the expression of acetylcholinesterase (AChE) in cell lines to achieve protection against organophosphate (OP) poisoning. Trichostatin A (TSA), an inhibitor of histone deacetylase that de-condenses chromatin and increases the binding of transcription factors and mRNA synthesis, induced three- to four-fold extracellular and 8-10-fold intracellular AChE expression at the optimal dose of 165-333 nM in Neuro 2A cells. Pre-treatment with TSA protected against OP exposure. Thus, transcriptional inducers, such as TSA, up-regulate AChE, which then can scavenge the OP and protect the cells from OP-induced toxicity, and are potential novel ways to treat chemical warfare nerve agent (CWNA) exposure.

Role of carbon fibre implants in osteochondral defects of the knee.

Articular cartilage defects of the knee are a common condition diagnosed at arthroscopy. The management of these osteochondral lesions is controversial. We present our experience using carbon fibre implants to repair these defects in 18 patients. Eleven patients (61 per cent) had an osteochondral defect of the medial femoral condyle. Two patients had isolated patellar defects. The mean knee assessment and functional scores were 75 and 80 respectively using The Knee Society Clinical Rating System. Serial post-operative M.R.I. scanning revealed that there was no loss of implant position with an extensive local tissue response and good joint congruity. Overall, 11 patients (61 per cent) returned to their normal sporting activity, while 3 patients (18 per cent) had a poor result. One of these underwent a patellectomy. We conclude that carbon fibre implants may have a role to play in the management of osteochondral defects of the femoral condyles.

The modulation of ocular growth in rabbits with peripheral retinal ablation.

PURPOSE: To study the effects of transcleral cryotherapy and laser photocoagulation of anterior retina on ocular growth. METHODS: Twenty-one rabbits underwent transcleral cryotherapy or indirect ophthalmoscopic laser photocoagulation of the anterior retina on one of their eyes between 2 and 8 weeks of age. RESULTS: After the rabbits were killed between 3 and 6 months of age, treated rabbit eyes were found to be significantly smaller in axial length (P < 0.001), average equatorial diameter (P < 0.01), average corneal diameter (P < 0.05), and in total ocular volume (P < 0.01). The difference in eye size was not due to lowered intraocular pressure. CONCLUSIONS: The results demonstrate that these treatments slow growth of both the anterior and posterior segment of rabbit eyes.

Scleral reinforcement in rabbits using synthetic graft materials.

Because of disappointing results using homologous collagen for scleral reinforcement in the treatment of pathologic myopia in humans, we undertook a series of experiments in rabbits to test the mechanical properties and long-term biocompatibility of three different synthetic graft materials. Grafts made from two of these materials, Gore-Tex Soft Tissue Patch (expanded polytetrafluoroethylene) and Miragel (poly[methyl acrylate-co-hydroxy-ethyl acrylate]), were easy to position about the globe. Both materials, however, were resistant to invasion by fibrovascular tissue. The third material, woven Dacron (polyethylene terephthalate), though more difficult to position, permitted extensive invasion of fibrovascular tissue, which made all parts of the graft firmly adherent to the globe. Our results indicate the long-term compatibility of all three of these materials when used as periscleral grafts in rabbits. However, our results also suggest that a woven material such as commercially available Dacron is a more suitable graft material for scleral reinforcement in humans than collagen, Miragel, or Gore-Tex.

Scleral reinforcement: two case reports.

We report two cases of unilateral scleral reinforcement undergone for progressive pathologic myopia. Examination ten years after the operations showed the supportive effect of the scleral grafts. The effect, however, was localized and did not appear to block the overall progression of posterior staphyloma formation significantly.

Long-term results of scleral reinforcement surgery.

Of 40 scleral reinforcement operations for progressive severe myopia, 23 patients were followed up for a minimum of five years. Ten of 23 patients showed an essentially stable postoperative course (43%) while 13 (57%) had increases in myopia of -1.0 diopter or more. Among the operated on eyes, 17 of 23 eventually had some increase in myopia. Of the 20 eyes that had preoperative axial measurements, 18 (90%) had increases in axial diameter of 0.3 mm or more. There were complications in six of the 40 eyes, including anterior uveitis, motility disorders, and retinal detachment. Progression of posterior staphyloma formation or the onset of myopic fundus degeneration was observed in ten eyes. Two problems with this surgery are the limited scleral area reinforced by narrow grafts and the possible late involvement of graft collagen in the disease process of host sclera.

Scleral hyperplasia induced by heat.

We evaluated low-level heating as a stimulus to induce hyperplasia of normal rabbit sclera. Heat treatments were administered by placing an etched-element heater on bare sclera. Contact thermotherapy with a conductive device provided a favorable dose distribution for local scleral heating. A purely conductive heat source was selected to minimize intraocular heat penetration and to determine whether the scleral reaction was a primary thermal effect. Histologic examination of treated specimens showed thickening of normal rabbit sclera with preservation of the underlying normal ocular structures. Electron microscopic examination of treated sclera showed newly formed collagen fibrils adjacent to sclerocytes. These fibroblasts were activated, as manifested by well-developed rough-surfaced endoplasmic reticulum and hypertrophic Golgi complexes.

Prescribing behaviors of primary care nurse practitioners.

The prescribing practices of 18 primary care nurse practitioners (NPs) with 1,683 patients over a six-month period were examined through a randomly selected audit of over 1,700 prescriptions. The results showed that NPs prescribed a very limited number of well known, relatively simple drugs to a young, female healthy population. The prescription/visit rate was 0.26. Most drugs were initiated for the first time rather than refilled. There was minimal physician consultation regarding drug use during the visit. The results provide evidence of the ability of nurse practitioners to prescribe drugs and should aid in the further legalization of this aspect of the primary care role.

Physiologic vs pathologic myopia: genetics vs environment.

Physiologic myopia occurs as the result of a correlation failure of refraction components in the normal eye. Pathologic myopia is caused by excessive axial elongation that primarily involves the ora-equatorial area and the posterior pole. Peripheral fundus changes and posterior staphyloma formation are ophthalmoscopic evidences of this process. Heredity is the basic determinant of ocular refraction, but numerous agents produce both temporary and permanent myopias.