Testing quantum electrodynamics in extreme fields using helium-like uranium.

Quantum electrodynamics (QED), the quantum field theory that describes the interaction between light and matter, is commonly regarded as the best-tested quantum theory in modern physics. However, this claim is mostly based on extremely precise studies performed in the domain of relatively low field strengths and light atoms and ions1-6. In the realm of very strong electromagnetic fields such as in the heaviest highly charged ions (with nuclear charge Z ≫ 1), QED calculations enter a qualitatively different, non-perturbative regime. Yet, the corresponding experimental studies are very challenging, and theoretical predictions are only partially tested. Here we present an experiment sensitive to higher-order QED effects and electron-electron interactions in the high-Z regime. This is achieved by using a multi-reference method based on Doppler-tuned X-ray emission from stored relativistic uranium ions with different charge states. The energy of the 1s1/22p3/2 J = 2 → 1s1/22s1/2 J = 1 intrashell transition in the heaviest two-electron ion (U90+) is obtained with an accuracy of 37 ppm. Furthermore, a comparison of uranium ions with different numbers of bound electrons enables us to disentangle and to test separately the one-electron higher-order QED effects and the bound electron-electron interaction terms without the uncertainty related to the nuclear radius. Moreover, our experimental result can discriminate between several state-of-the-art theoretical approaches and provides an important benchmark for calculations in the strong-field domain.

Detection of metastable electronic states by Penning trap mass spectrometry.

State-of-the-art optical clocks1 achieve precisions of 10-18 or better using ensembles of atoms in optical lattices2,3 or individual ions in radio-frequency traps4,5. Promising candidates for use in atomic clocks are highly charged ions6 (HCIs) and nuclear transitions7, which are largely insensitive to external perturbations and reach wavelengths beyond the optical range8 that are accessible to frequency combs9. However, insufficiently accurate atomic structure calculations hinder the identification of suitable transitions in HCIs. Here we report the observation of a long-lived metastable electronic state in an HCI by measuring the mass difference between the ground and excited states in rhenium, providing a non-destructive, direct determination of an electronic excitation energy. The result is in agreement with advanced calculations. We use the high-precision Penning trap mass spectrometer PENTATRAP to measure the cyclotron frequency ratio of the ground state to the metastable state of the ion with a precision of 10-11-an improvement by a factor of ten compared with previous measurements10,11. With a lifetime of about 130 days, the potential soft-X-ray frequency reference at 4.96 × 1016 hertz (corresponding to a transition energy of 202 electronvolts) has a linewidth of only 5 × 10-8 hertz and one of the highest electronic quality factors (1024) measured experimentally so far. The low uncertainty of our method will enable searches for further soft-X-ray clock transitions8,12 in HCIs, which are required for precision studies of fundamental physics6.

Proof-of-Principle Experiment for Testing Strong-Field Quantum Electrodynamics with Exotic Atoms: High Precision X-Ray Spectroscopy of Muonic Neon.

To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high precision x-ray spectroscopy of the 5g-4f and 5f- 4d transitions (BSQED contribution of 2.4 and 5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the 5g_{9/2}- 4f_{7/2} transition energy to be 6297.08±0.04(stat)±0.13(syst) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.

Muonic atom spectroscopy with microgram target material.

Muonic atom spectroscopy-the measurement of the x rays emitted during the formation process of a muonic atom-has a long standing history in probing the shape and size of nuclei. In fact, almost all stable elements have been subject to muonic atom spectroscopy measurements and the absolute charge radii extracted from these measurements typically offer the highest accuracy available. However, so far only targets of at least a few hundred milligram could be used as it required to stop a muon beam directly in the target to form the muonic atom. We have developed a new method relying on repeated transfer reactions taking place inside a 100 bar hydrogen gas cell with an admixture of 0.25% deuterium that allows us to drastically reduce the amount of target material needed while still offering an adequate efficiency. Detailed simulations of the transfer reactions match the measured data, suggesting good understanding of the processes taking place inside the gas mixture. As a proof of principle we demonstrate the method with a measurement of the 2p-1s muonic x rays from a 5  µ g gold target.

Direct Q-Value Determination of the ß

The cyclotron frequency ratio of ^{187}Os^{29+} to ^{187}Re^{29+} ions was measured with the Penning-trap mass spectrometer PENTATRAP. The achieved result of R=1.000 000 013 882(5) is to date the most precise such measurement performed on ions. Furthermore, the total binding-energy difference of the 29 missing electrons in Re and Os was calculated by relativistic multiconfiguration methods, yielding the value of ΔE=53.5(10) eV. Finally, using the achieved results, the mass difference between neutral ^{187}Re and ^{187}Os, i.e., the Q value of the ß^{-} decay of ^{187}Re, is determined to be 2470.9(13) eV.

Deexcitation Dynamics of Muonic Atoms Revealed by High-Precision Spectroscopy of Electronic K X Rays.

We observed electronic K x rays emitted from muonic iron atoms using superconducting transition-edge sensor microcalorimeters. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic Kα and Kß x rays together with the hypersatellite K^{h}α x rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the L-shell electrons, accompanied by electron side feeding. Assisted by a simulation, these data clearly reveal the electronic K- and L-shell hole production and their temporal evolution on the 10-20 fs scale during the muon cascade process.

Mass-Difference Measurements on Heavy Nuclides with an eV/c

First ever measurements of the ratios of free cyclotron frequencies of heavy, highly charged ions with Z>50 with relative uncertainties close to 10^{-11} are presented. Such accurate measurements have become realistic due to the construction of the novel cryogenic multi-Penning-trap mass spectrometer PENTATRAP. Based on the measured frequency ratios, the mass differences of five pairs of stable xenon isotopes, ranging from ^{126}Xe to ^{134}Xe, have been determined. Moreover, the first direct measurement of an electron binding energy in a heavy highly charged ion, namely of the 37th atomic electron in xenon, with an uncertainty of a few eV is demonstrated. The obtained value agrees with the calculated one using two independent, different implementations of the multiconfiguration Dirac-Hartree-Fock method. PENTATRAP opens the door to future measurements of electron binding energies in highly charged heavy ions for more stringent tests of bound-state quantum electrodynamics in strong electromagnetic fields and for an investigation of the manifestation of light dark matter in isotopic chains of certain chemical elements.

Observation of 2p3d(1Po)→1s3d(1De) radiative transition in He-like Si, S, and Cl ions.

We present an experimental determination of the 2p3d(1Po)→1s3d(1De) x-ray line emitted from He-like Si, S, and Cl projectile ions, excited in collisions with thin carbon foils, using a high-resolution bent-crystal spectrometer. A good agreement between the observation and state-of-the-art relativistic calculations using the multiconfiguration Dirac-Fock formalism including the Breit interaction and QED effects implies the dominance of fluorescent decay over the autoionization process for the 2p3d(^{1}P^{o}) state of He-like heavy ions. This is the first observation of the fluorescence-active doubly excited states in He-like Si, S, and Cl ions.

Urinary CTX-II concentrations are elevated and associated with knee pain and function in subjects with ACL reconstruction.

OBJECTIVE: Post-traumatic knee osteoarthritis (OA) is prevalent after anterior cruciate ligament reconstruction (ACLR). Biomarkers that identify individuals likely to develop OA, especially symptomatic OA, can help target preventative and therapeutic strategies. This study examined the magnitude and change over time in urinary CTX-II (uCTX-II) concentrations shortly after ACL reconstruction, and, secondarily, the associations with knee pain and function. DESIGN: Subjects were 28 patients with ACLR and 28 age- and sex-matched controls (CNTRL). Testing was conducted at four time points spaced 4 weeks apart (4, 8, 12 and 16 weeks post-operative in ACLR). Measures included demographics, urine samples, Numeric Pain Rating Scale (NPRS) and International Knee Documentation Committee Subjective Knee Form (IKDC-SKF). uCTX-II concentrations were determined with competitive enzyme-linked immunosorbent assay (ELISA). uCTX-II concentrations at each time point in ACLR were compared to the mean concentration over time in CNTRL, with and without adjustment for body mass index (BMI). Changes over time in each measure and correlations between the slopes of change were examined. RESULTS: uCTX-II concentrations were significantly higher in ACLR than CNTRL through 16 weeks post-operative when adjusted for BMI. In ACLR, uCTX-II concentrations significantly decreased over time, and the slope was associated with NPRS (r = 0.406, P = 0.039) and IKDC-SKF (r = -0.402, P = 0.034) slopes. CONCLUSION: uCTX-II concentrations shortly after ACLR were elevated compared to CNTRL and declined over time. Decreasing uCTX-II concentrations were associated with decreasing knee pain and improving function. uCTX-II may have a role as a prognostic marker following ACLR and warrants further investigation.

Management of obstructive pathology of the salivary glands in elderly patients: a preliminary study.

BACKGROUND: Obstructive pathology is a benign condition of the salivary glands that can affect elderly and co-morbid people. Sialoendoscopy is a minimally invasive surgical procedure with a success rate comparable to standard sialoadenectomy and has the advantage that it can be performed under local anaesthesia. METHODS: This study aimed to assess sialoendoscopy benefits in elderly patients unfit for general anaesthesia. A group of elderly patients (aged 65 years or more) undergoing sialoendoscopy under local anaesthesia were evaluated. Age, co-morbidities, surgical time, hospital stay, and complication and recurrence rates were assessed. RESULTS: Nineteen sialoendoscopies were performed in 18 elderly patients with a mean age of 69.7 ± 5.6 years, with some of them suffering from multiple co-morbidities. Surgery was successful in 16 patients, while surgery was unsuccessful in 2 patients because of intraglandular stones. The average surgical duration was 54.5 ± 30.1 minutes, and all patients were discharged 2-3 hours after surgery. No post-operative complications were found and only one patient had recurrence during follow up. CONCLUSION: Sialoendoscopy under local anaesthesia is a safe and effective procedure in elderly patients who are more prone to complications.

Precision determination of the dpi<-->NN transition strength at threshold.

An unusual but effective way to determine at threshold the dpi<-->NN transition strength alpha is to exploit the hadronic ground-state broadening Gamma(1s) in pionic deuterium, accessible by x-ray spectroscopy. The broadening is dominated by the true absorption channel dpi(-)-->nn, which is related to s-wave pion production pp-->dpi(+) by charge symmetry and detailed balance. Using the exotic atom circumvents the problem of Coulomb corrections to the cross section as necessary in the production experiments. Our dedicated measurement finds Gamma(1s)=(1171(-49)(+23)) meV yielding alpha=(252(-11)(+5)) microb.

First direct observation of coulomb explosion during the formation of exotic atoms

A Doppler broadening of x-ray transitions from pionic nitrogen and muonic oxygen, which is attributed to Coulomb explosion of the molecules, has been observed by using a crystal spectrometer. Large linewidths indicate fast ionization of the molecules and a charge of (3-4)e for the accelerated fragments.

Efficacy of diflunisal versus acetaminophen with codeine in controlling mild to moderate pain after arthroscopy.

An open, randomized clinical study was performed to evaluate the efficacy of diflunisal versus acetaminophen with codeine in patients who underwent outpatient arthroscopy of the knee. Twenty patients were randomly assigned to each treatment group. Nineteen patients in each group successfully completed the study, which consisted of both objective and subjective evaluations. The results showed equal efficacy between the two drugs. However, a larger percentage of patients viewed diflunisal as providing good to excellent results overall compared with acetaminophen with codeine.

Comparison of diflunisal and acetaminophen with codeine in the treatment of mild to moderate pain due to strains and sprains.

Fifty college athletes with acute sprains and strains from football-related activities were randomly assigned to treatment with either diflunisal or acetaminophen with codeine for seven days. Additional treatment in both groups included rest, elevation, local application of cold or heat, splinting, and physical therapy, as indicated. Both treatment groups exhibited clinically significant improvements in pain, tenderness, and swelling. The results of this study show that diflunisal, a peripherally acting nonnarcotic nonsteroidal anti-inflammatory agent with analgesic properties, was as effective as acetaminophen with codeine in relieving mild to moderate pain due to musculo-skeletal sprains and strains. The long duration of action of diflunisal permits less frequent dosing, an important consideration when prescribing medication for active young adults.

Bone tunnel enlargement after anterior cruciate ligament replacement.

Radiographic increase in the size of tibial and femoral tunnels has been observed. This retrospective study compared tibial tunnel diameter in 56 autograft and 87 allograft patellar tendon bone-tendon-bone anterior cruciate ligament replacements whose observed tunnel changes were correlated with clinical results at 1 year postoperatively. Tibial tunnel sclerotic margins were measured approximately 1 cm below the joint line. Exact tunnel dimension was calculated by using a magnification factor determined by the interference screw of known diameter within the same tunnel. Average allograft tunnel enlargement was 1.2 mm (-2.5 to 6.0) compared with the autograft tunnel enlargement of 0.26 mm (-2.5 to 2.7); the difference was significant (P > 0.0002). No significant difference was seen in KT-1000 arthrometer measurements between autograft or allograft groups, and no correlation was seen between increased tunnel size and clinical outcome as determined by the modified Hughston knee evaluation system. Tunnel measurement reproducibility was confirmed by independent repeated measurements. The significance of this tunnel enlargement is unknown and does not appear to adversely affect clinical outcome of allograft utilization. Possible explanations include an immune response with resorption, stress shielding proximal to the interference screw resulting in resorption, or an inflammatory response by synovium in the tunnel.

The results of fresh-frozen patellar tendon allografts for chronic anterior cruciate ligament deficiency of the knee.

This prospective study was done to evaluate the clinical outcome of fresh-frozen patellar bone-tendon-bone allograft tissue used as a substitute for chronic insufficiency of the anterior cruciate ligament. Forty-one patients were followed at a mean of 27 months after surgery. The mean time from injury to reconstruction was 34 months. The same operative procedure and postoperative rehabilitation was performed on each patient. The evaluation method consisted of subjective, objective, and instrumented laxity testing. Thirty-seven patients (90%) thought their knee was normal or improved after surgery and had no further episodes of giving way. The combined modified Hughston Knee Score revealed 30 patients (73%) with an excellent or good result and 9 patients (22%) with a fair or poor result. The mean postoperative Lysholm Knee Score was 91 (range, 56 to 100). Thirty-two had a negative pivot shift (78%). The postoperative KT-1000 arthrometer revealed 37 patients had an injured-to-uninjured difference of 5 mm or less (mean, 1.32 mm; range, 0 to 5). There were three traumatic failures at 24 months postoperatively in this group. There was no rejection phenomenon noted postoperatively. In addition, clinical observation showed less postoperative morbidity when compared to a matched autogenous patellar tendon control group.

The Gore-Tex anterior cruciate ligament prosthesis. Two versus three year results.

A prospective clinical study of the results of prosthetic ligament replacement of the ACL with the Gore-Tex polytetrafluoroethylene prosthesis was undertaken. Thirty-three (80%) of 41 patients were available at a minimum 36 month followup (mean, 48 months; range, 36 to 62). Kaplan-Meier survival analysis revealed an 82% probability of survival of the polytetrafluoroethylene ligament at the 48 month followup. When compared to the same data at a minimum 24 month followup, the results appeared to have deteriorated somewhat over time. Three possible "predictors" of failure at later followup were identified: preoperative subjective symptoms of swelling, subjective symptoms of giving way at 2 years, and an increased anterior drawer sign at 2 years.

Observations on the treatment of lumbar disk disease in college football players.

Over a 4 year period, 12 college players were treated for diskogenic injury. The most common position affected was down-lineman. Symptoms consisted of low back and/or radicular pain. No players could recall the onset of symptoms relative to football activity; weightlifting was associated with symptoms in three cases. Tentative clinical diagnosis was herniated disk disease. Method of diagnosis in the athletic population is presented along with results of surgical treatment. Percutaneous diskectomy appears to be successful for disk herniations occurring at the L4-5 space or higher.

Comparison of an optical catheter office arthroscope with a standard rigid rod-lens arthroscope in the evaluation of the knee.

In a prospective, randomized study, 47 patients underwent arthroscopic evaluation of the knee in an operating room setting with both a standard rod-lens arthroscope and a newer flexible optical catheter fiberoptic system. The goal of the study was to assess the diagnostic accuracy of the newer catheter system, which is recommended for use in the office setting. Forty-four patients were included in the data analysis, three were eliminated because we were unable to perform an adequate examination with the catheter scope secondary to intraarticular adhesions or excessive bleeding. A comparison of the two systems revealed an overall underestimation and underrecognition of intraarticular knee pathologic changes. Anterior cruciate ligament tears were missed in 3 of 21 knees; no posterior cruciate ligament tears were detected by the rod-lens arthroscope in 44 knees, but one false-positive result was "seen" using the optical catheter device. Similar trends in diagnosis (sensitivity, 25% to 67%; specificity, 96% to 99%) were seen for tears of the medial and lateral menisci, chondral lesions, and the identification of loose bodies. We conclude from the results of this study that the use of the optical catheter system for arthroscopic evaluation and treatment of the knee in the office setting may result in a significant compromise in visual acuity, resulting in missed and incorrect diagnoses.

Early experience with the GORE-TEX polytetrafluoroethylene anterior cruciate ligament prosthesis.

A prospective study of 41 patients with acute and chronic ACL deficiency underwent reconstruction with the GORE-TEX polytetrafluoroethylene (PTFE) ACL prosthesis beginning in November 1983. Thirty-nine patients who were at least 2 years from their surgical procedure were available for follow-up evaluation, which included subjective questionnaire, clinical examination, and instrumented ligamentous laxity tests. Eight patients had an acute injury to the ACL and 31 patients had chronic ACL insufficiency for which reconstruction was performed. Thirty-four patients had satisfactory results, allowing full return to activity with no appreciable symptomatology. Of the remaining five patients, four had a complete rupture of the prosthesis. The average knee arthrometric measurement improved from a 5.4 mm left/right difference preoperatively to a 2.0 mm left/right difference at 2 year followup. Nine patients had postoperative complications of one or more atraumatic episodes of a sterile effusion. Six patients had recurrent effusions; in five, arthroscopy revealed partial tears of less than one-third of the prosthesis. Three patients who had recurrent effusions had PTFE particles in their synovial biopsies. One patient had an immediate postoperative infection and to data has had salvage of the prosthesis and currently has a stable knee with full return to activities. Based on the early results of this study, the GORE-TEX PTFE ACL prosthesis provided a satisfactory method of reconstruction for ACL deficient knees. Based on the evaluation used, 87% of the patients had satisfactory results. Problems associated with use of this prosthesis include partial or complete tears of the prosthesis and sterile effusions, possibly due to synovial irritation from the PTFE particles.(ABSTRACT TRUNCATED AT 250 WORDS)