What a difference a day makes

With the availability of group A beta-hemolytic streptococcal (GABHS) antigen detection tests, the management of adult pharyngitis is being reassessed. A decision analytic model was developed which considered four strategies: immediate treatment, no treatment, performing a rapid antigen test, or obtaining a bacterial culture. Patient outcomes were expressed in “well” days, which were reduced by the “sick” days associated with adverse reactions to treatment or complications of GABHS infection. When immediate test results are available, testing is the optimal strategy for probabilities of GABHS between 1 and 49 per cent. This range includes almost all patients, using probability estimates based on clinical criteria. The absolute benefit of testing was 0.1 days. The major advantage of a rapid test is the avoidance of penicillin reactions. Variations in the symptomatic benefits of treatment had minimal effects on the analysis. The analysis supports the use of an antigen test for adult patients with pharyngitis. Received from the Division of General Medicine and Primary Care. Department of Internal Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond. Virginia. A preliminary version of this work was presented at the seventh annual meeting of the Society for Medical Decision Making, October 21, 1985.     

Charge of a quasiparticle in a superconductor

Nonlinear charge transport in superconductor–insulator–superconductor (SIS) Josephson junctions has a unique signature in the shuttled charge quantum between the two superconductors. In the zero-bias limit Cooper pairs, each with twice the electron charge, carry the Josephson current. An applied bias V_SD leads to multiple Andreev reflections (MAR), which in the limit of weak tunneling probability should lead to integer multiples of the electron charge ne traversing the junction, with n integer larger than 2Δ/eV_SD and Δ the superconducting order parameter. Exceptionally, just above the gap eV_SD ≥ 2Δ, with Andreev reflections suppressed, one would expect the current to be carried by partitioned quasiparticles, each with energy-dependent charge, being a superposition of an electron and a hole. Using shot-noise measurements in an SIS junction induced in an InAs nanowire (with noise proportional to the partitioned charge), we first observed quantization of the partitioned charge q = e*/e = n, with n = 1–4, thus reaffirming the validity of our charge interpretation. Concentrating next on the bias region eV_SD ～ 2Δ, we found a reproducible and clear dip in the extracted charge to q? ～ 0.6, which, after excluding other possibilities, we attribute to the partitioned quasiparticle charge. Such dip is supported by numerical simulations of our SIS structure.Excitations in superconductors (Bogoliubov quasiparticles) can be described according to the Bardeen–Cooper–Schrieffer (BCS) theory (1) as an energy-dependent superposition of an electron with amplitude u(ε), and a hole with amplitude v(ε), where the energy ε is measured relative to the Fermi energy (2). Evidently, the expectation value of the charge operator (applied to the quasiparticle wave function), which we address as the quasiparticle charge e* = q(ε)e, is smaller than the charge of an electron, q(ε) = |u(ε)|² ? |ν(ε)|² (3). Solving the Bogoliubov–de Gennes equations, one finds that |u(ε)|2=1/2[1+(ε2−Δ2/ε)] and |v(ε)|2=1/2[1−(ε2−Δ2/ε)], with the expected charge evolving with energy according to q(ε)=ε2−Δ2/ε––vanishing altogether at the superconductor gap edges (3). Note, however, that the quasiparticle wave function is not an eigenfunction of the charge operator (3, 4). Properties of quasiparticles, such as the excitation spectra (5), lifetime (6–10), trapping (11), and capturing by Andreev bound states (12, 13), had already been studied extensively; however, studies of their charge are lagging. In the following we present sensitive shot-noise measurements in a Josephson junction, resulting in a clear observation of the quasiparticle charge being smaller than e, q(eV_SD∼2Δ) < 1, and evolving with energy, as expected from the BCS theory.To observe the BCS quasiparticles in transport we study a superconductor–insulator–superconductor (SIS) Josephson junction in the nonlinear regime. The overlap between the wave functions of the quasiparticles in the source and in the drain is expected to result in a tunneling current of their effective charge. This is in contrast with systems which are incoherent (14, 15) or with an isolated superconducting island, where charge conservation leads to traversal of multiples of e – Coulomb charge (16). As current transport in the nonlinear regime results from “multiple Andreev reflections” (MAR), it is prudent to make our measurements credible by first measuring the charge in this familiar regime.In short, the MAR process, described schematically in Fig. 1, carries a signature of the shuttled charge between the two superconductors (SCs), being a consequence of n traversals through the junction (as electron-like and hole-like quasiparticles), with n an integer larger than 2Δ/eV_SD. A low transmission probability t (via tunneling through a barrier) in the bias range 2Δ/n < eV_SD < 2Δ/(n ? 1) assures dominance of the lowest order MAR process (higher orders are suppressed as tⁿ), with the charge evolving in nearly integer multiples of the electron charge. Although there is already a substantial body of theoretical (3, 17–23) and experimental (24–29) studies of the MAR process, charge determination without adjustable parameters is still missing. An important work by Cron et al. (27) indeed showed a staircase-like behavior of the charge using “metallic break junctions;” however, limited sensitivity and the presence of numerous conductance channels some of which with relatively high transmission probabilities did not allow exact charge quantization. Our shot-noise measurements, performed on a quasi-1D Josephson junction (single-mode nanowire) allowed clear observation of charge quantization without adjustable parameters. To count a few advantages: (i) the transmission of the SIS junction could be accurately controlled using a back-gate; (ii) this, along with our high sensitivity in noise measurements, enabled us to pinch the junction strongly (thus suppressing higher MAR orders); and (iii) with the Fermi level located near the 1D channel van Hove singularity, a rather monoenergetic distribution could be injected (SI Appendix, section S7).Open in a separate windowFig. 1.MAR. Illustrations of the leading processes contributing to the current as function of bias. In general, for 2Δ/(n ? 1) > eV_SD > 2Δ/n the leading charge contribution to the current is ne. An electron-like quasiparticle is denoted by a full circle, whereas a hole-like quasiparticle is denoted by an empty circle. (A) When the bias is larger than the energy gap, eV_SD > 2Δ, the leading process is a single-path tunneling of single quasiparticles from the full states (Left) to the empty states (Right). This current is proportional to the transmission coefficient t. Higher-order MAR process (dashed box), being responsible for tunneling of Cooper pairs, is suppressed as t². (B) For 2Δ > eV_SD > Δ, the main charge contributing to the current is 2e with probability t². (C) For Δ > eV_SD > 2Δ/3, the main charge contributing to the current is 3e with probability t³.     

Between a Clot and a Scarred Place

Immobilized orthopedic trauma patients face an elevated risk of venous thromboembolism (VTE). We present a case in which a patient undergoing staged repair of traumatic orthopedic injuries developed deep venous thrombosis (DVT) during hospitalization, prior to repair of a lower extremity injury for which delay in operation might result in poor functional outcome. We provide an overview of recommendations regarding pharmacologic prophylaxis of VTE in orthopedic patients. We review the importance of cultivating a high index of suspicion for VTE in such patients, even when receiving appropriate prophylaxis and lacking overt symptoms. Finally, we outline the multidisciplinary decision-making process regarding optimizing care for the patient in a precarious position of developing acute VTE while awaiting urgent surgery. Specifically, we review the safety, efficacy, and management of retrievable inferior vena cava filters (rIVCF) for this population.     

Report of a case of a giant phytobezoar in a patient with a duodenal bulb ulcer.

A case of a large phytobezoar (750 g weight and with the length of 29 cm) due to Khormalou (Persimmon) is being reported in a young patient with chief complaint of abdominal pains and concomitant duodenal ulcer. Review of the literature in this subject shows that bezoars of this size and weight are relatively rare in healthy individuals.     

Image of a left atrial mass after a cardiopulmonary bypass in a child

Invagination of an appendage into the left atrium is a rare complication. It occurs spontaneously or after open‐heart surgery. In our case, a postoperative transesophageal echocardiogram, after closure of a ventricular septal defect in a 5‐month‐old infant, revealed a large mass in the left atrium. A diagnosis of a left appendage inversion was confirmed after external examination of the heart. Herein, we provide echocardiographic images before, during, and after manual reversion of the left appendage. Misdiagnosis of this complication could have led to an additional unnecessary surgical procedure that could have impacted on the patient's morbidity.     

Ochronosis: a report of a case and a review of literature

A patient with alkaptonuria and ochronotic pigment deposited in articular cartilage and sclerae clinically manifested a serious osteoarthritis of the peripheral and axial joints and synchondrosis, typically involved in long lasting cases of this hereditary defect of homogentisic acid oxidase. This is the first patient with this disorder reported, where a non-cemented total knee prosthesis (PCAR) was applied on both knees. This was possible due to the good quality of the bone stock, which did not seem to be impaired by ochronosis. Our patient had no cardiac symptoms or murmurs, but had a slight calcification in the annulus of aorta observed with echocardiography, a useful new method for screening this disease manifestation. A third new aspect reported is the immunopathology of the synovial tissue. Small pieces of torn-off cartilage were seen embedded in the synovial stroma. This was associated with a slight hyperplasia of the C3bi-receptor positive and proline hydroxylase positive type A and B synovial lining cells. Perivenular infiltrates contained CD2 positive T lymphocytes, mostly belonging to the CD4 subset, and some C3bi-receptor positive monocytes. Activated CD25 positive and immunoglobulin light chain positive T and B lymphocytes were absent or few. Because modern medicine has much to offer to those suffering from this ancient inborn error of metabolism in the form of new specific diagnostic methods and new surgical modes of treatment, such as endoprosthesis surgery and cardiac valve replacement, we also present a literature overview of this interesting condition.     

Cryptogenic stroke in a patient with a PFO: a decision analysis

BACKGROUND: Octogenarian Israeli prime-minister Ariel Sharon recently sustained a mild, reversible stroke. A patent foramen ovale (PFO) was detected and anticoagulants were given pending PFO closure. A few days later, he sustained major intracerebral hemorrhage and has since remained in vegetative state. The events triggered serious criticism in the mass media, experts promoting one management option over others. Because knowledge of outcome and hindsight bias evaluation of appropriateness of care, we sought to systematically review the clinical case. METHODS: We performed a formal decision analysis to identify the preferred management between anticoagulation, antiplatelets, PFO closure, or no treatment. Using the best evidence available, we built a decision tree. Main outcomes: recurrent stroke and treatment complications within 1 year. RESULTS: Optimal decision was found to be critically sensitive to assumptions about etiology, efficacy and safety of treatments, recurrence risk, and to small changes in utilities. In multiway sensitivity analysis, when the risk of recurrent stroke was <0.12 per year, no treatment was the best management. PFO closure is dominant only when the risk of recurrent stroke is >0.12 per year closure effectiveness is assumed to be <0.28. When closure effectiveness is >0.6, it is inferior to anticoagulation and antiplatelet management. CONCLUSIONS: Uncertainties precluded a clear-cut answer and choice was found to be a "toss-up," often associated with much controversy. Use of novel therapies, such as PFO closure, outside clinical trials will not reduce uncertainty about efficacy.