High-resolution laser resonances of antiprotonic helium in superfluid 4He.

When atoms are placed into liquids, their optical spectral lines corresponding to the electronic transitions are greatly broadened compared to those of single, isolated atoms. This linewidth increase can often reach a factor of more than a million, obscuring spectroscopic structures and preventing high-resolution spectroscopy, even when superfluid helium, which is the most transparent, cold and chemically inert liquid, is used as the host material1-6. Here we show that when an exotic helium atom with a constituent antiproton7-9 is embedded into superfluid helium, its visible-wavelength spectral line retains a sub-gigahertz linewidth. An abrupt reduction in the linewidth of the antiprotonic laser resonance was observed when the liquid surrounding the atom transitioned into the superfluid phase. This resolved the hyperfine structure arising from the spin-spin interaction between the electron and antiproton with a relative spectral resolution of two parts in 106, even though the antiprotonic helium resided in a dense matrix of normal matter atoms. The electron shell of the antiprotonic atom retains a small radius of approximately 40 picometres during the laser excitation7. This implies that other helium atoms containing antinuclei, as well as negatively charged mesons and hyperons that include strange quarks formed in superfluid helium, may be studied by laser spectroscopy with a high spectral resolution, enabling the determination of the particle masses9. The sharp spectral lines may enable the detection of cosmic-ray antiprotons10,11 or searches for antideuterons12 that come to rest in liquid helium targets.

Laser spectroscopy of pionic helium atoms.

Charged pions1 are the lightest and longest-lived mesons. Mesonic atoms are formed when an orbital electron in an atom is replaced by a negatively charged meson. Laser spectroscopy of these atoms should permit the mass and other properties of the meson to be determined with high precision and could place upper limits on exotic forces involving mesons (as has been done in other experiments on antiprotons2-9). Determining the mass of the π- meson in particular could help to place direct experimental constraints on the mass of the muon antineutrino10-13. However, laser excitations of mesonic atoms have not been previously achieved because of the small number of atoms that can be synthesized and their typically short (less than one picosecond) lifetimes against absorption of the mesons into the nuclei1. Metastable pionic helium (π4He+) is a hypothetical14-16 three-body atom composed of a helium-4 nucleus, an electron and a π- occupying a Rydberg state of large principal (n ≈ 16) and orbital angular momentum (l ≈ n - 1) quantum numbers. The π4He+ atom is predicted to have an anomalously long nanosecond-scale lifetime, which could allow laser spectroscopy to be carried out17. Its atomic structure is unique owing to the absence of hyperfine interactions18,19 between the spin-0 π- and the 4He nucleus. Here we synthesize π4He+ in a superfluid-helium target and excite the transition (n, l) = (17, 16) â†’ (17, 15) of the π--occupied π4He+ orbital at a near-infrared resonance frequency of 183,760 gigahertz. The laser initiates electromagnetic cascade processes that end with the nucleus absorbing the π- and undergoing fission20,21. The detection of emerging neutron, proton and deuteron fragments signals the laser-induced resonance in the atom, thereby confirming the presence of π4He+. This work enables the use of the experimental techniques of quantum optics to study a meson.

Recent progress of laser spectroscopy experiments on antiprotonic helium.

The Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA) collaboration is currently carrying out laser spectroscopy experiments on antiprotonic helium [Formula: see text] atoms at CERN's Antiproton Decelerator facility. Two-photon spectroscopic techniques have been employed to reduce the Doppler width of the measured [Formula: see text] resonance lines, and determine the atomic transition frequencies to a fractional precision of 2.3-5 parts in 109 More recently, single-photon spectroscopy of buffer-gas cooled [Formula: see text] has reached a similar precision. By comparing the results with three-body quantum electrodynamics calculations, the antiproton-to-electron mass ratio was determined as [Formula: see text], which agrees with the known proton-to-electron mass ratio with a precision of 8×10-10 The high-quality antiproton beam provided by the future Extra Low Energy Antiproton Ring (ELENA) facility should enable further improvements in the experimental precision.This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.

Buffer-gas cooling of antiprotonic helium to 1.5 to 1.7 K, and antiproton-to-electron mass ratio.

Charge, parity, and time reversal (CPT) symmetry implies that a particle and its antiparticle have the same mass. The antiproton-to-electron mass ratio [Formula: see text] can be precisely determined from the single-photon transition frequencies of antiprotonic helium. We measured 13 such frequencies with laser spectroscopy to a fractional precision of 2.5 × 10-9 to 16 × 10-9 About 2 × 109 antiprotonic helium atoms were cooled to temperatures between 1.5 and 1.7 kelvin by using buffer-gas cooling in cryogenic low-pressure helium gas; the narrow thermal distribution led to the observation of sharp spectral lines of small thermal Doppler width. The deviation between the experimental frequencies and the results of three-body quantum electrodynamics calculations was reduced by a factor of 1.4 to 10 compared with previous single-photon experiments. From this, [Formula: see text] was determined as 1836.1526734(15), which agrees with a recent proton-to-electron experimental value within 8 × 10-10.

Impact of continuous deterioration of kidney function 6 to 8 months after percutaneous coronary intervention for acute coronary syndrome.

Preprocedural chronic kidney disease and contrast-induced acute kidney injury are predictors of in-hospital death and long-term mortality. However, neither the time course of kidney function after percutaneous coronary intervention (PCI) nor the relation between the time course of kidney function and prognosis has been adequately studied. We studied 531 patients who underwent PCI for acute coronary syndrome. The continuous deterioration of kidney function (CDKF) was defined as a >25% increase in serum creatinine level or serum creatinine >0.5 mg/dl above baseline at 6 to 8 months after PCI. CDKF was observed in 87 patients (16.4%). Independent risk factors for CDKF were contrast-induced acute kidney injury, preprocedural hemoglobin level, and proteinuria. Patients with CDKF exhibited significant higher 5-year mortality rate than patients without CDKF (25% vs 9.4%, log-rank p = 0.0006). Independent risk factors for 5-year mortality were age >75 year, anemia, New York Heart Association class III or IV, low ejection fraction, and CDKF. CDKF is associated with an increased risk of all-cause mortality of 5 years in patients with acute coronary syndrome undergoing PCI.

Bleeding risk with triple antithrombotic therapy in patients with atrial fibrillation and drug-eluting stents.

In the era of drug-eluting stents (DES), a long-term dual antiplatelet therapy is required to prevent late stent thrombosis. However, in patients with atrial fibrillation (AF), there is a concern that combining warfarin with dual antiplatelet therapy may increase the risk of bleeding. We analyzed 1274 consecutive patients with coronary artery disease who were treated with coronary intervention from January 2006 through January 2009. Of these, we enrolled 74 AF patients treated with DES and dual antiplatelet therapy as well as warfarin. The primary endpoint was the incidence of major bleeding within 3 years; the predictive factor of major bleeding was also analyzed. To evaluate the efficacy of anticoagulant therapy, time in therapeutic range (TTR) was also measured. The 3-year incidence of major bleeding was 12.2 % (nine of 74 patients). The average observation period was 25.7 ± 20.2 months. Mean TTR value was 44.6 ± 33.0 % and was maintained at a relatively low level. Multivariate analysis revealed that a higher CHADS2 score (2-point more) was an independent predictor of increased risk of major bleeding. Major bleeding in the patients with triple antithrombotic therapy including warfarin occurred at a relatively high rate. Although the higher CHADS2-score indicates a high risk of thrombotic events, it was strongly associated with bleeding complications.

Incidence and predictors of the late catch-up phenomenon after drug-eluting stent implantation.

BACKGROUND: Although clinical restenosis within 1 year after percutaneous coronary intervention has been remarkably reduced with the advent of drug-eluting stents (DES), the late catch-up (LCU) phenomenon remains an issue despite medical advances. The aim of this study was to investigate the incidence and predictive factors of the LCU phenomenon in an unselected population treated with first-generation DES. METHODS: A total of 923 patients treated with DES between June 2004 and August 2008 were analyzed. The LCU phenomenon was defined as secondary revascularization 1 year after index stenting. Retreatment for very late stent thrombosis was considered as part of the LCU phenomenon. RESULTS: Incidence of the LCU phenomenon was seen in 33 patients (3.6%). Very late stent thrombosis was observed in 5 patients (0.6%) and very late in-stent restenosis was observed in 28 patients (3.0%). At the 12-month landmark analysis, the cumulative rate of cardiac death was significantly higher in patients with the LCU phenomenon than in those without any target lesion revascularization (9.0% vs. 0.9%, p<0.001). In the multivariate analysis, hemodialysis [odds ratio (OR) 6.07, p=0.003], number of stents (OR 1.58, p=0.02), and coronary bifurcation lesions (OR 2.06, p=0.048) were identified as independent predictors of the LCU phenomenon. CONCLUSION: The LCU phenomenon is associated with serious consequences and adverse events and remains an important issue in modern practice, despite medical advances. DES should be deployed with a minimum number of stents, and special consideration must be given to patients on hemodialysis and those with coronary bifurcation lesions.

Two-photon laser spectroscopy of antiprotonic helium and the antiproton-to-electron mass ratio.

Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium (pHe(+)) is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton (p) occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively n and l, such that n ≈ l + 1 ≈ 38. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiproton-to-electron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report two-photon spectroscopy of antiprotonic helium, in which p(3)He(+) and p(4)He(+) isotopes are irradiated by two counter-propagating laser beams. This excites nonlinear, two-photon transitions of the antiproton of the type (n, l) → (n - 2, l - 2) at deep-ultraviolet wavelengths (λ = 139.8, 193.0 and 197.0 nm), which partly cancel the Doppler broadening of the laser resonance caused by the thermal motion of the atoms. The resulting narrow spectral lines allowed us to measure three transition frequencies with fractional precisions of 2.3-5 parts in 10(9). By comparing the results with three-body quantum electrodynamics calculations, we derived an antiproton-to-electron mass ratio of 1,836.1526736(23), where the parenthetical error represents one standard deviation. This agrees with the proton-to-electron value known to a similar precision.

Higher body mass index at the time of acute myocardial infarction is associated with a favorable long-term prognosis (8-year follow-up).

Obesity is an important public health problem, especially among patients with cardiovascular disease. However, little is known about the impact of obesity on the long-term prognoses of patients with acute myocardial infarction (AMI). Major adverse cardiac and cerebrovascular events (MACCE) consist of all causes of death, stroke, target lesion revascularization, target vessel revascularization, non-fatal myocardial infarction, and hospitalization. From January 2001 to March 2005, we analyzed 121 patients who survived >30 days after suffering their first AMI of the left anterior descending artery for MACCE. The mean follow-up period for this study was 59 ± 26 months. Seventy-five patients presented with normal weight (BMI <25 kg/m(2)) and 46 were obese (BMI >25 kg/m(2)). During the follow-up period, 56 patients presented MACCE, including 18 deaths, 11 strokes, and seven non-fatal myocardial infarctions. Normal weight was significantly associated with the occurrence of MACCE (p = 0.012). Grouping of the patients by BMI and homeostasis model assessment ratio (HOMA-R) indicated that the combination of a higher BMI (>25) and lower insulin resistance (HOMA-R < 2.0) provided the best prognosis (p = 0.0006). Kaplan-Meier curves stratified to the four groups, sorted by diabetes mellitus and BMI at admission, showed that the normal weight patients with diabetes mellitus presented the highest risk of MACCE (p < 0.0001). Patients with higher BMI and no insulin resistance or diabetes mellitus present better long-term outcomes following anterior AMI.

Error-Prone Translesion DNA Synthesis by Escherichia coli DNA Polymerase IV (DinB) on Templates Containing 1,2-dihydro-2-oxoadenine.

Escherichia coli DNA polymerase IV (Pol IV) is involved in bypass replication of damaged bases in DNA. Reactive oxygen species (ROS) are generated continuously during normal metabolism and as a result of exogenous stress such as ionizing radiation. ROS induce various kinds of base damage in DNA. It is important to examine whether Pol IV is able to bypass oxidatively damaged bases. In this study, recombinant Pol IV was incubated with oligonucleotides containing thymine glycol (dTg), 5-formyluracil (5-fodU), 5-hydroxymethyluracil (5-hmdU), 7,8-dihydro-8-oxoguanine (8-oxodG) and 1,2-dihydro-2-oxoadenine (2-oxodA). Primer extension assays revealed that Pol IV preferred to insert dATP opposite 5-fodU and 5-hmdU, while it inefficiently inserted nucleotides opposite dTg. Pol IV inserted dCTP and dATP opposite 8-oxodG, while the ability was low. It inserted dCTP more effectively than dTTP opposite 2-oxodA. Pol IV's ability to bypass these lesions decreased in the order: 2-oxodA > 5-fodU~5-hmdU > 8-oxodG > dTg. The fact that Pol IV preferred to insert dCTP opposite 2-oxodA suggests the mutagenic potential of 2-oxodA leading to A:T→G:C transitions. Hydrogen peroxide caused an ~2-fold increase in A:T→G:C mutations in E. coli, while the increase was significantly greater in E. coli overexpressing Pol IV. These results indicate that Pol IV may be involved in ROS-enhanced A:T→G:C mutations.

Chirp-corrected, nanosecond Ti:sapphire laser with 6 MHz linewidth for spectroscopy of antiprotonic helium.

A nanosecond titanium sapphire laser with spectral linewidth Gamma(pl)~6 MHz and pulse energy of 50-100 mJ was demonstrated by using an intracavity electro-optic modulator to correct the frequency chirp in the output beam. The laser was referenced against a femtosecond frequency comb and used to measure the 6s-8s (F=4) two-photon transition frequency of Cs with a precision of 1.4 parts in 10(9).

Acute-on-chronic massive pulmonary embolism treated with 3-loop snare.

A 70-year-old man presented with acute massive pulmonary embolism (PE). His clinical condition deteriorated despite regular heparin and thrombolytic agent treatment, and he eventually developed cardiogenic shock. A thrombus originating from the inferior vena cava was detected and acute-on-chronic embolization resulted, with an unusual clinical course. Aggressive catheter thrombectomy with pigtail rotation failed to fragment the organized thrombus, but it was successfully removed by a 3-loop snare device combined with guiding catheter under percutaneous cardiopulmonary support.

Naloxone reversal of opioid anesthesia revisited: clinical evaluation and plasma concentration analysis of continuous naloxone infusion after anesthesia with high-dose fentanyl.

PURPOSE: In spite of several advantages, the need for postoperative ventilatory support limits the use of high-dose opioid anesthesia. We prospectively evaluated the effectiveness of naloxone infusion for the reversal of high-dose fentanyl anesthesia. METHODS: Anesthesia was maintained with fentanyl in patients undergoing major abdominal surgery. After anesthesia, the trachea was extubated when intravenous naloxone, which was titrated in separate 50- micro g doses, established an acceptable level of consciousness and arterial blood gas (ABG) status under spontaneous respiration; this was followed by continuous infusion started at the rate of the sum of the bolus doses per hour. The naloxone infusion was terminated based on evaluation of the level of consciousness, ABG, and acute abstinence symptoms. Postoperative pain was evaluated using self-reported four-step categorical terms (none, mild, moderate, and severe). Plasma concentrations of fentanyl and naloxone were analyzed in 12 patients, using high-performance liquid chromatography. RESULTS: Fifty-seven out of 59 eligible patients were successfully extubated at 34 +/- 14 min after termination of fentanyl (total dose, 127 +/- 64 micro g.kg(-1); mean +/- SD) with naloxone (total bolus, 3.4 +/- 2.6 micro g.kg(-1)). All these patients recovered fully without ventilatory support under the naloxone infusion, which was terminated at 11 +/- 7 h. The reduction of the naloxone infusion rate effectively relieved the increased pain, and no supplemental analgesic was used in any patients during the naloxone infusion. Pharmacokinetic analysis did not indicate any correlations between plasma fentanyl and naloxone concentrations. CONCLUSION: The results suggest that naloxone infusion with individual dose titration facilitates the use of high-dose opioid anesthesia, maintaining the advantager of this anesthesia.

[A sheared off and sequestered epidural catheter: a case report].

This is a report of a retained epidural catheter segment after placement of 20-G polyethylene catheter (Hakko Medical) through 17-G Tuohy needle and 25-G spinal needle (Top Company) for a patient receiving combined spinal-epidural anesthesia. Retained catheter fragment (approximately 10.6 cm) was removed easily with small incision under local anesthesia. Electron microscopic findings of the catheter showed that the catheter might have been traumatized by the Tuohy needle through which the catheter was placed or by the spinal needle for intrathecal anesthesia, resulting in having been sheared off.

Resolution enhancement of pHe+ atomic line profiles measured with a pulsed dye laser and a Fizeau wavelength meter.

A Fizeau wavelength meter was used to compensate for fluctuations in the longitudinal mode structure and wavelength of a pulsed dye laser. The average laser linewidth was effectively narrowed by selection of laser pulses with a single longitudinal mode. These techniques were recently employed to measure some atomic transition wavelengths in pHe+ to fractional precisions greater than 1 part in 10(7). The wavelengths were absolutely calibrated against iodine or tellurium lines by absorption spectroscopy or against neon or argon lines by optogalvanic spectroscopy.

Identification of high excision capacity for 5-hydroxymethyluracil mispaired with guanine in DNA of Escherichia coli MutM, Nei and Nth DNA glycosylases.

The oxidation and deamination of 5-methylcytosine (5mC) in DNA generates a base-pair between 5-hydroxymethyluracil (5hmU) and guanine. 5hmU normally forms a base-pair with adenine. Therefore, the conversion of 5mC to 5hmU is a potential pathway for the generation of 5mC to T transitions. Mammalian cells have high levels of activity of 5hmU-DNA glycosylase, which excises 5hmU from DNA. However, glycosylases that similarly excise 5hmU have not been observed in yeast or Escherichia coli. Recently, we found that E.coli MutM, Nei and Nth have DNA glycosylase activity for 5-formyluracil, which is another type of oxidation product of the thymine methyl group. In this study, we examined whether or not E.coli MutM, Nei and Nth have also DNA glycosylase activity that acts on 5hmU in vitro. When incubated with synthetic duplex oligonucleotides containing 5hmU:G or 5hmU:A, purified MutM, Nei and Nth cleaved the 5hmU:G oligonucleotide 58, 5 and 37 times, respectively, more efficiently than the 5hmU:A oligonucleotide. In E.coli, the 5hmU-DNA glycosylase activities of MutM, Nei and Nth may play critical roles in the repair of 5hmU:G mispairs to avoid 5mC to T transitions.