Limits on the Existence of sub-MeV Sterile Neutrinos from the Decay of

Sterile neutrinos are natural extensions to the standard model of particle physics and provide a possible portal to the dark sector. We report a new search for the existence of sub-MeV sterile neutrinos using the decay-momentum reconstruction technique in the decay of ^{7}Be. The experiment measures the total energy of the ^{7}Li daughter atom from the electron capture decay of ^{7}Be implanted into sensitive superconducting tunnel junction (STJ) quantum sensors. This first experiment presents data from a single STJ operated at a low count rate for a net total of 28 days, and provides exclusion limits on sterile neutrinos in the mass range from 100 to 850 keV that improve upon previous work by up to an order of magnitude.

Direct Measurement of the

We report a high-statistics measurement of the L/K orbital electron capture ratio in ^{7}Be embedded in cryogenic Ta. The thin Ta film formed part of a high-resolution superconducting tunnel junction radiation detector that was used to identify the signals from different decay channels. The measured L/K capture ratio of 0.070(7) is significantly larger than the only previous measurement of this quantity and the theoretical predictions that include in-medium effects. This value is a uniquely sensitive probe of the 1s and 2s orbital overlaps with the nucleus and is of relevance to nuclear and atomic physics, as well as Li production in novae and other astrophysical scenarios. This is the first experiment that uses superconducting tunnel junctions for nuclear-recoil detection, opening a new experimental avenue for low-energy precision measurements with rare isotopes.

Conformational landscape and inertial defect of methoxyphenol isomers studied by mm-wave spectroscopy and quantum chemistry calculations.

Because methoxyphenols (MP) are emitted in significant quantities during biomass fires and contribute to the secondary organic aerosols formation which impacts the climate, their gas phase monitoring in the atmosphere is crucial and requires accurate rovibrational cross sections determined with a good knowledge of their ground state (GS) and vibrationally excited state (ES) molecular parameters. Therefore, the rotational spectra of the two isomers, 2-MP (guaïacol) and 4-MP (mequinol), have been measured in absorption and in emission at room temperature using a frequency multiplication chain and a mm-wave Fourier transform chirped-pulse spectrometer, respectively. Guided by quantum chemistry calculations, the conformational landscape has been characterised and the observation of only one rotamer in the spectra of 2-MP and 4-MP has been explained. For 2-MP, the most stable conformation is justified by an intramolecular O-H⋯OCH3 hydrogen-bond which has been characterised by a topology analysis of the electron density. In a global fit including more than 30 000 line assignments, rotational and quartic centrifugal constants of the GS and the three lowest energy ES have been determined allowing to reproduce the millimeter-wave spectra at the experimental accuracy. The same work has been performed on the cis-rotamer of 4-MP highlighting some perturbations marring the fit quality for two vibrationally ES. Finally, the isomeric dependence of the negative inertial defect ΔI agrees with that of the lowest energy out of plane mode ν45, and the variation of ΔI with the degree of vibrational excitation allows a fine estimation of v45 = 1 vibrational wavenumber.

Observation of photo-induced plasmon-phonon coupling in PbTe via ultrafast x-ray scattering.

We report the observation of photo-induced plasmon-phonon coupled modes in the group IV-VI semiconductor PbTe using ultrafast x-ray diffuse scattering at the Linac Coherent Light Source. We measure the near-zone-center excited-state dispersion of the heavily screened longitudinal optical (LO) phonon branch as extracted from differential changes in x-ray diffuse scattering intensity following above bandgap photoexcitation. We suggest that upon photoexcitation, the LO phonon-plasmon coupled (LOPC) modes themselves become coupled to longitudinal acoustic modes that drive electron band shifts via acoustic deformation potentials and possibly to low-energy single-particle excitations within the plasma and that these couplings give rise to displacement-correlations that oscillate in time with a period given effectively by the heavily screened LOPC frequency.

Characterization of the Observed Electric Field and Molecular Relaxation Times for Millimeter-Wave Chirped Pulse Instrumentation.

In a chirped pulse experiment, the strength of the signal level is proportional to the amplitude of the electric field, which is weaker in the millimeter-wave or submillimeter-wave region than in the microwave region. Experiments in the millimeter region thus require an optimization of the coupling between the source and the molecular system and a method to estimate the amplitude of the electric field as seen by the molecular system. We have developed an analytical model capable of reproducing the coherent transient signals obtained with a millimeter-wave chirped pulse setup operated in a monochromatic pulse mode. The fit of the model against the experimental data allowed access to the amplitude of the electric field and, as a byproduct, to the molecular relaxation times T 1 and T 2.

Chemical behavior of residential lead in urban yards in the United States.

Long after federal regulations banned the use of lead-based paints and leaded gasoline, residential lead remains a persistent challenge. Soil lead is a significant contributor to this hazard and an improved understanding of physicochemical properties is likely to be useful for in situ abatement techniques such as phytoremediation and chemical stabilization. A laboratory characterization of high-lead soils collected from across the United States shows that the lead contaminants were concentrating in the silt and clay fractions, in the form of discrete particles of lead, as observed by scanning electron microscopy coupled with energy dispersive X-ray analysis. Soil lead varied widely in its solubility behavior as assessed by sequential and chelate extractions. Because site-specific factors (e.g., soil pH, texture, etc.) are believed to govern the solubility of the lead, understanding the variability in these characteristics at each site is necessary to optimize in situ remediation or abatement of these soils.

The origin of incipient ferroelectricity in lead telluride.

The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV-VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.

Lesions in post-ribosomal supernatant fractions associated with loss of viability in pea (Pisum arvense) seed.

RNA synthesis and protein synthesis in viable pea embryonic axis tissue commences during the first hour of water imbibition whilst DNA synthesis commences after 8 h of imbibition. Neither DNA synthesis nor protein synthesis could be detected in non-viable axis tissue during the first 24 h of imbibition but some RNA synthesis is detectable during this period. Both post-ribosomal supernatant and ribosomal fractions from imbibed non-viable embryonic axis tissue were impaired in their ability to support polyphenylalanine synthesis in a cell-free protein-synthesising system, yet the same fractions isolated from unimbibed non-viable axis tissue were as efficient as equivalent fractions from unimbibed viable axis tissue in the support of polyphenylalanine synthesis in the cell-free system. A major lesion in elongation factor 1 activity and additional lesions in elongation factor 2 and phenylalanyl-tRNA synthetase activities were detected in the post-ribosomal supernatants isolated from non-viable embryonic axis tissue.

Lesions in the ribosomes of non-viable pea (Pisum arvense) embryonic axis tissue.

Ribosomes isolated from either dry viable or non-viable pea embryonic axis tissue were equally effective in the support of polyphenylalanine synthesis in a poly(U)-directed cell-free protein-synthesising system. Ribosomes isolated from imbibed non-viable axis tissue were impaired in their ability to support polyphenylalanine synthesis in the cell-free system. RNA isolated from ribosomes and 40-S ribosomal subunits of dry or imbibed viable axis tissue was found not to be degraded, whereas the equivalent RNA species isolated from non-viable axis tissue showed an increased degree of breakdown as imbibition proceeded. Even though rRNA of imbibed non-viable axis tissue was degraded, the ribosomes and ribosomal subunits of these embryos appeared intact. In viable embryonic axis tissue the percentage of ribosomes present in the cell in the form of polysomes increased during imbibition whereas no polysomes could be detected in ribosomal preparations from dry or imbibed non-viable axis tissue. The breakdown of rRNA in ribosomal particles from non-viable axis tissue may be a contributory factor to senescence and loss of viability in Pisum arvense.

Relationship between angiographically assessed coronary artery disease, plasma insulin levels and lipids in Asians and Caucasians.

In the present study the association between angiographically demonstrated coronary artery disease lipid subfractions and insulin in Caucasians, Asian migrants to the UK and Asians in India was studied. Patients having at least one angiographic lesion of more than 50% were recruited and angiograms scored by two independent observers, blindly. There were 87 Caucasian, 83 British Asian and 30 Indian Asian patients. Lipid subfractions measured were cholesterol, HDL cholesterol, triglyceride, apo A1, apo B, Lp(a). Estimation of glucose and insulin was carried out at fasting and after two hours of oral 75 g glucose. Asians were younger than Caucasians. They did not differ in their body mass index, systolic and diastolic blood pressure or cigarette consumption. In all three ethnic groups cholesterol, LDL cholesterol and apo B showed significant positive association. Insulin levels at fasting or post glucose challenge failed to show any association. Apo B may be an additional marker for coronary artery disease in the ethnic groups studied.

Growth activity in hyperplastic and neoplastic human thyroid determined by an immunohistochemical staining procedure using monoclonal antibody MIB-1.

To increase our understanding of the basic biological mechanisms of thyroid diseases, growth activity (GA) in 232 thyroid lesions was determined by immunohistochemistry using monoclonal antibody MIB-1. The GA tended to be higher in hyperplastic lesions, adenomatous goiter (MIB-1-positive cell rate, 0.73%), and Graves' disease (1.68%) than in normal tissue (0.19%). The GA for differentiated thyroid carcinomas (2.00%) was much lower than for adenocarcinomas of other organs, such as breast, lung, stomach and colon (44.67%). Of the thyroid carcinomas, the highest GA was observed in undifferentiated carcinomas (32.67%), and follicular carcinomas (3.18%) showed a higher GA than papillary carcinomas (1.83%). There was no significant difference between the GA of follicular carcinomas and solid/trabecular adenomas, although widely invasive follicular carcinomas showed a higher GA than minimally invasive carcinomas. No significant correlations between GA and patient age, sex, and tumor diameter, metastasis, or histological features were observed in papillary carcinomas. Familial medullary carcinomas showed a higher GA than sporadic tumors. All latent papillary carcinomas had a very low GA. Our findings suggest that immunohistochemical investigation using the antibody MIB-1 contributes to the understanding of growth characteristics and biological activities in thyroid diseases.

Surgical repair of acquired ventricular septal defect. Determinants of early and late outcome.

Between January 1970 and June 1985, 60 patients underwent surgical repair of postinfarction ventricular septal defect. The preoperative cineangiograms of all patients were reviewed to measure left ventricular ejection fraction and to quantitatively assess right ventricular function by measuring the percentage reduction in right ventricular midcavity diameter. There were 23 early deaths (within 30 days) and 14 late deaths occurring between 1 and 92 months after operation. Of the 23 long-term survivors, 87% are in New York Heart Association Class I or II. The early mortality was significantly higher for inferior infarction (58%) than for anterior infarction (25%). Early mortality was also influenced by the time interval between infarction and operation (under 1 week 41%, over 4 weeks 22%). Early survival was favored by good preoperative right ventricular function; the percentage reduction in right ventricular midcavity diameter was 16.5% +/- 9.5% (mean +/- standard deviation) for the early death group and 26.7% +/- 10.6% for the early survival group. However, the early outcome was not influenced by left ventricular function before operation. Conversely, long-term survival was favored by preserved preoperative left ventricular function; left ventricular ejection fraction was 26.2% +/- 9.3% for the late death group and 35% +/- 8.5% for the late survival group. Long-term survival was not, however, affected by right ventricular function before operation. The results of surgical closure of postinfarction ventricular septal defect have improved between two successive time frames in this series, which is the largest to date.

Factors predisposing to and outcome of gestational diabetes.

Two hundred thirteen women with abnormal glucose tolerance tests (GTTs) were diagnosed over 9 years by a screening program involving the total antenatal population. Each subject was matched for age, parity, and ethnic group with a control. The gestational diabetics were subdivided into classes A1 or A2 based on the fasting plasma glucose value of their GTT: A1 when below 6.0 mmol/L (108 mg/dL) and A2 when 6.0 mmol/L (108 mg/dL) or higher. All received treatment with dietary advice and some with insulin. Birth weight was not related to maternal age or severity of diabetes, but was related to maternal obesity. However, neonatal morbidity indices such as admission to the special care baby unit for longer than 48 hours and polycythemia (hematocrit above 65%) were related significantly to the severity of the diabetes and not to maternal age or obesity.

Actuarial analysis of late results after closed mitral valvotomy.

The long-term results of closed mitral valvotomy performed between 1978 and 1985 in 198 patients with noncalcific mitral stenosis were analyzed. Follow-up data were available on 185 patients (93%); 1 patient died in the postoperative period, and 12 foreign patients were lost to follow-up. At the 4-year and 8-year intervals, 91% and 80% of patients, respectively, were event free (not in need of further operative procedures). By multivariate analysis, the factor preoperative mild mitral regurgitation showed a tendency to influence the event-free period. By univariate analysis, postoperative mitral regurgitation significantly reduced the event-free period. Twenty-one patients subsequently underwent mitral valve replacement; 8 for mitral regurgitation, 10 for mitral stenosis, and 3 for mixed mitral regurgitation and stenosis. By multivariate analysis, the reason for reoperation significantly influenced the length of the event-free period. The patients with mitral regurgitation required mitral valve replacement sooner than those with mitral stenosis. Advanced age, sex, previous valvotomy, preoperative New York Heart Association Functional Class, low mitral valve leaflet excursion, and pulmonary hypertension had no influence on the long-term result.

Asian Indians, coronary artery disease, and physical exercise.

OBJECTIVE: To evaluate the relation of physical activity to different clinical and biochemical risk factors for coronary artery disease among people from different ethnic groups with angiographically proven coronary artery disease. SUBJECTS: British Asians, Indian Asians, and white people suffering from coronary artery disease, and their respective controls. INTERVENTIONS: History, physical examination, coronary angiography (at baseline), laboratory investigations. MAIN OUTCOME MEASURES: Relation of physical activity level to serum insulin, glucose, cholesterol, triglycerides, and high density lipoproteins, systolic and diastolic blood pressures, and body mass index in patients and controls. RESULTS: 391 male patients were studied, of whom 260 (66.5%) were classified as sedentary. Mean serum insulin at 0, 1, and 2 hours after 75 g oral glucose was higher among the sedentary population (17.1 v 11.6, 88.2 v 62.1, and 57.9 v 36.2 microU/ml, respectively (all p < 0.0001). Mean body mass index was also higher among the sedentary population (25.53 v 23.95, p < 0.0001), as were mean serum triglycerides (1.85 v 1.60 mmol/l, p < 0.01) and systolic and diastolic blood pressures (133.9 v 129.4, p < 0.05, and 81.1 v 79.0, p < 0.01). There was no difference in the mean serum cholesterol and high density lipoprotein between the two groups. British Asians were the most sedentary and Indian Asians the most physically active. CONCLUSIONS: There are marked differences in the level of physical activity among the various ethnic groups in the United Kingdom. In each ethnic group, physical activity reduced mean serum insulin, body mass index, and serum triglycerides and had a favourable effect on systolic and diastolic blood pressures. Promotion of physical activity could be of value for the Asian community in the United Kingdom.

The significance of psychosocial factors in predicting coronary disease in patients with valvular heart disease.

Several prognostic indices for predicting various aspects of coronary artery disease were significantly improved by the inclusion of psychosocial factors. 218 patients with valvular heart disease who had undergone routine coronary arteriography before valve replacement were studied in terms of cigarettes smoked, family history of ischaemic heart disease, HDL:cholesterol ratio, angina, sex, blood pressure and four psychosocial characteristics (i.e. social support, work stress, life events and Type A behavior). It was found that the psychosocial factors improved the preoperative predictive power of significant coronary artery disease on four criteria: previous history of hypertension, previous history of myocardial infarction, signs of peripheral vascular disease and ECG evidence of myocardial infarction.

Are Asian coronary arteries smaller than Caucasian? A study on angiographic coronary artery size estimation during life.

Asian immigrants to the UK have a higher mortality from coronary artery disease (CAD) than native Caucasians. There is a clinical impression that Asians have smaller coronary arteries than Caucasians. In the present study, consecutive series of 72 male Caucasian and 70 male Asian patients undergoing diagnostic coronary angiography were recruited. Measurements of proximal disease-free segments of the three major coronary arteries were made using the catheter tip as the calibrating object. Electronic callipers were used for all measurements. Total coronary artery diameter was derived by adding the diameters of right, left anterior descending and circumflex arteries. Asians had significantly smaller total vessel diameter compared to Caucasians. They also had smaller body surface areas. This observation has important therapeutic implications regarding coronary intervention in this ethnic group already suffering excess mortality from CAD.

Accelerated atherosclerosis and myocardial infarction complicating anomalous origin of the right from the left coronary artery.

A patient is described in whom a previously unstenosed single coronary artery was complicated 12 months later by anterior myocardial infarction. Full clinical features documented by exercise thallium scintigraphy and coronary angiography before and after myocardial infarction are described.

Comparison of once and twice daily oral dosing schedules of bevantolol, a new beta-adrenoceptor antagonist with alpha-adrenoceptor partial antagonist activity in patients with angina of effort.

In a placebo controlled double-blind cross-over study following a dose titration phase, we compared the efficacy of benantolol, a new beta 1 adrenoceptor antagonist with alpha-adrenoceptor partial antagonist activity at 12 and 24 hours after dosing in patients with angina of effort. Twenty patients aged 43-65 years were studied. Each study phase lasted four weeks. Efficacy was determined by treadmill exercise testing using the standard Bruce protocol at the end of each phase. Fifteen patients satisfactorily completed the study. Data from five protocol violators were not analysed. In the four patients who received bevantolol 200 mg daily, exercise time increased from 395 +/- 192 (mean +/- 1 SD) sec on placebo to 468 +/- 171 sec at 10-12 hours and to 442 +/- 230 sec at 22-24 hours after dosing with bevantolol. In the eleven patients who received bevantolol 400 mg daily, exercise tolerance of 290 +/- 103 sec on placebo increased to 408 +/- 112 sec at 10-12 hours (P = 0.001) and to 400 +/- 98 sec at 22-24 hours (P = 0.001) after dosing with bevantolol. Maximum exercise capacity at 10-12 and 22-24 hours after dosing with bevantolol were comparable. Maximum exercise heart rate and systolic blood pressure on placebo and on bevantolol at 10-12 and at 22-24 hours after dosing were comparable. Thus, bevantolol has salutary effects on exertional angina up to 24 hours after dosing.

Thallium-201 myocardial imaging in patients with angina pectoris and anomalous aortic origin of the circumflex coronary artery.

Anomalous aortic origin of the circumflex coronary artery is the commonest coronary artery anomaly. In this study, the significance of anomalous aortic origin of the circumflex coronary artery was investigated in seven patients with exertional chest pain using exercise thallium scintigraphy. Five patients with circumflex coronary arterial disease served as controls. Myocardial perfusion was normal in the five patients with a nonstenosed anomalous artery. In these patients, exercise heart rate and blood pressure response were normal. Two patients with a stenosed anomalous circumflex coronary artery and four of the five control patients had posterolateral myocardial perfusion defects. It is concluded that anomalous aortic origin of the circumflex coronary artery does not cause impairment of myocardial perfusion unless it is the site of significant coronary arterial stenosis.