Very- and ultra-long-period seismic signals prior to and during caldera formation on La Réunion Island.

Early detection of the onset of a caldera collapse can provide crucial information to understand their formation and thus to minimize risks for the nearby population and visitors. Here, we analyse the 2007 caldera collapse of Piton de la Fournaise on La Réunion Island recorded by a broadband seismic station. We show that this instrument recorded ultra-long period (ULP) signals with frequencies in the range (0.003-0.01 Hz) accompanied by very-long period (VLP) signals (between 0.02 and 0.50 Hz) prior to and during the caldera formation suggesting it is possible to detect the beginning of the collapse at depth and anticipate its surface formation. Interestingly, VLP wave packets with a similar duration of 20 s are identified prior to and during the caldera formation. We propose that these events could result from repeating piston-like successive collapses occurring through a ring-fault structure surrounding a magma reservoir from the following arguments: the source mechanism from the main collapse, the observations of slow source processes as well as observations from the field and the characteristic ring-fault seismicity.

Probing molecular dynamics at the nanoscale via an individual paramagnetic centre.

We demonstrate a protocol using individual nitrogen-vacancy centres in diamond to observe the time evolution of proton spins from organic molecules located a few nanometres from the diamond surface. The protocol records temporal correlations among the interacting protons, and thus is sensitive to the local dynamics via its impact on the nuclear spin relaxation and interaction with the nitrogen vacancy. We gather information on the nanoscale rotational and translational diffusion dynamics by analysing the time dependence of the nuclear magnetic resonance signal. Applying this technique to liquid and solid samples, we find evidence that liquid samples form a semi-solid layer of 1.5-nm thickness on the surface of diamond, where translational diffusion is suppressed while rotational diffusion remains present. Extensions of the present technique could be exploited to highlight the chemical composition of molecules tethered to the diamond surface or to investigate thermally or chemically activated dynamical processes such as molecular folding.

Nuclear magnetic resonance spectroscopy on a (5-nanometer)3 sample volume.

Application of nuclear magnetic resonance (NMR) spectroscopy to nanoscale samples has remained an elusive goal, achieved only with great experimental effort at subkelvin temperatures. We demonstrated detection of NMR signals from a (5-nanometer)(3) voxel of various fluid and solid organic samples under ambient conditions. We used an atomic-size magnetic field sensor, a single nitrogen-vacancy defect center, embedded ~7 nanometers under the surface of a bulk diamond to record NMR spectra of various samples placed on the diamond surface. Its detection volume consisted of only 10(4) nuclear spins with a net magnetization of only 10(2) statistically polarized spins.

Argon-lead isotopic correlation in mid-atlantic ridge basalts

Step-heating analyses for Mid-Atlantic Ridge glass samples show that maximum 40Ar/36Ar values correlate with 206,207,208Pb/204Pb. These correlations hold for the whole Atlantic Ocean and therefore are unlikely to result from shallow-level contamination processes. Instead, they are taken as mixing hyperbolae between the degassed-depleted upper mantle and a recycled component characterized by high 206Pb/204Pb ratios (19 to 21) and low 40Ar/36Ar ratios (300 to 1000). These relations imply that argon may also be a tracer of mantle recycling.

[Schizophreniform psychosis with polydipsia and electrolyte imbalance in multiple sclerosis]. / Schizophreniforme Psychose mit Polydipsie und Elektrolytentgleisung bei multipler Sklerose.

We present the case report of a young woman who suffered from schizophrenia-like psychosis leading to polydipsia and consequent water intoxication. Because of progressive somnolence and epileptic seizures therapy on the intensive care unit became necessary. Findings of MRI and cerebrospinal fluid were consistent with the diagnosis of chronic inflammatory disease of the central nervous system. As other possible causes could be excluded, multiple sclerosis seemed to be most probable. Simultaneous incidence of schizophrenia and multiple sclerosis and the differential diagnosis of central pontine myelinolysis following hyponatremia are discussed.

Plutonium-fission xenon found in Earth's mantle

Data from mid-ocean ridge basalt glasses indicate that the short-lived radionuclide plutonium-244 that was present during an early stage of the development of the solar system is responsible for roughly 30 percent of the fissiogenic xenon excesses in the interior of Earth today. The rest of the fissiogenic xenon can be ascribed to the spontaneous fission of still live uranium-238. This result, in combination with the refined determination of xenon-129 excesses from extinct iodine-129, implies that the accretion of Earth was finished roughly 50 million to 70 million years after solar system formation and that the atmosphere was formed by mantle degassing.

[Ondine's curse with convulsive syncope. Clinical and Doppler ultrasound observations]. / Undines Fluch mit konvulsiver Synkope. Klinische und dopplersonographische Beobachtungen.

In a 31 years old woman with primary alveolar hypoventilation (Ondine's curse) and noctural seizures the arterial blood gases, EEG and blood flow velocity in the middle cerebral artery were measured before, during and after a phase of apnea terminated by a convulsive syncope. The blood flow velocity abruptly increased to the 2.5 fold of the initial value with the beginning of the convulsions, which is interpreted as a break down of the cerebral autoregulation.

[The basis for ultrasonic phenomena during the injection of x-ray contrast media]. / Zur Grundlage der Ultraschallphänomene während der Injektion von Röntgenkontrastmitteln.

During the injection of contrast media for cerebral angiography, high-intensity ultrasound reflections can be recorded by Doppler sonography and B-mode scanning. This phenomenon was examined during carotid angiography and by in vitro experiments in tube models. Our results show that these high-intensity reflections are caused by: (1) transient interfaces of impedance between small compartments of contrast medium and blood and (2) small gas bubbles, which are always present in freshly aspirated contrast medium. Therefore, intraarterially injected contrast medium acts as an ultrasound contrast medium as well.

[Neuro-borreliosis or intervertebral disk prolapse?]. / Neuroborreliose oder Bandscheibenvorfall?

Between September 1986 and November 1988, 17 patients were hospitalized and treated for neuro-borreliosis. Ten of them had been admitted with suspected lumbar or cervical root or compression syndrome. Only four patients recalled a tick bite, only three an erythema migrans. Uni- or bilateral facial paresis was a prominent feature in six patients. Three of 14 patients had no IgG antibodies against Borrelia, either in serum or cerebrospinal fluid at the initial examination, two had positive titres in serum only. Despite antibiotic treatment (usually 10 mega U penicillin three times daily) six patients had a recurrence by April, 1989, treated with penicillin again or with twice daily 100 mg doxycycline or 2 g ceftriaxon. In four of them a residual painful polyneuropathy remains.

[Subclavian steal: transcranial Doppler sonography of the basilar artery]. / Subclavian steal: Transkranielle Doppler-Sonographie der Arteria basilaris.

In 32 patients with high-grade obstruction of the proximal subclavian artery or of the brachiocephalic trunk and complete or incomplete forms of subclavian steal in the ipsilateral vertebral artery, blood flow in the basilar artery was investigated by transcranial Doppler sonography. With complete steal effect in respect of the vertebral artery, we found, contrary to other investigators, in most cases alterations of the flow in the basilar artery even at rest. These alterations are a systolic deceleration of flow velocity or an alternating flow directed towards the arm in systole and towards the brain in diastole. In about 40% of cases blood flow in the basilar artery could not be assessed, either because the depth of investigation reached was too low, or because--especially in cases with systolic deceleration in one vertebral artery--it was impossible to define the origin of the basilar artery.

[Identification of the basilar artery with transcranial Doppler sonography]. / Die Identifizierung der Arteria basilaris mit der transkraniellen Doppler-Sonographie.

In 100 normal subjects the flow velocity in the terminal segments of the vertebral arteries and the basilar artery was investigated by suboccipital transcranial Doppler sonography. In normal cases, flow velocity and direction are not sufficient criteria to differentiate these arteries. Using anatomical and haemodynamical parameters it can be shown that a Doppler signal originating from the basilar artery cannot be expected in a depth of less than 85 mm, thus being deeper than it is usually reported in the literature. Due to methodological limitations, the basilar artery cannot be insonated in about 30% of cases.

Vertebral artery Doppler sonography.

We have examined the vertebral and subclavian arteries in 1,205 patients using directional continuous-wave (c-w) Doppler sonography, and compared the sonographic findings with the results of unilateral or bilateral retrograde brachial arteriographies in the same patients. Doppler sonography revealed 33 false positives among 909 cases with normal angiographic findings. Some types of vertebral artery (VA) lesions allowed an excellent, others a fairly good differentiation by Doppler sonography: the complete subclavian steal syndrome with constant reversal of VA flow was reliably detected (16 cases). In the incomplete steal syndrome (5 cases) sonography was superior to angiography. Two bilateral distal VA occlusions and seven basilar artery occlusions - six in the proximal third and one in the rostral third - were detected sonographically; four basilar occlusions sparing the caudal third and one case exhibiting rete mirabile anastomoses were not identified by Doppler sonography. Our acoustically defined sonographic criteria did not permit an unequivocal assignment to an anatomical variant or a vascular lesion. The sensitivity in the detection of a severe stenosis at the VA origin amounted to 16 out of 31, and to 12 of 25 in cases with a proximal VA occlusion and reconstitution of the distal VA through cervical collaterals. Our results confirm that the conventional hand-held c-w Doppler sonography cannot replace angiography in the evaluation of vertebro-basilar insufficiency. It rather serves as an aid to the decision for or against angiography, and in the follow-up of angiographically proven lesions. However, several therapeutically important lesions are readily diagnosed by sonography.

[Value of visual evoked potentials (VEP) in compression of the anterior visual pathway, especially in the area of the chiasm]. / Die Wertigkeit der visuell evozierten Potentiale (VEP) bei Kompression der vorderen Sehbahn, speziell in der Chiasmaregion.

We investigated 86 patients by pattern half-field stimulation presenting clinically with temporal field-defects or with a mass causing compression of the visual pathways found by C.T.-scanning. Pattern half-field stimulation proved to be a very sensitive method for detecting a compression of the anterior visual pathways. In 65 cases the results of perimetry and VEP were congruent, 6 times the evoked potential was pathologic the perimetry showing no abnormalities, only 1 false negative VEP was observed. Thus we stress the importance of an investigation by VEP including half-field stimulation in all patients with suspected compression of the anterior visual pathways.

Doppler sonography in basilar artery occlusion.

We have investigated 6,972 patients with directional continuous-wave Doppler sonography within the last three and a half years, and have derived criteria for the sonographic diagnosis of basilar artery occlusion or tight stenosis in conjunction with 1,071 retrograde brachial angiograms. By sonographic patterns, we have suspected obstruction of the basilar artery or of both distal vertebral arteries in nine cases. Either bilateral sonographic silence or the absence of a diastolic flow component of the vertebral arteries served as criteria in the sonographic evaluation. Angiography of the vertebro-basilar system, performed in eight cases, showed near or complete occlusion in the distal vertebrals or in the proximal basilar artery. Degrees of stenosis less than an 80 percent reduction in lumen diameter could not be detected sonographically. Two further basilar artery occlusions were detected by means of angiography despite negative Doppler sonography: one of these patients showed an extensive collateral circulation between the posterior inferior and the superior cerebellar arteries, and one patient had an occlusion only of the middle and rostral thirds of the basilar artery, the proximal third and the anterior inferior cerebellar arteries being widely patent. Thus, we believe that directional CW Doppler sonography is very useful in the diagnosis of near or complete occlusion of both distal vertebral arteries or of the proximal basilar artery.