ESR dating of barite in sulphide deposits formed by the sea-floor hydrothermal activities.

Barite is a mineral newly found to be practically useful for electron spin resonance (ESR) dating of sulphide deposits formed by the sea-floor hydrothermal activities. The recent studies for the properties of the ESR dating signal in barite are summarised in the present paper as well as the formulas for corrections for accurate dose-rate estimation are developed including the dose-rate conversion factors, shape correction for gamma-ray dose and decay of (226)Ra. Although development of the techniques for ESR dating of barite has been completed, further comparative studies with other dating techniques such as U-Th and (226)Ra-(210)Pb dating are necessary for the technique to be widely used.

Somatosensory evoked potentials (SEPs) for the evaluation of cervical spondylotic myelopathy: utility of the onset-latency parameters.

OBJECTIVE: Peak latencies have been traditionally employed for the evaluation of somatosensory evoked potentials (SEPs). Some authors have argued for the theoretical superiority of the onset latencies, which has never been verified in actual clinical cases. We aimed to investigate the utility of onset-latency parameters of median nerve SEPs in the cervical spondylotic myelopathy (CSM) patients, as well as several other issues concerned with the SEP diagnosis of CSM. METHODS: We retrospectively enrolled 42 CSM patients and investigated their SEP findings. RESULTS: The N9o (N9 onset)-P13/14o interval showed the highest sensitivity (83%) followed by N9o-N20o (74%). The sensitivities of corresponding peak latency parameters were lower (62% and 33%). The amplitude of the lower cervical N13 also showed the highest sensitivity (83%). The sensitivity of tibial nerve SEPs examined in 21 patients was lower (71%) than that of median nerve SEPs (90%). When clinical signs alone were used as the gold standard, the sensitivity of median SEPs was 90% whereas that of MRI was 88%. CONCLUSIONS: Higher diagnostic yield of onset-latency parameters of median nerve SEPs has been documented in CSM. SIGNIFICANCE: SEPs are useful in the diagnosis of CSM having equal sensitivity and probably higher specificity than MRI.

Modified ion exchange separation for tungsten isotopic measurements from kimberlite samples using multi-collector inductively coupled plasma mass spectrometry.

Tungsten isotope composition of a sample of deep-seated rock can record the influence of core-mantle interaction of the parent magma. Samples of kimberlite, which is known as a carrier of diamond, from the deep mantle might exhibit effects of core-mantle interaction. Although tungsten isotope anomaly was reported for kimberlites from South Africa, a subsequent investigation did not verify the anomaly. The magnesium-rich and calcium-rich chemical composition of kimberlite might engender difficulty during chemical separation of tungsten for isotope analyses. This paper presents a simple, one-step anion exchange technique for precise and accurate determination of tungsten isotopes in kimberlites using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Large quantities of Ca and Mg in kimberlite samples were precipitated and removed with aqueous H(2)SO(4). Highly pure fractions of tungsten for isotopic measurements were obtained following an anion exchange chromatographic procedure involving mixed acids. That procedure enabled efficient removal of high field strength elements (HFSE), such as Hf, Zr and Ti, which are small ions that carry strong charges and develop intense electrostatic fields. The tungsten yields were 85%-95%. Advantages of this system include less time and less use of reagents. Precise and accurate isotopic measurements are possible using fractions of tungsten that are obtained using this method. The accuracy and precision of these measurements were confirmed using various silicate standard rock samples, JB-2, JB-3 and AGV-1.