[1] The gravity disturbance caused by groundwater is derived based on hydrological physics by solving nonlinear hydrological diffusion equations for three-dimensional and temporal groundwater distributions. The gravity disturbance is then estimated by the spatial integral of the groundwater distributions. This approach aims to resolve the problems of previous methods for the correction of groundwater disturbances in gravity data, such as instrumental drift of relative gravimeters, empirical estimation of gravity assuming a linear gravity response to precipitation, and the use of lower-dimensional water transfer models. The disturbance estimated using the proposed model is consistent with the observed gravity change at Asama Volcano in Central Japan during the rainy summer of 2006. The model reproduces the rapid increase and subsequent gradual decrease in gravity following rainfall events. The water mass within 150 m of the gravimeter is shown to dominate the observed gravity change during precipitation. It is also demonstrated that the use of adequately representative soil parameters is essential in order to accurately estimate the groundwater distributions and consequent gravity variations. This study shows that correcting for hydrological disturbances requires a more sophisticated model of water movements, particularly during heavy rainfall.Citation: Kazama, T., and S. Okubo (2009), Hydrological modeling of groundwater disturbances to observed gravity: Theory and application to Asama Volcano, Central Japan,

We set out to retrospectively review the clinical and imaging features of patients with post-radiation sarcoma, especially in the head and neck region. We reviewed the records of 4194 patients with carcinoma of the head and neck region who had a history of radiation. They had undergone CT and/or MRI. Medical records were reviewed for the primary diagnosis, radiation history and latency period to the development of sarcoma. The patients included four men and two women with a mean age of 64.5 years. The mean latency period for the development of sarcoma was 11.5 years. Primary diagnoses were maxillary carcinoma, nasopharyngeal carcinoma, adenoid cystic carcinoma of the oral floor, tonsilar carcinoma, soft palate carcinoma and tongue carcinoma. Histopathological examinations revealed osteosarcoma, spindle cell sarcoma, chondrosarcoma, malignant peripheral nerve sheath tumour, spindle cell carcinoma and malignant fibrous histiocytoma, respectively. Common findings were a heterogeneous and well-enhanced soft tissue mass and bone destruction. There is at present little or no prospect for the effective prevention of radiation-induced sarcoma of the head and neck. This emphasizes the importance of the earliest possible diagnosis for such patients. The imaging findings are not diagnosis specific, but strict follow-up within the radiation field by CT and MRI and an appreciation of the expected latency period may help to provide the diagnosis. When radiotherapy is performed for head and neck neoplasms, periodic follow-up observations may be necessary for many years.

We describe two Japanese female patients with pigmented extramammary Paget's disease (EMPD); one patient had a dark brown plaque and the other had a reddish patch with a pigmented area, both affecting the vulval region. Histochemical and immunohistochemical examinations confirmed EMPD with melanocyte colonization; plump tumour cells with a large nucleus and pale cytoplasm that were positive for CAM 5.2 and CEA proliferated singly or in nests in the epidermis, and scattered among the tumour cells were many dendritic cells with a large amount of melanin that were positive for HMB-45 and S-100 protein. Fontana-Masson (FM) stain showed many positive cells with well-developed dendritic processes within and around tumour nests. Histochemical and immunohistochemical studies of non-pigmented EMPD cases on the same region showed that HMB-45 positive cells were sparse or not detected at all, and that also FM staining-positive cells were decreased or not detected, and their dendritic processes were poorly formed. The present study suggests that there might be heterogeneity in EMPD in terms of relationships between Paget's cells and melanocytes.

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