The application of tree bark as bio-indicator for the assessment of Cr(VI) in air pollution

The impact of a chromium smelter on pollution was evaluated by determining Cr(VI) in topsoil, grass and tree bark by electrothermal atomic absorption spectrometry (ETAAS). It was found that bark reflected the levels of air pollution better than soil and grass due to its high accumulative ability of Cr(VI). The tree bark was contaminated with Cr(VI) by a factor of 9 than in soil. It is therefore suggested that the bark be used as an indicator of air pollution for long-term exposure. The concentration of Cr(VI) in the bark was always a fraction of the total concentration of Cr and ranges between 1.6 and 3%. The method used in the preparation of samples was validated by the analysis of certified reference materials.     

斜交高架桥对城市河道流场的影响

以青岛市新疆路快速路工程昌乐河段为例,采用平面二维水动力学数值计算方法,模拟了20 a一遇洪水时斜交高架桥工程前后河道沿程位及洪水流速的变化,并利用实体模型试验对其进行了验证.结果表明:受桥墩相互作用的影响,斜交桥桥墩的墩后尾流区具有弱偏移现象;桥墩群对水流的壅高值具有非线性叠加的特点,对河道水流具有明显的分割和控导作...     

Functional characterization of caudal hypoglossal neurons by spectral patterns of neuronal discharges in the rat

This study evaluated the spectral characteristics of neuronal discharges in the caudal hypoglossal nucleus and their physiological relevance in adult, male Sprague Dawley rats which were anaesthetized and maintained with pentobarbital sodium. Based on auto-spectral analysis of extracellular single-neuron activity, three spectral patterns were identified in the spontaneous discharges of hypoglossal neurons. Neurons that exhibited a rhythmic pattern manifested a concentrated peak in the auto-spectrogram that corresponded to the mean discharge rate. A majority of hypoglossal neurons displayed the modulated pattern, which was manifested either as scattered power densities (wide-band modulated pattern) or with a peak frequency component that was different from the mean discharge rate (narrow-band modulated pattern). Neurons that exhibited a mixed pattern displayed both rhythmic and modulated spectral patterns. Cross-spectral analysis further revealed that respiratory modulation constituted a major physiological influence on caudal hypoglossal neurons. The respiratory modulated pattern, however, could be converted to a mixed pattern in the presence of a central dipsogen, angiotensin III. The results suggest that the spectral patterns of neuronal discharges in caudal hypoglossal neurons represent manifestations of multiple physiological information, including that regarding respiration and dipsogenesis, which is encoded in these neurons. It was also shown that this information may only be revealed by auto-spectral and cross-spectral analysis of neuronal discharge signals.     

Reproducibility of the histologic diagnosis of pneumonia among a panel of four pathologists: analysis of a gold standard

STUDY OBJECTIVE: To establish a histologic diagnosis of pneumonia by consensus of a panel of pathologists, to test the interobserver and intraobserver variation in the histologic diagnosis of pneumonia, to compare the diagnostic accuracy of diagnosing pneumonia with and without preselected histologic criteria, and to establish more specific histologic criteria for the diagnosis of pneumonia. METHODS: The study group consisted of 39 patients who died after a mean of 14 days of mechanical ventilation. A postmortem open lung biopsy was performed on all patients. The tissue was reviewed independently by four pathologists who categorized the slides from each patient as showing or not showing pneumonia. Interobserver variation was calculated using the kappa statistic. Six months following the initial evaluation, the same slides were resubmitted to one of the pathologists for reevaluation to look for intraobserver error. Finally, the slides were reviewed and categorized by the criteria of Johanson et al into no pneumonia, mild, moderate, or severe bronchopneumonia. A comparison was made of the patients selected as demonstrating histologic pneumonia by each of the examinations. RESULTS: The reliability coefficient (kappa) measuring agreement among the four pathologists was good at 0.916. However, the prevalence of pneumonia as determined by each of the four pathologists varied; pathologist A, 15 of 39 (38%); pathologist B, 12 of 39 (31%); pathologist C, 9 of 39 (23%); and pathologist D, 7 of 39 (18%). Resubmitting the same slides to the same pathologist 6 months later resulted in reclassification of 2 of 39 patients. Using the histologic criteria of Johanson and colleagues, 14 patients were selected as having pneumonia compared with only nine patients selected by consensus of three of four pathologists. CONCLUSIONS: Recognition of histologic pneumonia varies among pathologists. The preselected criteria of Johanson and colleagues detected histologic pneumonia in eight of nine patients picked by consensus of pathologists, but six additional patients classified as "no histologic pneumonia" by the consensus of pathologists were judged to have histologic pneumonia by these criteria. The results established the necessity for standardization of histologic criteria for studies using biopsy as the gold standard for bacterial pneumonia. An atlas showing the criteria used in our selection was developed.