Calibration of a high spectral resolution lidar using a Michelson interferometer, with data examples from ORACLES.

The NASA Langley airborne second-generation High Spectral Resolution Lidar (HSRL-2) uses a density-tuned field-widened Michelson interferometer to implement the HSRL technique at 355 nm. The Michelson interferometer optically separates the received backscattered light between two channels, one of which is dominated by molecular backscattering, while the other contains most of the light backscattered by particles. This interferometer achieves high and stable contrast ratio, defined as the ratio of particulate backscatter signal received by the two channels. We show that a high and stable contrast ratio is critical for precise and accurate backscatter and extinction retrievals. Here, we present retrieval equations that take into account the incomplete separation of particulate and molecular backscatter in the measurement channels. We also show how the accuracy of the contrast ratio assessment propagates to error in the optical properties. For both backscattering and extinction, larger errors are produced by underestimates of the contrast ratio (compared to overestimates), more extreme aerosol loading, and-most critically-smaller true contrast ratios. We show example results from HSRL-2 aboard the NASA ER-2 aircraft from the 2016 ORACLES field campaign in the southeast Atlantic, off the coast of Africa, during the biomass burning season. We include a case study where smoke aerosol in two adjacent altitude layers showed opposite differences in extinction- and backscatter-related Ångström exponents and a reversal of the lidar ratio spectral dependence, signatures which are shown to be consistent with a relatively modest difference in smoke particle size.

Magnetic resonance cholangiopancreatography and contrast-enhanced magnetic resonance cholangiopancreatography versus endoscopic ultrasonography in the diagnosis of extrahepatic biliary pathology.

PURPOSE: This study compared the diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasonography (EUS) in evaluating the cause of extrahepatic bile duct dilatation. MATERIALS AND METHODS: Forty-five patients (26 men, mean age 57 years) with extrahepatic biliary dilatation, as shown by transabdominal ultrasound, with or without elevated biliary and pancreatic serum indices, were prospectively studied with MRCP and EUS between September 2007 and October 2008. EUS and MRCP were performed within no more than 24 h of each other to reduce the possibility of changes due to stone migration. Image analysis was carried out in a double-blind fashion. RESULTS: MRCP had 88.9% diagnostic accuracy, 91.9% sensitivity and 75% specificity, with 94.4% positive predictive value and 66.7% negative predictive value. EUS had 93.3% diagnostic accuracy, 97.3% sensitivity and 75% specificity; the positive and negative predictive values were 94.7% and 85.7%, respectively. CONCLUSIONS: MRCP and EUS do not show significant statistical differences in diagnostic accuracy. MRCP is an accurate, noninvasive modality in the study of extrahepatic biliary pathology. EUS is especially reliable in patients with extrahepatic biliary obstruction caused by endoluminal sludge.

Double diagnostic meaning of serum transferrin receptor in hemodialysis patients: two case reports.

Hemodialysis patients on maintenance erythropoietin need an adequate supply of iron to optimize therapy and achieve and maintain target levels of hemoglobin. Evaluation of iron stores and early detection of iron deficiency are essential for management of erythropoiesis in chronic renal failure, but there is still no single biochemical or hematological parameter that is sensitive or specific enough to completely describe the distribution of iron in the body. Serum transferrin receptor (sTfR) is a marker of iron that is available for erythropoiesis. We selected 2 clinical cases in which hemodialysis patients were receiving maintenance erythropoietin. To suggest how sTfR can be used in its double diagnostic meaning according to the clinical context of the patient, sTfR was evaluated in one case as a marker of iron deficiency and in the other as a marker of erythropoiesis. The association of sTfR with hematological parameters of iron-deficient erythropoiesis (reticulocyte hemoglobin content, percentage of hypochromic erythrocytes, ratio of reticulocyte hemoglobin content to hemoglobin content) and parameters of stimulated erythropoiesis (absolute reticulocyte count, immature reticulocyte fraction) increases the accuracy of sTfR in its double diagnostic power.

Bronchial reactivity and intracellular magnesium: a possible mechanism for the bronchodilating effects of magnesium in asthma.

1. Increased bronchial smooth muscle contractility with consequent bronchial hyperreactivity are characteristic physiopathological events of asthma. Since magnesium intervenes in calcium transport mechanisms and intracellular phosphorylation reactions, it constitutes an important determinant of the contraction/relaxation state of bronchial smooth muscle. In the present study we investigated the relationship between bronchial reactivity, assessed by methacholine-provocation test, and magnesium concentrations both at extracellular and intracellular levels measured by spectrophotometry. Twenty-two patients with mild-to-moderate asthma and 38 non-asthmatic subjects with allergic rhinitis (24 allergic to Parietaria pollen and 14 allergic to Grass pollen) were recruited to the study. Exclusion criteria included renal failure, hepatic diseases, heart failure and arterial hypertension. 2. The salient finding of our study is that there is a strong positive correlation between bronchial reactivity and the level of intracellular magnesium (r=0.72, P<0.0001), both when the groups are analysed separately or together. Intracellular magnesium concentrations in the group of patients with asthma were significantly lower (1.8+/-0. 01 mmol/l; n=22) when compared with levels in rhinitis subjects allergic to Parietaria (1.9+/-0.01 mmol/l; n=24, P<0.05), and with levels in rhinitis subjects allergic to Grass pollen (2.0+/-0.03 mmol/l; n=14, P<0.05). Serum levels of the ion were similar in all groups. 3. We conclude that the level of intracellular magnesium may be an important determinant of bronchial hyperreactivity, as supported by the significant positive correlation between these two parameters in allergic patients with known bronchial hyperresponsiveness. This finding, in addition to reports of the bronchodilating effects of magnesium administration in patients with asthma, confirms the proposed role of this ion in the pathogenesis and treatment of asthma.

Dentinal dysplasia type I. A subclassification.

Dentinal Dysplasia Type I is a rare condition affecting the deciduous and permanent dentitions, in which the teeth present with short roots and considerably reduced or obliterated pulp spaces. These features were observed on the radiographs of a patient referred for orthodontic assessment, and an investigation of other members of the family revealed that the father and two siblings were also affected. There were variations in the lengths of the roots in those affected, and thus a subclassification of the dysplasia is proposed.