Toward the improvement of total nitrogen deposition budgets in the United States.

Frameworks for limiting ecosystem exposure to excess nutrients and acidity require accurate and complete deposition budgets of reactive nitrogen (Nr). While much progress has been made in developing total Nr deposition budgets for the U.S., current budgets remain limited by key data and knowledge gaps. Analysis of National Atmospheric Deposition Program Total Deposition (NADP/TDep) data illustrates several aspects of current Nr deposition that motivate additional research. Averaged across the continental U.S., dry deposition contributes slightly more (55%) to total deposition than wet deposition and is the dominant process (>90%) over broad areas of the Southwest and other arid regions of the West. Lack of dry deposition measurements imposes a reliance on models, resulting in a much higher degree of uncertainty relative to wet deposition which is routinely measured. As nitrogen oxide (NOx) emissions continue to decline, reduced forms of inorganic nitrogen (NHx = NH3 + NH4+) now contribute >50% of total Nr deposition over large areas of the U.S. Expanded monitoring and additional process-level research are needed to better understand NHx deposition, its contribution to total Nr deposition budgets, and the processes by which reduced N deposits to ecosystems. Urban and suburban areas are hotspots where routine monitoring of oxidized and reduced Nr deposition is needed. Finally, deposition budgets have incomplete information about the speciation of atmospheric nitrogen; monitoring networks do not capture important forms of Nr such as organic nitrogen. Building on these themes, we detail the state of the science of Nr deposition budgets in the U.S. and highlight research priorities to improve deposition budgets in terms of monitoring and flux measurements, leaf- to regional-scale modeling, source apportionment, and characterization of deposition trends and patterns.

Acoustic reflectometry in the detection of middle ear effusion.

Acoustic reflectometry, a new technique for detecting middle ear effusion, was compared with results from tympanocentesis or myringotomy in 75 patients (141 ears). There was a highly significant association (P less than .0001) for ears having middle ear effusion with high reflectivity (5 through 9 units) and for ears having no middle ear effusion with low reflectivity (0 through 4 units). In a pediatric population with middle ear effusion present in 98 of 141 ears and using reflectivity readings greater than 4 to indicate middle ear effusion, the sensitivity of this technique was 86.7% and the specificity was 69.8%. False-positive errors usually occurred in ears with thick tympanic membranes, or in ears in which reflectivity was determined prior to the induction of anesthesia. False-negative errors usually occurred in ears with both air and fluid. This technique was validated by direct comparison with tympanocentesis or myringotomy and can be used with pneumatic otoscopy and impedance tympanometry to follow children with middle ear effusion.

Metastatic basal cell carcinoma: report of a case.

Although basal cell carcinoma (BCC) accounts for as high as 75% of all malignant skin tumors, its metastatic rate is only 0.1%. Predisposing factors for metastasis are generally thought to be: 1. a head and neck primary BCC; 2. a long standing lesion; 3. deep local invasion with ulceration. This paper presents a patient with metastatic BCC with a history of other malignancies and probable immune system compromise. These factors should also alert the clinician to the possibility of metastatic BCC.

Hypercoagulability as a cause of sudden neurosensory hearing loss.

Fourteen patients with a documented sudden neurosensory hearing loss and four patients with other diseases causing neurosensory hearing loss were studied. The standardized coagulation workup included hematocrit, activated partial thromboplastin generation time, thrombin generation, prothrombin time, phase platelet count, platelet adhesivity, protamine sulfate, serum antithrombin III activity, fibrinogen, and Factor VIII values. Ony those patients having documented evidence of a neurosensory hearing loss occurring within hours or days were included in this study. Eight of the 14 paitents with a documented sudden neurosensory hearing loss satisfied our laboratory criteria for a diagnosis of in vitro hypercoagulability. Three of these patients had abnormal thrombin generation values, 4 had abnormal serum antithrombin III values, and 1 had an elevated platelet count. Four other patients with other diseases causing neurosensory hearing loss did not show evidence of in vitro hypercoagulability. It would appear from this data that coagulation abnormalities play a role in the pathogenesis of sudden neurosensory hearing loss.