Reaction products of aquatic humic substances with chlorine.

A major concern of the chlorination of aquatic humic materials is the ubiquitous production of trihalomethanes. A large number of other chlorinated organic compounds, however, have been shown to be formed by chlorine's reaction with humic substances. In this study, humic material was concentrated from a coastal North Carolina lake and chlorinated at a chlorine to carbon mole ratio of 1.5 at pH 12. A high pH was necessary for complete dissolution of the humic material and for production of adequate quantities of oxidation and chlorination products for extraction, separation and mass spectrometric identification. After concentration in ether, samples were methylated, separated with a 50-m OV-17 glass capillary column or a 25 m SP-2100 fused-silica column and identified. A Hewlett-Packard 5710A gas chromatograph interfaced to a VG Micromass 7070F double-focusing mass spectrometer was used. Low resolution, accurate mass measurements were made with a combined EI-Cl source. The ability to do low resolution, accurate mass measurements made possible a rapid scan function necessary for capillary column gas chromatography. Accurate mass measurements allowed increased confidence in the identification of compounds, most of which are not available as standards. The products identified in these studies were chlorinated aliphatic straight-chain acids dominated by di- and trichloroacetic acid and the chlorinated dicarboxylic acids: succinic, fumaric and maleic acids. Chlorinated and unchlorinated aliphatic mono- and dicarboxylic acids and unchlorinated polycarboxylic aromatic acids comprise the remaining bulk of the compounds identified.

Alveolar air-tissue interface and nuclear magnetic resonance behavior of lung.

Inflated lungs are characterized by a short nuclear magnetic resonance (NMR) free induction decay (rapid disappearance of NMR signal), likely due to internal (tissue-induced) magnetic field inhomogeneity produced by the alveolar air-tissue interface. This phenomenon can also be detected using temporally symmetric and asymmetric NMR spin-echo sequences; these sequences generate a pair of NMR images from which a difference signal (delta) is obtained (reflecting the signal from lung water experiencing the air-tissue interface effect). We measured delta in normal excised rat lungs at inflation pressures of 0-30 cmH2O for asymmetry times (a) of 1-6 ms. Delta was low in degassed lungs and increased markedly with alveolar opening when measured at a = 6 ms (delta 6 ms); delta 6 ms varied little during the rest of the inflation-deflation cycle. Delta 1 ms (a = 1 ms) did not vary significantly on inflation and deflation. Measurements of delta at a = 3 and 5 ms generally lay between those of delta 1 ms and delta 6 ms. These findings, which are consistent with theoretical predictions, suggest that measurements of delta at appropriate asymmetry times are particularly sensitive to alveolar opening and may provide a means of distinguishing alveolar recruitment from alveolar distension in the pressure-volume behavior of the lung.

Tuberculosis screening in private physicians' offices, Pennsylvania, 1996.

OBJECTIVE: To assess tuberculin skin testing practices of physicians after community-wide screening of 1400 children exposed to a pediatrician with active tuberculosis (TB). DESIGN: A self-administered questionnaire. SETTING: Medium-sized city in eastern Pennsylvania. PARTICIPANTS: Pediatricians and family practitioners seeing pediatric patients. MAIN OUTCOME MEASURES: Percentages of physicians who followed published recommendations for placement and reading of TB skin tests published by the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC). RESULTS: Questionnaires were completed by 60/80 (75%) physicians. The 60 physicians had practiced a mean of 17 years (range 3-38 years), and only one did not do TB skin testing for pediatric patients. The 59 physicians doing TB skin testing reported routinely tuberculin testing more than 900 children per month. Only 8/59 (14%) physicians followed published guidelines for placement and reading of tuberculin tests. Those physicians screened 158 (17%) of the pediatric patients undergoing TB skin testing in a typical month. CONCLUSION: In this community where a highly publicized TB case prompted massive pediatric screening, most physicians seeing children in private practice do not follow standard TB skin testing guidelines. Increased understanding of how private-practice physicians learn about and decide to use recommended standards are needed if tuberculin tests are to be correctly performed and TB appropriately diagnosed.

Rapid line scan technique for artifact-free images of moving objects.

Moving objects (e.g., heart, lung, chest wall, etc.) typically cause artifacts to appear in two-dimensional Fourier transform ("spin warp") images. The rapid line scan (RLS) technique is a simple inexpensive technique that can rapidly produce artifact-free images of moving objects, without requiring enormous magnetic field gradients or periodic motions. The basic concepts and potential industrial applications of the RLS technique are described.

Chemistry of mutagenic by-products of water chlorination.

The strong Ames mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2 (5H)-furanone (MX) and its geometric isomer E-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (E-MX) have been shown to be present in chlorinated drinking waters. MX accounts for approximately 30% and E-MX for a few percent of the overall mutagenicity. MX and E-MX are unstable in water and undergo both pH dependent isomerization (MX in equilibrium E-MX) and hydrolytic degradation. Alternative methods of disinfection have been found to produce mutagenicity, and MX and E-MX but to a lesser extent than disinfection with chlorine. The MX analogues 3-chloro-4-(dichloromethyl)-2 (5H)-furanone (red-MX) and 2-chloro-3-(dichloromethyl)-2-butenedioic acid (ox-MX) have also been identified in chlorinated water. However, the relatively low mutagenicity of these compounds suggests that their contribution to the overall mutagenicity of chlorinated water is of only moderate significance.

A systematic approach for radiographically evaluating joint disease in the foot.

A methodic analysis of foot radiographs is valuable when evaluating for joint disease. The author presents a system that allows the interpreter to establish a list of expected differential diagnoses. This is especially useful when the arthritide does not present with its classic radiographic appearance.

Radiographic anatomy of the first metatarsal.

Normal radiographic anatomy of the first metatarsal bone is established through cadaver dissection, examination of bone specimens, and radiography. Extra-articular and distal articular anatomical landmarks are identified with wire markers. Dorsoplantar, lateral, lateral oblique, and medial oblique radiographs of 15 osteologic sites are presented, including the articular margins of the first metatarsal head, the borders of the three diaphyseal surfaces, the origins of the metatarsophalangeal collateral and metatarsosesamoid suspensory ligaments, and the insertions of the first cuneiform-metatarsal joint ligaments and the tibialis anterior and peroneus longus tendons. The correlation of gross anatomy and radiographs is described.

Coexistent gout and rheumatoid arthritis.

Gout and rheumatoid arthritis are relatively common entities individually; however, the coexistence of these two conditions has been reported rarely in the literature. The authors present a case that was followed for 20 years. The patient was seen by the acknowledged internist and podiatrist. Criteria for the evaluation and diagnosis of each disease entity are discussed and correlated to the case reported. Various theories and research attempting to explain the negative coexistence of gout and rheumatoid arthritis are presented.

1993 William J. Stickel Silver Award. Anatomical considerations of the peroneal tubercle.

Gross discrepancy and error regarding the identification and location of the peroneal tubercle have been found in the literature. Furthermore, the authors found no evidence of a repeatable measurement technique in applicable descriptions of this osteologic landmark. In accordance with interrater reliability procedures, the authors established repeatability of peroneal tubercle measurements. In conjunction with the instrumentation's accuracy and resolution, the investigators infer reliability for these measurements. To the best of the authors' knowledge, this study is the only one in which interrater reliability was established for the morphometric assessment of the peroneal tubercle and the retrotrochlear eminence. The results also reestablish the correct anatomical presentation of the retrotrochlear eminence and the peroneal tubercle along the lateral surface of the calcaneus.

Radiographic analysis of metatarsus primus elevatus: a preliminary study.

The authors investigated the effect of x-ray tube head angulation and central ray direction on the position of the first metatarsal relative to the second metatarsal in the lateral foot radiographic view. This preliminary study shows that these variables may influence the perception of metatarsus primus elevatus in the weightbearing lateral foot radiograph.

The radiographic presentation of osteomyelitis in the foot.

Numerous authors have described the radiographic findings associated with osteomyelitis. Knowledge of these findings and their presentation radiographically may make diagnosis of this pathology quite simple. The challenge comes not in diagnosing osteomyelitis based on gross radiographic evidence; by this time, the disease has significantly progressed. The challenge is to be able to recognize early, subtle changes, and, in conjunction with clinical findings, to diagnose and treat the disease before classic radiographic evidence is demonstrated.

Radiologic aspects of aging in the foot.

This article discusses technical and radiologic aspects that should be considered when evaluating the geriatric population. Potential errors and accidents will be reduced and the office will function more efficiently by advance preparation. The interpreter must be aware of anatomic variations that could potentially be misdiagnosed as a pathologic condition. Finally, the radiographic presentation of disease may differ from that presenting in younger age groups.