Kinesin hydrolyses one ATP per 8-nm step.

Kinesin is a two-headed, ATP-dependent motor protein that moves along microtubules in discrete steps of 8 nm. In vitro, single molecules produce processive movement; motors typically take approximately 100 steps before releasing from a microtubule. A central question relates to mechanochemical coupling in this enzyme: how many molecules of ATP are consumed per step? For the actomyosin system, experimental approaches to this issue have generated considerable controversy.

A simple model describing nitrate and nitrite reduction in fluidized bed biological reactors.

A uniquely simple model is developed to describe the NO(3) (-) and NO(2) (-) concentration profiles within a dentrification fluidized bed biological reactor. This simple model is compared to experimental data, and to a more complex model similar to those previously proposed in the literature. The simple model fits the experimental data at least as well as the more complex model.

Histomorphometric assessment of bone mass, structure, and remodeling: a comparison between healthy black and white premenopausal women.

While noninvasive studies of bone mass and turnover in blacks and whites abound, histologic evaluations are very rare. We have performed a comparative bone histomorphometric study of iliac biopsies from 55 healthy, premenopausal women including 21 blacks (mean age 33.4 + 1.

Bone structure in postmenopausal hyperparathyroid, osteoporotic, and normal women.

The purpose of this study was to test the hypothesis that patients with mild primary hyperparathyroidism are protected against postmenopausal (PM) loss of cancellous bone architecture. To achieve this, we compared bone structure and turnover in iliac bone biopsies from three groups: 16 women with mild primary hyperparathyroidism (PHPT; 58.2 +/- 2.

The regression hypothesis: communicative continuum vs. parametrically defined grammars.

Proposals concerning the regression hypothesis in aphasia presented in Grodzinsky (1990) and Schnitzer (1989, 1990) are compared. It is argued that Grodzinsky's model, which is syndrome-based, is observationally inadequate, and thus fails to lend aphasiological support to a neurophysiologically realized central language system along the lines of Chomsky's Theory of Principles and Parameters. Schnitzer's approach rejects the notion of mental grammars and interprets aphasic regression microgenetically, along the lines of Givón's continuum.

The development of segmental phonological production in a bilingual child.

A longitudinal diary-and-videotape study of the production of phonological segments by a Spanish-English bilingual child, age I; I-3; 9, revealed four stages in consonantal acquisition: presystematic variation, formation of a single system, separation into two systems corresponding to the two languages, and achievement of adult target values with later interference of one language in the other. Vocalic acquisition proceeded with widespread variation, followed by stabilization at target adult values, without any apparent intermediate unitary-system stage. Relevance of the data adduced here to the issue of whether bilingual children first function with a single system before acquiring two discrete languages is discussed.

Steady as a rock: does the steady state represent cognitive fossilization?

A study was performed in which data were obtained from adults and children with respect to their control of the inflexional morphology of the Spanish verbal system. Results indicate that adults have inferior knowledge of the paradigm compared to the children. Based on the types of errors committed, it is argued that linguistic knowledge may be more an ability to analogize correctly than to follow (unconscious) rules.

Severe visual deficits in infancy in northern Israel: an epidemiological perspective.

The characteristics of 193 legally blind children ranging in ages from birth to 4 years were analyzed. The overall incidence was 1/1000 live births; however, the ethnic specific incidence varies. All children were diagnosed before the age of 20 months and the most frequent alerting sign was lack of visual tracking.

Relationships between quantitative histological measurements and noninvasive assessments of bone mass.

We performed a comprehensive analysis of the relationships between histologic indices in the iliac crest (cancellous bone volume, trabecular structural indices, cortical width, and core width) and bone density in the spine, hip, and wrist in 81 patients with various metabolic bone diseases including osteoporosis, osteomalacia, hyperparathyroidism, and Paget's disease. In the whole group, all of the histologic indices correlated significantly with bone mineral density (BMD) of the spine and the three regions of the hip (r = 0.28-0.

Pragmatic-mode mediation of sentence comprehension among aphasic bilinguals and hispanophones.

A test of sentence comprehension administered in four input-output modality combinations to a group of aphasic bilinguals and monolingual hispanophones provides evidence that aphasics tend to use pragmatic-mode (in the sense of Givón, 1979, On understanding-grammar, New York, Academic Press) strategies in approaching this task. When five factors were identified and dichotomized with respect to the pragmatic-mode-syntactic-mode dimension, the patients performed significantly better on items classified as pragmatic than on those classified as syntactic, in both languages. The results support a vertical/hierarchical view of aphasic language dissolution.

A pediatric approach to visual handicap.

When dealing with a visually handicapped child, the pediatrician's responsibility is considerable. He or she plays a key role in establishing the pathologic diagnosis and in coordinating the subsequent medical therapy and genetic counseling if required. These responsibilities also include providing emotional support to the family, and advice regarding the various medical, developmental, and educational decisions that the family will face in the future.

Effects of pollution on humic substances.

To assess effects of industrial and environmental pollution on analytical characteristics of humic substances, we isolated humic acids (HA's) and fulvic acids (FA's) from unpolluted and polluted soils and sediments. Following purification, the HA's and FA's were characterized by elemental (C, H, O, N, S) and functional group (CO2H, phenolic OH, total acidity) analyses, infrared (IR) spectrophotometry, differential thermal analysis (DTA) and by metal (Fe, Al, Cu, Mn, Pb, Ni, Co, Zn, Cr, Cd, Hg, Ca and Mg) analyses. Si was also determined in all samples.

Humic substances: fulvic acid-dialkyl phthalate complexes and their role in pollution.

Fulvic acid is a water-soluble humic material with relatively low molecular weight that occurs widely in soils and waters. It can combine with lyophobic organic compounds such as alkanes, fatty acids, and dialkyl phthalates to form stable "complexes" that are soluble in water. Fulvic acid in an aquatic environment may act as a vehicle for the mobilization, transport, and immobilization of organic compounds, some of which may be toxic pollutants.

Montmorillonite: Effect of pH on Its Adsorption of a Soil Humic Compound.

The d(001) spacing of sodium montmorillonite increased from 9.87 to 17.50 angstroms after interaction of the compound with fulvic acid at pH 2.