Effect of electrostatic interaction on phase separation behaviour of chitin crystallite suspensions

Optical and electron microscopy were used to observe the dynamics of the phase separation in aqueous chitin suspensions prepared by HCl hydrolysis of crab chitin. Freeze-fracture transmission electron microscopy reveals that chitin crystallites are partially aggregated in the suspension and have an average length of 200 nm and an average width of 8 nm. They exhibit a positive surface charge of approximately 0.5 e/nm2 when fully protonated. The liquid crystal-forming aqueous suspensions of such crystallites are investigated through phase diagrams and Zeta potential measurements for different ionic strength. Exposure of the suspension to a low concentration of univalent electrolyte has a negligible effect on phase separation because of the contribution of the charged crystallites themselves to the ionic strength. The thickness of the effective repulsive layer is estimated both from the phase diagrams according to Onsager's theory and from the computed interaction energy derived from the Poisson-Boltzmann equation using the experimental Zeta potential as surface potential. When the contribution of crystallites to the ionic strength is taken into account and an hypothetical linear charge density close to the Manning limit is assumed, there is good agreement with the Debye length.     

Chest wall motion in preterm infants using respiratory inductive plethysmography

Preterm infant tidal breathing may be different from that of healthy full-term infants because of various features of the premature thorax. The purpose of this project was to describe chest wall motion in the preterm infant (gestational age <37 weeks) and compare it with chest wall motion data in a group of healthy, full-term infants. We wanted to use an objective bedside method for assessment with minimal disruption to the infant. The study population consisted of 61 preterm human infants whose mean(+/-sD) postconceptional age at time of study was 35.3+/-2.1 weeks. During the study, the infants were quietly awake in a prone position. Preterm infants had initially been admitted to a level III neonatal intensive care unit for acute management and had been transferred to a step-down area, where they were in stable condition for study. Data were collected with a semiquantitatively calibrated, noninvasive respiratory inductive plethysmograph. Mean(+/-SD) phase angle was significantly greater in preterm infants than in full-term infants (60.6+/-39.8 degrees versus 12.5+/-5.0 degrees, respectively, p < or = 0.0001). The laboured breathing index was significantly greater in preterm infants than in full-term infants (1.35+/-0.35 versus 1.01+/-0.01, respectively, p = 0.001). The ribcage contribution to breathing did not differ significantly between preterm and full-term infants (25.5+/-17.7% versus 36.3+/-14.4%, respectively, p = 0.11). These results indicate a significant increase in the degree of ribcage and abdomen asynchrony in the preterm subjects compared to the full-term infants. Plethysmography provided a time-efficient and objective method of assessing chest wall motion in this fragile population.     

Myoarchitecture and connective tissue in hearts with tricuspid atresia

The Wiskott-Aldrich syndrome (WAS) is a X-linked hematologic disorder characterized by thrombocytopenia, eczema, and immunodeficiency of variable severity. Reported here are the results of a morphologic, morphometric, and immunophenotypic analysis of splenic lymphoid tissue in 12 WAS patients with documented molecular defect and with different disease severity. Spleens from 29 age-matched patients with different diseases were used as controls. Paraffin-embedded tissue (from all cases) and fresh-frozen samples (from 5 WAS patients and 4 control subjects) were used to study the different white pulp compartments by classic morphologic, immunophenotyping, and image analysis techniques. Data were statistically analyzed by both parametric and nonparametric tests. Spleens from WAS patients showed a significant depletion of the total white pulp (p = 0.0008), T cell (p < 0.05), and B cell (p = 0.0002) areas and marginal zone (MZ) thickness (p < 0.0001). Among WAS patients, a negative correlation was found between the score of severity of the disease and all variables considered (Spearman's rank correlation coefficient, r = -0.79, r = -0.73, r = -0.68, and r = -0.56, respectively). In conclusion, this study shows that in WAS a general depletion of the splenic white pulp occurs, supporting the evidence that WAS is characterized by a combined immune defect. The significant reduction of the MZ may explain the inability of WAS patients to mount a response to T-independent antigens.     

Comparison of the various electrocardiographic scoring codes for estimating anatomically documented sizes of single and multiple infarcts of the left ventricle

It is clinically important to estimate the size of a myocardial infarction (MI) to predict patient prognosis, to determine the ability of a therapy to limit its size, and to evaluate its effect on left ventricular function. Various electrocardiographic methods have been used for these purposes but their accuracies have not been compared with each other using an identical reference population of anatomically measured infarcts. The capability of 4 electrocardiographic scoring methods (the Selvester score, the Minnesota code, the Novacode, and the Cardiac Infarction Injury Score) to estimate MI size was compared using anatomic MI size in a group of 100 deceased patients. All patients had a standard 12-lead electrocardiogram of sufficient quality to perform manual waveform measurements and without confounding factors such as ventricular hypertrophy, fascicular block, or bundle branch block. The location and size of the left ventricular infarction was measured postmortem using the anatomic method of Ideker et al. All methods' size estimates correlated best with anatomic MI size in the anterior location (r = 0.65 to 0.89). The Selvester score was superior in estimating the sizes of inferior (r = 0.70) and posterolateral (r = 0.74) infarcts. For multiple infarcts all methods performed poorly (r = 0.18 to 0.44).     

Soil management enhancing hydrocarbon biodegradation in the polluted Kuwaiti desert

Oil-polluted Kuwaiti desert samples, exposed to the open air, were subjected to specific types of management, once every 2 weeks, throughout a year; control samples were not treated. The total amounts of extractable alkanes from the control samples remained fairly constant during the dry hot months, but decreased during the rainy months reaching, after 1 year, slightly more than one-half of the amount at zero time. This result demonstrates the self-cleaning of the Kuwaiti desert and the essential role of moisture in this process. Out of the eight types of management studied, the repeated fertilization of the polluted sample with 3% KNO3 solution was most efficient, reducing the extractable alkanes after 1 year to about one-third of zero reading. Repeated fertilization with treated sewage effluent was inhibitory to alkane biodegradation, probably because of increasing soil acidity. The latter inhibitory effect was annulled by liming. Repeated irrigation with 3% NaCl solution was inhibitory, but 1% NaCl solution slightly promoted alkane biodegradation. The various samples contained 10(10)-10(11) oil-utilizing bacteria/g soil, predominantly Bacillus, Pseudomonas, Rhodococcus and Streptomyces. Oil-utilizing fungi were much less frequent and were predominantly Aspergillus and Penicillium species. The microbial numbers varied not only according to the type of soil management but also to the season.     

Assessing the physical and architectural features of sheltered care settings

The Physical and Architectural Features Checklist (PaF) measures the physical resources of sheltered care settings in terms of nine conceptually unified and empirically derived dimensions. The development of the PAF is described, and psychometric characteristics, based on data from 93 representative facilities, are presented. These data show that facilities which have more physical resources are seen as attractive by outside observers and pleasant by residents. Larger facilities are more likely to provide barrier-free environments, more flexible physical settings, and more staff facilities. Cost is not related to any PAF dimension; however, nonprofit facilities score higher on several dimensions than do proprietary facilities. Richer physical settings tend to offer residents more policy resources. They are more selective, provide more privacy, allow residents a higher degree of influence and choice, and have clearer policies. Sample profiles illustrate the usefulness of this instrument for describing and comparing facilities; additional uses are discussed.