Modified hippocampal long-term potentiation in PKC gamma-mutant mice

Calcium-phospholipid-dependent protein kinase (PKC) has long been suggested to play an important role in modulating synaptic efficacy. We have created a strain of mice that lacks the gamma subtype of PKC to evaluate the significance of this brain-specific PKC isozyme in synaptic plasticity. Mutant mice are viable, develop normally, and have synaptic transmission that is indistinguishable from wild-type mice. Long-term potentiation (LTP), however, is greatly diminished in mutant animals, while two other forms of synaptic plasticity, long-term depression and paired-pulse facilitation, are normal. Surprisingly, when tetanus to evoke LTP was preceded by a low frequency stimulation, mutant animals displayed apparently normal LTP. We propose that PKC gamma is not part of the molecular machinery that produces LTP but is a key regulatory component.     

Continuous measurement of cardiac output by the Fick principle in infants and children: comparison with the thermodilution method

OBJECTIVE: To compare a system that continuously monitors cardiac output by the Fick principle with measurements by the thermodilution technique in pediatric patients. DESIGN: Prospective direct comparison of the above two techniques. SETTING: Pediatric intensive care unit of a university hospital. PATIENTS: 25 infants and children, aged 1 week to 17 years (median 10 months), who had undergone open heart surgery were studied. Only patients without an endotracheal tube leak and without a residual shunt were included. METHODS: The system based on the Fick principle uses measurements of oxygen consumption taken by a metabolic monitor and of arterial and mixed venous oxygen saturation taken by pulse- and fiberoptic oximetry to calculate cardiac output every 20s. INTERVENTIONS: In every patient one pair of measurements was taken. Continuous Fick and thermodilution cardiac output measurements were performed simultaneously, with the examiners remaining ignorant of the results of the other method. RESULTS: Cardiac output measurements ranged from 0.21 to 4.55 l/min. A good correlation coefficient was found: r2 = 0.98; P < 0.001; SEE = 0.41 l/min. The bias is absolute values and in percent of average cardiac output was - 0.05 l/min or - 4.4% with a precision of 0.32 l/min or 21.3% at 2 SD, respectively. The difference was most marked in a neonate with low cardiac output. CONCLUSION: Continuous measurement of cardiac output by the Fick principle offers a convenient method for the hemodynamic monitoring of unstable infants and children.     

Water-Quality Monitoring in Anguilla

Anguilla is a UK overseas (non-independent) territory in the Caribbean. It is a small middle-income island with a population of 13 000, and recent statistics indicate that it is more dependent on tourism than any other country or territory in the world. Rapid population growth and development have placed more emphasis on the need for human health and environmental protection. For the first time, a systematic water-quality monitoring programme has been developed, based on the realities of the local situation, e.g. low resource base, limited capabilities, dependence on household rainwater catchment, storage cisterns, and a poor water-supply network. Development of the programme incorporated the key themes of pragmatic, realistic, incremental, responsive, and consultative approaches.     

Analysis of a stiffener intersection eccentricity in a steel containment

Containment structures have several regions in which the continuity of the cylindrical pressure boundary is interrupted, e.g., shell penetrations, discontinuous stiffeners, and changes in the shell thickness. Significant strain concentrations can occur in these areas of discontinuity. The Sandia National Laboratories 1:8-scale steel containment equipment hatch was analyzed as an example of an eccentricity at a stiffener intersection.A portion of the as-built 1:8-scale model was modeled with the ANSYS general purpose finite element program using triangular, thin shell finite elements. The overall size of the model was determined from Saint-Venant type considerations of the stress field around the hatch. Shell elements were used to model the ring and formed stiffeners. Geometric and material nonlinear behavior were included. The model was loaded using discrete load steps up to a pressure of 165 psig. At this pressure, the maximum strain was 19.7 percent in the formed stiffener near its intersection with the ring stiffener. The finite element solution demonstrated the very localized nature of the strain field near the ring/formed stiffener intersection.In an attempt to reduce analysis costs, a small portion of the 1:8-scale model immediately surrounding the ring/formed stiffener intersection was selected for further analysis. Two smaller models, a ring/formed stiffener intersection and a ring/circular stiffener intersection, were studied. The models were significantly smaller than the regions used previously. A comparison of the two intersection models showed that the circular stiffener is a more efficient configuration.     

Structural characterisation of apatite coatings

The current, most frequently employed, commercial route to produce hydroxyapatite prosthetic coatings is plasma spraying. However, this has several important limitations especially for textured surfaces. Low temperature methods of coating fabrication such as cathodic electrodeposition are attractive alternatives. However, quantitative characterisation of the phase composition of thin electrodeposited coatings can be problematic. An X-ray diffraction method, which provides quantitative compositional information without reference to external or internal standards, is introduced and validated. The method can also be applied when Bragg peaks from the supporting substrate are apparent within the data and preferred orientation can be tolerated. This method has been used to examine in detail the microstructure of electrodeposited coatings which are compared directly with those formed by a commercial plasma spraying process.We show that, unlike the plasma sprayed coatings, the electrodeposited material consists of a single crystalline phase (hydroxyapatite) and a significantly reduced amorphous phase. The electrodeposited coatings also possess significantly more microstrain and a smaller crystallite size than the corresponding plasma sprayed material.     

Characteristics of Milk Powders Produced by Spray Freeze Drying

Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles.     

System requirements for Ka-band Earth-satellite propagation data

Accurate estimates of the propagation impairments that affect link quality and availability and determine signal interference fields are essential for the reliable design of telecommunication systems and the efficient use of the electromagnetic spectrum. Recent announcements by commercial entities of their intent to use Ka-band spectrum to supply satellite services have heightened interest in propagation data and models for these frequencies. This paper provides a brief overview of Ka-band Earth-satellite systems and requirements in relation to the need for specific types of propagation data