Pressure probe measurements have been interpreted as showing that xylem pressures below c. -0-4MPa do not exist and that pressure chamber measurements of lower negative pressures are invalid. We present new evidence supporting the pressure chamber technique and the existence of xylem pressures well below -0-4 MPa. We deduced xylem pressures in water-stressed stem xylem from the following experi...

BACKGROUND Many studies have shown a consistent association between ambient air pollution and an increase in death due to cardiovascular causes. An increase in blood pressure is a common risk factor for a variety of cardiovascular diseases. However, the association between air pollution and blood pressure has not been evaluated extensively. METHODS In this cross-sectional study, we measured b...

The unidirectional flow through the gas-exchanging bronchi of bird lungs is known to be effected by (1) the structure of the major bronchi and (2) a pressure difference between the cranial and caudal air sacs. To study the effects of bronchial structure, simple physical models of bird lungs were constructed. They suggested that, to achieve unidirectional flow, air in the caudal portion of the p...

The air separation plays an extremely important role in the development of metallurgical industry. And the air compressor which provides not only the required pressure air for the cooling equipment and refrigeration plant but also the raw material required for the separation plant is a key device in the air separation plant. Utilization of the air compressor is extremely extensive in many signi...

Frost is one of the atmospheric phenomena which seriously threaten crop production. It also causes numerousaccidents in mountainous roads. In this research the Spatial Synoptic Classification SSC method was employed toclassify the type of air masses. For the classification, such meteorological data as: temperature, dew point, mean sealevel pressure, cloudiness, direction and speed of wind were ...

A portable wiltmeter instrument to estimate leaf turgor pressure according to an adaptation of the flattening method was developed. In the instrument, a flexible inflating membrane presses the leaf against a flattening plate having small orifices surrounded by a finely engraved network of obtuse indentations through which air flow is delivered. During a measurement, as the compression builds up...

To determine the effect of perfluorocarbon (PFC) hemodilution on myocardial vessel capacity to autoregulate, circumflex coronary artery pressure-flow relations were studied in anesthetized dogs under three conditions: maximal vasodilatation before and after PFC; autoregulation before and after PFC with 100% oxygen supplemented with room air ventilation, and autoregulation with PFC hemodilution ...

The interaction of sensory stressors with the cardiovascular response to blood loss has not been studied. The cardiovascular response to a stressor (i.e., the defense reaction) includes increased skeletal muscle blood flow and perhaps a reduction in arterial baroreflex function. Arterial pressure maintenance during blood loss requires baroreflex-mediated skeletal muscle vasoconstriction. Theref...

BACKGROUND Noninvasive ventilation (NIV) via helmet or total facemask is an option for managing patients with respiratory infections in respiratory failure. However, the risk of nosocomial infection is unknown. METHODS We examined exhaled air dispersion during NIV using a human patient simulator reclined at 45° in a negative pressure room with 12 air changes/h by two different helmets via a v...

Purpose: The purpose of this study was to investigate the effects of two air-abrasive prophylaxis systems and the effect of inlet air pressure on the surface of Brhnemark titanium abutment cylinders. Materials and Methods: Single abutment cylinders were treated with either the Prophy-Jet system (sodium bicarbonate abrasive) (Dentsply International, York, PA) or the Microprophy system (aluminum ...