As the evidence for the myogenic response has become more substantial over the years, questions have been raised as to the underlying mechanism. On the one hand, it is well known that when smooth muscle is stretched it will respond by contracting. However, the behavior that is observed goes well beyond a simple transient response to stretch, because, in the steady state, the vessel is smaller with higher intravascular pressure. How can a vessel maintain the smaller diameter if the stimulus is stretch of the smooth muscle cells? Two ways are discussed. Sensitivity of the vessels to blood flow was observed. There may be an interaction between pressure-dependent and flow-dependent mechanisms such that the reaction of the pressure-dependent mechanism would be modulated somewhat by the flow sensitivity of the arteriole. If the myogenic mechanism were weak, it would be augmented, and, if it were strong, it would be attenuated by the flow-dependent mechanism. The 2 mechanisms may act in combination to give a reasonably constant flow through an organ, although the basic mechanism might be a myogenic response with the fine tuning, so to speak, carried out by the flow-dependent mechanism. Microscopic studies provide evidence in favor of the myogenic hypothesis.
Rencang Bu
Hong S. He
Yuanman Hu
Yu Chang
David. R. Larsen
The Small Khingan Mountains in northeastern China provide most of the timber and wood products in the country. Evaluating the long-term effects of harvesting and planting strategies is important especially as the climate changes. In this study, we evaluated the effects of the projected climate warming on potential changes in species’ coverage (percent cover), area harvested (percentage of the study area) and species harvested, using the LANDIS model. Our evaluation was based on the harvest and planting plans specified in Natural Forest Protection Project (NFPP). Our simulated results show that the coverage of southern species such as Korean pine (Pinus koraiensis) and ribbed birch (Betula costata) increases, whereas the coverage of northern species like larch (Larix gmelinii), Kingan fir (Abies nephrolepis), spruces (Picea koraiensis and P. jezoensis) and Dahur birch (Betula davurica) decreases under the warming climate in the region. The species harvested primarily consist of the southern species, especially deciduous species under the warming climate. The warming climate leads to 11.2%increase in area harvested compared to that under the current climate, when planting is not simulated. When planting is simulated, tradeoffs between planting and area harvested are complex. The area harvested only increases in places where moderate planting is implemented, and decreases in places with both low (≤5%area planted) and high (≥30%) planting percentage. This is because when the planting percentage is low, the rate of increase of harvestable species due to planting is lower than the rate of decrease of warming-declining species. When the planting percentage is high, the rate of increase of planted species is higher than the rate of colonization of warming-adapted deciduous species, and the planted species delay the establishment of the warming-adaptable species that have short harvest rotations (due to lower harvestable ages). Our results suggest that the management strategy with planting area of 20%is the best among all the scenarios simulated. Under this warming climate, moderate planting area (e.g. 20%) increases the area harvested to about 43%, which is still less than that (58%) designated in the NFPP. These results have important implications for forest managers designing sustainable forest harvest and reforestation strategies for the landscape under the warming climate.
A composition comprising a homopolymer or a copolymer comprising bithiophene units for use in, for example, low band gap materials including uses in organic photovoltaic active layers. The band gap and other properties can be engineered by polymerization methods including selection of monomer structure and ratio of monomer components. In addition, a dimer adapted for making alternating copolymers further comprising one first monomer moiety comprising at least one bithiophene moiety compound covalently linked to one second monomer moiety comprising a different bithiophene moiety or at least one moiety that is not a bithiophene. The composition can be copolymerized to form an alternating copolymer that can be further processed to form a polymeric film used in a printed organic electronic device. A series of novel copolymers are designed that would allow fabrication of materials with tailor made electronic and/or mechanical properties that can be easily manipulated through molecules chemical structure and potentially result in long term stability under ambient conditions that can be advantageous for use in organic electronics (e.g., OPVs, OLEDs, OFETs). Improved methods are disclosed for making monomers comprising a benzo[2,1-b:3,4-b′]dithiophene moiety that are useful as electronics materials.
A fracturing system for wells has a propellant charge having a known surface area for combustion, and a combustion rate as a function of pressure with lower combustion rates at lower pressures and rapidly increasing combustion rates at higher pressures separated by a knee in the combustion rate function. The propellant charge is initially sealed within a vessel as it is inserted into a well. The system also includes means for creating openings in the vessel on ignition of the propellant charge in the well, such that the openings have a known combined flow area selected to create a condition of choked flow of combustion gases from within the vessel and maintain pressures within the vessel below the knee in the combustion rate function.
Variation of a parameter of interest is reduced over a field of interest in, for example, an object design, such as a circuit design. The field of interest is divided into tiles. A parameter value is found for each tile and for a group of tiles around each tile. Using these values, variation of the parameter is determined. An adjusted value of the parameter for each tile is determined taking limits into account, iterating until variation is below a threshold value. Parameter uniformity is improved in some applications by over 30% with runtime reduced by an order of magnitude.
A sensor configured to detect exhaust gas temperature of an exhaust, the sensor including a housing and a sensing element at least partially disposed within the housing. A filler material, including a first media and at least one additional media, is disposed within the housing and at least partially surrounds the sensing element. The first media is configured to be stable in reducing atmospheres up to 800° C. and in oxidizing atmospheres up to 850° C. and the second media is configured to provide oxygen storage capacity and enhance chemical stability and/or oxygen entrapment.