Well design as a factor contributing to loss of water from the Floridan Aquifer, eastern Clay County, Florida

A number of wells penetrating the Floridan aquifer in eastern Clay County were found to be losing water to permeable zones above this aquifer. A differential in artesian pressure was observed in closely spaced wells of similar depth. Further investigation. revealed that the pressure differential in the wells was due to the design of the wells, of which there were four principal types. A comparison of the four types of wells in relation to the subsurface geology showed that three types of wells were open to the permeable zones above the Floridan aquifer. In such wells water of relatively high head from the Floridan aquifer moves up through the well bore and out into zones of relatively low head. The estimated water loss from poorly designed wells ranged from 32 to 180 gpm (gallons per minute). The artesian head loss in leaky wells ranged from 3 to 15 feet. A total loss of water of 39 mgd (million gallons per day) was estimated from all the leaky wells in the area. A significant decline of the piezometric surface of the Floridan aquifer was observed in eastern Clay County. Some of this decline can be attributed to the loss of water from the Floridan aquifer through these poorly designed wells. (Document has 16 pages.

Quantum coherence and entanglement induced by the continuum between distant localized states

It is demonstrated that two distant quantum wells separated by a reservoir with a continuous spectrum can possess bound eigenstates embedded in the continuum. These represent a linear superposition of quantum states localized in the wells. We show that such a state can be isolated in the course of free evolution from any initial state by a null-result measurement in the reservoir. The latter might not be necessary in the many-body case. The resulting superposition is regulated by ratio of couplings between the wells and the reservoir. In particular, one can lock the system in one of the wells by enhancing this ratio. By tuning parameters of the quantum wells, many-body entangled states in distant wells can be produced through interactions and statistics.Comment: small modifications, one reference is added, to appear in Phys. Rev.

Auger Recombination in Semiconductor Quantum Wells

The principal mechanisms of Auger recombination of nonequilibrium carriers in semiconductor heterostructures with quantum wells are investigated. It is shown for the first time that there exist three fundamentally different Auger recombination mechanisms of (i) thresholdless, (ii) quasi-threshold, and (iii) threshold types. The rate of the thresholdless Auger process depends on temperature only slightly. The rate of the quasi-threshold Auger process depends on temperature exponentially. However, its threshold energy essentially varies with quantum well width and is close to zero for narrow quantum wells. It is shown that the thresholdless and the quasi-threshold Auger processes dominate in narrow quantum wells, while the threshold and the quasi-threshold processes prevail in wide quantum wells. The limiting case of a three-dimensional (3D)Auger process is reached for infinitely wide quantum wells. The critical quantum well width is found at which the quasi-threshold and threshold Auger processes merge into a single 3D Auger process. Also studied is phonon-assisted Auger recombination in quantum wells. It is shown that for narrow quantum wells the act of phonon emission becomes resonant, which in turn increases substantially the coefficient of phonon-assisted Auger recombination. Conditions are found under which the direct Auger process dominates over the phonon-assisted Auger recombination at various temperatures and quantum well widths.Comment: 38 pages, 7 figure

Subband Engineering Even-Denominator Quantum Hall States

Proposed even-denominator fractional quantum Hall effect (FQHE) states suggest the possibility of excitations with non-Abelian braid statistics. Recent experiments on wide square quantum wells observe even-denominator FQHE even under electrostatic tilt. We theoretically analyze these structures and develop a procedure to accurately test proposed quantum Hall wavefunctions. We find that tilted wells favor partial subband polarization to yield Abelian even-denominator states. Our results show that tilting quantum wells effectively engineers different interaction potentials allowing exploration of a wide variety of even-denominator states