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Completion Report: Arkansas State Pesticides in Ground Water Monitoring Project Phase V: Vulnerable areas in Jackson, Monroe, Lawrence and Lonoke Counties
In 1996, sixty-seven water samples were drawn from 65 wells, including 62 new wells and 3 wells sampled previously . One Woodruff County well and two Pulaski County wells were resampled. Thirty-two samples were drawn from 30 wells in Monroe County (well #1 was sampled 3 times during this phase) . Ten wells in Jackson County, 12 wells in Lawrence County and 10 wells in Lonoke were also tested (Figures 1-5) . With the completion of Phase V, the number of wells tested has risen to 231 with a total of 258 samples analyzed . Initially, the wells were tested for 13 pesticides and ni~rate. Two more pesticides, aldicarb and carbofuran were added to the analyte list during Phase V. The analyte list is shown in Table 3 . All results from all the wells are listed in Appendix A. Quality control information for these data follow the results. The Phase V Quality Assurance Report is included in this document as Part II
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.
Bacterial Quality of Private Water Wells in Clark County, Arkansas
Most private water wells in Clark County appeared to be contaminated by bacteria, apparently entering the wells from surface water seepage. Eighteen to 24% of the wells investigated were positive for fecal contamination. Deeper wells were less often contaminated. More than one-half of the wells sampled exceeded recommended limits of inorganic chemicals for safe potable water. High concentrations of iron and manganese were most common, exceeding recommended limits in more than 40% of the well
Analysis of the gain distribution across the active region of InGaAs-InAlGaAs multiple quantum well lasers
Spectral gain measurements for two InGaAs-InAlGaAs multiple width quantum well structures, with inverse-configured active regions, have been presented. One structure consisted of wide quantum wells near the p-side and narrow quantum wells near the n-side of the active region. The other structure consisted of narrow quantum wells near the p-side of the active region with wider quantum wells near the n-side. It is shown that, for the same operating conditions, the structure with wide quantum wells on the p-side of the active region provided a 15% broader gain spectrum in comparison to the structure with narrow quantum wells on the p-side of the active region. The analysis of the results shows non-uniform carrier distribution across the active region of the structures, where the structure with wide quantum wells near the p-side of the active region provided 65% more gain in comparison to the structure with narrow quantum wells near the p-side of the active region. The gain distribution results have been compared with that obtained for the phosphorous quaternary structures in other literature and have shown there is some evidence to suggest that the gain distribution is more uniform in aluminium quaternary than phosphorous quaternary material
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.
Hole spin relaxation in -type (111) GaAs quantum wells
Hole spin relaxation in -type (111) GaAs quantum wells is investigated in
the case with only the lowest hole subband, which is heavy-hole like in (111)
GaAs/AlAs and light-hole like in (111) GaAs/InP quantum wells, being relevant.
The subband L\"{o}wdin perturbation method is applied to obtain the effective
Hamiltonian including the Dresselhaus and Rashba spin-orbit couplings. Under a
proper gate voltage, the total in-plane effective magnetic field in (111)
GaAs/AlAs quantum wells can be strongly suppressed in the whole momentum space,
while the one in (111) GaAs/InP quantum wells can be suppressed only on a
special momentum circle. The hole spin relaxation due to the D'yakonov-Perel'
and Elliott-Yafet mechanisms is calculated by means of the fully microscopic
kinetic spin Bloch equation approach with all the relevant scatterings
explicitly included. For (111) GaAs/AlAs quantum wells, extremely long
heavy-hole spin relaxation time (upto hundreds of nanoseconds) is predicted. In
addition, we predict a pronounced peak in the gate-voltage dependence of the
heavy-hole spin relaxation time due to the D'yakonov-Perel' mechanism. This
peak origins from the suppression of the unique inhomogeneous broadening in
(111) GaAs/AlAs quantum wells. Moreover, the Elliott-Yafet mechanism influences
the spin relaxation only around the peak area due to the small spin mixing
between the heavy and light holes in quantum wells with small well width. We
also show the anisotropy of the spin relaxation. In (111) GaAs/InP quantum
wells, a mild peak, similar to the case for electrons in (111) GaAs quantum
wells, is also predicted in the gate-voltage dependence of the light-hole spin
relaxation time. The contribution of the Elliott-Yafet mechanism is always
negligible in this case.Comment: 9 pages, 4 figure
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