Memphis Metropolitan Area Research Articles

Outcome of surgical resection for pathologic Nx and N0 non-small cell lung cancer (NSCLC)

7513 Background: Metastasis to lymph nodes (LN) connotes poor prognosis in NSCLC. Sufficient LN must be examined to accurately determine LN negativity. Patients with no LN examined (pNx) may be incompletely staged and erroneously assigned to a low risk group. To evaluate this possibility, we compared the survival of patients with node negative disease and at least 1 LN examined (pN0) to those with pNx. Methods: Retrospective analysis of all resections for NSCLC from January 1, 2004 to December 31, 2007 identified through a search of pathology databases at hospitals in the Memphis Metropolitan Area. Benign and metastatic disease, pre-operative chemo/radio therapy, bronchoalveolar cell, small cell lung, carcinoid tumors and repeat lung resection were excluded. Date of death was obtained from a National Death Index search. Variables were compared by chi-squared test, survival estimates calculated by Kaplan Meier analysis, survival estimates compared by log-rank test. Results: 746 of 809 resections met inclusion criteria. 86 (11.5%) were pNx and 510 (68.4%) pN0. Demographic and histologic characteristics were similar ( Table 1 ). 55.8% of the pNx group had sublobar resection, compared to 5.7% of pN0 (p<0.0001). 179 pN0 patients (35.1%) had only hilar-intrapulmonary LN (stations 10–14), median 3 (range 1–18) examined. 46 patients (9.02%) had only mediastinal LN (stations 1–9), median 2 (1–13); 281 patients (55.1%) had both stations 10–14 and 1–9, median 7 (2–45). 85% of pN0 patients had <10 LNs examined. 3-year survival estimate for the T1NxM0 vs T1N0M0 patients was 69% vs 70% (p= 0.14); for T2NxM0 vs T2N0M0 it was 25% vs 65% (p <0.01). Conclusions: A high percentage of patients (11.5%) undergoing surgical resection for NSCLC had pNx. These patients were more likely to have sublobar resections. Most (85%) patients with pN0 had <10 nodes examined and a large proportion (35.1%) had no mediastinal LNs, raising the possibility of understaging. Patients with pT2NxM0 did significantly worse than those with pT2N0M0. [Table: see text] [Table: see text]

The geochemistry and mixing of leakage in a semi-confined aquifer at a municipal well field, Memphis, Tennessee, USA

The Memphis aquifer in southwestern Tennessee is confined to a semi-confined unconsolidated sand aquifer and is the primary municipal water source in the Memphis metropolitan area. Past studies have identified regions in the metropolitan area in which the overlying upper Claiborne confining unit lacks significant clay and provides a hydraulic connection between the shallow aquifer and the Memphis aquifer. In this study, major solute chemistry, 3H, and 3H/ 3He groundwater dating are used to investigate the extent and chemical effects of leakage through the confining unit to the Memphis aquifer in the vicinity of a municipal well field. The 3H/ 3He dates and geochemical modeling of the chemical data are used to constrain mixing fractions and the timing of modern recharge. Tritium activities of as much as 2.8 TU are observed in shallow production wells, but deeper production wells have 3H activities that approach the detection limit. Trends in water chemistry indicate vertical mixing in the aquifer of shallow Na–SO 4–Cl-rich water and deeper Ca–Mg–HCO 3-rich water. Water chemistry does not vary consistently with seasonal pumping, but 3H activity generally decreases during low use periods. Stable O and H isotopes show little variation and are not useful groundwater tracers for this study. The 3H-bearing, Na–SO 4–Cl-rich water is interpreted to reflect recharge of modern water through the upper Claiborne confining unit. The 3H/ 3He dates from 5 production wells indicate modern recharge, that infiltrated 15–20 a ago, is present in the shallow production wells. Geologic data and hydrologic boundary conditions suggest that the most likely source for continued leakage is a nearby stream, Nonconnah Creek. Geochemical reaction modeling using the NETPATH computer code suggests that proportions of shallow aquifer water leaking into the Memphis aquifer range from 6 to 32%. The 3H/ 3He dating and NETPATH modeling results correlate well, suggesting that these complementary analytical tools provide an effective means to evaluate proportions of modern water leaking into semi-confined aquifers. These results also indicate a need to carefully consider connections between surface water and semi-confined groundwater resources in wellhead protection programs.

Microtremor observations of deep sediment resonance in metropolitan Memphis, Tennessee

We measured site resonance periods throughout metropolitan Memphis, Tennessee. The site-resonance was derived from recordings of ambient ‘microtremor’ and is a direct measurement of seismic ground shaking. In the Memphis metropolitan area, the period, T0 (in s) is predicted by the empirical relation T0=−0.39899+7.8922×10−3H−3.0634×10−6H2, [350<H<1100m], where H is the thickness (in m) of the unconsolidated sediments that overly hard Paleozoic rocks. Assuming that a quarter-wavelength relationship governs the relationship between resonant period, sediment thickness, and average shear wave speed, we estimate the average shear wave speed of unconsolidated sediments as a function of sediment thicknesses: Vs=521.15+0.37459H [350<H<1100m]. The scatter in the observations, and discordance with earlier work suggests that caution is warranted in applying these values of wave speed indiscriminately to sites in the absence of further detailed work.