pKa-critical Interpretations of Solubility–pH Profiles: PG-300995 and NSC-639829 Case Studies

Two weak bases, PG-300995 (anti-HIV agent) and NSC-639829 (anti-tumor agent), whose log S – pH profiles had been previously published, but whose pKa values had not been reported, were analyzed using a method which can determine pKa values from log S – pH data. This “SpH-pKa” technique, although often practiced, can result in inaccurate pKa values, for a variety of reasons. The operational SpH-pKa values were compared to those predicted by MarvinSketch (ChemAxon), ADMET Predictor (Simulation Plus), and ACD/Percepta (ACD/Labs). The agreement for the sparingly-soluble PG-300995 was reasonably good. However, a substantial difference was found for the practically-insoluble NSC-639829. To probe this further, the pKa of NSC-639829 was measured by an independent spectrophotometric cosolvent technique. The log S - pH profile of NSC-639829 was then re-analyzed with the independently-measured pKa. It was found that the equilibrium model which best fit the solubility data is consistent with the presence of a monocationic NSC-639829 dimeric species below pH 4. This illustrates that an independently-determined accurate pKa is critical to mechanistic interpretations of solubility-pH data. Apparently, the Henderson-Hasselbalch equation holds for PG-300995, but not NSC-639829

Shoreline Evolution Chesapeake Bay Shoreline Northampton County, VA

Shoreline evolution is the change in shore position through time. In fact, it is the material resistance of the coastal geologic underpinnings against the impinging hydrodynamic (and aerodynamic) forces. Along the shores of the Chesapeake Bay, it is a process-based response system. The processes at work include winds, waves, tides, and currents, which together provide the energy which shapes and modifies coastlines by eroding, transporting, and depositing sediments. The shore line is commonly plotted and measured to provide a rate of change, but it is as important to understand the geomorphic patterns of change. Shore analysis provides the basis to know how a particular coast has changed through time and how it may proceed in the future. The purpose of this report is to document how the Bay shore of Northampton County, Virginia (Figure 1) has evolved since 1938. Aerial imagery was taken for most of the Bay region beginning that year, and it is this imagery that allows one to assess the geomorphic nature of shore change. Aerial imagery shows how the nature of the coast has changed, how beaches, dunes, bars, and spits have grown or decayed, how barriers have breached, how inlets have changed course, and how one shore type has displaced another or has not changed at all. Shore change is a natural process but, quite often, the impacts of man through shore hardening or inlet stabilization come to dominate a given shore reach. Most of the shore positions will be quantified in this report. Others, particularly very irregular coasts, around inlets, and other areas will be subject to interpretation

Shoreline evolution, Chesapeake Bay shoreline, City of Virginia Beach, Virginia

Shoreline evolution is the change in shore position through time. In fact, it is the material resistance of the coastal geologic underpinnings against the impinging hydrodynamic (and aerodynamic) forces. Along the shores of Chesapeake Bay, it is a process-response system. The processes at work include winds, waves, tides and currents, which shape and modify coastlines by eroding, transporting and depositing sediments. The shore line is commonly plotted and measured to provide a rate of change but it is as important to understand the geomorphic patterns of change. Shore analysis provides the basis to know how a particular coast has changed through time and how it might proceed in the future. The purpose of this report is to document how the Bay shore of Virginia Beach (Figure 1) has evolved since 1937. Aerial imagery was taken for most of the Bay region beginning that year, and it is this imagery that allows one to assess the geomorphic nature of shore change. Aerial imagery shows how the nature of the coast has changed, how beaches, dunes, bars, and spits have grown or decayed, how barriers have breached, how inlets have changed course, and how one shore type has displaced another or has not changed at all. Shore change is a natural process but, quite often, the impacts of man through shore hardening or inlet stabilization come to dominate a given shore reach. Most of the change in shore positions will be quantified in this report. Others, particularly very irregular coasts, around inlets, and other areas will be subject to interpretation

Shoreline Evolution Chesapeake Bay Shoreline City of Norfolk, VA

Shoreline evolution is the change in shore position through time. In fact, it is the material resistance of the coastal geologic underpinnings against the impinging hydrodynamic (and aerodynamic) forces. Along the shores of Chesapeake Bay, it is a process-response system. The processes at work include winds, waves, tides and currents, which together shape and modify coastlines by eroding, transporting and depositing sediments. The shore line is commonly plotted and measured to provide a rate of change, but it is as important to understand the geomorphic patterns of change. Shore analysis provides the basis to know how a particular coast has changed through time and how it might proceed in the future. The purpose of this report is to document how the Chesapeake Bay shore of Norfolk (Figure 1) has evolved since 1937. This is the first year that aerial imagery was taken for most of the Bay region, and it is this imagery that allows one to assess the geomorphic nature of shore change. Aerial imagery shows how the nature of the coast has changed, how beaches, dunes, bars and spits have grown or decayed, how barriers have breached, how inlets have changed course and how one shore type has displaced another or has not changed at all. Shore change is a natural process but, quite often, the impacts of man through shore hardening, beach nourishment or inlet stabilization will come to dominate a given shore reach. Most of the change in shore positions will be quantified in this report. Others, particularly around inlets and very irregular coasts, will be interpreted