In this paper, we focus on the implementation and verification of an extended Boussinesq model for surf zone hydrodynamics in two horizontal dimensions. The time-domain numerical model is based on the fully nonlinear Boussinesq equations. As described in Part I of this two-part paper, the energy dissipation due to wave breaking is modeled by introducing an eddy viscosity term into the momentum equations, with the viscosity strongly localized on the front face of the breaking waves. Wave runup on the beach is simulated using a permeable-seabed technique. We apply the model to simulate two laboratory experiments in large wave basins. They are wave transformation and breaking over a submerged circular shoal and solitary wave runup on a conical island. Satisfactory agreement is found between the numerical results and the laboratory measurements.

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SummaryBackground and objectives Severe hyponatremia (Ͻ120 mEq/L) in hospitalized patients has a high mortality rate. We hypothesized that underlying diseases causing hyponatremia attribute to mortality rather than hyponatremia itself. Design, setting, participants, & measurementsThe relationship between mortality and serum sodium (sNa) was examined in 45,693 patients admitted to a single community teaching hospital between January 1996 and December 2007. We conducted a comprehensive retrospective review of the medical records of 53 patients who died after developing sNa Ͻ120 mEq/L before or after admission and of 32 patients who survived after developing sNa Ͻ110 mEq/L.Results Mortality rates tended to increase as the sNa fell from 134 to 120 mEq/L, rising above 10% for patients with sNa of 120 to 124 mEq/L. However, below sNa of 120 mEq/L, the trend reversed, such that the mortality rate progressively decreased as sNa fell. More than two thirds of patients who died after sNa Ͻ120mEq/L had at least two additional acute severe progressive illnesses, most commonly sepsis and multiorgan failure. Three deaths (5.6%) in 12 years could plausibly be related to adverse consequences of hyponatremia, and one (1.8% of the fatal cases and 0.15% of all patients with sNa Ͻ120 mEq/L) was from cerebral edema. Most patients who survived with sNa Ͻ110 mEq/L had medication-induced hyponatremia. Severe underlying illnesses were uncommon in this group. ConclusionsThe nature of underlying illness rather than the severity of hyponatremia best explains mortality associated with hyponatremia. Neurologic complications from hyponatremia are uncommon among patients who die with hyponatremia.

[1] In this paper we study the energy dissipation due to current-limited wave breaking in monochromatic and random waves with the help of experimental tests. The opposing currents are strong enough for wave blocking to occur. A modified bore model is used to simulate the dissipation rate in the monochromatic waves, and an empirical bulk dissipation formula for wave breaking in random waves is proposed. The effects of wave blocking on the dynamics of the wave field are also discussed. INDEX TERMS: 4546

Background There is a decreased interest in nephrology such that the number of trainees likely will not meet the upcoming workforce demands posed by the projected number of patients with kidney disease. We conducted a survey of US internal medicine subspecialty fellows in fields other than nephrology to determine why they did not choose nephrology. Methods A web-based survey with multiple choice, yes/no, and open-ended questions was sent in summer 2011 to trainees reached through internal medicine subspecialty program directors. Results 714 fellows responded to the survey (11% response rate). All non-nephrology internal medicine subspecialties were represented, and 90% of respondents were from university-based programs. Of the respondents, 31% indicated that nephrology was the most difficult physiology course taught in medical school, and 26% had considered nephrology as a career choice. Nearly one-fourth of the respondents said they would have considered nephrology if the field had higher income or the subject were taught well during medical school and residency training. The top reasons for not choosing nephrology were the belief that patients with end-stage renal disease were too complicated, the lack of a mentor, and that there were insufficient procedures in nephrology. Conclusions Most non-nephrology internal medicine subspecialty fellows never considered nephrology as a career choice. A significant proportion were dissuaded by factors such as the challenges of the patient population, lack of role models, lack of procedures, and perceived difficulty of the subject matter. Addressing these factors will require the concerted effort of nephrologists throughout the training community.

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The long-term response of circulation processes to external forcing has been quantified for the Columbia River estuary using in situ data from an existing coastal observatory. Circulation patterns were determined from four Acoustic Doppler Profilers (ADP) and several conductivity-temperature sensors placed in the two main channels. Because of the very strong river discharge, baroclinic processes play a crucial role in the circulation dynamics, and the interaction of the tidal and subtidal baroclinic pressure gradients plays a major role in structuring the velocity field. The input of river flow and the resulting low-frequency flow dynamics in the two channels are quite distinct. Current and salinity data were analyzed on two time scales-subtidal (or residual) and tidal (both diurnal and semidiurnal components). The residual currents in both channels usually showed a classical two-layer baroclinic circulation system with inflow at the bottom and outflow near the surface. However, this two-layer system is transient and breaks down under strong discharge and tidal conditions because of enhanced vertical mixing. Influence of shelf winds on estuarine processes was also observed via the interactions with upwelling and downwelling processes and coastal plume transport. The transient nature of residual inflow affects the long-term transport characteristics of the estuary. Effects of vertical mixing could also be seen at the tidal time scale. Tidal velocities were separated into their diurnal and semidiurnal components using continuous wavelet transforms to account for the nonstationary nature of velocity amplitudes. The vertical structure of velocity amplitudes were considerably altered by baroclinic gradients. This was particularly true for the diurnal components, where tidal asymmetry led to stronger tidal velocities near the bottom.