Sverdrup (1953. On conditions for the vernal blooming of phytoplankton. Journal du Conseil International pour l'Exploration de la Mer, 18: 287-295) was quite careful in formulating his critical depth hypothesis, specifying a "thoroughly mixed top layer" with mixing "strong enough to distribute the plankton organisms evenly through the layer". With a few notable exceptions, most subsequent tests of the critical depth hypothesis have ignored those assumptions, using estimates of a hydrographically defined mixed-layer depth as a proxy for the actual turbulence-driven movement of the phytoplankton. However, a closer examination of the sources of turbulence and stratification in turbulent layers shows that active turbulence is highly variable over time scales of hours, vertical scales of metres, and horizontal scales of kilometres. Furthermore, the mixed layer as defined by temperature or density gradients is a poor indicator of the depth or intensity of active turbulence. Without time series of coincident, in situ measurements of turbulence and phytoplankton rates, it is not possible to properly test Sverdrup's critical depth hypothesis.

Background: A characterization of an organism's thermoregulatory ability informs our understanding of its physiology, ecology and behavior. Biotelemetry studies on thermoregulation increasingly rely on in situ body temperature measurements from surgically implanted data loggers. To protect the organism and the instrument, the electronics and the temperature sensor are often encased in non-conductive materials prior to insertion into the organism. These materials thermally insulate the sensor, thus potentially biasing temperature measurements to suggest a greater degree of thermoregulation than is actually the case. Results: Here we present methodology to quantify and correct for the effect of sensor coatings on temperature measurements by data recording tags. We illustrate these methods using Wildlife Computer's Mk9 archival tag, field data from the peritoneal cavity of a juvenile albacore tuna (Thunnus alalunga) and simulated data of several species of ectotherms (fish: Hemitripterus americanus, Catostomus commersoni and Maxostoma macrolepidotum; reptiles: Macroclemys temminckii, Varanus spp.), ranging in size from 10 to 1000 g. Mk9 tags had rate constants (measures of the sensor's ability to respond to changes in temperature) of 1.79 ± 0.06 and 0.81 ± 0.07 min-1 for the external and internal sensors, respectively. The higher rate constant of the external sensor produced smaller errors than the internal sensor. Yet, both sensors produced instantaneous errors of over 1 °C for all species tested, with the exception of T. alalunga. Conclusions: The effect of sensor coatings on body temperature measurements is shown to depend on the relative values of the sensor's and the organism's rate constant and the rate of change of environmental temperature. If the sensor's rate constant is lower than that of the organism, the temperature measurements will reflect the thermal properties of the sensor rather than the organism.

Background

Obese workers incur greater health care costs than normal weight workers. Possibly viewed by employers as an increased financial risk, they may be at a disadvantage in procuring employment that provides health insurance. This study aims to evaluate the association between body mass index [BMI, weight in kilograms divided by the square of height in meters] of employees and their likelihood of holding jobs that include employment-based health insurance [EBHI].

Methods

We used the 2004 Household Components of the nationally representative Medical Expenditure Panel Survey. We utilized logistic regression models with provision of EBHI as the dependent variable in this descriptive analysis. The key independent variable was BMI, with adjustments for the domains of demographics, social-economic status, workplace/job characteristics, and health behavior/status. BMI was classified as normal weight (18.5-24.9), overweight (25.0-29.9), or obese (> or = 30.0). There were 11,833 eligible respondents in the analysis.

Results

Among employed adults, obese workers [adjusted probability (AP) = 0.62, (0.60, 0.65)] (P = 0.005) were more likely to be employed in jobs with EBHI than their normal weight counterparts [AP = 0.57, (0.55, 0.60)]. Overweight workers were also more likely to hold jobs with EBHI than normal weight workers, but the difference did not reach statistical significance [AP = 0.61 (0.58, 0.63)] (P = 0.052). There were no interaction effects between BMI and gender or age.

Conclusion

In this nationally representative sample, we detected an association between workers' increasing BMI and their likelihood of being employed in positions that include EBHI. These findings suggest that obese workers are more likely to have EBHI than other workers.

Interventions tailored to psychological factors such as personal and vicarious behavioral experiences can enhance behavioral self-efficacy but are complex to develop and implement. Information seeking theory suggests tailoring acquisition of health knowledge (without concurrent psychological factor tailoring) could enhance self-efficacy, simplifying the design of tailored behavior change interventions. To begin to examine this issue, the authors conducted exploratory analyses of data from a randomized controlled trial, comparing the effects of an experimental colorectal cancer screening intervention tailoring knowledge acquisition with the effects of a nontailored control on colorectal cancer screening knowledge and self-efficacy in 1159 patients comprising three ethnicity/language strata (Hispanic/Spanish, 23.4%, Hispanic/English, 27.2%, non-Hispanic/English, 49.3%) and 5 recruitment center strata. Adjusted for study strata, the mean postintervention knowledge score was significantly higher in the experimental group than in the control group. Adjusted experimental intervention exposure (B = 0.22, 95% CI [0.14, 0.30]), preintervention knowledge (B = 0.11, 95% CI [0.05, 0.16]), and postintervention knowledge (B = 0.03, 95% CI [0.01, 0.05]) were independently associated with subsequent colorectal cancer screening self-efficacy (p < .001 all associations). These exploratory findings suggest that tailoring knowledge acquisition may enhance self-efficacy, with potential implications for tailored intervention design, but this implication requires confirmation in studies specifically designed to examine this issue.

Locally enhanced biological production and increased carbon export are persistent features at oceanic density fronts. Studies often assume biological properties are uniform along fronts or hypothesize that along- and across-front gradients reflect physical-biological processes occurring in the front. However, the residence times of waters in fronts are often shorter than biological response times. Thus, an alternate—often untested—hypothesis is that observed biological patchiness originates upstream of a front. To test these two hypotheses, we explore an eddy-associated front in the California Current System sampled during two surveys, separated by 3 weeks. Patches of high phytoplankton biomass were found at the northern ends of both surveys, and phytoplankton biomass decreased along the front. While these patches occurred in similar locations, it was unclear whether the same patch was sampled twice, or whether the two patches were different. Using an advection-reaction framework combined with field and satellite data, we found that variations in along-front gradients in dissolved oxygen, particle biovolume, and salinity support the conclusion that the two phytoplankton patches were different. They were only coincidentally sampled in similar locations. Backward- and forward-in-time tracking of water parcels showed that these phytoplankton patches had distinct origins, associated with specific, strong coastal upwelling pulses upstream of the front. Phytoplankton grew in these recently upwelled waters as they advected into and along the frontal system. By considering both local and upstream physical-biological forcings, this approach enables better characterizations of critical physical and biogeochemical processes that occur at fronts across spatial and temporal scales.

Objective

CRC screening interventions tailored to the Expanded Health Belief Model (EHBM) socio-psychological factors have been developed, but the contributions of individual factors to screening outcomes are unclear.

Methods

In observational analyses of data from a randomized intervention trial, we examined the independent associations of five EHBM factors - CRC screening knowledge, self-efficacy, stage of readiness, barriers, and discussion with a provider - with objectively measured CRC screening after one year.

Results

When all five factors were added simultaneously to a base model including other patient and visit characteristics, three of the factors were associated with CRC screening: self-efficacy (OR=1.32, p=0.001), readiness (OR=2.72, p<0.001), and discussion of screening with a provider (OR=1.59, p=0.009). Knowledge and barriers were not independently associated with screening. Adding the five socio-psychological factors to the base model improved prediction of CRC screening (area under the curve) by 7.7%.

Conclusion

Patient CRC screening self-efficacy, readiness, and discussion with a provider each independently predicted subsequent screening.

Practice implications

Self-efficacy and readiness measures might be helpful in parsimoniously predicting which patients are most likely to engage in CRC screening. The importance of screening discussion with a provider suggests the potential value of augmenting patient-focused EHBM-tailored interventions with provider-focused elements.

A key goal in understanding the ocean's biogeochemical state is estimation of rates of change of critical tracers, particularly components of the planktonic ecosystem. Unfortunately, because ship survey data are not synoptic, it is difficult to obtain spatially resolved estimates of the rates of change of tracers sampled in a moving fluid. Here we present a pseudo-Lagrangian transformation to remap data from underway surveys to a pseudo-synoptic view. The method utilizes geostrophic velocities to back advect and relocate sampling positions, removing advection aliasing. This algorithm produces a map of true relative sampling locations, and allows for determination of the relative locations of observations acquired along streamlines, as well as a corrected view of the tracer's spatial gradients. We then use a forward advection scheme to estimate the tracer's relative change along streamlines, and use these to calculate spatially resolved, net specific rates of change. Application of this technique to Chlorophyll-a (Chl-a) fluorescence data around an ocean front is presented. We obtain 156 individual estimates of Chl-a fluorescence net specific rate of change, covering ∼1200 km2. After incorporating a diffusion-like model to estimate error, the method shows that the majority of observations (64%) were significantly negative. This pseudo-Lagrangian approach generates more accurate spatial maps than raw survey data, and allows spatially resolved estimates of net rates of tracer change. Such estimates can be used as a rate budget constraint that, in conjunction with standard rate measurements, will better determine biogeochemical fluxes.