Including sheath effects in the interpretation of planar retarding potential analyzer's low-energy ion data.

The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector's response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP's density measurement is likely due to simplifications in the SPIS model geometry.

The effect of selective serotonin reuptake inhibitor treatment of panic disorder on emergency room and laboratory resource utilization.

BACKGROUND: While it has been well documented that patients with untreated panic disorder frequently utilize emergency room (ER) and laboratory services, no published data evaluate whether selective serotonin reuptake inhibitor (SSRI) treatment of patients with panic disorder is associated with decreased use of these services in the managed care organization setting. METHOD: A medical and pharmacy claims database representing individuals from several managed care organizations was used to analyze ER and laboratory resource utilization and cost for 120 patients with panic disorder (ICD-9-CM criteria) who received SSRI treatment. RESULTS: SSRI treatment was associated with a reduction in the mean number of ER and laboratory visits and costs in the 6-month period following therapy initiation compared with the 6-month period prior to therapy initiation (sertraline: visits, -79.5%; costs, -85.2%; p < .05; fluoxetine: visits, -25.0%; costs, -69.5%; p = NS; and paroxetine: visits, -8.6%; costs, -30.8%; p = NS). CONCLUSION: The results of the current study suggest that appropriate treatment of panic disorder may decrease unnecessary resource utilization for the medical symptoms associated with panic disorder.

Predictors of response to acute treatment of chronic and double depression with sertraline or imipramine.

BACKGROUND: The literature on predictors of response to treatment of nonchronic major depression has identified shorter duration of illness, acute onset, and less severity of illness as positive predictors. Unfortunately, there are almost no data on predictors of response to treatment for chronic depression. This study examined predictors of response to pharmacotherapy (sertraline or imipramine) in the treatment of outpatients who had DSM-III-R-defined chronic major or double depression. METHOD: The acute phase of the Chronic Major Depression and Double Depression Study is a double-blind, randomized, parallel-group 12-week comparison of sertraline and imipramine. Analyses are based on 623 patients who comprised the intent-to-treat sample, of whom 299 were nonresponders and 324 were responders, defined by a priori criteria as either remission or satisfactory therapeutic response. A stepwise logistic multiple regression analysis was performed on candidate clinical, psychosocial, and demographic variables previously identified as statistically significant in an attempt to develop a predictive model of positive antidepressant response. RESULTS: The sociodemographic variables that were predictive of positive response included living with spouse or partner or being at least a high school graduate. With regard to symptomatology and clinical history, responders had significantly lower baseline depression severity scores. In general, comorbid anxiety, substance abuse, and personality disorders did not influence rates of response. However, the presence of depressive personality traits was associated with a higher nonresponse rate. Among psychosocial variables, longer duration of personal relationships as well as higher baseline quality of life were associated with positive response. A stepwise logistic multiple regression identified 5 variables-living with spouse or partner, higher educational level, passive-aggressive personality, lower introverted-tense personality traits, and higher quality of life--that significantly and independently contributed to the predictive model. This model correctly classified 67% of patients. CONCLUSION: A higher baseline quality of life, living with spouse or partner, and having more education were the strongest predictors of response to acute pharmacotherapy among chronically depressed patients. Clinical variables and comorbidity were not identified as independent predictors, although personality traits did appear to influence treatment response. Overall, the predictive value of these baseline measures was modest, and therefore of limited clinical utility.

The treatment of chronic depression, part 1: study design and rationale for evaluating the comparative efficacy of sertraline and imipramine as acute, crossover, continuation, and maintenance phase therapies.

BACKGROUND: Chronic depressions are common, disabling, and undertreated, and prior chronicity predicts future chronicity. However, few studies directly inform the acute or maintenance phase treatments of chronic depressions and even less is known about the effects of treatment on psychosocial functioning. METHOD: We describe the design and rationale for 2 parallel double-blind, randomized, multicenter acute and maintenance phase treatment trials. One focused on DSM-III-R major depression currently in a chronic (> or = 2 years) major depressive episode, the other on DSM-III-R major depression with concurrent DSM-III-R dysthymia ("double depression"). RESULTS: Considering the critical knowledge deficits, we designed a 12-week acute phase safety and efficacy trial of sertraline versus imipramine, followed by a 16-week continuation treatment phase for subjects with a satisfactory therapeutic response. Patients receiving sertraline who successfully completed the continuation phase entered a 76-week maintenance trial to compare sertraline with placebo; those taking imipramine continued without a placebo substitution. As part of the acute trial, subjects completing but failing to respond to the initial 12-week acute phase medication were crossed over (double-blind) to the alternative medication for a 12-week acute phase trial. We obtained naturalistic follow-up data (up to 18 months) for subjects exiting the protocol at any time. CONCLUSION: Multiphase protocols for chronic depression can test efficacy by randomized contrasts as well as shed light on key clinical issues such as the degree of response or attrition expected at particular times in a trial or the preferred medication sequence in a potential multistep treatment program.