A simplified approach to solving finite rough surface scattering problems.

In this paper a simplified approach is described for the computation of scattering from finite length rough surfaces. In an earlier paper [Fawcett, J. Acoust. Soc. 118, 1348-1357 (2005)], it was described how to solve such problems by considering a scattering chamber and using the method of wavefield superposition to satisfy the various boundary and continuity conditions. In this paper, a form of the field in the interior of the scattering chamber is assumed and the solution to the scattering problem is reduced to solving a system of equations just along the rough surface. The solution to this system of equations can then be used to compute the scattered or total fields anywhere in the half-space. The results of this approach are compared to those obtained by other methods.

Using NetMeeting for remote configuration of the Otto Bock C-Leg: technical considerations.

Telehealth has the potential to be a valuable tool for technical and clinical support of computer controlled prosthetic devices. This pilot study examined the use of Internet-based, desktop video conferencing for remote configuration of the Otto Bock C-Leg. Laboratory tests involved connecting two computers running Microsoft NetMeeting over a local area network (IP protocol). Over 56 Kbs(-1), DSL/Cable, and 10 Mbs(-1) LAN speeds, a prosthetist remotely configured a user's C-Leg by using Application Sharing, Live Video, and Live Audio. A similar test between sites in Ottawa and Toronto, Canada was limited by the notebook computer's 28 Kbs(-1) modem. At the 28 Kbs(-1) Internet-connection speed, NetMeeting's application sharing feature was not able to update the remote Sliders window fast enough to display peak toe loads and peak knee angles. These results support the use of NetMeeting as an accessible and cost-effective tool for remote C-Leg configuration, provided that sufficient Internet data transfer speed is available.

Modeling of high-frequency scattering from objects using a hybrid Kirchhoff/diffraction approach.

In this paper a numerical discretization and transformation into the time domain of a hybrid Kirchhoff/diffraction method is presented for the modeling of high-frequency pulse scattering from rigid bodies. A series of benchmark cases, for smooth and rough spheres and cylinders, is presented to establish the accuracy of the method in the time domain.

Scattering from a partially fluid-filled, elastic-shelled sphere.

In this article a sphere is taken to be partially filled with fluid so that its interior is part fluid and part air. A set of basis of functions, based upon an origin at the fluid/air interface, is used for the interior and a set of basis functions based upon the center of the sphere is used for the shell and exterior of the sphere. These sets of basis functions are coupled at the shell/interior interface and the resulting coupled system of equations solved to yield the scattered field. Numerical computations using this approach are presented for varying amounts of fluid-fill and for varying incident plane waves.

Maintenance phase efficacy of sertraline for chronic depression: a randomized controlled trial.

CONTEXT: The chronic form of major depression is associated with a high rate of prevalence and disability, but no controlled research has examined the impact of long-term treatment on the course and burden of illness. OBJECTIVE: To determine if maintenance therapy with sertraline hydrochloride can effectively prevent recurrence of depression in the high-risk group of patients experiencing chronic major depression or major depression with antecedent dysthymic disorder ("double depression"). DESIGN: A 76-week randomized, double-blind, parallel-group study, conducted from September 1993 to November 1996. SETTING: Outpatient psychiatric clinics at 10 academic medical centers and 2 clinical research centers. INTERVENTION: Maintenance treatment with either sertraline hydrochloride (n = 77) in flexible doses up to 200 mg or placebo (n = 84). PATIENTS: A total of 161 outpatients with chronic major or double depression who responded to sertraline in a 12-week, double-blind, acute-phase treatment trial and continued to have a satisfactory therapeutic response during a subsequent 4-month continuation phase. MAIN OUTCOME MEASURE: Time to recurrence of major depression. RESULTS: Sertraline afforded significantly greater prophylaxis against recurrence than did placebo (5 [6%] of 77 in the sertraline group vs 19 [23%] of 84 in the placebo group; P = .002 for the log-rank test of time-to-recurrence distributions). Clinically significant depressive symptoms reemerged in 20 (26%) of 77 patients treated with sertraline vs 42 (50%) of 84 patients who received placebo (P = .001). With use of a Cox proportional hazards model, patients receiving placebo were 4.07 times more likely (95% CI, 1.51-10.95; P = .005) to experience a depression recurrence, after adjustment for study site, type of depression, and randomization strata. CONCLUSIONS: Maintenance therapy with sertraline is well tolerated and has significant efficacy in preventing recurrence or reemergence of depression in chronically depressed patients.

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.

The treatment of chronic depression, part 2: a double-blind, randomized trial of sertraline and imipramine.

BACKGROUND: Chronic depression appears to be a common, frequently disabling illness that is often inadequately treated. Unlike episodic depressions with shorter illness duration, neither acute nor long-term treatment approaches for chronic depression have been well studied. METHOD: 635 outpatients at 12 sites who met DSM-III-R criteria for chronic major depression or double depression were randomly assigned to 12 weeks of double-blind treatment with either sertraline (in daily doses of 50-200 mg) or imipramine (in daily doses of 50-300 mg). Efficacy and safety were assessed either weekly or every 2 weeks during the 12 weeks of acute treatment. RESULTS: Despite high rates of chronicity (mean duration of major depression = 8.9+/-9.1 years; mean duration of dysthymia = 23+/-13 years) and high rates of comorbidity, 52% of patients achieved a satisfactory therapeutic response to sertraline or imipramine (by a conservative, intent-to-treat analysis). Approximately 21% of the patients who had achieved a therapeutic response at week 12 had not done so at week 8, confirming the longer time to response in depressions with high chronicity. Patients treated with sertraline reported significantly fewer adverse events and were significantly less likely to discontinue treatment due to side effects than imipramine-treated patients (6.3% vs. 12.0%). CONCLUSION: These results indicate that patients suffering from depression with high chronicity can achieve a good therapeutic response to acute treatment with either sertraline or imipramine, although sertraline is better tolerated.

Treatment of chronic depression with sertraline or imipramine: preliminary blinded response rates and high rates of undertreatment in the community.

Despite the prevalence of chronic depression and its associated morbidity, there has been little systematic study of pharmacotherapy for this disorder. In this article, we report a preliminary analysis of the first 12-week phase of a multicenter clinical trial that will eventually include approximately 635 patients in acute, continuation, crossover, and maintenance studies of sertraline, a selective serotonin reuptake inhibitor (SSRI), and imipramine, a tricyclic antidepressant, for the treatment of chronic depression. Of the first 212 patients to enter the study, 168 completed all 12 weeks; of these, 61.3 percent were responders, including 58.9 percent of the 73 patients with chronic major depression and 63.2 percent of the 95 patients with double depression. Only 26.8 percent of the 198 patients for whom such data were available had ever had an adequate trial of an antidepressant medication, defined as 150 mg/day of imipramine or its equivalent taken for at least 4 consecutive weeks. In general, demographic and diagnostic characteristics were more similar than different for patients with chronic major and double depression. However, comorbid generalized anxiety disorder was significantly more common in patients with chronic major depression (11.2% threshold for chronic versus 4.9% threshold for double depression, p = .02). The results of this study provide preliminary evidence of the responsiveness of patients with chronic major or double depression to an SSRI or a tricyclic antidepressant.

Interactions of risk factors in predicting suicide.

The authors examined interactions among risk factors for suicide, a strategy not typically followed in suicide research. Their results suggest an explanation for gender differences in suicide rates and qualifications in the relationship between hopelessness and suicide based on history of drug and alcohol abuse.

Concordance of symptoms in recurrent depressive episodes.

The presence or absence of 12 depressive symptoms was examined in 93 bipolar and 108 unipolar patients who had two discrete episodes of major depression over a 5-year period. For each symptom the concordance of its presence or absence across episodes was low. The agreement observed was largely that to be expected by chance. A substantial amount of concordance was obtained if differences in episode intensity (propensity to have symptoms) were taken into account. This suggests that although there may be factors related to depression which remain stable across episodes, symptom presentation is moderated by other factors, such as intensity, which vary from episode to episode.

Sex differences in the lifetime prevalence of depression: does varying the diagnostic criteria reduce the female/male ratio?

Most studies report the lifetime prevalence of major depressive disorder to be higher among women than men. One possible explanation is that this finding is the result of the diagnostic criteria used, in particular the inclusion of criterion symptoms associated with depressed mood. The number of criterion symptoms required for a diagnosis were varied and applied to 2163 first-degree relatives of affectively disordered probands of the NIMH Collaborative Study of the Psychobiology of Depression. Results indicated that differences between men and women in number of symptoms reported could not account for the difference in rates of depression. Women had a greater number of associated symptoms only at higher symptom levels, suggesting an excess of women only above a diagnostic threshold. Thus, findings supported a true difference in rates of major depressive disorder rather than a general trend for women to remember or report more criterion symptoms.

Lack of stability of the RDC endogenous subtype in consecutive episodes of major depression.

The stability of the endogenous subtype of major depressive disorder was examined within individuals across consecutive episodes. The subjects were 119 probands from the NIMH Collaborative Depression Study who experienced at least two episodes of unipolar major depressive disorder within a two-year period of biannual evaluations. Structured data collection methods and Research Diagnostic Criteria were employed. The inter-episode stability of subtype diagnosis was low, never producing a kappa of greater than 0.25. This result was not attributable to threshold for diagnosis, time between episodes, differences in severity, or changes in raters.

Urinary MHPG excretion and treatment with desipramine or amitriptyline: prediction of response, effect of treatment, and methodological hazards.

Urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) excretion was measured in 49 unipolar depressed outpatients to examine the relationship between pretreatment MHPG levels and therapeutic response to desipramine and amitriptyline and to determine the effects of these agents on MHPG excretion. Pretreatment MHPG excretion was greater in amitriptyline responders than amitriptyline nonresponders, but no different in desipramine responders compared to desipramine nonresponders. Pretreatment MHPG excretion did not differentiate desipramine from amitriptyline responders. Treatment for 3 weeks was associated with a decrement in MHPG excretion, particularly in the desipramine responders and combined desipramine and amitriptyline responders. Among patients within the postulated optimal desipramine plasma level range and patients with plasma amitriptyline plus nortriptyline levels greater than 70 ng/ml, high pretreatment MHPG excretion predicted therapeutic response and response was accompanied by a reduction in MHPG excretion. The interpretation of these findings is possibly confounded by the demonstration of a poor correlation (r = 0.61) between duplicate MHPG samples analyzed by a widely employed gas chromatography method and a gas chromatography/mass spectrometry technique. The methodological pitfalls encountered in the course of this investigation and their possible implications for similar studies are discussed.

Treatment received by depressed patients.

We report on the treatment received by 217 patients in the community with a diagnosis of major depressive disorder of at least one month's duration. Only a low proportion of subjects received intensive treatment with antidepressant medication or electroconvulsive therapy, as judged by research standards and current clinical teaching. Specific associations emerge between treatment and several clinical, sociodemographic, and diagnostic variables; however, taken together these variables account for only a small fraction of the variance in treatment received. Even among patient subgroups based on severity and long duration of illness, high proportions did not receive adequate therapeutic trials. Substantial differences are found in treatment across community centers that are not attributable to variation in the clinical characteristics of patients. We conclude that more research is needed to determine how patients and practitioners contribute to this phenomenon of low intensity of somatic treatment.

Alprazolam: pharmacokinetics, clinical efficacy, and mechanism of action.

Alprazolam, a triazolobenzodiazepine, is the first of this new class of benzodiazepine drugs to be marketed in the United States and Canada. It achieves peak serum levels in 0.7 to 2.1 hours and has a serum half-life of 12 to 15 hours. When given in the recommended daily dosage of 0.5 to 4.0 mg, it is as effective as diazepam and chlordiazepoxide as an anxiolytic agent. Its currently approved indication is for the treatment of anxiety disorders and symptoms of anxiety, including anxiety associated with depression. Although currently not approved for the treatment of depressive disorders, studies published to date have demonstrated that alprazolam compares favorably with standard tricyclic antidepressants. Also undergoing investigation is the potential role of alprazolam in the treatment of panic disorders. Alprazolam has been used in elderly patients with beneficial results and a low frequency of adverse reactions. Its primary side effect, drowsiness, is less than that produced by diazepam at comparable doses. Data on toxicity, tolerance, and withdrawal profile are limited, but alprazolam seems to be at least comparable to other benzodiazepines. Drug interaction data are also limited, and care should be exercised when prescribing alprazolam for patients taking other psychotropic drugs because of potential additive depressant effects.

Urinary catecholamine metabolites during behavioral changes in a patient with manic-depressive cycles.

3-Methoxy-4-hydroxyphenylglycol and normetanephrine were analyzed in daily urine specimens of a patient with manic-depressive cycles who was studied longitudinally. The quantities of these catecholamine metabolites excreted into urine were decreased during periods of depression as compared with periods of mania. Urinary excretion of 3-methoxy-4-hydroxyphenylglycol varied cyclically with a period length of approximately 20 days. Changes in this metabolite, and perhaps in normetanephrine, preceded the affective and behavioral shifts.