A theory of crack healing in polymers is presented in terms of the stages of crack healing, namely, (a) surface rearrangement, (b) surface approach, (c) wetting, (d) diffusion, and (e) randomization. The recovery ratio R of mechanical properties with time was determined as a convolution product, R = Rh (t)*φ(t), where Rh (t) is an intrinsic healing function, and φ(t) is a wetting distribution function for the crack interface or plane in the material. The reptation model of a chain in a tube was used to describe self-diffusion of interpenetrating random coil chains which formed a basis for Rh (t). Applications of the theory are described, including crack healing in amorphous polymers and melt processing of polymer resins by injection or compression molding. Relations are developed for fracture stress σ, strain ε, and energy E as a function of time t, temperature T, pressure P, and molecular weight M. Results include (i) during healing or processing at t<t∞, σ,ε∼t1/4, E∼t1/2; (ii) at constant t<t∞, σ,ε∼M−1/4, E∼M−1/2; (iii) in the fully interpenetrated healed state at t = t∞, σ,ε∼M1/2, E∼M; (iv) the time to achieve complete healing, t∞ ∼M3, ∼exp P, ∼exp 1/T. Chain fracture, creep, and stress relaxation are also discussed. New concepts for strength predictions are introduced.

No abstract

Bilateral ECT is effective in relieving severe major depression. Remission rates are higher and occur earlier in psychotic depressed patients than in nonpsychotic depressed patients. These data support the argument that psychotic depression is a distinguishable nosological entity that warrants separate treatment algorithms.

No abstract

Objective-This study assessed the incidence, severity, and course of expressed suicidal intent in depressed patients who were treated with ECT. The data are from the first phase of an ongoing, collaborative multicenter study, the overall aim of which was to compare continuation ECT with pharmacotherapy in the prevention of relapse after a successful course of ECT.Method-Suicidal intent, as expressed by patients during an interview, was scored at baseline and before each ECT session with item 3 on the 24-item Hamilton Depression Rating Scale in 444 patients with unipolar depression.Results-One hundred thirty-one patients (29.5%) reported suicidal thoughts and acts (score of 3 or 4) at baseline. Scores decreased to 0 after 1 week (three ECT sessions) in 38.2% of the patients, after 2 weeks (six ECT sessions) in 61.1%, and in 80.9% at the end of the course of treatment.Conclusions-Expressed suicidal intent in depressed patients was rapidly relieved with ECT. Evidence-based treatment algorithms for major depressive mood disorders should include dichotomization according to suicide risk, as assessed by interview. For patients at risk, ECT should be considered earlier than at its conventional "last resort" position.Suicide and suicide attempts are risks of the major psychiatric illnesses, with mortality rates markedly higher than for the general population (1). A lifetime risk of 15% for suicide was the conclusion of a meta-analysis of hospitalized patients by Guze and Robins (2). A reanalysis of studies of suicide in affective illness in three groups of patients-outpatients, inpatients, and suicidal patients-found a risk of those ever hospitalized of 8.6% (3). Other studies confirmed the risk of suicide to be particularly high in hospitalized depressed patients (4-6). Profound hopelessness, hypochondriacal ruminations or delusions, and thoughts of suicide or self-harm during depression predict future suicide (7).Antidepressant medications are the principal agents used to treat affective disorders today. Their impact on suicide risk is not well defined, however, and they are generally viewed as less effective than ECT in relieving depression and suicidal thoughts. Hordern et al. (8) reported no suicides at the 6-month follow-up in 34 women treated with ECT but found two in the 84 patients treated with antidepressants (2.4%). Avery and Winokur (9) suicidal behavior in the 6 months following the treatment of depression in 519 patients. Suicide attempts were recorded in 0.8% of the ECT patients compared to 4.2% of those who had received "adequate" and 7% "inadequate" antidepressant medication treatment. Khan et al. (10) found antidepressant drugs to be no more effective than placebo in reducing suicide rates in seriously ill depressed patients.The experience with ECT is also unclear. A comparison of the frequency of suicides in different decades found decreased rates when ECT was the dominant treatment for mental illness (11). An examination of the records of 1,397 completed suicides in Finland within a 12-m...