10 research outputs found

    Exploring the Potential Linkages Between Oil-Field Brine Reinjection, Crystalline Basement Permeability, and Triggered Seismicity for the Dagger Draw Oil Field, Southeastern New Mexico, USA, Using Hydrologic Modeling

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    We used hydrologic models to explore the potential linkages between oil-field brine reinjection and increases in earthquake frequency (up to Md 3.26) in southeastern New Mexico and to assess different injection management scenarios aimed at reducing the risk of triggered seismicity. Our analysis focuses on saline water reinjection into the basal Ellenburger Group beneath the Dagger Draw Oil field, Permian Basin. Increased seismic frequency (\u3eMd 2) began in 2001, 5 years after peak injection, at an average depth of 11 km within the basement 15 km to the west of the reinjection wells. We considered several scenarios including assigning an effective or bulk permeability value to the crystalline basement, including a conductive fault zone surrounded by tighter crystalline basement rocks, and allowing permeability to decay with depth. We initially adopted a 7 m (0.07 MPa) head increase as the threshold for triggered seismicity. Only two scenarios produced excess heads of 7m five years after peak injection. In the first, a hydraulic diffusivity of 0.1 m2s-1 was assigned to the crystalline basement. In the second, a hydraulic diffusivity of 0.3 m2s-1 was assigned to a conductive fault zone. If we had considered a wider range of threshold excess heads to be between 1 and 60m, then the range of acceptable hydraulic diffusivities would have increased (between 0.1-0.01 m2s-1 and 1-0.1 m2s-1 for the bulk and fault zone scenarios, respectively). A permeability–depth decay model would have also satisfied the 5-year time lag criterion. We also tested several injection management scenarios including redistributing injection volumes between various wells and lowering the total volume of injected fluids. Scenarios that reduced computed excess heads by over 50% within the crystalline basement resulted from reducing the total volume of reinjected fluids by a factor of 2 or more

    Rational Treatment Choices for Non-major Depressions in Primary Care: An Evidence-based Review

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    OBJECTIVE: This review synthesizes available evidence for managing clinically significant dysphoric symptoms encountered in primary care, when formal criteria for major depression or dysthymia are not met. Discussion is focused on premenstrual dysphoric disorder (PMDD) and minor depression because of their significant prevalence in the primary care setting and the lack of clear practice guidelines for addressing each illness. DESIGN: English language literature from prior systematic reviews was supplemented by searching medline, embase, the Cochrane Controlled Trials Registry, the Agency for Healthcare Research and Quality National Guideline Clearinghouse, and bibliographies of selected papers. Studies addressing the natural history or treatment of minor depression or PMDD were selected for review. Data were abstracted by 1 of 2 independent reviewers and studies were synthesized qualitatively. RESULTS: Five individual studies that compared antidepressant or psychological treatments to placebo in patients with minor depression suggest short-term improvements in depressive symptoms with paroxetine, problem-solving therapy, and cognitive behavioral therapy, but not with amitryptiline. Modest benefits on mental health function were reported with paroxetine and with problem-solving therapy, but only in patients with severe functional impairment at baseline. Twenty-four controlled trials were identified that compared antidepressant or psychological treatments to placebo in patients with premenstrual dysphoric disorder. Pooled results from a recent systematic review of 15 randomized controlled trials and one additional trial abstract provide strong evidence for a significantly greater improvement in physical and psychological symptoms with serotonin-selective reuptake inhibitor medications when compared with placebo. Individual trials also suggest significantly greater improvements in symptom scores with venlafaxine, but not with tricyclic antidepressants. CONCLUSIONS: The limited evidence base for minor depression provides only mixed support for a small to moderate benefit for few antidepressant medications and psychological treatments tested. For the treatment of severe psychological or physical symptoms causing functional impairment in patients with PMDD, sertraline and fluoxetine are clearly beneficial in carefully selected patients

    Disillusionment and Change: A Cognitive-Emotional Theory of Gang Exit

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    Exit from street gangs has received increased attention in recent years; however, a number of important questions regarding the process of leaving remain unanswered. Relying on identity theory, we present a cognitive-emotional theory of gang exit that emphasizes functional dimensions of anger in terms of motivating individuals to pursue identity change related to gang membership. Specifically, anger provides gang members with an opportunity to identify the gang as a major source of their problems. According to identity theory, anger is generated when there is an inability to meet an identity standard. This article argues that an inability to meet identity goals produces disillusionment and anger, which reduces the relative importance of the gang identity and facilitates exit from gangs

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