Assessing the Relative Importance of Satellite-Detected Methane Superemitters in Quantifying Total Emissions for Oil and Gas Production Areas in Algeria.

Methane emissions from oil and gas production provide an important contribution to global warming. We investigate 2020 emissions from the largest gas field in Algeria, Hassi R'Mel, and the oil-production-dominated area Hassi Messaoud. We use methane data from the high-resolution (20 m) Sentinel-2 instruments to identify and estimate emission time series for 11 superemitters (including 10 unlit flares). We integrate this information in a transport model inversion that uses methane data from the coarser (7 km × 5.5 km) but higher-precision TROPOMI instrument to estimate emissions from both the 11 superemitters (>1 t/h individually) and the remaining diffuse area source (not detected as point sources with Sentinel-2). Compared to a bottom-up inventory for 2019 that is aligned with UNFCCC-reported emissions, we find that 2020 emissions in Hassi R'Mel (0.16 [0.11-0.22] Tg/yr) are lower by 53 [24-73]%, and emissions in Hassi Messaoud (0.22 [0.13-0.28] Tg/yr) are higher by 79 [4-188]%. Our analysis indicates that a larger fraction of Algeria's methane emissions (∼75%) come from oil production than national reporting suggests (5%). Although in both regions the diffuse area source constitutes the majority of emissions, relatively few satellite-detected superemitters provide a significant contribution (24 [12-40]% in Hassi R'Mel; 49 [27-71]% in Hassi Messaoud), indicating that mitigation efforts should address both. Our synergistic use of Sentinel-2 and TROPOMI can produce a unique and detailed emission characterization of oil and gas production areas.

A one-year follow-up study into the course of depression after stroke.

BACKGROUND: Stroke patients commonly suffer from neuropsychiatric disorders, such as depression, that negatively influence stroke outcome. Diagnosis, treatment and prevention of post-stroke psychiatric disorders including depression are under debate. OBJECTIVE: To study the course of depression after stroke. METHODS: One hundred and ninety first-ever stroke patients were screened for depressive symptoms at 1, 3, 6, 9, and 12 months after stroke. Diagnosis of depression was made according to the DSM-IV criteria of major and minor depression. RESULTS: Follow-up was completed in 138 patients. The cumulative incidence of post-stroke depression (PSD) in 1 year was 36.2%. One month after stroke the prevalence of PSD was 18.8%. Thirty percent of patients who were depressed in the first three months did not reach cut-off levels on depression screening instruments at the following assessments. In 44% of these patients symptoms recurred. Recurrent cases were older than patients with limited disease. In 40% of PSD patients depression persisted for at least two consecutive following follow-up visits. Persistent cases were more disabled and suffered more often from major depression. CONCLUSION: Half of PSD patients become depressed within the first month after stroke. Although most patients recover, a clinician has to be aware that symptoms can recur especially in older patients and that in patients with major depression symptoms may be persistent. In these patients treatment should be considered, whereas in patients with limited disease an observational approach may suffice.

The symptomatology of post-stroke depression: comparison of stroke and myocardial infarction patients.

BACKGROUND: Depression is a frequent problem in stroke patients but, all too often, the problem goes unrecognized. How depression-like symptoms in post-stroke depression (PSD) should be interpreted is still subject to debate. If PSD has a distinct symptom profile of depression accompanying other chronic vascular somatic conditions then this could imply that PSD is a specific disease entity. OBJECTIVE: To study whether depressed stroke patients exhibit other signs and symptoms than patients suffering from depression after myocardial infarction (MI). METHODS: Depressive signs and symptoms were measured using the Hospital Anxiety and Depression Scale and the 17-item Hamilton Depression Rating Scale. The results of 190 stroke patients were compared with the results of 198 MI patients every 3 months during the first year after the event. RESULTS: Depressed stroke patients exhibited more loss of interest, psychomotor retardation, and gastro-intestinal complaints as compared to depressed MI patients. However, in multivariate analyses including both depressed and non-depressed stroke and MI patients, no specific symptom profile was found to differentiate between the two depressive syndromes by looking at the modifying effect of stroke vs MI on the occurrence of specific symptoms in depression. CONCLUSION: Although in their clinical presentation, depressed stroke patients exhibit a symptom profile different from depressed MI patients, this is not due to differences in the depressive syndrome in these two patient groups but it reflects differences between stroke and MI patients in general.

Depression after a cerebrovascular accident. The importance of the integration of neurobiological and psychosocial pathogenic models.

Stroke survivors frequently suffer from depression. Research has focused on the incidence, phenomenology, course and risk factors of poststroke depression (PSD). Special attention has been paid to biological explanatory models, such as the lesion location and vascular depression hypotheses. In addition to such biological approaches, the role of psychosocial factors should not be neglected. This review critically discusses the proceedings in PSD research emphasizing the need for a biopsychosocial approach.

Focal or generalized vascular brain damage and vulnerability to depression after stroke: a 1-year prospective follow-up study.

BACKGROUND: Both the lesion location hypothesis and the vascular depression hypothesis have been proposed to explain the high incidence of depression in stroke patients. However, research studying both hypotheses in a single cohort is, at present, scarce. OBJECTIVE: To test the independent effects of lesion location (left hemisphere, anterior region) and of co-occurring generalized vascular damage on the development of depression in the first year after ischemic stroke, while other risk factors for depression are controlled for. METHODS: One hundred and ninety consecutive patients with a first-ever, supratentorial infarct were followed up for one year. CT was performed in the acute phase of stroke, while in 75 patients an additional MRI scan was also available. Depression was assessed at 1, 3, 6, 9, and 12 months after stroke using self-rating scales as screening tools and the SCID-I to diagnose depression according to DSM-IV criteria. RESULTS: Separate analyses of the lesion location hypothesis and the vascular depression hypothesis failed to reveal significant support for either of these biological models of post-stroke depression. Similar negative results appeared from one overall, multivariate analysis including variables of both focal and generalized vascular brain damage, as well as other non-cerebral risk factors. In addition, level of handicap and neuroticism were independent predictors of depression in this cohort, as has been reported previously. CONCLUSION: This study supports neither the lesion location nor the vascular depression hypothesis of post-stroke depression. A biopsychosocial model including both premorbid (prior to stroke) vulnerability factors, such as neuroticism and (family) history of depression, as well as post-stroke stressors, such as level of handicap, may be more appropriate and deserves further study.

Molecules with large-amplitude torsional motion partially oriented in a nematic liquid crystal: ethane and isotopomers.

An NMR study on ethane and five isotopomers dissolved in the nematic liquid crystal Merck ZLI 1132 is performed. A consistent set of dipolar and quadrupolar couplings is obtained. The dipolar couplings are corrected for harmonic vibrational effects, while the contribution from the torsional motion is incorporated classically. The corrected dipolar couplings cannot be understood in terms of a reasonable molecular structure unless effects of the reorientation-vibration interaction are taken into account. Assuming that the reorientation-vibration contributions that are known for the methyl group in methyl fluoride are transferable to ethane, excellent agreement between observed and calculated dipolar couplings is obtained on the basis of the ethane gas-phase structure. The observed and calculated deuterium quadrupolar couplings show discrepancies supporting the notion that average electric field gradients are important in liquid-crystal solvents. An important consequence of the transferability of the reorientation-vibration correlation is that in other molecules with a methyl group the same procedure as for ethane can be followed. Inclusion of this effect generally removes the need to interpret changes in observed dipolar couplings in terms of elusive chemical effects.

A comparative study into the one year cumulative incidence of depression after stroke and myocardial infarction.

BACKGROUND: The high incidence of post-stroke depression has been claimed to reflect a specific, stroke related pathogenesis in which lesion location plays an important role. To substantiate this claim, post-stroke depression should occur more often than depression after another acute, life threatening, disabling disease that does not involve cerebrovascular damage. OBJECTIVES: To compare the cumulative one year incidence of depression after stroke and after myocardial infarction, taking into consideration differences in age, sex, and the level of handicap. METHODS: In a longitudinal design, 190 first ever stroke patients and 200 first ever myocardial infarction patients were followed up for one year. Depression self rating scales were used as a screening instrument to detect patients with depressive symptoms. Major and minor depression was assessed at one, three, six, nine, and 12 months after stroke or myocardial infarction according to DSM-IV criteria, using the structured clinical interview from DSM-IV. The severity of depressive symptoms was measured with the Hamilton depression rating scale. Level of disability and handicap was rated with the Rankin handicap scale. RESULTS: The cumulative one year incidence of major and minor depression was 37.8% in stroke patients and 25% in patients with myocardial infarction (hazard ratio 1.6; p = 0.06). This difference disappeared after controlling for sex, age, and level of handicap. In addition, no differences were found in the severity of depressive symptoms or in the time of onset of the depressive episode after stroke or myocardial infarction. CONCLUSIONS: Depression occurs equally often during the first year after stroke and after myocardial infarction when non-specific factors such as sex, age, and level of handicap are taken into account. Thus the relatively high incidence of post-stroke depression seems not to reflect a specific pathogenic mechanism. Further research is needed to investigate whether vascular factors play a common role in the development of depression after stroke and myocardial infarction.

Research into the specificity of depression after stroke: a review on an unresolved issue.

Iwo decades of research have failed to generate consistent insight into the specificity of poststroke depression (PSD). This is, at least in part, caused by methodological difficulties. Differences in symptom profile between PSD and depression with no or another medical cause were described, but no specific and unequivocal clinical picture has been established so far. Prevalence rates of PSD varied largely between studies. In community based studies using standardised diagnostic instruments for depression, relatively low prevalence rates were reported compared to inpatient or rehabilitation studies. PSD occurs most frequently in the first few months after stroke, while a new incidence peak may occur 2-3 years after stroke. Two systematic reviews on the relation between lesion location and depression did not support the claim that left hemisphere lesions are a risk factor for PSD. A new concept of vascular depression has been proposed, which relates depression in the elderly to acute or chronic damage to the cerebral vascular system. Future efforts should aim at increasing the uniformity of study designs, assessment tools should be further improved for use in cognitively impaired patients and appropriate control groups should be defined to study the characteristic features of PSD.