The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO ₂) ...concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO ₂ by the ocean.
Significance A key factor regulating the air−sea balance of carbon dioxide (CO ₂) is the sinking of particles containing organic carbon from the surface to the deep ocean. The depth at which this carbon is released back into the water (remineralization) has a strong influence on atmospheric CO ₂ concentration. Here we show a significant relationship between the remineralization depth of sinking organic carbon flux in the upper ocean and water temperature, with shallower remineralization in warmer waters. Our results contrast with data from deep-sea sediment traps, highlighting the importance of upper ocean remineralization to our understanding of the ocean’s biological carbon pump. Our results suggest that predicted future increases in ocean temperature will result in reduced CO ₂ storage by the oceans.
The ocean's biological carbon pump is a key component of the global carbon cycle. Only a small fraction of the carbon fixed by primary production is exported to the deep ocean, yet this flux sets to ...first order the efficiency with which carbon is sequestered out of further contact with the atmosphere on long time scales. Here we examine global patterns in particle export efficiency (PEeff), the proportion of primary production that is exported from the surface ocean, and transfer efficiency (Teff), the fraction of exported organic matter that reaches the deep ocean. Previous studies have found a positive correlation between Teff and deep ocean calcite fluxes recovered from sediment traps, implying that ballasting by calcium carbonate may play an important role in regulating Teff. An alternative explanation is that this correlation is not causative, as regions where the dominant biomineral phase is calcite tend to be subtropical systems, which are hypothesized to produce sinking aggregates highly resistant to degradation. We attempt to distinguish between these alternative hypotheses on the control of Teff by examining the relationship between Teff and biomineral phases exported from the upper ocean, rather than those collected in deep traps. Global scale estimates derived from satellite data show, in keeping with earlier studies, that PEeff is high at high latitudes and low at low latitudes, but that Teff is low at high latitudes and high at low latitudes. However, in contrast to the relationship observed for deep biomineral fluxes in previous studies, we find that Teff is strongly negatively correlated with opal export flux from the upper ocean, but uncorrelated with calcium carbonate export flux. We hypothesize that the underlying factor governing the spatial patterns observed in Teff is ecosystem function, specifically the degree of recycling occurring in the upper ocean, rather than the availability of calcium carbonate for ballasting.
Key Points
Global maps of export efficiency and transfer efficiency are presented
Upper ocean export flux of CaCO3 is not correlated with transfer efficiency
Ecosystem structure, particularly extent of recycling, drives transfer efficiency
This study aims to estimate the risk of hot flashes relative to natural menopause and to evaluate the associations of hormone levels, behavioral variables, and demographic variables with the risk of ...hot flashes after menopause.
We performed annual assessment of 255 women who were premenopausal at baseline and reached natural menopause within 16 years of follow-up.
The prevalence of moderate/severe hot flashes increased in each premenopausal year, reaching a peak of 46% in the first 2 years after the final menstrual period (FMP). Hot flashes decreased slowly after menopause and did not return to premenopausal levels until 9 years after the FMP. The mean (SD) duration of moderate/severe hot flashes after the FMP was 4.6 (2.9) years (for any hot flashes, 4.9 3.1 y). One third of women at 10 years or more after menopause continued to experience moderate/severe hot flashes. African-American women (obese and nonobese) and obese white women had significantly greater risks of hot flashes compared with nonobese white women (interaction, P = 0.01). In multivariable analysis, increasing follicle-stimulating hormone levels before the FMP (P < 0.001), decreasing estradiol (odds ratio, 0.87; 95% CI, 0.78-0.96; P = 0.008), and increasing anxiety (odds ratio, 1.05; 95% CI, 1.03-1.06; P < 0.001) were significant risk factors for hot flashes, whereas higher education levels were protective (odds ratio, 0.66; 95% CI, 0.47-0.91; P = 0.011).
Moderate/severe hot flashes continue, on average, for nearly 5 years after menopause; more than one third of women observed for 10 years or more after menopause have moderate/severe hot flashes. Continuation of hot flashes for more than 5 years after menopause underscores the importance of determining individual risks/benefits when selecting hormone or nonhormone therapy for menopausal symptoms.
The flux of organic carbon from the surface ocean to mesopelagic depths is a key component of the global carbon cycle and is ultimately derived from primary production (PP) by phytoplankton. Only a ...small fraction of organic carbon produced by PP is exported from the upper ocean, referred to as the export efficiency (herein e‐ratio). Limited observations of the e‐ratio are available, and there is thus considerable interest in using remotely sensed parameters such as sea surface temperature to extrapolate local estimates to global annual export flux. Currently, there are large discrepancies between export estimates derived in this way; one possible explanation is spatial or temporal sampling bias in the observations. Here we examine global patterns in the spatial and seasonal variability in e‐ratio and the subsequent effect on export estimates using a high‐resolution global biogeochemical model. The model used here represents export as separate slow‐ and fast‐sinking detrital material whose remineralization is respectively temperature dependent and a function of ballasting minerals. We find that both temperature and the fraction of export carried by slow‐sinking particles are factors in determining e‐ratio, suggesting that current empirical algorithms for e‐ratio that only consider temperature are overly simple. We quantify the temporal lag between PP and export, which is greatest in regions of strong variability in PP where seasonal decoupling can result in large e‐ratio variability. Extrapolating global export estimates from instantaneous measurements of e‐ratio is strongly affected by seasonal variability and can result in errors in estimated export of up to ±60%.
Key Points
Seasonal and spatial variability in export ratio quantified
Empirical algorithms for e‐ratio may be overly simple
Assuming e‐ratio is seasonally invariant results in large errors in export
Diagnosis of thoracic outlet syndrome Sanders, Richard J., MD; Hammond, Sharon L., MD; Rao, Neal M., BA
Journal of vascular surgery,
09/2007, Letnik:
46, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Thoracic outlet syndrome (TOS) is a nonspecific label. When employing it, one should define the type of TOS as arterial TOS, venous TOS, or neurogenic TOS. Each type has different symptoms and ...physical findings by which the three types can easily be identified. Neurogenic TOS (NTOS) is by far the most common, comprising well over 90% of all TOS patients. Arterial TOS is the least common accounting for no more than 1%. Many patients are erroneously diagnosed as “vascular” TOS, a nonspecific misnomer, whereas they really have NTOS. The Adson Test of noting a radial pulse deficit in provocative positions has been shown to be of no clinical value and should not be relied upon to make the diagnosis of any of the three types. The test is normal in most patients with NTOS and at the same time can be positive in many control volunteers. Arterial TOS is caused by emboli arising from subclavian artery stenosis or aneurysms. Symptoms are those of arterial ischemia and x-rays almost always disclose a cervical rib or anomalous first rib. Venous TOS presents with arm swelling, cyanosis, and pain due to subclavian vein obstruction, with or without thrombosis. Neurogenic TOS is due to brachial plexus compression usually from scarred scalene muscles secondary to neck trauma, whiplash injuries being the most common. Symptoms include extremity paresthesia, pain, and weakness as well as neck pain and occipital headache. Physical exam is most important and includes several provocative maneuvers including neck rotation and head tilting, which elicit symptoms in the contralateral extremity; the upper limb tension test, which is comparable to straight leg raising; and abducting the arms to 90° in external rotation, which usually brings on symptoms within 60 seconds.
Background:
Children and adolescents with intellectual disability are at risk of developing psychiatric symptoms and disorders; yet, the estimates reported in the literature have been inconsistent, ...presenting a potential barrier for service planning and delivery. Sources of variability could arise from differences in measurement instruments as well as subgroup membership by severity of intellectual disability, gender and age. This systematic review aimed to address these gaps.
Method:
MEDLINE and PsycINFO databases were searched from inception to 2018 and selected studies were reviewed. Studies were included if they reported point prevalence estimates of mental health symptomology or diagnoses in a general population of 6- to 21-year-old individuals with intellectual disability. The Joanna Briggs Institute Prevalence Critical Appraisal Checklist was applied to eligible papers to appraise their scientific strength. Pooled prevalence for mental health symptomology was determined using a random-effects meta-analysis.
Results:
A total of 19 studies were included, including 6151 children and adolescents. The pooled prevalence estimate captured by the Developmental Behaviour Checklist was 38% (95% confidence interval = 31, 46), contrasting with 49% (95% confidence interval = 46, 51) captured by the Child Behaviour Checklist; both rates were higher than a non-intellectual disability population. Severity of intellectual disability did not significantly influence the Developmental Behaviour Checklist risks. Insufficient data were available to conduct statistical analyses on the effects of age, gender and socioeconomic status. Of diagnosed psychiatric disorders, attention deficit/hyperactivity disorder (30%), conduct disorder (3–21%) and anxiety disorders (7–34%) were the most prevalent conditions.
Conclusion:
This review consists of the largest sample hitherto evaluated. In the intellectual disability population, mental health comorbidities could be better detected by a symptom phenotype than a psychiatric diagnostic phenotype. Crucially, future research needs to address the effect of measurement validity in the intellectual disability population. Estimated prevalence rates were high compared to the general population, indicating the importance of systematic screening, case detection and appropriate management.
•North Sea fluorescent DOM field sampled to map terrestrial inputs and distributions.•DOM pool characterised via absorbance and excitation-emission fluorescent spectra.•Three distinct FDOM ...fluorophores identified.•No clear evidence found for significant terrestrial DOM export to the Atlantic Ocean.•North Sea terrestrial DOM distributions appear stable over multi-decadal timescales.
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The flow of terrestrial carbon to rivers and inland waters is a major term in the global carbon cycle. The organic fraction of this flux may be buried, remineralized or ultimately stored in the deep ocean. The latter can only occur if terrestrial organic carbon can pass through the coastal and estuarine filter, a process of unknown efficiency. Here, data are presented on the spatial distribution of terrestrial fluorescent and chromophoric dissolved organic matter (FDOM and CDOM, respectively) throughout the North Sea, which receives organic matter from multiple distinct sources. We use FDOM and CDOM as proxies for terrestrial dissolved organic matter (tDOM) to test the hypothesis that tDOM is quantitatively transferred through the North Sea to the open North Atlantic Ocean. Excitation emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) revealed a single terrestrial humic-like class of compounds whose distribution was restricted to the coastal margins and, via an inverse salinity relationship, to major riverine inputs. Two distinct sources of fluorescent humic-like material were observed associated with the combined outflows of the Rhine, Weser and Elbe rivers in the south-eastern North Sea and the Baltic Sea outflow to the eastern central North Sea. The flux of tDOM from the North Sea to the Atlantic Ocean appears insignificant, although tDOM export may occur through Norwegian coastal waters unsampled in our study. Our analysis suggests that the bulk of tDOM exported from the Northwest European and Scandinavian landmasses is buried or remineralized internally, with potential losses to the atmosphere. This interpretation implies that the residence time in estuarine and coastal systems exerts an important control over the fate of tDOM and needs to be considered when evaluating the role of terrestrial carbon losses in the global carbon cycle.
Thoracic outlet syndrome (TOS) is a group of disorders all having in common compression at the thoracic outlet. Three structures are at risk: the brachial plexus, the subclavian vein, and the ...subclavian artery, producing neurogenic (NTOS), venous (VTOS), and arterial (ATOS) thoracic outlet syndromes, respectively. Each of these three are separate entities, though they can coexist and possibly overlap. The treatment of NTOS, in particular, has been hampered by lack of data, which in turn is the result of inconsistent definitions and diagnosis, uncertainty with regard to treatment options, and lack of consistent outcome measures. The Committee has defined NTOS as being present when three of the following four criteria are present: signs and symptoms of pathology occurring at the thoracic outlet (pain and/or tenderness), signs and symptoms of nerve compression (distal neurologic changes, often worse with arms overhead or dangling), absence of other pathology potentially explaining the symptoms, and a positive response to a properly performed scalene muscle test injection. Reporting standards for workup, treatment, and assessment of results are presented, as are reporting standards for all phases of VTOS and ATOS. The overall goal is to produce consistency in diagnosis, description of treatment, and assessment of results, in turn then allowing more valuable data to be presented.
Photosynthesis in the surface ocean produces approximately 100 gigatonnes of organic carbon per year, of which 5 to 15 per cent is exported to the deep ocean. The rate at which the sinking carbon is ...converted into carbon dioxide by heterotrophic organisms at depth is important in controlling oceanic carbon storage. It remains uncertain, however, to what extent surface ocean carbon supply meets the demand of water-column biota; the discrepancy between known carbon sources and sinks is as much as two orders of magnitude. Here we present field measurements, respiration rate estimates and a steady-state model that allow us to balance carbon sources and sinks to within observational uncertainties at the Porcupine Abyssal Plain site in the eastern North Atlantic Ocean. We find that prokaryotes are responsible for 70 to 92 per cent of the estimated remineralization in the twilight zone (depths of 50 to 1,000 metres) despite the fact that much of the organic carbon is exported in the form of large, fast-sinking particles accessible to larger zooplankton. We suggest that this occurs because zooplankton fragment and ingest half of the fast-sinking particles, of which more than 30 per cent may be released as suspended and slowly sinking matter, stimulating the deep-ocean microbial loop. The synergy between microbes and zooplankton in the twilight zone is important to our understanding of the processes controlling the oceanic carbon sink.
The ocean contributes to regulating atmospheric CO2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e., the e ratio). Southern ...Ocean studies have found that contrary to global‐scale analyses, an inverse relationship exists between e ratio and PP. This relationship remains unexplained, with potential hypotheses being (i) large export of dissolved organic carbon (DOC) in high PP areas, (ii) strong surface microbial recycling in high PP regions, and/or (iii) grazing‐mediated export that varies inversely with PP. We find that the export of DOC has a limited influence in setting the negative e ratio/PP relationship. However, we observed that at sites with low PP and high e ratios, zooplankton‐mediated export is large and surface microbial abundance low suggesting that both are important drivers of the magnitude of the e ratio in the Southern Ocean.
Key Points
High productivity low export regions are widespread in the Southern Ocean
This may be due to high surface bacterial activity and low fecal pellet export in high PP regions
These two processes must be implemented in POC export algorithms
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