Carotenoids are the likely precursor of a significant fraction of marine dissolved organic matter.

The ocean's biota sequester atmospheric carbon dioxide (CO2) in part by producing dissolved organic matter (DOM) that persists in the ocean for millennia. This long-term accumulation of carbon may be facilitated by abiotic and biotic production of chemical structures that resist degradation, consequently contributing disproportionately to refractory DOM. Compounds that are selectively preserved in seawater were identified in solid-phase extracted DOM (PPL-DOM) using comprehensive gas chromatography (GC) coupled to mass spectrometry (MS). These molecules contained cyclic head groups that were linked to isoprenoid tails, and their overall structures closely resembled carotenoid degradation products (CDP). The origin of these compounds in PPL-DOM was further confirmed with an in vitro β-carotene photooxidation experiment that generated water-soluble CDP with similar structural characteristics. The molecular-level identification linked at least 10% of PPL-DOM carbon, and thus 4% of total DOM carbon, to CDP. Nuclear magnetic resonance spectra of experimental CDP and environmental PPL-DOM overlapped considerably, which indicated that even a greater proportion of PPL-DOM was likely composed of CDP. The CDP-rich DOM fraction was depleted in radiocarbon (14C age > 1500 years), a finding that supports the possible long-term accumulation of CDP in seawater. By linking a specific class of widespread biochemicals to refractory DOM, this work provides a foundation for future studies that aim to examine how persistent DOM forms in the ocean

Expert Relativity: Identify the Expert Just Ahead

Experts are often viewed as individuals with a vast storehouse of knowledge beyond the normal participants in a domain. In reality, the expert may have just enough additional knowledge beyond those they interface with to propel their team to success. This research explores the accumulation of knowledge and prior skill set necessary to successfully participate in a business simulation emulating the cash-to-cash cycle of a manufacturing/distribution company. Students participate in simulated organizations where the skill level of novice is designated by freshmen/sophomores/juniors with little to no business education. Experts are designated as seniors/graduate students with business educations that include aspects of the entire cash-to-cash cycle of an organization. Comparisons across simulation games indicate that minor background differences in specific participant ability can make significant differences in simulation standings

Accounting for Comorbidity in Assessing the Burden of Epilepsy Among US Adults: Results from the National Comorbidity Survey Replication (NCS-R)

Although epilepsy is associated with substantial role impairment, it is also highly comorbid with other physical and mental disorders, making unclear the extent to which impairments associated with epilepsy are actually due to comorbidities. This issue was explored in the National Comorbidity Survey Replication (NCS-R), a nationally representative household survey of 5,692 US adults. Medically-recognized epilepsy was ascertained with self-report, comorbid physical disorders with a chronic conditions checklist, and comorbid DSM-IV mental disorders with the Composite International Diagnostic Interview (CIDI). Lifetime epilepsy prevalence was estimated at 1.8%. Epilepsy was comorbid with numerous neurological and general medical conditions and with a sporadic cluster of mental comorbidities (panic, PTSD, conduct disorder, and substance use disorders). Although comorbid disorders explain part of the significant gross associations of epilepsy with impairment, epilepsy remains significantly associated with work disability, cognitive impairment, and days of role impairment after controlling comorbidities. The net association of epilepsy with days of role impairment after controlling for comorbidities is equivalent to an annualized 89.4 million excess role impairment days among US adults with epilepsy, arguing that role impairment is a major component of the societal costs of epilepsy per se rather than merely due to disorders comorbid with epilepsy. This estimated burden is likely conservative as some parts of the effects of epilepsy are presumably mediated by secondary comorbid disorders

IS Success Model in E-Learning Context Based on Students\u27 Perceptions

This study utilized the Information Systems Success (ISS) model in examining e-learning systems success. The study was built on the premise that system quality (SQ) and information quality (IQ) influence system use and user satisfaction, which in turn impact system success. A structural equation model (SEM), using LISREL, was used to test the measurement and structural models using a convenience sample of 674 students at a Midwestern university. The results revealed that both system quality and information quality had significant positive impact on user satisfaction and system use. Additionally, the results showed that user satisfaction, compared to system use, had a stronger impact on system success. Implications for educators and researchers are reported

Exploring Cancer Metabolism Using Stable Isotope-Resolved Metabolomics (SIRM)

Metabolic reprogramming is a hallmark of cancer. The changes in metabolism are adaptive to permit proliferation, survival, and eventually metastasis in a harsh environment. Stable isotope-resolved metabolomics (SIRM) is an approach that uses advanced approaches of NMR and mass spectrometry to analyze the fate of individual atoms from stable isotope-enriched precursors to products to deduce metabolic pathways and networks. The approach can be applied to a wide range of biological systems, including human subjects. This review focuses on the applications of SIRM to cancer metabolism and its use in understanding drug actions

Identification of Mammalian Mediator Subunits with Similarities to Yeast Mediator Subunits Srb5, Srb6, Med11, and Rox3

The Mediator is a multiprotein coactivator required for activation of RNA polymerase II transcription by DNA binding transactivators. We recently identified a mammalian homologue of yeast Mediator subunit Med8 and partially purified a Med8-containing Mediator complex from rat liver nuclei (Brower, C. S., Sato, S., Tomomori-Sato, C., Kamura, T., Pause, A., Stearman, R., Klausner, R. D., Malik, S., Lane, W. S., Sorokina, I., Roeder, R. G., Conaway, J. W., and Conaway, R. C. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 10353-10358). Analysis of proteins present in the most highly purified Med8-containing fractions by tandem mass spectrometry led to the identification of many known mammalian Mediator subunits, as well as four potential Mediator subunits exhibiting sequence similarity to yeast Mediator subunits Srb5, Srb6, Med11, and Rox3. Here we present direct biochemical evidence that these four proteins are bona fide mammalian Mediator subunits. In addition, we identify direct pairwise binding partners of these proteins among the known mammalian Mediator subunits. Taken together, our findings identify a collection of novel mammalian Mediator subunits and shed new light on the underlying architecture of the mammalian Mediator complex

Cryopreserved homograft valves in the pulmonary position: Risk analysis for intermediate-term failure

AbstractObjective: The purpose of this study was to examine the durability of cryopreserved homografts used to replace the “pulmonary” valve and to identify factors associated with their late deterioration. Methods: We reviewed our entire experience (1985-1997) with 331 survivors in whom cryopreserved homograft valves (pulmonary, n = 304; aortic, n = 27) were used to reconstruct the pulmonary outflow tract. Median age was 14 years (range, 2 days–62 years). Operations included Ross operation (n = 259), tetralogy of Fallot (n = 41), truncus arteriosus (n = 14), Rastelli operation (n = 11), and others (n = 6). Median follow-up was 3.8 years (range, 0.2–11.2 years); late echographic follow-up was complete for 97% of patients. Homograft failure was defined as the need for explantation and valve-related death; homograft dysfunction was defined as a pulmonary insufficiency grade 3/4 or greater and a transvalvular gradient of 40 mm Hg or greater. Results: Homograft failure occurred in 9% (30 of 331 patients; Kaplan-Meier); freedom from failure was 82% ± 4% at 8 years. Homograft dysfunction occurred in 12% (39 of 331 patients), although freedom from dysfunction was 76% ± 4% at 8 years. For aortic homografts, this was 56% ± 11%, compared to 80% ± 4% for pulmonary homografts (P = .003). For patients aged less than 3 years (n = 38), this was 51% ± 12%, compared with 87% ± 4% for older patients (P = .0001). By multivariable analysis, younger age of homograft donors, non-Ross operation, and later year of operation were associated with homograft failure; younger age of homograft donors, later year of operation, and use of an aortic homograft were associated with homograft dysfunction. Conclusions: Homograft valves function satisfactorily in the pulmonary position at mid-term follow-up. The pulmonary homograft valve appears to be more durable than the aortic homograft valve in the pulmonary position. (J Thorac Cardiovasc Surg 1999;117:141-7