1,793 research outputs found
Competition Drives Clumpy Species Coexistence in Estuarine Phytoplankton
Understanding the mechanisms that maintain biodiversity is a fundamental problem in ecology. Competition is thought to reduce diversity, but hundreds of microbial aquatic primary producers species coexist and compete for a few essential resources (e.g., nutrients and light). Here, we show that resource competition is a plausible mechanism for explaining clumpy distribution on individual species volume (a proxy for the niche) of estuarine phytoplankton communities ranging from North America to South America and Europe, supporting the Emergent Neutrality hypothesis. Furthermore, such a clumpy distribution was also observed throughout the Holocene in diatoms from a sediment core. A Lotka-Volterra competition model predicted position in the niche axis and functional affiliation of dominant species within and among clumps. Results support the coexistence of functionally equivalent species in ecosystems and indicate that resource competition may be a key process to shape the size structure of estuarine phytoplankton, which in turn drives ecosystem functioning
The electronic structure of zircon-type orthovanadates: Effects of high-pressure and cation substitution
The electronic structure of four ternary-metal oxides containing isolated
vanadate ions is studied. Zircon-type YVO4, YbVO4, LuVO4, and NdVO4 are
investigated by high-pressure optical-absorption measurements up to 20 GPa.
First-principles calculations based on density-functional theory were also
performed to analyze the electronic band structure as a function of pressure.
The electronic structure near the Fermi level originates largely from molecular
orbitals of the vanadate ion, but cation substitution influence these
electronic states. The studied ortovanadates, with the exception of NdVO4,
undergo a zircon-scheelite structural phase transition that causes a collapse
of the band-gap energy. The pressure coefficient dEg/dP show positive values
for the zircon phase and negative values for the scheelite phase. NdVO4
undergoes a zircon-monazite-scheelite structural sequence with two associated
band-gap collapses.Comment: 35 pages, 11 figures, 2 Tables, 52 reference
A combined high-pressure experimental and theoretical study of the electronic band-structure of scheelite-type AWO4 (A = Ca, Sr, Ba, Pb) compounds
The optical-absorption edge of single crystals of CaWO4, SrWO4, BaWO4, and
PbWO4 has been measured under high pressure up to ~20 GPa at room temperature.
From the measurements we have obtained the evolution of the band-gap energy
with pressure. We found a low-pressure range (up to 7-10 GPa) where
alkaline-earth tungstates present a very small Eg pressure dependence (-2.1 <
dEg/dP < 8.9 meV/GPa). In contrast, in the same pressure range, PbWO4 has a
pressure coefficient of -62 meV/GPa. The high-pressure range is characterized
in the four compounds by an abrupt decrease of Eg followed by changes in
dEg/dP. The band-gap collapse is larger than 1.2 eV in BaWO4. We also
calculated the electronic-band structures and their pressure evolution.
Calculations allow us to interpret experiments considering the different
electronic configuration of divalent metals. Changes in the pressure evolution
of Eg are correlated with the occurrence of pressure-induced phase transitions.
The band structures for the low- and high-pressure phases are also reported. No
metallization of any of the compounds is detected in experiments nor is
predicted by calculations.Comment: 26 pages, 1 table, 6 figure
Hepatitis B Virus Variants with Multiple Insertions and/or Deletions in the X Open Reading Frame 3 ' End: Common Members of Viral Quasispecies in Chronic Hepatitis B Patients
Hepatitis B virus; Insertions; Next-generation sequencingVirus de l'hepatitis B; Insercions; SeqĂźenciaciĂł de nova generaciĂłVirus de la hepatitis B; Inserciones; SecuenciaciĂłn de prĂłxima generaciĂłnDeletions in the 3Ⲡend region of the hepatitis B virus (HBV) X open reading frame (HBX) may affect the core promoter (Cp) and have been frequently associated with hepatocellular carcinoma (HCC). The aim of this study was to investigate the presence of variants with deletions and/or insertions (Indels) in this region in the quasispecies of 50 chronic hepatitis B (CHB) patients without HCC. We identified 103 different Indels in 47 (94%) patients, in a median of 3.4% of their reads (IQR, 1.3â8.4%), and 25% (IQR, 13.1â40.7%) of unique sequences identified in each quasispecies (haplotypes). Of those Indels, 101 (98.1%) caused 44 different altered stop codons, the most commonly observed were at positions 128, 129, 135, and 362 (putative position). Moreover, 39 (37.9%) Indels altered the TATA-like box (TA) sequences of Cp; the most commonly observed caused TA2 + TA3 fusion, creating a new putative canonical TATA box. Four (8%) patients developed negative clinical outcomes after a median follow-up of 9.4 (8.7â12) years. In conclusion, we observed variants with Indels in the HBX 3Ⲡend in the vast majority of our CHB patients, some of them encoding alternative versions of HBx with potential functional roles, and/or alterations in the regulation of transcription.This research was funded by Instituto de Salud Carlos III and co-financed by the European Regional Development Fund (ERDF), grant number PI18/01436; PI19/00301; and by the Centro para el Desarrollo TecnolĂłgico Industrial (CDTI) from the Spanish Ministry of Economy and Business, grant number IDI-20200297. The APC was funded by the grant PI18/01436
Standardized Hepatitis B Virus RNA Quantification in Untreated and Treated Chronic Patients: a Promising Marker of Infection Follow-Up.
The measurement and interpretation of HBV DNA and RNA levels in HBV infected patients treated with antiviral therapy supports the objective of HBV disease management. Here, we quantified circulating HBV RNA through a standardized and sensitive assay in follow-up samples from both naive and treated patients as a marker of infection evolution. HBV DNA (HBV DNA for use in Cobas 6800/8800 Automated Roche Molecular Systems), RNA (Roche HBV RNA Investigational Assay for use in the Cobas 6800/8800; Roche), HBeAg and HBsAg (Elycsys HBsAg chemiluminescence immunoassay by Cobas 8000; Roche), and core-related antigen (Lumipulse G chemiluminescence assay; Fujirebio) levels were measured in cohorts of untreated or nucleos(t)ide treated, HBV-infected subjects in an outpatient hospital setting. HBV DNA levels in untreated people were 3.6 log10 higher than corresponding RNA levels and were stable over 5 years of observation. While only five of 52 treated patients had DNA levels below the lower limit of quantification (10âIU/mL) at the end of follow-up, 13 had HBV RNA levels persistently above this limit, including eight with undetectable DNA. In samples with undetectable core-related antigen we observed a median HBsAg titer 2.7-fold higher than in samples with undetectable RNA (adjusted Pâ=â0.012). Detectable HBV RNA with undetectable HBV DNA was a negative predictor of HBsAg decrease to a level â¤100âIU/mL (P = 0.03). In naive patients the difference between HBV DNA and RNA was higher than previously reported. HBV RNA rapidly decreased during treatment. However, in some cases, it was detectable even after years of effective therapy, being a negative predictor of HBsAg decrease. The investigational RNA assay for use on the Cobas 6800/8800 instruments is a sensitive and standardized method that could be applied in general management of HBV infection. IMPORTANCE This study focused on the quantification of circulating HBV RNA by using a standardized and sensitive assay. Thanks to this system we observed a higher difference between circulating HBV DNA and RNA than previously reported. In treated patients, HBV RNA decreased together with DNA, although some patients presented detectable levels even after years of successful antiviral treatment, suggesting a persistent viral transcription. Of note, the detection of viral RNA when HBV DNA is undetectable was a negative predictor of HBsAg decrease to a level â¤100âIU/mL. This assay could be extremely helpful in HBV patients management to study viral transcription and to identify those treated patients that may achieve sustained viral suppression
Objective and subjective measures of physical functioning in women with fibromyalgia: what type of measure is associated most clearly with subjective well-being?
To find modifiable factors that are related to subjective well-being would be valuable for improving
interventions in fibromyalgia. Physical activity, sedentary behaviour, and physical fitness may represent potential
areas to optimize treatment regimens. In fibromyalgia, there is a discordance between clinical observations and
patient-reported outcomes (objective and subjective assessments). Therefore, the present study aims at analyzing
the associations of objective and subjective evaluations of physical activity, sedentary behaviour, and physical
fitness with subjective well-being and determine if and how objective and subjective associations differ In the most conservative multivariate analysis, we found independent associations of the objective
measures of physical activity with positive affect and life satisfaction and sedentary behaviour with
positive affect. No such relationship was seen with subjective measures of the same behaviours.
Moreover, we observed that objective and subjective physical fitness evaluations were independent of
each other related to subjective well-being. Independent associations of the objectivemeasures (but not the subjective assessments) of physical
activity with positive affect and life satisfaction, and of sedentary behaviour with positive affect were observed.
However, objective measures and subjective appraisals of physical fitness appear to be independently related to
well-being,which should be consideredwhen developing physical exercise interventions for fibromyalgiaThis work was supported by the Spanish Ministry of Economy and
Competitiveness [I+D+i DEP2010-15639, I+D+I DEP2013-
40908, and BES-2014â067612]; the Spanish Ministry of Education
[FPU15/00002]. This study has been partially funded by the
University of Granada, Plan Propio de InvestigaciĂłn 2016,
Excellence actions: Units of Excellence; Unit of Excellence on
Exercise and Health (UCEES), and by the Junta de AndalucĂa,
ConsejerĂa de Conocimiento, InvestigaciĂłn y Universidades and
European Regional Development Fund (ERDF), ref. SOMM17/6107/
UGR. This research was supported (in part) by the Intramural
Research program of the NIH, National Institute of Nursing
Research
A snapshot of cancer-associated thromboembolic disease in 2018-2019: First data from the TESEO prospective registry
BACKGROUND: The ever-growing complexity of cancer-associated thrombosis (CAT), with new antineoplastic drugs and anticoagulants, distinctive characteristics, and decisions with low levels of evidence, justifies this registry. METHOD: TESEO is a prospective registry promoted by the Spanish Society of Medical Oncology to which 34 centers contribute cases. It seeks to provide an epidemiological description of CAT in Spain. RESULTS: Participants (N=939) with CAT diagnosed between July 2018 and December 2019 were recruited. Most subjects had advanced colon (21.4%), non-small cell lung (19.2%), and breast (11.1%) cancers, treated with dual-agent chemotherapy (28.4%), monochemotherapy (14.4%), or immune checkpoint inhibitors (3.6%). Half (51%) were unsuspected events, albeit only 57.1% were truly asymptomatic. Pulmonary embolism (PE) was recorded in 571 (58.3%); in 120/571 (21.0%), there was a concurrent deep venous thromboembolism (VTE). Most initially received low molecular weight heparin (89.7%). Suspected and unsuspected VTE had an OS rate of 9.9 (95% CI, 7.3-non-computable) and 14.4 months (95% CI, 12.6-non-computable) (p=0.00038). Six-month survival was 80.9%, 55.9%, and 55.5% for unsuspected PE, unsuspected PE admitted for another reason, and suspected PE, respectively (p<0.0001). The 12-month cumulative incidence of venous rethrombosis was 7.1% (95% CI, 4.7-10.2) in stage IV vs 3.0% (95% CI, 0.9-7.1) in stages I-III. The 12-month cumulative incidence of major/clinically relevant bleeding was 9.6% (95% CI, 6.1-14.0) in the presence of risk factors. CONCLUSION: CAT continues to be a relevant problem in the era of immunotherapy and targeted therapies. The initial TESEO data highlight the evolution of CAT, with new agents and thrombotic risk factors
Bow shocks, nova shells, disc winds and tilted discs: the nova-like V341 Ara has it all
V341 Ara was recently recognized as one of the closest (d â 150 pc) and brightest (V â 10) nova-like cataclysmic variables. This unique system is surrounded by a bright emission nebula, likely to be the remnant of a recent nova eruption. Embedded within this nebula is a prominent bow shock, where the systemâs accretion disc wind runs into its own nova shell. In order to establish its fundamental properties, we present the first comprehensive multiwavelength study of the system. Long-term photometry reveals quasi-periodic, super-orbital variations with a characteristic time-scale of 10â16 d and typical amplitude of â1 mag. High-cadence photometry from theTransiting Exoplanet Survey Satellite (TESS) reveals for the first time both the orbital period and a ânegative superhumpâ period. The latter is usually interpreted as the signature of a tilted accretion disc. We propose a recently developed disc instability model as a plausible explanation for the photometric behaviour. In our spectroscopic data, we clearly detect antiphased absorption and emission-line components. Their radial velocities suggest a high mass ratio, which in turn implies an unusually low white-dwarf mass. We also constrain the wind mass-loss rate of the system from the spatially resolved [OâIII] emission produced in the bow shock; this can be used to test and calibrate accretion disc wind models. We suggest a possible association between V341 Ara and a âguest starâ mentioned in Chinese historical records in AD 1240. If this marks the date of the systemâs nova eruption, V341 Ara would be the oldest recovered nova of its class and an excellent laboratory for testing nova theory
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