595 research outputs found
Inter-annual ciliate distribution variation within the late stratification oxycline in a monomictic lake, Lake Alchichica (Mexico)
Deep stratified tropical water bodies pass through prolonged periods of meta-hypolimnetic anoxia, and ciliates might play a very
important role in the plankton community budget there. We analysed changes in the composition and biomass of the ciliate assemblage and other microbial loop components throughout the oxycline just at the end of stratification in a warm-monomictic lake, Lake Alchichica, Mexico (four samplings: 2006-2008, 2010); the results were compared with those obtained from another lake from the re- gion, La Preciosa, sampled in 2010. Bacteria, autotrophic picoplankton (APP) and flagellates were analysed using epifluorescence microscopy. Ciliates were evaluated either in DAPI stained samples (looking for pigmented organelles and/or ingested phototrophs) or in quantitative protargol stain (QPS) permanent preparations, where they were identified at the genus or species level. The end of the stratification period in Lake Alchichica was characterized by almost uniform heterotrophic picoplankton (HPP) numbers (106 cells mL–1
) throughout the water column. Meanwhile, APP showed epilimnetic and/or metalimnetic maxima of 105
cells mL–1 followed
by an order of magnitude drop in the hypolimnion. A very important peak (105
cells mL–1 ) of the autotrophic or mixotrophic flagellate
Pyramimonas sp. was observed repeatedly above and within the oxycline of Lake Alchichica. Ciliate biomass maxima were found around the oxycline and in the above-bottom layer. The top of the oxycline was dominated by Euplotes spp. and Spirostomum teres fine- to coarse-filter feeders (feeding upon APP, nanodiatoms and algae). Raptorial haptorids (in particular, Phialina sp.) were the second most important group, generally occupying the layer below euplotids, followed by Holophrya and Prorodon facultative anaer- obic prostomes. Sometimes, strictly anaerobic Caenomorpha sp. was found to be important in the anoxic hypolimnion. Minute pi- coplankton feeding species (both APP and heterotrophic bacteria feeders) were important throughout the water column: in the epilimnion, vorticellids (2006-2008) or scuticociliates (2010) dominated. Typically, the scuticociliate maximum was located in the oxycline and/or above the bottom. Some microaerophilic species were isolated; thus, their identification could be carried out. However, the apparent polymorphic ciliate life cycles were not described completely, and the species composition was only estimated: two dom- inant species (SC 1 - Cristigera-like and SC 2 - Cyclidim-like) covered nearly the total scuticociliate biomass. Strictly anaerobic scu- ticociliates were not isolated but observed in the deepest layers of the lake (bacteria symbiotic Isocyclidium globosum and Cristigera sp.). Significant statistical relation within the ciliate distribution and environmental variables was not confirmed due to unique species composition in the respective years. However, general trends in the distribution of ciliates on a species level were observed. Scutic- ociliates, including two important tentatively identified species, did not present unambiguous ecological position, and the study of their live cycle should be the next step in investigations
Miopatía por cuerpos de inclusión. Caso clínico y revisión de la literatura
La miositis por cuerpos de inclusión (MCI) es una patología poco común que se presenta en individuos mayores de 50 años y con mayor frecuencia en hombres; sin embargo, los síntomas pueden empezar 20 años antes de su diagnóstico. Hasta un 30% de los casos de miopatías inflamatorias pueden ser de MCI y su prevalencia varía en los diferentes países y grupos étnicos. Clínicamente se manifiesta como debilidad lentamente progresiva proximal y distal. En este artículo se presenta un caso de una paciente de 78 años con antecedentes previos de diabetes mellitus tipo 2, hipertensión arterial, e hipotiroidismo, con cuadro de 18 meses de evolución consistente en debilidad de miembros inferiores, incapacidad para subir y bajar escaleras, limitación en la marcha, acompañado de disestesias. Se realizó la medición de la creatin quinasa (CK) y su valor inicial fue 7820, la electromiografía y neuroconducciones mostraron polineuropatia axonal motora en las cuatro extremidades y miopatía inflamatoria. Se trató con glucorticoides a dosis de 1 mg/kg y después de seis meses de tratamiento no se observó mejoría. Se decide tomar biopsia muscular que mostró miopatía por cuerpos de inclusión, lo que explicó la falla terapéutica inicial. Este caso es interesante desde el punto de vista clínico, ya que no es frecuente la elevación de la CK en los niveles que presentó la paciente y por las múltiples comorbilidades asociadas
A connection between star formation activity and cosmic rays in the starburst galaxy M 82
Although Galactic cosmic rays (protons and nuclei) are widely believed to be
dominantly accelerated by the winds and supernovae of massive stars, definitive
evidence of this origin remains elusive nearly a century after their discovery
[1]. The active regions of starburst galaxies have exceptionally high rates of
star formation, and their large size, more than 50 times the diameter of
similar Galactic regions, uniquely enables reliable calorimetric measurements
of their potentially high cosmic-ray density [2]. The cosmic rays produced in
the formation, life, and death of their massive stars are expected to
eventually produce diffuse gamma-ray emission via their interactions with
interstellar gas and radiation. M 82, the prototype small starburst galaxy, is
predicted to be the brightest starburst galaxy in gamma rays [3, 4]. Here we
report the detection of >700 GeV gamma rays from M 82. From these data we
determine a cosmic-ray density of 250 eV cm-3 in the starburst core of M 82, or
about 500 times the average Galactic density. This result strongly supports
that cosmic-ray acceleration is tied to star formation activity, and that
supernovae and massive-star winds are the dominant accelerators.Comment: 18 pages, 4 figures; published in Nature; Version is prior to
Nature's in-house style editing (differences are minimal
Discovery of very high energy gamma rays from PKS 1424+240 and multiwavelength constraints on its redshift
We report the first detection of very-high-energy (VHE) gamma-ray emission
above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The
photon spectrum above 140 GeV measured by VERITAS is well described by a power
law with a photon index of 3.8 +- 0.5_stat +- 0.3_syst and a flux normalization
at 200 GeV of (5.1 +- 0.9_stat +- 0.5_syst) x 10^{-11} TeV^-1 cm^-2 s^-1, where
stat and syst denote the statistical and systematical uncertainty,
respectively. The VHE flux is steady over the observation period between MJD
54881 and 55003 (2009 February 19 to June 21). Flux variability is also not
observed in contemporaneous high energy observations with the Fermi Large Area
Telescope (LAT). Contemporaneous X-ray and optical data were also obtained from
the Swift XRT and MDM observatory, respectively. The broadband spectral energy
distribution (SED) is well described by a one-zone synchrotron self-Compton
(SSC) model favoring a redshift of less than 0.1. Using the photon index
measured with Fermi in combination with recent extragalactic background light
(EBL) absorption models it can be concluded from the VERITAS data that the
redshift of PKS 1424+240 is less than 0.66.Comment: accepted for publication, Ap
Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524
The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at
redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime
by VERITAS between November 2006 and April 2008. These data encompass the two-,
and three-telescope commissioning phases, as well as observations with the full
four-telescope array. \objectname{1ES 0806+524} is detected with a statistical
significance of 6.3 standard deviations from 245 excess events. Little or no
measurable variability on monthly time scales is found. The photon spectrum for
the period November 2007 to April 2008 can be characterized by a power law with
photon index between
300 GeV and 700 GeV. The integral flux above 300 GeV is
which corresponds to 1.8% of the Crab Nebula flux. Non contemporaneous
multiwavelength observations are combined with the VHE data to produce a
broadband spectral energy distribution that can be reasonably described using a
synchrotron-self Compton model.Comment: 14 pages, 4 figures, accepted to APJ
Multiwavelength Observations of LS I +61 303 with VERITAS, Swift and RXTE
We present results from a long-term monitoring campaign on the TeV binary LSI
+61 303 with VERITAS at energies above 500 GeV, and in the 2-10 keV hard X-ray
bands with RXTE and Swift, sampling nine 26.5 day orbital cycles between
September 2006 and February 2008. The binary was observed by VERITAS to be
variable, with all integrated observations resulting in a detection at the 8.8
sigma (2006/2007) and 7.3 sigma (2007/2008) significance level for emission
above 500 GeV. The source was detected during active periods with flux values
ranging from 5 to 20% of the Crab Nebula, varying over the course of a single
orbital cycle. Additionally, the observations conducted in the 2007-2008
observing season show marginal evidence (at the 3.6 sigma significance level)
for TeV emission outside of the apastron passage of the compact object around
the Be star. Contemporaneous hard X-ray observations with RXTE and Swift show
large variability with flux values typically varying between 0.5 and 3.0*10^-11
ergs cm^-2 s^-1 over a single orbital cycle. The contemporaneous X-ray and TeV
data are examined and it is shown that the TeV sampling is not dense enough to
detect a correlation between the two bands.Comment: 30 pages, 5 figures, 2 table, Accepted for publication in The
Astrophysical Journa
Detection of Extended VHE Gamma Ray Emission from G106.3+2.7 with VERITAS
We report the detection of very-high-energy (VHE) gamma-ray emission from
supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the
VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission
overlapping the elongated radio SNR. The 7.3 sigma (pre-trials) detection has a
full angular extent of roughly 0.6deg by 0.4deg. Most notably, the centroid of
the VHE emission is centered near the peak of the coincident 12CO (J = 1-0)
emission, 0.4deg away from the pulsar PSR J2229+6114, situated at the northern
end of the SNR. Evidently the current-epoch particles from the pulsar wind
nebula are not participating in the gamma-ray production. The VHE energy
spectrum measured with VERITAS is well characterized by a power law dN/dE =
N_0(E/3 TeV)^{-G} with a differential index of G = 2.29 +/- 0.33stat +/-
0.30sys and a flux of N_0 = (1.15 +/- 0.27stat +/- 0.35sys)x 10^{-13} cm^{-2}
s^{-1} TeV^{-1}. The integral flux above 1 TeV corresponds to ~5 percent of the
steady Crab Nebula emission above the same energy. We describe the observations
and analysis of the object and briefly discuss the implications of the
detection in a multiwavelength context.Comment: 5 pages, 2 figure
Reviving the Philippine Economy under a Responsible New Normal
After the reclassification of areas under enhanced community quarantine (ECQ) to general community quarantine (GCQ), the urgent task for the Philippine government is to provide an exit plan to revive the Philippine economy. Given the significant economic damage resulting from the shutdown of roughly 75 percent of the country’s total production in the National Capital Region (NCR) and in the CALABARZON and Central Luzon areas, a gradual reopening of the economy will be necessary to prevent further economic damage that could not only be difficult to repair, but also long to overcome. Indeed, based on recent directives from the government, a substantial number of industries and services have thus been allowed to operate in both the ECQ and GCQ areas. However, as the Philippine government begins to calibrate the opening of sectors, there remain concerns as to how this process will affect jobs and livelihoods now and beyond. In this context, an economic recovery plan that talks about short-term, a transition, and full recovery phases— encompassing a revision of the current Philippine Development Plan without losing sight of the long-term goals envisioned in Ambisyon Natin 2040— is still needed. Indeed, a key component of AmBisyon 2040 has been of building resiliency over the long-term, which includes resiliency in health and economic shocks apart from natural disasters. At the same time, this recovery plan should also be accompanied by structural reforms to enhance its implementation. The Department of Finance has crafted a four-pillar socio-economic strategy aimed at: (a) supporting the more vulnerable sectors of society; (b) increasing medical resources to contain the virus and offer safety to front-liners; (c) keeping the economy afloat through financial emergency initiatives; and (d) creating jobs and sustaining the economy. Yet while enumerating the costs of these plans, the said strategy lacked details on how the country could achieve some of the goals without the availability of widespread testing and adequate health facilities. Loan guarantees, cash transfers, and other forms of subsidies can revive disrupted supply chains but cannot restore productivity in the middle of a persisting health crisis, while the uncertainty of a possible outbreak can keep workers from supplying goods and services. It is crucial to have these programs and institutions in place since a number of cities, regions and provinces have started to reopen. A modified community quarantine without the necessary health system investments, protection measures, and economic recovery plan risks amounting to an unregulated herd immunity strategy. Opting for herd immunity allows governments to blame the failure of the health and economic system on the virus, rather than on bad governance. Under current GCQ protocols, the burden on containing the virus is mostly transferred to the public. Unless the government provides mass testing, the problem of information is aggravated, probably raising the transmission risks. Moreover, unregulated herd immunity will be differentially felt by the poor. As healthy workers may recover their earnings from the modified quarantine, the poor, who have limited access to the health services and are thus more susceptible to the virus, are unlikely to benefit from this system. In effect, this will only exacerbate the inequality that prevails in the country. Moving towards a responsible new normal requires a strategy that addresses both people’s wellbeing and the socio-economic weaknesses exposed by COVID-19. Thus, the strategy should have the following elements
Discovery of VHE -ray emission from the SNR G54.1+0.3
We report the discovery of very high energy gamma-ray emission from the
direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray
observatory. The TeV signal has an overall significance of 6.8 and
appears point-like given the 5 resolution of the instrument. The
integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant
emission is measured between 250 GeV and 4 TeV, well described by a power-law
energy spectrum dN/dE E with a photon index . We find no evidence of time variability among
observations spanning almost two years. Based on the location, the morphology,
the measured spectrum, the lack of variability and a comparison with similar
systems previously detected in the TeV band, the most likely counterpart of
this new VHE gamma-ray source is the PWN in the SNR G54.1+0.3. The measured
X-ray to VHE gamma-ray luminosity ratio is the lowest among all the nebulae
supposedly driven by young rotation-powered pulsars, which could indicate a
particle-dominated PWN.Comment: 5 pages, 2 figure, Latex, emulateapj style, accepted by the
Astrophysical Journal Letter
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