2,404 research outputs found
Sensitivity of Antarctic Urospora penicilliformis (Ulotrichales, Chlorophyta) to ultraviolet radiation is life stage dependent
The sensitivity of different life stages of the eulittoral green alga Urospora penicilliformis (Roth) Aresch. to ultraviolet radiation (UVR) was examinedin the laboratory. Gametophytic filaments and propagules (zoospores and gametes) released from filaments were separately exposed to different fluence of radiation treatments consisting of PAR (P = 400700 nm), PAR + ultraviolet A (UVA) (PA, UVA = 320400 nm), and PAR + UVA + ultraviolet B (UVB) (PAB, UVB = 280320 nm). Photophysiological indices (ETRmax, Ek, and a) derived from rapid light curves were measured in controls, while photosynthetic efficiency and amount of DNA lesions in terms of cyclobutane pyrimidine dimers (CPDs) were measured after exposure to radiation treatments and after recovery in low PAR; pigments of propagules were quantified after exposure treatment only. The photosynthetic conversion efficiency (a) and photosynthetic capacity (rETRmax) were higher in gametophytes compared with the propagules. The propagules were slightly more sensitive to UVB-induced DNA damage; however, both life stages of the eulittoral inhabiting turf alga were not severely affected by the negative impacts of UVR. Exposure to a maximum of 8 h UVR caused mild effects on the photochemical efficiency of PSII and induced minimal DNA lesions in both the gametophytes and propagules. Pigment concentrations were not significantly different between PAR-exposed and PAR + UVRexposed propagules. Our data showed that U. penicilliformis from the Antarctic is ratherinsensitive to the applied UVR. This amphi-equatorial species possesses different protective mechanisms that can cope with high UVR in coldtemperatewaters of both hemispheres and in polar regions under conditions of increasing UVR as a consequence of further reduction of stratosphericozone
False positives complicate ancient pathogen identifications using high-throughput shotgun sequencing
Background: Identification of historic pathogens is challenging since false positives and negatives are a serious risk. Environmental non-pathogenic contaminants are ubiquitous. Furthermore, public genetic databases contain limited information regarding these species. High-throughput sequencing may help reliably detect and identify historic pathogens. Results: We shotgun-sequenced 8 16th-century Mixtec individuals from the site of Teposcolula Yucundaa (Oaxaca, Mexico) who are reported to have died from the huey cocoliztli (âGreat Pestilenceâ in Nahautl), an unknown disease that decimated native Mexican populations during the Spanish colonial period, in order to identify the pathogen. Comparison of these sequences with those deriving from the surrounding soil and from 4 precontact individuals from the site found a wide variety of contaminant organisms that confounded analyses. Without the comparative sequence data from the precontact individuals and soil, false positives for Yersinia pestis and rickettsiosis could have been reported. Conclusions: False positives and negatives remain problematic in ancient DNA analyses despite the application of high-throughput sequencing. Our results suggest that several studies claiming the discovery of ancient pathogens may need further verification. Additionally, true single molecule sequencingâs short read lengths, inability to sequence through DNA lesions, and limited ancient-DNA-specific technical development hinder its application to palaeopathology
Accurate Determination of Phenotypic Information from Historic Thoroughbred Horses by Single Base Extension
Historic DNA have the potential to identify phenotypic information otherwise invisible in the historical, archaeological and palaeontological record. In order to determine whether a single nucleotide polymorphism typing protocol based on single based extension (SNaPshotâą) could produce reliable phenotypic data from historic samples, we genotyped three coat colour markers for a sample of historic Thoroughbred horses for which both phenotypic and correct geotypic information were known from pedigree information in the General Stud Book. Experimental results were consistent with the pedigrees in all cases. Thus we demonstrate that historic DNA techniques can produce reliable phenotypic information from museum specimens.© 2010 Campana et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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America's red gold: multiple lineages of cultivated cochineal in Mexico
Cultivated cochineal (Dactylopius coccus) produces carminic acid, a valuable red dye used to color textiles, cosmetics, and food. Extant native D. coccus is largely restricted to two populations in the Mexican and the Andean highlands, although the insect's ultimate center of domestication remains unclear. Moreover, due to Mexican D. coccus cultivation's near demise during the 19th century, the genetic diversity of current cochineal stock is unknown. Through genomic sequencing, we identified two divergent D. coccus populations in highland Mexico: one unique to Mexico and another that was more closely related to extant Andean cochineal. Relic diversity is preserved in the crops of small-scale Mexican cochineal farmers. Conversely, larger-scale commercial producers are cultivating the Andean-like cochineal, which may reflect clandestine 20th century importation
Black Hole and Neutron Star Transients in Quiescence
We consider the X-ray luminosity difference between neutron star and black
hole soft X-ray transients (NS and BH SXTs) in quiescence. The current
observational data suggest that BH SXTs are significantly fainter than NS SXTs.
The luminosities of quiescent BH SXTs are consistent with the predictions of
binary evolution models for the mass transfer rate if (1) accretion occurs via
an ADAF in these systems and (2) the accreting compact objects have event
horizons. The luminosities of quiescent NS SXTs are not consistent with the
predictions of ADAF models when combined with binary evolution models, unless
most of the mass accreted in the ADAF is prevented from reaching the neutron
star surface. We consider the possibility that mass accretion is reduced in
quiescent NS SXTs because of an efficient propeller and develop a model of the
propeller effect that accounts for the observed luminosities. We argue that
modest winds from ADAFs are consistent with the observations while strong winds
are probably not.Comment: LateX, 37 pages, 7 figures; Accepted for publication in The
Astrophysical Journa
Search for Nucleon Decays induced by GUT Magnetic Monopoles with the MACRO Experiment
The interaction of a Grand Unification Magnetic Monopole with a nucleon can
lead to a barion-number violating process in which the nucleon decays into a
lepton and one or more mesons (catalysis of nucleon decay). In this paper we
report an experimental study of the effects of a catalysis process in the MACRO
detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux
upper limits at the level of for
, based on the search for
catalysis events in the MACRO data. We also analyze the dependence of the MM
flux limit on the catalysis cross section.Comment: 12 pages, Latex, 10 figures and 2 Table
Forgiveness-Reconciliation and Communication-Conflict-Resolution Interventions Versus Retested Controls in Early Married Couples
The first 6 months of marriage are optimal for marriage enrichment interventions. The Hope-Focused Approach to couple enrichment was presented as two 9-hr interventions--(a) Handling Our Problems Effectively (HOPE), which emphasized communication and conflict resolution, and (b) Forgiveness and Reconciliation through Experiencing Empathy (FREE). HOPE and FREE were compared with repeated assessment controls. Couples were randomly assigned and were assessed at pretreatment (t1); 1 month posttreatment (t2) and at 3- (t3), 6- (t4), and 12-month (t5) follow-ups using self-reports. In addition to self-report measures, couples were assessed at t1, t2, and t5 using salivary cortisol, and behavioral coding of decision making. Of 179 couples who began the study, 145 cases were analyzed. Both FREE and HOPE produced lasting positive changes on self-reports. For cortisol reactivity, HOPE and FREE reduced reactivity at t2, but only HOPE at t5. For coded behaviors, control couples deteriorated; FREE and HOPE did not change. Enrichment training was effective regardless of the focus of the training
A combined analysis technique for the search for fast magnetic monopoles with the MACRO detector
We describe a search method for fast moving ()
magnetic monopoles using simultaneously the scintillator, streamer tube and
track-etch subdetectors of the MACRO apparatus. The first two subdetectors are
used primarily for the identification of candidates while the track-etch one is
used as the final tool for their rejection or confirmation. Using this
technique, a first sample of more than two years of data has been analyzed
without any evidence of a magnetic monopole. We set a 90% CL upper limit to the
local monopole flux of in the
velocity range and for nucleon decay
catalysis cross section smaller than .Comment: 29 pages (12 figures). Accepted by Astroparticle Physic
Search for massive rare particles with MACRO
Massive rare particles have been searched for in the penetrating cosmic
radiation using the MACRO apparatus at the Gran Sasso National Laboratories.
Liquid scintillators, streamer tubes and nuclear track detectors have been used
to search for magnetic monopoles (MMs).
Based on no observation of such signals, stringent flux limits are
established for MMs as slow as a few 10^(-5)c. The methods based on the
scintillator and on the nuclear track subdetectors were also applied to search
for nuclearites. Preliminary results of the searches for charged Q-balls are
also presented.Comment: 20 pages, 9 EPS figures included with epsfi
Final results of magnetic monopole searches with the MACRO experiment
We present the final results obtained by the MACRO experiment in the search
for GUT magnetic monopoles in the penetrating cosmic radiation, for the range
. Several searches with all the MACRO sub-detectors
(i.e. scintillation counters, limited streamer tubes and nuclear track
detectors) were performed, both in stand alone and combined ways. No candidates
were detected and a 90% Confidence Level (C.L.) upper limit to the local
magnetic monopole flux was set at the level of cm
s sr. This result is the first experimental limit obtained in
direct searches which is well below the Parker bound in the whole range
in which GUT magnetic monopoles are expected.Comment: 12 pages, Latex, 9 figures and 2 Table
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