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Lowest Frequency (lowest + frequency)
Selected AbstractsCross-spectral analysis of the X-ray variability of Markarian 421MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002Y. H. Zhang ABSTRACT Using the cross-spectral method, we confirm the existence of the X-ray hard lags discovered with cross-correlation function technique during a large flare of Mrk 421 observed with BeppoSAX. For the 0.1,2 versus 2,10 keV light curves, both methods suggest sub-hour hard lags. In the time domain, the degree of hard lag, i.e. the amplitude of the 3.2,10 keV photons lagging the lower energy ones, tends to increase with the decreasing energy. In the Fourier frequency domain, by investigating the cross-spectra of the 0.1,2/2,10 keV and the 2,3.2/3.2,10 keV pairs of light curves, the flare also shows hard lags at the lowest frequencies. However, with the present data, it is impossible to constrain the dependence of the lags on frequencies even though the detailed simulations demonstrate that the hard lags at the lowest frequencies probed by the flare are not an artefact of sparse sampling, Poisson and red noise. As a possible interpretation, the implication of the hard lags is discussed in the context of the interplay between the (diffusive) acceleration and synchrotron cooling of relativistic electrons responsible for the observed X-ray emission. The energy-dependent hard lags are in agreement with the expectation of an energy-dependent acceleration time-scale. The inferred magnetic field (B, 0.11 G) is consistent with the value inferred from the spectral energy distributions of the source. Future investigations with higher quality data that show whether or not the time-lags are energy-/frequency-dependent will provide a new constraint on the current models of the TeV blazars. [source] Worldwide allele frequencies of the human apolipoprotein E gene: Climate, local adaptations, and evolutionary historyAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Dan T.A. Eisenberg Abstract The ,4 allele of the apolipoprotein E (APOE) gene is associated with increased cholesterol levels and heart disease. Population allele frequencies of APOE have previously been shown to vary, with ,4 frequencies generally increasing with latitude. We hypothesize that this trend resulted from natural selection protecting against low-cholesterol levels. In high-latitude cold environments and low-latitude hot environments, metabolic rate is elevated, which could require higher cholesterol levels. To explore this hypothesis, we compiled APOE allele frequencies, latitude, temperature, and elevation from populations around the world. ,4 allele frequencies show a curvilinear relationship with absolute latitude, with lowest frequencies found in the mid-latitudes where temperatures generally require less expenditure on cooling/thermogenesis. Controlling for population structure in a subset of populations did not appreciably change this pattern of association, consistent with selection pressures that vary by latitude shaping ,4 allele frequencies. Temperature records also predict APOE frequency in a curvilinear fashion, with lowest ,4 frequencies at moderate temperatures. The model fit between historical temperatures and ,4 is less than between latitude and ,4, but strengthened after correcting for estimated temperature differences during the Paleolithic. Contrary to our hypothesis, we find that elevation did not improve predictive power, and an integrated measure of the cholesterol effect of multiple APOE alleles was less related to latitude than was ,4 alone. Our results lend mixed support for a link between past temperature and human APOE allele distribution and point to the need to develop better models of past climate in future analyses. Am J Phys Anthropol 143:13,20, 2010. © 2010 Wiley-Liss, Inc. [source] Field hearing measurements of the Atlantic sharpnose shark Rhizoprionodon terraenovaeJOURNAL OF FISH BIOLOGY, Issue 10 2009B. M. Casper Field measurements of hearing thresholds were obtained from the Atlantic sharpnose shark Rhizoprionodon terraenovae using the auditory evoked potential method (AEP). The fish had most sensitive hearing at 20 Hz, the lowest frequency tested, with decreasing sensitivity at higher frequencies. Hearing thresholds were lower than AEP thresholds previously measured for the nurse shark Ginglymostoma cirratum and yellow stingray Urobatis jamaicensis at frequencies <200 Hz, and similar at 200 Hz and above. Rhizoprionodon terraenovae represents the closest comparison in terms of pelagic lifestyle to the sharks which have been observed in acoustic field attraction experiments. The sound pressure levels that would be equivalent to the particle acceleration thresholds of R. terraenovae were much higher than the sound levels which attracted closely related sharks suggesting a discrepancy between the hearing threshold experiments and the field attraction experiments. [source] Possible relationship of cranial traumatic injuries with violence in the south-east Iberian Peninsula from the Neolithic to the Bronze AgeAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009S.A. Jiménez-Brobeil Abstract The main aim of this study was to analyze the presence and distribution of cranial trauma, as possible evidence of violence, in remains from the Neolithic to Bronze Age from the SE Iberian Peninsula. The sample contains skulls, crania, and cranial vaults belonging to 410 prehistoric individuals. We also studied 267 crania from medieval and modern times for comparative purposes. All lesions in the prehistoric crania are healed and none of them can be attributed to a specific weapon. In all studied populations, injuries were more frequent in adults than in subadults and also in males than in females, denoting a sexual division in the risk of suffering accidents or intentional violence. According to the archeological record, the development of societies in the SE Iberian Peninsula during these periods must have entailed an increase in conflict. However, a high frequency of cranial traumatic injuries was observed in the Neolithic series, theoretically a less conflictive time, and the lowest frequency was in crania from the 3rd millennium B.C. (Copper Age), which is characterized by the archeologists as a period of increasing violence. The relatively large size and the high rate of injuries in Neolithic crania and the practice of cannibalism are strongly suggestive of episodes of interpersonal or intergroup conflict. The number and distribution of injuries in Bronze Age is consistent with the increase in violence at that time described by most archeologists. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Variation in dental wear and tooth loss among known-aged, older ring-tailed lemurs (Lemur catta): a comparison between wild and captive individualsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 11 2010Frank P. Cuozzo Abstract Tooth wear is generally an age-related phenomenon, often assumed to occur at similar rates within populations of primates and other mammals, and has been suggested as a correlate of reduced offspring survival among wild lemurs. Few long-term wild studies have combined detailed study of primate behavior and ecology with dental analyses. Here, we present data on dental wear and tooth loss in older (>10 years old) wild and captive ring-tailed lemurs (Lemur catta). Among older ring-tailed lemurs at the Beza Mahafaly Special Reserve (BMSR), Madagascar (n=6), the percentage of severe dental wear and tooth loss ranges from 6 to 50%. Among these six individuals, the oldest (19 years old) exhibits the second lowest frequency of tooth loss (14%). The majority of captive lemurs at the Indianapolis Zoo (n=7) are older than the oldest BMSR lemur, yet display significantly less overall tooth wear for 19 of 36 tooth positions, with only two individuals exhibiting antemortem tooth loss. Among the captive lemurs, only one lemur (a nearly 29 year old male) has lost more than one tooth. This individual is only missing anterior teeth, in contrast to lemurs at BMSR, where the majority of lost teeth are postcanine teeth associated with processing specific fallback foods. Postcanine teeth also show significantly more overall wear at BMSR than in the captive sample. At BMSR, degree of severe wear and tooth loss varies in same aged, older individuals, likely reflecting differences in microhabitat, and thus the availability and use of different foods. This pattern becomes apparent before "old age," as seen in individuals as young as 7 years. Among the four "older" female lemurs at BMSR, severe wear and/or tooth loss do not predict offspring survival. Am. J. Primatol. 72:1026,1037, 2010. © 2010 Wiley-Liss, Inc. [source] Interactions between zoo-housed great apes and local wildlifeAMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2009S.R. Ross Abstract Although there are published reports of wild chimpanzees, bonobos, and orangutans hunting and consuming vertebrate prey, data pertaining to captive apes remain sparse. In this survey-based study, we evaluate the prevalence and nature of interactions between captive great apes and various indigenous wildlife species that range into their enclosures in North America. Our hypotheses were threefold: (a) facilities housing chimpanzees will report the most frequent and most aggressive interactions with local wildlife; (b) facilities housing orangutans and bonobos will report intermediate frequencies of these interactions with low levels of aggression and killing; and (c) facilities housing gorillas will report the lowest frequency of interactions and no reports of killing local wildlife. Chimpanzees and bonobos demonstrated the most aggressive behavior toward wildlife, which matched our predictions for chimpanzees, but not bonobos. This fits well with expectations for chimpanzees based on their natural history of hunting and consuming prey in wild settings, and also supports new field data on bonobos. Captive gorillas and orangutans were reported to be much less likely to chase, catch and kill wildlife than chimpanzees and bonobos. Gorillas were the least likely to engage in aggressive interactions with local wildlife, matching our predictions based on natural history. However unlike wild gorillas, captive gorillas were reported to kill (and in one case, eat) local wildlife. These results suggest that some behavioral patterns seen in captive groups of apes may be useful for modeling corresponding activities in the wild that may not be as easily observed and quantified. Furthermore, the data highlight the potential for disease transmission in some captive settings, and we outline the associated implications for ape health and safety. Am. J. Primatol. 71:458,465, 2009. © 2009 Wiley-Liss, Inc. [source] Polymorphic Alu Insertions and their Associations with MHC Class I Alleles and Haplotypes in the Northeastern ThaisANNALS OF HUMAN GENETICS, Issue 4 2005D. S. Dunn Summary Polymorphic Alu insertions (POALINs) are known to contribute to the strong polymorphic nature of the Major Histocompatibility Complex (MHC). Previous population studies on MHC POALINs were limited to only Australian Caucasians and Japanese. Here, we report on the individual insertion frequency of the five POALINs within the MHC class I region, their HLA-A and -B associations, and the three and four locus alpha block POALIN haplotype frequencies in the Northeastern (NE) Thai population. Of the five POALINs, the lowest frequency was 0.018 for AluyHF and the highest frequency was 0.292 for AluyHJ and AluyHG. The strongest positive associations between the POALINs and HLA class I alleles was between AluyMICB and HLA-B*57, AluyHJ and HLA-A*24 and HLA-A*01, and AluyHG and HLA-A*02, supporting previous findings in Caucasians and Japanese. Single POALIN haplotypes were found more frequently than multiple POALIN haplotypes. However, of the seven different POALIN haplotypes within the MHC alpha block, there were only two significant differences between the NE Thais, Caucasians and Japanese. This study confirms that the MHC POALINs are in linkage disequilibrium with HLA-A and ,B alleles and that there are significant frequency differences for some of the POALINs when compared between NE Thai, Caucasians and Japanese. [source] CYP1A2 polymorphism (C,>,A at position ,163) in Ovambos, Koreans and MongoliansCELL BIOCHEMISTRY AND FUNCTION, Issue 5 2007Junko Fujihara Abstract Cytochrome P450 1A2 (CYP1A2) plays an important role in metabolizing drugs and xenobiotics, and is a possible participant in the development of several human diseases. Recent studies have shown that genetic polymorphism of ,163 C,>,A single nucleotide mutation of CYP1A2 increases the risk of myocardial infarction and modulates CYP1A2 activity. In this study, we investigated the frequency of the ,163 C,>,A mutation in Ovambos (n,=,177), Koreans (n,=,250) and Mongolians (n,=,153) and compared our results with other studies. Detection of this single nucleotide polymorphism was by polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP). The frequencies of mutation (CYP1A2*,163A) in the Ovambos, Koreans and Mongolians were 0.46, 0.32 and 0.21, respectively. Ovambos showed a relatively higher frequency of mutation, similar to that of Tanzanians, while the Mongolians showed the lowest frequency of all study groups, including those from previous studies. This study is the first to investigate the distribution of the CYP1A2 (,163 C,>,A single nucleotide polymorphism) mutant allele in Ovambo, Korean and Mongolian populations. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||