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Multiplex polymerase chain reaction testing for gastrointestinal pathogens was performed on a longitudinal cohort of 110 men who have sex with men taking human immunodeficiency virus preexposure prophylaxis. At least 1 pathogen was detected among 50 (45%) participants, with some participants testing positive for the same pathogen on multiple consecutive visits over a period of months. [ABSTRACT FROM AUTHOR]

Abstract: Variation in the shell coiling, or chirality, of land snails provides an opportunity to investigate the potential for “single‐gene” speciation, because mating between individuals of opposite chirality is believed not possible if the snails mate in a face‐to‐face position. However, the evidence in support of single‐gene speciation is sparse, mostly based upon single‐gene mitochondrial studies and patterns of chiral variation between species. Previously, we used a theoretical model to show that as the chiral phenotype of offspring is determined by the maternal genotype, occasional chiral reversals may take place and enable gene flow between mirror image morphs, preventing speciation. Here, we show empirically that there is recent or ongoing gene flow between the different chiral types of Japanese Euhadra species. We also report evidence of mating between mirror‐image morphs, directly showing the potential for gene flow. Thus, theoretical models are suggestive of gene flow between oppositely coiled snails, and our empirical study shows that they can mate and that there is gene flow in Euhadra. More than a single gene is required before chiral variation in shell coiling can be considered to have created a new species. [ABSTRACT FROM AUTHOR]

Standard processing of seismic events for reporting in bulletins is usually done one-at-a time. State-of-the-art relative event methods, often involving cross correlation, are increasingly used and have improved estimates of event parameters for event detection, location and magnitude. This is because relative event techniques can simultaneously reduce measurement error and effects of model error. We show how cross correlation can be used to assign relative magnitudes for neighbouring seismic events distributed over a large region in east Asia and quantify to what extent the uncertainty in these values increases as waveform similarity breaks down. We find that cross correlation works well for magnitude comparison of two events when it is expected that they generate very similar signals even if these may be almost buried in large amounts of noise. This may be the case when investigating repeating earthquakes or nuclear explosions within a few kilometres of each other. Cross correlation is the optimal detector in these cases assuming noise is white and Gaussian, and also provides the least-squares solution for the relative amplitudes. However, when the waveform similarity of the underlying signals breaks down, due to interevent separation distance, source time function differences or focal mechanism differences, these assumptions are no longer valid and a bias is introduced into the relative magnitude measurement. This bias due to degradation of waveform similarity is modelled here with synthetics and an analytic expression for it is derived based on three terms—the cross-correlation coefficient (CC), and the signal-to-noise ratio (SNR) of the larger and smaller events. The analytic expression is a good match to the observed bias in the data. If the equation for relative magnitude is rewritten to correct for the bias due to the CC, a new equation results which is simply the log of the ratio of the L2 norms. The bias due to SNRs is still present because the observed waveforms inevitably contain both signal and noise. However, this bias is predicted to be minimal for typical detection thresholds. Making measurements of the ratio of the L2 norms is shown to remove the bias due to degradation of waveform similarity for real data. The scatter of these cross-correlation measurements of relative magnitude is much less than those obtained by differencing magnitudes in a traditional catalogue. Of 14 025 events in and near China, 34 per cent had over an order of magnitude reduction in the median standard deviation (0.0342 magnitude units) as compared to the estimated scatter in the catalogue (0.3454 magnitude units). And 78 per cent of the events show a factor 3 improvement or better in the precision of relative event size measured as the ratio of the L2 norms as compared to the precision of the catalogue for relative magnitudes. These results suggest that the ratio of the L2 norms is an appropriate measure of relative magnitudes for general seismicity of a monitoring region, when there is significant waveform dissimilarity for neighbouring events. This measure maintains a higher degree of measurement precision as compared to the catalogue. [ABSTRACT FROM AUTHOR]

Witchcraft has been documented across the globe. The widespread occurrence of such beliefs in modern Africa affects politics, economic development, and poverty alleviation. Anthropologists have analysed the semiotics of African witchcraft, but there is less information on distributional issues. An important question is which communities are most affected, and why? Using data from a survey of 182 villages and 2,443 household heads in the Gola Forest region of eastern Sierra Leone, we examine three manifestations of witchcraft – concerns, conflicts, and detection. We find that where patrimonial relations of agrarian production remain strong, and in settings where market forces are now well established, witchcraft is less of a concern. By contrast, witchcraft manifestations are higher in communities experiencing the competing pull of patrimonial and market norms. Witchcraft, we conclude, is a product of normative ambiguity. [ABSTRACT FROM PUBLISHER]

Was the civil war in Sierra Leone (1991–2002) fought for diamonds, or was it a peasant insurgency motivated by agrarian grievances? The evidence on both sides is less than conclusive. This article scrutinizes the peasant insurgency argument via a more rigorous methodology. Hypotheses concerning intra-peasant tensions over marriage and farm labour are derived from an examination of the anthropological literature. These are tested using econometric tools, applied to data from a randomized survey of 2,239 households in 178 villages surrounding the Gola Forest in eastern and southern Sierra Leone, the cradle of the war. It is shown that a decade after the war ended peasant disputes over marriage continue to mark out an incipient class divide in isolated rural communities, as evidenced by cases presented in local courts and family moots. Disputes mainly involve a village elder suing a young man with weak social protection. Fines are exceptionally high, and mostly paid off in the form of coerced farm labour. It is argued that grievance over this long-standing form of labour exploitation fed insurgency, and contributed to the otherwise puzzlingly high levels of peasant-upon-peasant violence associated with the war in Sierra Leone. [ABSTRACT FROM PUBLISHER]

We report on more than 100 earthquake waveform doublets in five subduction zones, including an earthquake nest in Bucaramanga, Colombia. Each doublet is presumed to be a pair of earthquakes that repeat at essentially the same location. These doublets are important for studying earthquake physics, as well as temporal changes of the inner core. Particularly, our observation from one South Sandwich Islands (SSI) doublet recorded at station INK in Canada shows an inner core traveltime change of ∼0.1 s over ∼6 yr, confirming the inner-core differential motion occurring beneath Central America. Observations from one Aleutian Islands doublet, recorded at station BOSA in South Africa, and from one Kuril Islands doublet, recorded at station BDFB in Brazil, show an apparent inner core traveltime change of ∼0.1 s over ∼7 yr and ∼6 yr, respectively, providing evidence for the temporal change of inner core properties beneath Central Asia and Canada, respectively. On the other hand, observations from one Tonga–Fiji–Solomon Islands doublet, recorded at station PTGA in Brazil, and from one Bucaramanga doublet, recorded at station WRAB in Australia and station CHTO in Thailand, show no/little temporal change (no more than 0.005 s yr−1, if any) of inner core traveltimes for the three corresponding ray paths for which the path in the inner core is nearly parallel to the equatorial plane. Such a pattern of observations showing both presence and possible absence of inner-core traveltime change can be explained by the geometry and relative directions of ray path, lateral velocity gradient and inner-core particle motion due to an eastward super-rotation of a few tenths of a degree per year. [ABSTRACT FROM AUTHOR]

The wars in Liberia and Sierra Leone have been linked to the condition of urbanized youth. Recent research in southeastern Sierra Leone and north-western Liberia suggests the rural context is of greater significance. The fighting was mainly in rural areas, involved mainly rural youth, and adapted itself to their local concerns. A model of war as the work of urban criminal gangs, reflecting local student politics in the 1970s and embraced internationally, is ripe for replacement by a model of war as agrarian revolt. This would open up the possibility of a more coherent regional analysis of recent West African conflicts. The key to conflict resolution in the region, it is suggested, is an emphasis on agrarian justice, including reform of customary land and marriage law. [ABSTRACT FROM AUTHOR]

The inner core has long been recognized as a part of the process by which fluid core convection is maintained and as an influence upon the magnetic field. Evidence from several seismological studies in recent years has mounted to indicate that the inner core has anisotropic velocities with large-scale (degree one) variation in strength of the differences from isotropy, and fine-scale (a few kilometres) inhomogeneities of structure. Indications have also been found of systematic changes in the travel time of seismic waves passing through the inner core – which have been interpreted as evidence that the inner core is rotating in an easterly direction, relative to the mantle, at a rate fast enough to be perceived on human timescales. The rate has been dismissed as too slow or physically impossible, but additional evidence has accumulated in support of what may be an emerging consensus that the inner core has a super-rotation of a few tenths of a degree per year. Paul G Richards presented the 1998 Harold Jeffreys Lecture to the RAS on 12 March 1999. [ABSTRACT FROM AUTHOR]

Reviews literature of the 1980's concerned with the social and political implications of famines. The study of famines in a social and political context is complicated by the schism between social and biological sciences that results in a stratification of the literature between predominantly political or predominantly ecological or biological concerns without merging the two into a coherent whole.

Background Pre-exposure prophylaxis (PrEP) effectively reduces HIV acquisition, but its efficacy depends on continued engagement through periods of high and low risk. Persistence in HIV prevention care has been low in real-world settings. In our program, 32% of patients are lost to care after their first visit and only 35% of patients are retained at their planned third visit. Reasons for low persistence in care are poorly described. Methods We identified all MSM who started PrEP between July 2015 and June 2018 at a sexual health clinic in an urban academic medical center in New York and had not had a visit in ≥6 months. We called patients between July 2018 and January 2019; those who were English speaking were given the option to complete an online questionnaire about current PrEP status, reasons for disengagement, and social and behavioral determinants of health (SBDH). Results Up to 710 patients were eligible for the study; over 700 calls were made. 125 participants agreed to participate and 57 (46%) completed the questionnaire. 24 patients (42%) were still actively taking PrEP. The most common reasons for starting PrEP were fear of getting HIV (58%), high self-perceived HIV risk (28%), and recommendations from friends (26%). Among those no longer taking PrEP, the most common reasons for discontinuation were cost/insurance issues (32%), lower perceived HIV risk (18%), concern about long-term side effects (12%), and trouble attending every-3-month appointments (12%). For those stopping due to lower perceived risk, 40% were in a monogamous relationship, 60% were less sexually active, and 20% always used a condom or did not engage in receptive anal intercourse. 56% of patients had at least 1 major life event in the preceding 3 months, including loss of a job (25%), breakup with a partner (12%), illness or death of a family member (11%), or unstable housing (8%). 47% used drugs or alcohol before sex in the past month including 39% not on PrEP. Conclusion Reasons for engagement, disengagement, and re-engagement are highly variable at the individual level. Cost and insurance issues were common in spite if clinic resources available to cover the cost of visits and medications. Life trauma was common. Individualized interventions to address SBDH may be required to engage and retain individuals in HIV prevention care. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]