Flood magnitude-frequency and lithologic control on bedrock river incision in post-orogenic terrain

Mixed bedrock-alluvial rivers - bedrock channels lined with a discontinuous alluvial cover - are key agents in the shaping of mountain belt topography by bedrock fluvial incision. Whereas much research focuses upon the erosional dynamics of such rivers in the context of rapidly uplifting orogenic landscapes, the present study investigates river incision processes in a post-orogenic (cratonic) landscape undergoing extremely low rates of incision (> 5 m/Ma). River incision processes are examined as a function of substrate lithology and the magnitude and frequency of formative flows along Sandy Creek gorge, a mixed bedrock-alluvial stream in arid SE-central Australia. Incision is focused along a bedrock channel with a partial alluvial cover arranged into riffle-pool macrobedforms that reflect interactions between rock structure and large-flood hydraulics. Variations in channel width and gradient determine longitudinal trends in mean shear stress (τb) and therefore also patterns of sediment transport and deposition. A steep and narrow, non-propagating knickzone (with 5% alluvial cover) coincides with a resistant quartzite unit that subdivides the gorge into three reaches according to different rock erodibility and channel morphology. The three reaches also separate distinct erosional styles: bedrock plucking (i.e. detachment-limited erosion) prevails along the knickzone, whereas along the upper and lower gorge rock incision is dependent upon large formative floods exceeding critical erosion thresholds (τc) for coarse boulder deposits that line 70% of the channel thalweg (i.e. transport-limited erosion). The mobility of coarse bed materials (up to 2 m diameter) during late Holocene palaeofloods of known magnitude and age is evaluated using step-backwater flow modelling in conjunction with two selective entrainment equations. A new approach for quantifying the formative flood magnitude in mixed bedrock-alluvial rivers is described here based on the mobility of a key coarse fraction of the bed materials; in this case the d84 size fraction. A 350 m3/s formative flood fully mobilises the coarse alluvial cover with τb200-300 N/m2 across the upper and lower gorge riffles, peaking over 500 N/m2 in the knickzone. Such floods have an annual exceedance probability much less than 10- 2 and possibly as low as 10- 3. The role of coarse alluvial cover in the gorge is discussed at two scales: (1) modulation of bedrock exposure at the reach-scale, coupled with adjustment to channel width and gradient, accommodates uniform incision across rocks of different erodibility in steady-state fashion; and (2) at the sub-reach scale where coarse boulder deposits (corresponding to <i>τ</i><sub>b</sub> minima) cap topographic convexities in the rock floor, thereby restricting bedrock incision to rare large floods. While recent studies postulate that decreasing uplift rates during post-orogenic topographic decay might drive a shift to transport-limited conditions in river networks, observations here and elsewhere in post-orogenic settings suggest, to the contrary, that extremely low erosion rates are maintained with substantial bedrock channel exposure. Although bed material mobility is known to be rate-limiting for bedrock river incision under low sediment flux conditions, exactly how a partial alluvial cover might be spatially distributed to either optimise or impede the rate of bedrock incision is open to speculation. Observations here suggest that the small volume of very stable bed materials lining Sandy Creek gorge is distributed so as to minimise the rate of bedrock fluvial incision over time

Cosmic-Ray Positrons: Are There Primary Sources?

Cosmic rays at the Earth include a secondary component originating in collisions of primary particles with the diffuse interstellar gas. The secondary cosmic rays are relatively rare but carry important information on the Galactic propagation of the primary particles. The secondary component includes a small fraction of antimatter particles, positrons and antiprotons. In addition, positrons and antiprotons may also come from unusual sources and possibly provide insight into new physics. For instance, the annihilation of heavy supersymmetric dark matter particles within the Galactic halo could lead to positrons or antiprotons with distinctive energy signatures. With the High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have measured the abundances of positrons and electrons at energies between 1 and 50 GeV. The data suggest that indeed a small additional antimatter component may be present that cannot be explained by a purely secondary production mechanism. Here we describe the signature of the effect and discuss its possible origin.Comment: 15 pages, Latex, epsfig and aasms4 macros required, to appear in Astroparticle Physics (1999

First-person narratives around sexuality in residential healthcare settings: a meta-ethnographic synthesis

The aim of this review is to identify, critically appraise, and synthesise the existing literature exploring adults’ narratives around sexuality within residential healthcare settings from a first-person perspective. A systematic literature review was undertaken. Six databases were searched. A meta-ethnographic approach was used to synthesise studies’ findings. Thirteen studies using qualitative methodology that met the inclusion criteria were identified. The synthesis revealed six key themes: how service users define sexuality, sexuality as something not to be discussed (“privates are private”), sexuality as a separate aspect of the self (“sectionality”), hopes and fears for the future, the impact of the environment (“physicality of being physical”), and adapted sexuality. The studies included were of varying quality. Sexuality remains an important aspect for many residents, yet is rarely noted or discussed with them by healthcare staff. The residential healthcare environment presents implicit and explicit barriers to sexuality expression, causing residents to adapt how they experience their sexuality. Findings from this review highlight the importance of considering service users’ perspectives, and the need for open communication between residents and practitioners to facilitate care provision that acknowledges the barriers of the environment on sexuality and considers the person beyond the presenting illness

Sodomía y masculinidad en la ciudad de México (1821-1870)

This article explores, through the discursive analysis of sodomy’s court records, the socio-cultural constructions that operated within the control device of sexuality in Mexico City. It also examines the mechanisms of reproduction of dichotomous gender categories within the context of a system of domination which, during the nineteenth century, put both men and women through a prescriptive masculinity doctrine.El artículo indaga en las construcciones socio-culturales que operaron dentro del dispositivo de control de la sexualidad en la capital mexicana, a través del análisis discursivo de expedientes judiciales relativos a casos de sodomía. Se exploran mecanismos de reproducción de las categorías dicotómicas de género, dentro de un sistema de dominación que, a lo largo del siglo XIX, sujetó tanto a hombres como a mujeres a través de una masculinidad prescriptiva

Disparities and risks of sexually transmissible infections among men who have sex with men in China: a meta-analysis and data synthesis.

BACKGROUND: Sexually transmitted infections (STIs), including Hepatitis B and C virus, are emerging public health risks in China, especially among men who have sex with men (MSM). This study aims to assess the magnitude and risks of STIs among Chinese MSM. METHODS: Chinese and English peer-reviewed articles were searched in five electronic databases from January 2000 to February 2013. Pooled prevalence estimates for each STI infection were calculated using meta-analysis. Infection risks of STIs in MSM, HIV-positive MSM and male sex workers (MSW) were obtained. This review followed the PRISMA guidelines and was registered in PROSPERO. RESULTS: Eighty-eight articles (11 in English and 77 in Chinese) investigating 35,203 MSM in 28 provinces were included in this review. The prevalence levels of STIs among MSM were 6.3% (95% CI: 3.5-11.0%) for chlamydia, 1.5% (0.7-2.9%) for genital wart, 1.9% (1.3-2.7%) for gonorrhoea, 8.9% (7.8-10.2%) for hepatitis B (HBV), 1.2% (1.0-1.6%) for hepatitis C (HCV), 66.3% (57.4-74.1%) for human papillomavirus (HPV), 10.6% (6.2-17.6%) for herpes simplex virus (HSV-2) and 4.3% (3.2-5.8%) for Ureaplasma urealyticum. HIV-positive MSM have consistently higher odds of all these infections than the broader MSM population. As a subgroup of MSM, MSW were 2.5 (1.4-4.7), 5.7 (2.7-12.3), and 2.2 (1.4-3.7) times more likely to be infected with chlamydia, gonorrhoea and HCV than the broader MSM population, respectively. CONCLUSION: Prevalence levels of STIs among MSW were significantly higher than the broader MSM population. Co-infection of HIV and STIs were prevalent among Chinese MSM. Integration of HIV and STIs healthcare and surveillance systems is essential in providing effective HIV/STIs preventive measures and treatments. TRIAL REGISTRATION: PROSPERO NO: CRD42013003721

No evidence for the localized heating of solar wind protons at intense velocity shear zones

Using measurements from the Wind spacecraft at 1 AU, the heating of protons in the solar wind at locations of intense velocity shear is examined. The 4321 sites of intense shear in fast coronal hole origin plasma are analyzed. The proton temperature, the proton specific entropy, and the proton number density at the locations of the shears are compared with the same quantities in the plasmas adjacent to the shears. A very slight but statistically significant enhancement of the proton temperature is seen at the sites of the shears, but it is accompanied by a larger enhancement of the proton number density at the sites of the shears. Consequently, there is no enhancement of the proton specific entropy at the shear sites, indicating no production of entropy; hence, no evidence for plasma heating is found at the sites of the velocity shears. Since the shearing velocities have appreciable Mach numbers, the authors suggest that there can be a slight adiabatic compression of the plasma at the shear zones. Key Points No proton heating is observed at the sites of intense velocity shear Temperature‐density signatures are consistent with adiabatic compressions The compressions could be associated with the large Mach numbers of the shearsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106821/1/jgra50896.pd

Pelvic tenderness is not limited to the prostate in chronic prostatitis/chronic pelvic pain syndrome (CPPS) type IIIA and IIIB: comparison of men with and without CP/CPPS

Background: We wished to determine if there were differences in pelvic and non-pelvic tenderness between men with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) Type III and men without pelvic pain. Methods: We performed the Manual Tender Point Survey (MTPS) as described by the American College of Rheumatology on 62 men with CP/CPPS Type IIIA and IIIB and 98 men without pelvic pain. We also assessed tenderness of 10 external pelvic tender points (EPTP) and of 7 internal pelvic tender points (IPTP). All study participants completed the National Institutes of Health Chronic Prostatitis Symptom Inventory (NIH CPSI). Results: We found that men with CPPS were significantly more tender in the MTPS, the EPTPS and the IPTPS. CPSI scores correlated with EPTP scale but not with IPTP scale or prostate tenderness. Prostatic tenderness was present in 75% of men with CPPS and in 50% of men without CPPS. Expressed prostatic fluid leukocytosis was not associated with prostatic tenderness. Conclusion: Men with CP/CPPS have more tenderness compared to men without CPPS. Tenderness in men with CPPS is distributed throughout the pelvis and not specific to the prostate