Cohesion development in disrupted soils as affected by clay and organic matter content and temperature

Soils were dispersed and separated into sand, silt, and clay fractions that were reconstituted to give mixtures of each soil with 5 to 40% clay. In the range from 0 to 35% clay, higher clay contents resulted in greater stability. Rate of cohesion recovery was over 10 times as fast at 90°C as it was at 23°C, showing that the processes Involved are physical-chemical rather than biological. Maximum rates of cohesion recovery occurred at moderate soil water tensions, probably because some tension is needed to pull the particles into direct contact, but a continuous water phase is also essential to allow diffusion of bonding agents to the contact points. Since diffusion rates in water increase 300%, while rate of cohesion recovery increased 1000% when temperature was raised from 23 to 90°C, other factors, such as higher Mobilities at higher temperatures of compounds contributing hooding ions to the solution. probably play a role In the rate of cohesion recovery. Recovery of cohesion was more rapid in the soil with organic C contents of 0.004 kg/kg than in the soil with 0.012 kg/kg. When the organic matter was removed with H2O2 from the soil with 0.012 kg C/kg, its rate of cohesion recovery increased. Rate of cohesion recovery of this high organic matter soil was also increased by aging it at 0.1 kg H2O/kg soil compared to 0.2 kg/kg. A possible explanation is that organic coatings, tending to prevent direct contact and bonding of adjacent projections of mineral surfaces, are forced away from contact points by extremely strong forces that pull the adjacent minerals together when soil water tensions are high. When the higher organic matter soil had been consolidated by air-drying and rehydrated, its rate of cohesion recovery was just as rapid as that of the soil with low organic matter

Screening for Syphilis Infection in Nonpregnant Adults and Adolescents: US Preventive Services Task Force Recommendation Statement

Clinical Review & Education US Preventive Services Task Force | RECOMMENDATION STATEMENT Screening for Syphilis Infection in Nonpregnant Adults and Adolescents US Preventive Services Task Force Recommendation Statement US Preventive Services Task Force (USPSTF) Editorial page 2281 IMPORTANCE In 2014, 19 999 cases of syphilis were reported in the United States. Left untreated, syphilis can progress to late-stage disease in about 15% of persons who are infected. Late-stage syphilis can lead to development of inflammatory lesions throughout the body, which can lead to cardiovascular or organ dysfunction. Syphilis infection also increases the risk for acquiring or transmitting HIV infection. OBJECTIVE To update the 2004 US Preventive Services Task Force (USPSTF) recommendation on screening for syphilis infection in nonpregnant adults. Screening for syphilis in pregnant women was updated in a separate recommendation statement in 2009 (A recommendation). EVIDENCE REVIEW The USPSTF reviewed the evidence on screening for syphilis infection in asymptomatic, nonpregnant adults and adolescents, including patients coinfected with other sexually transmitted infections (such as HIV). Author Audio Interview at jama.com Related article page 2328 and JAMA Patient Page page 2367 CME Quiz at jamanetworkcme.com and CME Questions page 2342 Related articles at jamadermatology.com, jamaneurology.com, jamapediatrics.com FINDINGS The USPSTF found convincing evidence that screening for syphilis infection in asymptomatic, nonpregnant persons at increased risk for infection provides substantial benefit. Accurate screening tests are available to identify syphilis infection in populations at increased risk. Effective treatment with antibiotics can prevent progression to late-stage disease, with small associated harms, providing an overall substantial health benefit. CONCLUSIONS AND RECOMMENDATION The USPSTF recommends screening for syphilis infection in persons who are at increased risk for infection. (A recommendation) Authors/Group Information: The USPSTF members are listed at the end of the article. JAMA. 2016;315(21):2321-2327. doi:10.1001/jama.2016.5824 Corresponding Author: Kirsten Bibbins-Domingo, PhD, MD, MAS ([email protected]). T he US Preventive Services Task Force (USPSTF) makes recommendations about the effectiveness of specific preventive care services for patients without obvious related signs or symptoms. It bases its recommendations on the evidence of both the benefits and harms of the service and an assessment of the bal- ance. The USPSTF does not consider the costs of providing a ser- vice in this assessment. The USPSTF recognizes that clinical decisions involve more con- siderations than evidence alone. Clinicians should understand the evidence but individualize decision making to the specific patient or situation. Similarly, the USPSTF notes that policy and coverage decisions involve considerations in addition to the evidence of clini- cal benefits and harms. Summary of Recommendation and Evidence The USPSTF recommends screening for syphilis infection in per- sons who are at increased risk for infection. (A recommendation) (Figure 1) jama.com See the Clinical Considerations section later in this article for in- formation on risk factors for infection. Rationale Importance The number of cases of primary and secondary syphilis have been in- creasing since 2000. In 2014, 19 999 cases (6.3 cases per 100 000 persons)ofprimaryandsecondarysyphiliswerereportedintheUnited States. 1 Left untreated, syphilis can progress to late-stage disease in approximately 15% of persons who are infected. 2 Consequences of late-stage syphilis include development of inflammatory lesions throughout the body (eg, aortitis, gummatous lesions, and osteitis), which can lead to cardiovascular or organ dysfunction. Syphilis in- fection of the central nervous system (neurosyphilis) can occur at any stage of disease and can result in blindness, paresis, tabes dor- salis, and dementia. Syphilis infection also increases the risk for ac- quiring or transmitting HIV infection. The USPSTF addresses screening for syphilis in pregnant women in a separate recommendation statement. 3 (Reprinted) JAMA June 7, 2016 Volume 315, Number 21 Copyright 2016 American Medical Association. All rights reserved. Downloaded From: http://jamanetwork.com/ by a University of California - Los Angeles User on 09/21/201