Pathogenesis of black stones

We used infrared absorption spectroscopy to clarify the characteristics of black pigment in gallstones, which is insoluble and amorphous, and is considered to be a polymer of bilirubin or calcium bilirubinate with tetrapyrrol units. Black stones contain several metallic elemental components that exist as complex compounds with bilirubin. Chemical analysis of gallbladder bile indicates that the mechanism by which unconjugated bilirubin is precipitated depends on the pH level or on bile acid components. Black pigment is formed by the bridging action of mucin, forming complexes with metal ions in the bile. Hemolytic jaundice, liver cirrhosis, and cardiac valve replacement have been implicated in the etiology of black stone formation. In hemolytic jaundice and cardiac valve replacement, overproduction of bilirubin, due to hemolysis, is responsible for black stone formation, while in liver cirrhosis, a high concentration of ionized calcium and increased pH levels are the main factors in such stone formation.     

Formation and emission of large furans and oxygenated hydrocarbons from flames

Many oxygenated hydrocarbon species formed during combustion, such as furans, are highly toxic and detrimental to human health and the environment. These species may also increase the hygroscopicity of soot and strongly influence the effects of soot on regional and global climate. However, large furans and associated oxygenated species have not previously been observed in flames, and their formation mechanism and interplay with polycyclic aromatic hydrocarbons (PAHs) are poorly understood. We report on a synergistic computational and experimental effort that elucidates the formation of oxygen-embedded compounds, such as furans and other oxygenated hydrocarbons, during the combustion of hydrocarbon fuels. We used ab initio and probabilistic computational techniques to identify low-barrier reaction mechanisms for the formation of large furans and other oxygenated hydrocarbons. We used vacuum-UV photoionization aerosol mass spectrometry and X-ray photoelectron spectroscopy to confirm these predictions. We show that furans are produced in the high-temperature regions of hydrocarbon flames, where they remarkably survive and become the main functional group of oxygenates that incorporate into incipient soot. In controlled flame studies, we discovered ∼100 oxygenated species previously unaccounted for. We found that large alcohols and enols act as precursors to furans, leading to incorporation of oxygen into the carbon skeletons of PAHs. Our results depart dramatically from the crude chemistry of carbon- and oxygen-containing molecules previously considered in hydrocarbon formation and oxidation models and spearhead the emerging understanding of the oxidation chemistry that is critical, for example, to control emissions of toxic and carcinogenic combustion by-products, which also greatly affect global warming.Oxygenated hydrocarbons produced during combustion can have a wide range of detrimental effects on human health, air quality, and regional and global climate. Furans, for example, are compounds that contain five-membered rings with four carbon atoms and one oxygen atom. They are frequently observed in the exhaust plumes and nearby environment of combustion sources. Many studies have shown that they are toxic, whether ingested or inhaled, and thus pose a considerable threat to human health (1–4). The simplest of these compounds (i.e., unsubstituted furan, C₄H₄O) is a cyclic, dienic ether with a low molecular weight, high volatility, and high lipophilicity. Studies on rats and mice have shown a dose-dependent increase in hepatocellular adenomas and carcinomas, indicating that furan is carcinogenic (4), and furan is marked as a high-priority substance and a carcinogenic risk by the World Health Organization (5).Combustion sources of furans include biomass burning (6–9), cigarette and pipe smoke (10, 11), waste incineration (12), electronic waste recycling (13, 14), and volcanic activity (15). The polychlorinated dibenzofurans (PCDFs) are among the most notorious environmental pollutants, and the main source of PCDFs is biomass burning (6–9, 16). Nonchlorinated furans and PCDFs have been shown to be kinetically linked (17, 18). Furans released during combustion are often partitioned into particles and are found in ash from peat (9) and wood (6) burning, in primary organic aerosols from meat cooking (19), and in secondary organic aerosols from hydrocarbon oxidation (20, 21). Wood burning for heating and cooking constitute a major human exposure to airborne particulate PCDFs in some parts of the world (22, 23).Previous work has suggested that oxygenated species can be attached to surfaces of soot particles of varying maturity emitted from flames and diesel engines, even before atmospheric processing (24–32). Functional groups that have been identified include alcohols/enols, carbonyls, peroxies, and ethers. Oxygen atoms bound to organic species on the particle surface have been shown to greatly affect soot hygroscopicity (28) and the ability of soot particles to adsorb atmospheric water vapor and act as cloud-condensation or ice nuclei. Soot particles emitted from combustors, such as diesel engines, are generally hydrophobic, and enhancements in hygroscopic particle emissions could have substantial indirect climate effects via their influence on cloud formation (33). The effect of soot emissions on cloud-nucleation properties is a major uncertainty in climate predictions (34–36).Despite the impact of large oxygenated hydrocarbons on combustion chemistry, the environment, and human health, very little is known about their formation mechanisms and emissions. In this paper we present evidence of the formation of oxygenated compounds, including furans, during the combustion of hydrocarbon fuels. Via a synergistic approach that includes ab initio methods and a stochastic model in conjunction with experimental measurements, we identify reaction pathways leading to formation of oxygenated compounds during the combustion of ethylene. We recorded aerosol mass spectra sampled from premixed and diffusion flames, using synchrotron-generated vacuum-UV (VUV) radiation for ionization, for comparison with masses of the predicted chemical compositions. The mass spectra show masses of oxygenated species that agree with the atomic compositions predicted by the simulations. Both experiments and simulations demonstrate that ∼50% of the mass peaks observed at some flame heights in the mass range 140–350 u (unified atomic mass units) contain signal from oxygenated species. We also recorded X-ray photoelectron spectroscopy (XPS) spectra of soot samples extracted from these flames for further validation of these mechanisms by comparison with functional groups of the predicted oxygenated species incorporated into particles. The XPS measurements confirm formation of furan precursors, hydroxyl groups, early in the soot-formation process and evolution of furan signatures, ether groups, as the combustion and particles evolve.The present study represents an important step toward the development of predictive models for the oxidation of hydrocarbons, which will require that the presence and reactivity of these oxygenated compounds are taken into account. Understanding the chemistry related to high-temperature hydrocarbon oxidation may provide a key to controlling emissions of harmful combustion byproducts, such as soot, nonchlorinated furans, and PCDFs, leading to multiple environmental and health benefits.     

The contribution of black carbon to global ice nucleating particle concentrations relevant to mixed-phase clouds

Black carbon (BC) aerosol plays an important role in the Earth’s climate system because it absorbs solar radiation and therefore potentially warms the climate; however, BC can also act as a seed for cloud particles, which may offset much of its warming potential. If BC acts as an ice nucleating particle (INP), BC could affect the lifetime, albedo, and radiative properties of clouds containing both supercooled liquid water droplets and ice particles (mixed-phase clouds). Over 40% of global BC emissions are from biomass burning; however, the ability of biomass burning BC to act as an INP in mixed-phase cloud conditions is almost entirely unconstrained. To provide these observational constraints, we measured the contribution of BC to INP concentrations ([INP]) in real-world prescribed burns and wildfires. We found that BC contributes, at most, 10% to [INP] during these burns. From this, we developed a parameterization for biomass burning BC and combined it with a BC parameterization previously used for fossil fuel emissions. Applying these parameterizations to global model output, we find that the contribution of BC to potential [INP] relevant to mixed-phase clouds is ∼5% on a global average.

Black carbon (BC) is the primary light-absorbing aerosol in the atmosphere. Its short lifetime (days to weeks) relative to CO2 and methane makes it an intriguing target for near-term climate mitigation (1). Errors associated with BC climate forcing, however, obfuscate its efficacy as a climate mitigator. The largest contributions to BC’s forcing uncertainties are often attributed to its effects on clouds, in particular mixed-phase clouds [i.e., clouds containing supercooled cloud droplets and ice particles, (2)]. Efforts to reduce these uncertainties are hindered by the complexity of aerosol–cloud interactions (3). Particularly vexing is quantifying the abundance and identity of ice nucleating particles (INPs). INPs provide the only pathway for primary ice formation in mixed-phase clouds; however, they are rare [e.g., ∼1 in 106 particles are INPs at −20 °C (4)]. Despite their rarity, INPs influence mixed-phase cloud ice concentrations and precipitation and therefore alter cloud albedo and lifetime (5). Furthermore, the INP properties of aerosols, such as BC, will affect their own lifetime, vertical structure, and transport to climate-sensitive regions such as the Arctic (6). Despite its importance to the Earth’s climate and near-term climate mitigation strategies, the INP efficiency of BC relevant to mixed-phase clouds remains almost entirely unconstrained from direct observations, encumbering attempts to estimate BC’s impact on mixed-phase clouds in modeling studies (7).BC’s efficacy as an immersion-freezing INP (henceforth, INP will refer only to freezing by particles encapsulated within supercooled cloud droplets, termed immersion freezing and pertinent to mixed-phase cloud conditions) has been studied in the laboratory for decades, with starkly conflicting results. Early laboratory studies showed that acetylene and kerosene flame-generated soot can nucleate ice below −20 °C. (8, 9); after normalizing for surface area, these studies indicated that BC may be more ice active than the well-known INP mineral dust (10). Results from later laboratory studies were contradictory, suggesting that BC was not active as an INP above instrument limits of detection. These included soot aerosols from miniCAST soot generators, graphite spark generator soot, hydrocarbon flame-generated soot, and fullerene soot, as well as various lamp blacks and carbon blacks (11–15).Unfortunately, field study measurements of the contribution of BC to INP concentrations ([INP]) have also been inconclusive. For example, in-cloud measurements from the high-altitude observatory at Jungfraujoch, Switzerland saw that BC is enriched in ice-particle residuals and therefore may efficiently nucleate ice (16); later measurements at the same site, however, saw that BC is depleted in the ice phase, which suggests that BC does not play a significant role in mixed-phase cloud ice nucleation (17, 18).These contradictions in laboratory and field studies suggest that fuel type and combustion conditions determine the ice nucleation properties of BC. Such conditions prescribe BC’s physical and morphological properties as well as its coemitted and coagulated species. Major BC fuel types include fossil fuels and flammable biomass, and major combustion sources include diesel exhaust, residential fuel burning, prescribed burns, and wildfires (2). BC particles from fossil fuel combustion and anthropogenic pollution are not significant sources of INPs. For example, studies on diesel exhaust have shown that less than 1 in 109 BC particles are ice nucleation active at −30 °C (19). Furthermore, ambient [INP] in Beijing, China were relatively constant over several weeks despite BC concentrations varying by a factor of 30 and reaching values as high as 17.26 μg⋅m−3 (20).Elevated [INP] have been observed in biomass-burning smoke during laboratory and field studies (21–23); however, it is unclear from these studies if the INPs are actually BC. Some studies have shown that BC may be the dominant INP type in select biomass burning conditions. For example, soot particles were found to contribute up to 64% of the INPs in prescribed burns within a predominantly wiregrass understory (24). Furthermore, BC contributed up to 70% to [INP] in controlled laboratory burns of grasses (25). As biomass burning represents ∼40% of global BC emissions (2), BC from biomass burning could be a significant source of INP globally. In both of these studies, however, the overall ice-active fractions may be too low to influence [INP], even on the regional level (21). Thus, it remains unclear whether BC contributes to [INP] outside of thick plumes and on a global scale (26).Regional- and global-scale estimates of BC [INP] rely on models that can implement theory-based or empirical ice nucleation parameterizations. Using parameterizations based on BC INP activity from the acetylene and kerosene-burner soot studies, models have found that BC contributes ∼50% to [INP] in springtime low-level Arctic mixed-phase clouds (27), and 23 to 61% to global [INP] depending on dust loadings (28). Taking into account the aforementioned negative results, these modeling studies highlight that BC’s contribution to [INP] is poorly constrained and is estimated to vary from no contribution to being the most abundant INP globally.To assess the role of BC from biomass burning as an INP, we determined the contribution of refractory BC (rBC)-containing particles to [INP] from field measurements of both prescribed burns and wildfires using the single-particle soot photometer coupled to a continuous-flow diffusion chamber (SP2-CFDC) (29, 30). The SP2-CFDC selectively removes rBC from an aerosol stream and quantifies that effect on [INP]. From these burns, we found that rBC-containing particles contributed ≤10% to [INP]. From these results, we developed a surface-area normalized parameterization for BC INPs from biomass burning. The parameterization aligns well with other surface-area normalized parameterizations derived from laboratory proxies of BC and diesel exhaust BC (15, 19, 31). These parameterizations are over four orders of magnitude lower than the parameterization derived from acetylene and kerosene-burner soot studies and used in the aforementioned modeling studies. Assuming the INP characteristics of BC from the burns in this study can be extended to different biomass-burning fuel types and combustion conditions, this study strongly suggests that BC is not an efficient INP. Under this assumption, we assessed the global importance of BC as an INP by applying our parameterization to simulated biomass-burning aerosol from a global chemical transport model. A similar parameterization for diesel exhaust (19) was applied to simulated fossil fuel BC. From these treatments, we estimate that BC’s contribution to simulated, potential [INP] is only ∼5% on a global average.     

Posttraumatic Symptomatology and Alcohol Misuse Among Black College Students: Examining the Influence of Anxiety Sensitivity

Objective: Posttraumatic stress symptoms (PTSS) have been found to be associated with alcohol (mis)use among college students. Anxiety sensitivity has been theoretically and empirically linked to both PTSS and alcohol (mis)use. The goal of the present study was to extend research by examining the relations among PTSS, anxiety sensitivity, and alcohol misuse within a sample of trauma-exposed Black college students. Methods: Participants were 121 Black undergraduate college students who endorsed exposure to a traumatic event (M age = 22.98, 77.7% female). Results: Correlational findings provide support for significant positive relations between PTSS and both anxiety sensitivity and alcohol misuse. Further, analyses revealed a significant indirect effect of anxiety sensitivity on alcohol misuse through PTSS. Specifically, greater anxiety sensitivity was associated with higher levels of PTSS, which, in turn, were associated with higher levels of alcohol misuse. Conclusions: These findings suggest that the assessment of anxiety sensitivity may be useful in identifying trauma-exposed Black individuals who are likely to experience alcohol misuse and the clinical utility of addressing PTSS in this population reporting anxiety sensitivity to possibly prevent alcohol misuse and related negative consequences.     

Perspectives of middle-aged African-American women in the Deep South on antiretroviral therapy adherence

Despite evidence of stabilization in some areas of the USA, HIV infection in black women is not declining in the Deep South. Using a phenomenological approach to qualitative inquiry, we investigated women's experiences influencing their adherence to highly active antiretroviral therapy (HAART) in an urban setting. Inclusion criteria specified black women who had been aware of their HIV status for at least two years and were engaged in HIV outpatient care. Twelve single face-to-face confidential in-depth semi-structured interviews were conducted from a sample of predominantly middle-aged women retained in care at an HIV clinic in Atlanta, Georgia. Data were analyzed by two independent reviewers and three themes emerged from the group of women's accounts of their experiences. First, sentinel events led to changes in perspective and motivated women to adhere to HAART. Second, recognition that one had the personal strength necessary to cope with HIV fostered adherence. Finally, relationships with healthcare providers especially trust issues surrounding this relationship, impacted adherence both positively and negatively. These findings suggest that HAART adherence is a complex issue among middle-aged urban black women with HIV in the Deep South. Providers caring for this patient population should recognize that sentinel events, personal strength, and positive healthcare relationships are opportunities to improve adherence.     

Volcano-induced regime shifts in millennial tree-ring chronologies from northeastern North America

Dated records of ice-cap growth from Arctic Canada recently suggested that a succession of strong volcanic eruptions forced an abrupt onset of the Little Ice Age between A.D. 1275 and 1300 [Miller GH, et al. (2012) Geophys Res Lett 39(2):L02708, 10.1029/2011GL050168]. Although this idea is supported by simulation experiments with general circulation models, additional support from field data are limited. In particular, the Northern Hemisphere network of temperature-sensitive millennial tree-ring chronologies, which principally comprises Eurasian sites, suggests that the strongest eruptions only caused cooling episodes lasting less than about 10 y. Here we present a new network of millennial tree-ring chronologies from the taiga of northeastern North America, which fills a wide gap in the network of the Northern Hemisphere''s chronologies suitable for temperature reconstructions and supports the hypothesis that volcanoes triggered both the onset and the coldest episode of the Little Ice Age. Following the well-expressed Medieval Climate Anomaly (approximately A.D. 910–1257), which comprised the warmest decades of the last millennium, our tree-ring-based temperature reconstruction displays an abrupt regime shift toward lower average summer temperatures precisely coinciding with a series of 13th century eruptions centered around the 1257 Samalas event and closely preceding ice-cap expansion in Arctic Canada. Furthermore, the successive 1809 (unknown volcano) and 1815 (Tambora) eruptions triggered a subsequent shift to the coldest 40-y period of the last 1100 y. These results confirm that series of large eruptions may cause region-specific regime shifts in the climate system and that the climate of northeastern North America is especially sensitive to volcanic forcing.Tree-ring chronologies are the type of proxy record most used to develop climate reconstructions covering the last millennium (1). These chronologies have been integrated into large-scale networks, often with additional proxies, to document the amplitude, duration, and forcing mechanisms of the Medieval Climate Anomaly, the Little Ice Age, and the recent warming trend. However, the spatial coverage of long tree-ring records must be improved to allow a better understanding of regional variations in past climate (1, 2). For example, in eastern North America, millennial climate reconstructions have been constructed from tree species and sites sensitive to drought and precipitation (3), whereas temperatures were inferred solely from low-resolution proxies, such as pollen data (4, 5). Furthermore, only tree-ring-based climate reconstructions shorter than a millennium or using chronologies poorly replicated before A.D. 1500 have been published for the entire North American boreal forest (6, 7), whereas several millennial, highly replicated, temperature-sensitive tree-ring records have been developed across the Eurasian boreal zone. This lack of data is an important issue that causes the poor representation of North America in long-term, large-scale temperature reconstructions (1, 4).The feasibility of reconstructing volcanic forcing from tree-ring data has been debated, especially in regards to large and successive eruptions. Two of the largest eruptions of the last millennium, the A.D. 1257 Samalas and A.D. 1815 Tambora events, were both closely followed and preceded by additional large eruptions in 1227, 1275, 1284, 1809, and 1835 (8−11). Whereas general circulation model experiments suggest that the impacts of large and successive eruptions might have influenced climate systems for periods ranging from 20 y to several decades, or even centuries (12–16), Northern Hemisphere tree-ring-based temperature reconstructions only display negative temperature anomalies lasting between 2 and 10 y (17–20). Region-specific responses of the climate system to volcanic forcing may in part explain this discrepancy (17). For example, large and successive eruptions may have had stronger impacts on summer temperatures in northeastern North America (hereafter NENA) than elsewhere. An extensive Northern Hemisphere network of tree-ring density chronologies supports this idea, showing that the coldest 1816 temperature anomalies occurred over the Quebec-Labrador Peninsula (21), where they may have persisted for several decades (7). The idea is also supported by the abrupt acceleration of ice-cap growth in the Eastern Canadian Arctic during A.D. 1275–1300, at the onset of the Little Ice Age, as a consequence of a series of eruptions (22). However, the lack of millennial, well-replicated, and temperature-sensitive tree-ring chronologies in the NENA sector precludes the examination of the volcano−temperature relationship in a long-term context with an annual resolution.In this study, we have built a network of six highly replicated millennial tree-ring chronologies from large stocks of black spruce [Picea mariana (Mill.) B.S.P.] subfossil trees preserved in lakes of the NENA taiga from which we developed a millennial reconstruction (A.D. 910–2011) of regional July−August temperatures. For this purpose, we selected homogeneous sites with infrequent and well-documented ecological disturbances (23), and sampled homogeneous subfossil and living samples to maximize the robustness of our reconstruction. We then used a Bayesian mixture of probability distributions with dependence (also referred to as hidden Markov models or Markov switching models; see refs. 24 and 25) to detect possible regime shifts in summer temperatures triggered by series of large eruptions and to provide new insights concerning the climate history of NENA during the last 1,100 y.     

骨质疏松性胸腰椎骨折MRI STIR黑色线性信号与外力程度的关系

背景:随着社会老龄化加重,骨质疏松椎体骨折患者日益增多,主要表现为胸腰椎体压缩性骨折,严重影响老年人的日常生活。因此,研究外力程度与骨质疏松胸腰椎体骨折在影像MRI STIR上表现的关系,可以更好的为临床诊疗提供依据。目的:探讨外力作用程度与骨质疏松性胸腰椎骨折MRI STIR黑色线性信号的相关性。方法:回顾性分析2013年9月至2016年9月在广西中医药大学第一附属医院脊柱外科住院,明确诊断为骨质疏松性胸腰椎骨折的患者,3组中所有病例均行定量CT检查确诊为骨质疏松(骨密度值≤80 mg/cm^3)。所有患者对治疗方案均知情同意,且得到医院伦理委员会批准。根据创伤史,分为无明显外力作用组(无明显诱因、无外力作用等)、低能量外力作用组(扭伤、弯腰提重物、扛重物等)、高能量外力作用组(平路摔倒臀部着地、跌倒、撞伤等),统计各组间性别、年龄、骨折部位(胸腰段和非胸腰段)、MRI STIR黑色线性信号椎体例数及所在的部位(胸腰段和非胸腰段)。3组间年龄属于计量资料采用方差分析;性别、骨折部位、MRI STIR黑色线性信号的椎体数量及所在部位属于计数资料,用Pearson χ~2检验。结果与结论:①纳入的3组病例共782例。无明显外力作用组334例,其中椎体内黑色线性信号114例;低能量外力作用组186例,其中椎体内黑色线性信号124例,高能量外力作用组262例,其中椎体内黑色线性信号87例;②3组间年龄、性别、骨折部位、MRI STIR黑色线性信号所在椎体部位差异均无显著性意义(P> 0.05);③3组间MRI STIR黑色线性信号比较差异有显著性意义(P<0.05),分割P值,降低检验水准(α’=0.05/3=0.017)。低能量外力作用组分别与无明显外力作用组、高能量外力作用组比较,差异有显著性意义(P<0.017);无明显外力作用组与高能量外力作用组比较,差异无显著性意义(P> 0.017);④并且低能量外力作用组中MRI STIR黑色线性信号出现率为66.7%,明显大于其他2组的43.1%和33.2%;⑤提示在创伤史中,相对于无明显外力作用和高能量外力作用,低能量外力作用的骨质疏松性胸腰椎骨折更容易导致MRI STIR黑色线性信号的出现,并且多见于胸腰段椎体。     

成人前牙区黑三角病因的探讨

黑三角在上下前牙部位较为常见,不仅影响美观,并且还会引起食物残渣堆积、发音变化等功能性问题,甚至威胁牙周组织的健康。随着人们保健意识和美观要求的提高,牙周组织等软组织的美学受到越来越多的关注。黑三角由多因素发病所致,本文分析国内外学者对黑三角成因的研究进展,阐述成人前牙区黑三角发生的相关危险因素,以期为口腔临床工作提供参考。     

Production and Upgrading of Recovered Carbon Black from the Pyrolysis of End-of-Life Tires

Increasing awareness regarding fossil fuel dependence, waste valorization, and greenhouse gas emissions have prompted the emergence of new solutions for numerous markets over the last decades. The tire industry is no exception to this, with a global production of more than 1.5 billion tires per year raising environmental concerns about their end-of-life recycling or disposal. Pyrolysis enables the recovery of both energy and material from end-of-life tires, yielding valuable gas, liquid, and solid fractions. The latter, known as recovered carbon black (rCB), has been extensively researched in the last few years to ensure its quality for market applications. These studies have shown that rCB quality depends on the feedstock composition and pyrolysis conditions such as type of reactor, temperature range, heating rate, and residence time. Recent developments of activation and demineralization techniques target the production of rCB with specific chemical, physical, and morphological properties for singular applications. The automotive industry, which is the highest consumer of carbon black, has set specific targets to incorporate recycled materials (such as rCB) following the principles of sustainability and a circular economy. This review summarizes the pyrolysis of end-of-life tires for the production of syngas, oil, and rCB, focusing on the process conditions and product yield and composition. A further analysis of the characteristics of the solid material is performed, including their influence on the rCB application as a substitute of commercial CB in the tire industry. Purification and modification post-treatment processes for rCB upgrading are also inspected.