Growth of ice particle mass and projected area during riming

There is a long-standing challenge in cloud and climate models to simulate the process of ice particle riming realistically, partly due to the unrealistic parameterization of the growth of ice particle mass (m) and projected area (A) during riming. This study addresses this problem, utilizing ground-based measurements of m and ice particle maximum dimension (D) as well as theory to formulate simple expressions describing the dependence of m and A on riming. It was observed that β in the m − D power law m  = α Dβ appears independent of riming during the phase 1 (before the formation of graupel), with α accounting for the ice particle mass increase due to riming. This semi-empirical approach accounts for the degree of riming and renders a gradual and smooth ice particle growth process from unrimed ice particles to graupel, and thus avoids discontinuities in m and A during accretional growth. Once the graupel with quasi-spherical shape forms, D increases with an increase in m and A (phase 2 of riming). The treatment for riming is explicit, and includes the parameterization of the ice crystal–cloud droplet collision efficiency (Ec) for hexagonal columns and plates using hydrodynamic theory. In particular, Ec for cloud droplet diameters less than 10 µm are estimated, and under some conditions observed in mixed-phase clouds, these droplets can account for roughly half of the mass growth rate from riming. These physically meaningful yet simple methods can be used in models to improve the riming process

Frequency of ochratoxin A in bread consumed in Shahrekord

زمینه و هدف: با اکراتوکسین A مایکوتوکسینی است که به علت اثرات نفروتوکسیک، ایمونوتوکسیک، موتاژنیک، تراتوژنیک و کار سینوژنیک خطر بالقوه ی برای سلامت انسان دارد. این مطالعه با هدف تعیین حضور و میزان اکراتوکسین A در نان های مصرفی شهرکرد انجام شده است. روش بررسی: در این مطالعه مقطعی تحلیلی، 86 نمونه انواع نان عرضه شده در نانوایی های شهرستان شهرکرد از پاییز 1389 تا بهار 1390 جمع آوری و از نظر حضور اکراتوکسین A به وسیله روش الایزا مورد بررسی قرار گرفت. داده ها به کمک آزمون های آماری تحلیل واریانس یک طرفه و آزمون t تجزیه و تحلیل شد. یافته ها: اکراتوکسین A در 45 نمونه از 86 نمونه (3/52 درصد) نان بررسی شده ردیابی شد. محدوده غلظت اکراتوکسین A در نمونه های مثبت بین 19/0 تا 37/10 نانو گرم بود و میانگین آلودگی نمونه های آلوده 47/1±61/2 نانو گرم در گرم به دست آمد. سطح آلودگی 15 نمونه (4/17درصد) از مجموع 86 نمونه آزمایش شده بیش از حداکثر مجاز (5 نانو گرم در گرم) تأیید شده در قوانین اتحادیه اروپا بود. اختلاف آماری معنی داری بین سطوح آلودگی و تعداد موارد آلوده در فصول مختلف وجود نداشت (p>0.05). نتیجه گیری: نتایج این مطالعه نشان می دهد که بررسی منظم سطح اکراتوکسین A در غلات به خصوص گندم از اهمیت ویژه ای برخوردار است؛ زیرا بر این اساس می توان روش های مناسبی جهت کاهش آلودگی به اکراتوکسین A و بهبود کیفیت نان ارائه نمود

Attraction, selection, and attrition in online health communities: Initial conversations and their association with subsequent activity levels.

BACKGROUND:The effectiveness of online health communities (OHCs) for improving outcomes for health care consumers, health professionals, and health services has already been well investigated. However, research on determinants of OHC users' activity levels, what is associated with attrition or attraction to these communities, and the impacts of initial posts is limited. OBJECTIVES:We sought to explore topic exchanges in OHCs and determine how users' initial posts and community reactions to them are associated with their subsequent activity levels. We also aimed to extend the theory of Attraction-Selection-Attrition for Online Communities (OCASA) to this area. METHODS:We examined exchanges in a major Australian OHC for cancer patients, analyzing about 2500 messages posted over 2009-18. We developed a novel annotation scheme to examine new members' initial posts and the community's reactions to them. RESULTS:The annotation scheme includes five themes: informational support provision, emotional support provision, requests for help, self-reflection & disclosures, and conversational cues. Initial conversations were associated with future activity levels in terms of active posting versus non-active engagement in the community. We found that most OHC members disclosed personal reflections to bond with the community, and many actively posted to the community solely to provide informational and emotional support to others. CONCLUSION:Our work extends OCASA theory to bond-based contexts, presents a new annotation scheme for OHC support topics, and makes an important contribution to knowledge about the relationship between users' activity levels and their initial posts. The findings help managers and owners understand how members use OHCs and how to encourage active participation. They also suggest how to attract new members and minimize attrition among existing members

Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance

Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma

The Dark Side of Using Online Social Networks: A Review of Individuals' Negative Experiences

Research on online social networks (OSNs) has focused overwhelmingly on their benefits and potential, with their negative effects overlooked. This study builds on the limited existing work on the so-called ‘dark side’ of using OSNs. The authors conducted a systematic review of selected databases and identified 46 negative effects of using OSNs from the users’ perspective, which is a rich spectrum of users’ negative experiences. This article then proposed nomenclature and taxonomy for the dark side of using OSNs by grouping these negative effects into six themes: cost of social exchange, cyberbullying, low performance, annoying content, privacy concerns and security threats. This study then conducted structured interviews with experts to confirm the sense-making and validity of the proposed taxonomy. This study discusses the confirmed taxonomy and outlines directions for future research.</jats:p

Application of stem cells in targeted therapy of breast cancer: A systematic review

Background: The aim of this systematic review was to investigate whether stem cells could be effectively applied in targeted therapy of breast cancer. Material and Method: A systematic literature search was performed for original articles published from January 2007 until May 2012. Results: Nine studies met the inclusion criteria for phase I or II clinical trials, of which three used stem cells as vehicles, two trials used autologous hematopoetic stem cells and in four trials cancer stem cells were targeted. Mesenchymal stem cells (MSCs) were applied as cellular vehicles to transfer therapeutic agents. Cell therapy with MSC can successfully target resistant cancers. Cancer stem cells were selectively targeted via a proteasome-dependent suicide gene leading to tumor regression. Wnt/�-catenin signaling pathway has been also evidenced to be an attractive CSC-target. Conclusions: This systematic review focused on two different concepts of stem cells and breast cancer marking a turning point in the trials that applied stem cells as cellular vehicles for targeted delivery therapy as well as CSC-targeted therapies. Applying stem cells as targeted therapy could be an effective therapeutic approach for treatment of breast cancer in the clinic and in therapeutic marketing; however this needs to be confirmed with further clinical investigations