Experimental study of the coherent vorticity in slightly under-expanded supersonic screeching jets

2019 ◽  
Vol 18 (2-3) ◽  
pp. 207-230
Author(s):  
Bertrand Mercier ◽  
Thomas Castelain ◽  
Christophe Bailly

The noise generation mechanism of screech tone by shock leakage in underexpended round jets is experimentally investigated by means of phase-averaged velocity fields. Two jet flows at Mach numbers 1.10 and 1.15 are measured by a particle image velocimetry apparatus simultaneously with their near acoustic fields and sorted according to their phase with respect to a screech period. The coherent vorticity fields are then computed and analyzed. They depict two distinct regions of high level of vorticity fluctuations. Thanks to the knowledge about shock leakage gathered in previous studies, the role of both regions in the acoustic generation process is identified and a region of the flow is recognized as suitable for emitting acoustic waves. Phase-averaged schlieren visualizations are also computed and used to determine the motion of the first five shocks over a screech period. For both jets, the peak shock motion is found at the fourth shock tip. This shock is also located in the region recognized as favorable for the shock leakage to be observed.

1998 ◽  
Vol 4 (S2) ◽  
pp. 232-233
Author(s):  
E. Lifshin ◽  
L. A. Peluso ◽  
R. Gauvin

In conventional quantitative electron microprobe analysis, methods like ZAF and φ(ρz), are used to convert x-ray intensity data to chemical composition utilizing equations that describe electron solid interactions, the x-ray generation process, absorption of the generated x-rays and secondary fluorescence effects. These equations capture the overall response of a sample or standard rather than consider the fate of individual electrons over time. For example, f(χ) is simply the ratio of x-rays emitted to the number generated. While for the most part these methods are built on solid physical models, the models were never exact enough to completely match measured data. Consequently, they have been modified by various adjustable parameters to ensure a high level of accuracy for a wide variety of systems and experimental conditions. However, since most of the adjustments were based on data taken at normal incidence, there has always been a question of how to obtain accurate results from tilted samples.


2017 ◽  
Vol 14 (1) ◽  
pp. 101-112 ◽  
Author(s):  
Melissa Kelly

This article uses the concepts of ‘transnational social fields’ and ‘habitus’ to explore the multifaceted role families play in shaping the aspirations of onward migrating youth. The article draws on biographical life history interviews conducted with the children of Iranian migrants who were raised in Sweden but moved to London, UK as adults. The findings of the study suggest that from a young age, all the participants were pressured by their parents to perform well academically, and to achieve high level careers. These goals were easier to achieve in London than in Sweden for several reasons. Interestingly, however, participants’ understandings of what constituted success and their motivations for onward migration were nuanced and varied considerably by gender. The study contributes to an understanding of the role of multi-sited transnational social fields in shaping the aspirations of migrant youths, as well as the strategies taken up by these migrants to achieve their goals.


2018 ◽  
Vol 9 (01) ◽  
Author(s):  
Parul Gill ◽  
Poonam Malik ◽  
Pankaj Gill

The present study was undertaken to explore the decision making patterns of college girls in relation to clothing and their satisfaction level with these decision making patterns. Thirty under graduate college girls from Panipat city were approached to record their responses regarding decision making in relation to clothing and satisfaction level through a well structured questionnaire. It was found that most of the girls (56.66%) themselves made the decisions about the type of garment (Indian, western or both) they wear and majority of girls (70%) were highly satisfied with this decision making. Parents performed the role of buyers for their college going daughters' garments in most of the cases (63.33%) and the 73.33% girls had high level of satisfaction with this. In most of the cases (60%) the decision about the garment design was made by the girls themselves and they were highly satisfied with it. Keywords: clothing, college, girls, decision making.


Author(s):  
D.R. Zhantiev

Аннотация В статье рассматривается роль и место Сирии (включая Ливан и Палестину) в системе османских владений на протяжении нескольких веков от османского завоевания до периода правления султана Абдул-Хамида II. В течение четырех столетий османского владычества территория исторической Сирии (Билад аш-Шам) была одним из важнейших компонентов османской системы и играла роль связующего звена между Анатолией, Египтом, Ираком и Хиджазом. Необходимость ежегодной организации хаджа с символами султанской власти и покровительства над святынями Мекки и Медины определяла особую стратегическую важность сирийских провинций Османской империи. Несмотря на ряд серьезных угроз во время общего кризиса османской государственности (конец XVI начало XIX вв.), имперскому центру удалось сохранить контроль над Сирией путем создания сдержек и противовесов между местными элитами. В XIX в. и особенно в период правления Абдул- Хамида II (18761909 гг.), сохранение Сирии под османским контролем стало вопросом существования Османской империи, которая перед лицом растущего европейского давления и интервенции потеряла большую часть своих владений на Балканах и в Северной Африке. Задача укрепления связей между имперским центром и периферией в сирийских вилайетах в последней четверти XIX в. была в целом успешно решена. К началу XX в. Сирия была одним из наиболее политически спокойных и прочно связанных со Стамбулом регионов Османской империи. Этому в значительной степени способствовали довольно высокий уровень общественной безопасности, развитие внешней торговли, рост образования и постепенная интеграция местных элит (как мусульман, так и христиан) в османские государственные и социальные механизмы. Положение Сирии в системе османских владений показало, что процесс ослабления и территориальной дезинтеграции Османской империи в эпоху реформ не был линейным и наряду с потерей владений и влияния на Балканах, в азиатской части империи в течение XIX и начала XX вв. происходил параллельный процесс имперской консолидации.Abstract The article examines the role and place of Greater Syria (including Lebanon and Palestine) in the system of Ottoman possessions over several centuries from the Ottoman conquest to the period of the reign of Abdul Hamid II. For four centuries of Ottoman domination, the territory of historical Syria (Bilad al-Sham) was one of the most important components in the Ottoman system and played the role of a link between Anatolia, Egypt, Iraq and Hijaz. The need to ensure the Hajj with symbols of Sultan power and patronage over the shrines of Mecca and Medina each year determined the special strategic importance of the Syrian provinces of the Ottoman Empire. Despite a number of serious threats during the general crisis of the Ottoman state system (late 16th early 19th centuries), the imperial center managed to maintain control over Syria by creating checks and balances between local elites. In the 19th century. And especially during the reign of Abdul Hamid II (18761909), keeping Syria under Ottoman control became a matter of existence for the Ottoman Empire, which, in the face of increasing European pressure and intervention, lost most of its possessions in the Balkans and North Africa. The task of strengthening ties between the imperial center and the periphery in Syrian vilayets in the last quarter of the 19th century was generally successfully resolved. By the beginning of the 20th century, Syria was one of the most politically calm and firmly connected with Istanbul regions of the Ottoman Empire. This was greatly facilitated by a fairly high level of public safety, the development of foreign trade, the growth of education and the gradual integration of local elites (both Muslims and Christians) into Ottoman state and social mechanisms. Syrias position in the system of Ottoman possessions clearly showed that the process of weakening and territorial disintegration of the Ottoman Empire during the era of reform was not linear, and along with the loss of possessions and influence in the Balkans, in the Asian part of the empire during the 19th and early 20th centuries there was a parallel process of imperial consolidation.


The productivity of land has been often discussed and deliberated by the academia and policymakers to understand agriculture, however, very few studies have focused on the agriculture worker productivity to analyze this sector. This study concentrates on the productivity of agricultural workers from across the states taking two-time points into consideration. The agriculture worker productivity needs to be dealt with seriously and on a time series basis so that the marginal productivity of worker can be ascertained but also the dependency of worker on agriculture gets revealed. There is still disguised unemployment in all the states and high level of labour migration, yet most of the states showed the dependency has gone down. Although a state like Madhya Pradesh is doing very well in terms of income earned but that is at the cost of increased worker power in agriculture as a result of which, the productivity of worker has gone down. States like Mizoram, Meghalaya, Nagaland and Tripura, though small in size showed remarkable growth in productivity and all these states showed a positive trend in terms of worker shifting away from agriculture. The traditional states which gained the most from Green Revolution of the sixties are performing decently well, but they need to have the next major policy push so that they move to the next orbit of growth.


1994 ◽  
Vol 30 (10) ◽  
pp. 213-219 ◽  
Author(s):  
Hendrik Pieters ◽  
Victor Geuke

Samples of yellow eel from various locations in the Dutch Rhine area have been analyzed for trend monitoring of mercury since 1977. In the western Rhine delta mercury levels in eels have hardly changed since the seventies, whereas in the eastern part of the Dutch Rhine area a considerable decrease of mercury concentrations in eel has occurred. Because of continuous sedimentation of contaminated suspended matter transported from upstream regions, accumulation rates and concentrations of mercury in eel in the western Rhine delta remained at a relatively high level. Analyses of methyl mercury in biota have been performed to elucidate the role of methyl mercury in the mercury contamination of the Dutch Rhine ecosystem. Low percentages of methyl mercury were observed in zooplankton (3 to 35%). In benthic organisms (mussels) percentages of methyl mercury ranged from 30 to 57%, while in fish species and liver of aquatic top predator birds almost all the mercury was present in the form of methyl mercury (> 80%). During the period 1970-1990 mercury concentrations of suspended matter in the eastern Rhine delta have drastically decreased. These concentrations seemed to be highly correlated with mercury concentrations of eel (R = 0.84). The consequences of this relation are discussed.


2019 ◽  
Vol 18 (1) ◽  
pp. 78-87 ◽  
Author(s):  
Jian-kai Yang ◽  
Hong-jiang Liu ◽  
Yuanyu Wang ◽  
Chen Li ◽  
Ji-peng Yang ◽  
...  

Background and Objective: Exosomes communicate inter-cellularly and miRNAs play critical roles in this scenario. MiR-214-5p was implicated in multiple tumors with diverse functions uncovered. However, whether miR-214-5p is mechanistically involved in glioblastoma, especially via exosomal pathway, is still elusive. Here we sought to comprehensively address the critical role of exosomal miR-214-5p in glioblastoma (GBM) microenvironment.Methods:The relative expression of miR-214-5p was determined by real-time PCR. Cell viability and migration were measured by MTT and transwell chamber assays, respectively. The secretory cytokines were measured with ELISA kits. The regulatory effect of miR-214-5p on CXCR5 expression was interrogated by luciferase reporter assay. Protein level was analyzed by Western blot.Results:We demonstrated that miR-214-5p was aberrantly overexpressed in GBM and associated with poorer clinical prognosis. High level of miR-214-5p significantly contributed to cell proliferation and migration. GBM-derived exosomal miR-214-5p promoted inflammatory response in primary microglia upon lipopolysaccharide challenge. We further identified CXCR5 as the direct target of miR-214- 5p in this setting.Conclusion:Overexpression of miR-214-5p in GBM modulated the inflammatory response in microglia via exosomal transfer.


2021 ◽  
Vol 13 (9) ◽  
pp. 5004
Author(s):  
Raquel Ferreras-Garcia ◽  
Jordi Sales-Zaguirre ◽  
Enric Serradell-López

There is currently an increasing interest for sustainable innovation in our society. The European agendas highlight the role of higher education institutions in the formation and development of innovation competences among students. Our study aimed to contribute to the analysis of the level of achievement of students’ innovation competences by considering two sustainable development goals (SDG) of the 2030 United Nations’ Agenda: Gender Equality (SDG 5) and Quality Education (SDG 4). This article tries to answer how business students perceive their own innovation competences and which innovative competences are best achieved by students, as well as if there are differences in the achievement of these competences depending on the students’ gender. Our results, from a sample of 360 students in the Business Administration and Management Bachelor’s Degree at the Universitat Oberta de Catalunya, confirm the extensive development of innovation competences. Moreover, female students present a high level of preparation for innovation-oriented action. These findings have educational implications for potentiating the innovation competences and environments where females can attain innovation skills.


Genetics ◽  
2000 ◽  
Vol 155 (4) ◽  
pp. 1831-1839
Author(s):  
Emily Harms ◽  
Tehyen Chu ◽  
Gwénola Henrion ◽  
Sidney Strickland

Abstract The grauzone and cortex genes are required for the completion of meiosis in Drosophila oocytes. The grauzone gene encodes a C2H2-type zinc-finger transcription factor that binds to the cortex promoter and is necessary for high-level activation of cortex transcription. Here we define the region of the cortex promoter to which Grauzone binds and show that the binding occurs through the C-terminal, zinc-finger-rich region of the protein. Mutations in two out of the five grauzone alleles result in single amino acid changes within different zinc-finger motifs. Both of these mutations result in the inability of Grauzone to bind DNA effectively. To determine the mechanism by which Grauzone regulates meiosis, transgenic flies were produced with an extra copy of the cortex gene in homozygous grauzone females. This transgene rescued the meiosis arrest of embryos from these mutants and allowed their complete development, indicating that activation of cortex transcription is the primary role of Grauzone during Drosophila oogenesis. These experiments further define a new transcriptional pathway that controls the meiotic cell cycle in Drosophila oocytes.


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