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Study on Breeding Practices and Reproductive Performance of Black-Head Somali Sheep under Traditional Management System: The Case of Awbarre District, Eastern Ethiopia
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作者 Abdi Abdilahi Kawnin Abdimahad +1 位作者 Abdulahi Mahamed Abdimawlid Ali 《Open Journal of Animal Sciences》 CAS 2023年第1期20-33,共14页
The study was conducted in the Awbarre district of the Fafen zone of the Somali regional state of Ethiopia. The objective of the study was to assess the breeding practices and reproductive performance of Black-head So... The study was conducted in the Awbarre district of the Fafen zone of the Somali regional state of Ethiopia. The objective of the study was to assess the breeding practices and reproductive performance of Black-head Somali sheep under a traditional management system. Purposive and simple random sampling techniques were used to select targeted kebeles and households, respectively. A total of 120 households were selected from four kebeles, each of 30 households, based on the production system and sheep population. Semi-structured questionnaires, group discussions, key informants interviews and field observations were used to generate the required data. The primary purpose of keeping sheep was for income generation, followed by saving as a future asset. The majority (89.2%) of the respondents separated male and female animals during herding. The selection criteria for breeding rams were appearance, growth, pedigree, and color while for breeding ewes were appearance, adaptability, pedigree, color, and lamb growth. The overall weaning age of Black-head Somali sheep in the study area was 3.7 months for both males & females. The castration of male sheep was common for the purpose of fattening, fattening with breeding control and breeding control as well. The castration is mainly performed during the summer and autumn and the methods of castration were both traditional and modern methods, the traditional castration method being the most important one in pastoral areas. The age of sexual maturity was 7.64 months for rams and 8.97 months for ewe’s male and female lambs in the pastoral area and 8.42 & 8.38 for rams & ewes in agro-pastoral and overall lambing interval was 11 months. On average, the ewe of Black-head Somali sheep in pastoral & agro-pastoral could produce 9.49 & 9.57 lambs, respectively in their lifetime. As the pastoralists and agro-pastoralists indicated the source of the breeding ram was their own, so the exchange of breeding ram is recommended to minimize the risk of inbreeding and further studies of on-farm performance investigation would be necessary to be carried out so as to understand the uniqueness of the breed better. 展开更多
关键词 Black-Head somali Sheep Breeding Practice Reproductive Performance Selection Criteria
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Variations of the Summer Somali and Australia Cross-Equatorial Flows and the Implications for the Asian Summer Monsoon 被引量:18
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作者 祝亚丽 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2012年第3期509-518,共10页
The temporal variations during 1948-2010 and vertical structures of the summer Somali and Australia cross-equatorial flows (CEFs) and the implications for the Asian summer monsoon were explored in this study. The st... The temporal variations during 1948-2010 and vertical structures of the summer Somali and Australia cross-equatorial flows (CEFs) and the implications for the Asian summer monsoon were explored in this study. The strongest southerly and northerly CEFs exist at 925 hPa and 150 hPa level, respectively. The low-level Somali (LLS) CEFs were significantly connected with the rainfall in most regions of India (especially the monsoon regions), except in a small area in southwest India. In comparison to the climatology, the low- level Australia (LLA) CEFs exhibited stronger variations at interannual time scale and are more closely connected to the East Asian summer monsoon circulation than to the LLS CEFs. The East Asian summer monsoon circulation anomalies related to stronger LLA CEFs were associ- ated with less water vapor content and less rainfall in the region between the middle Yellow River and Yangtze River and with more water vapor and more rainfall in southern China. The sea-surface tempera- ture anomalies east of Australia related to summer LLA CEFs emerge in spring and persist into summer, with implications for the seasonal prediction of summer rainfall in East Asia. The connection between the LLA CEFs and East Asian summer monsoon rainfall may be partly due to its linkage with E1 Nino-Southern Oscillation. In addition, both the LLA and LLS CEFs .exhibited interdecadal shifts in the late 1970s and the late 1990s, consistent with the phase shifts of Pacific Decadal Oscillation (PDO). 展开更多
关键词 cross-equatorial flow Asian summer monsoon low-level jet somali
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Teleconnected Influence of the Boreal Winter Antarctic Oscillation on the Somali Jet: Bridging Role of Sea Surface Temperature in Southern High and Middle Latitudes 被引量:1
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作者 Wenjing SHI Ziniu XIAO Jianjun XUE 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2016年第1期47-57,共11页
The teleconnection impact of the boreal winter Antarctic Oscillation(AAO) on the Somali Jet(SMJ) intensity in the following spring and summer is examined in this paper.The variability of the boreal winter AAO is p... The teleconnection impact of the boreal winter Antarctic Oscillation(AAO) on the Somali Jet(SMJ) intensity in the following spring and summer is examined in this paper.The variability of the boreal winter AAO is positively related to the SMJ intensity in both spring and summer.The analyses show that the SST in southern high and middle latitudes seems to serve as a bridge linking these two systems.When the AAO is in strong positive phase,SST over the Southern Ocean cools in the high latitudes and warms in the middle latitudes,which persists into summer;however,the variability of SST in southern high and middle latitudes is also closely correlated to SMJ intensity.A possible mechanism that links SST variability with the AAO-SMJ relationship is also discussed.The AAO in boreal winter produces an SST anomaly pattern in southern high and middle latitudes through the air-sea coupling.This AAOrelated SST anomaly pattern modulates the local Ferrel cell anomaly in summer,followed by the regional Hadley cell anomaly in tropics.The anomalous vertical motion in tropics then changes the land-sea thermal contrast between the tropical Indian Ocean and the Asian continent through the variability of low cloud cover and downward surface longwave radiation flux.Finally,the land-sea thermal contrast anomaly between the tropical Indian Ocean and the Asian continent changes the SMJ intensity.The results from Community Atmosphere Model experiments forced by the SST anomaly in southern high and middle latitudes also confirm this diagnostic physical process to some extent. 展开更多
关键词 Antarctic Oscillation somali Jet intensity teleconnection influence sea surface temperature longwave radiation flux
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Impact of the Preceding Boreal Winter Southern Annular Mode on the Summertime Somali Jet 被引量:1
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作者 SHI Wen-Jing XIAO Zi-Niu 《Atmospheric and Oceanic Science Letters》 CSCD 2014年第6期534-539,共6页
One of the major high-latitude circulation systems in the Southern Hemisphere is the Southern Annular Mode(SAM). Its effect on the Somali Jet(SMJ), which connects the Southern and Northern hemispheres, cannot be ignor... One of the major high-latitude circulation systems in the Southern Hemisphere is the Southern Annular Mode(SAM). Its effect on the Somali Jet(SMJ), which connects the Southern and Northern hemispheres, cannot be ignored. The present reported results show that time series of both the Southern Annular Mode Index(SAMI) during the preceding winter and the summertime Somali Jet intensity Index(SMJI) display a significant increasing trend and have similar interdecadal variation. The latter was rather strong around 1960, then became weaker up to the mid-1980 s, before starting to strengthen again. The lead-lag correlations of monthly mean SAMI with the following summertime SMJI showed significant positive correlations in November, December, and January. There are thus connections across two seasons between the SAM and the SMJ. The influence of the winter SAM on the summer SMJ was explored via analyses of SST anomalies in the Southern Indian Ocean. During strong(weak) SAM/SMJ years, the SST east of Madagascar is colder(warmer) while the SST west of Australia is warmer(colder), corresponding to the positive(negative) Southern Indian Ocean Dipole-like(SIODL) event. Subsequently, the SIODL excites an anticyclone located over the Arabian Sea in summer through air-sea coupling from winter to summer, which causes an increase in the summer SMJ intensity. The anticyclone/high branch of the SAM over the Southern Hemisphere subtropics and the cyclone/low over the east coast of Madagascar play an important role in the formation of Southern Indian Ocean "bridge" from winter to summer. 展开更多
关键词 Southern Annular Mode somali Jet Southern Indian Ocean Dipole ocean-atmosphere coupled bridge
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Barriers to Optimal Maternal and Child Feeding Practices in Pastoralist Areas of Somali Region, Eastern Ethiopia: A Qualitative Study
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作者 Abdulahi Haji Abas Ahmed Tahir Ahmed +1 位作者 Abdifatah Elmi Farah Girma Taddese Wedajo 《Food and Nutrition Sciences》 2020年第6期540-561,共22页
Maternal and child nutrition is critical for child health and survival. Appropriate feeding practices are of fundamental importance for health, nutrition, survival and development of infants and children. In pastoral ... Maternal and child nutrition is critical for child health and survival. Appropriate feeding practices are of fundamental importance for health, nutrition, survival and development of infants and children. In pastoral areas of Ethiopia, barriers related to cultu</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">re</span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">, knowledge, social norms, beliefs, behaviors, decision making in the household and burden of other responsibilities contribute to nutritional status of women and children to deteriorate. Policies and strategies are recommending assessment of barriers for designing programs and interventions to improve maternal and child nutrition practices. This study is aimed to assess barriers of optimal maternal and child feeding practices in Pastoralist areas of Somali region, Eastern Ethiopia</span><i><span style="font-family:Verdana;">. </span></i><span style="font-family:Verdana;">A q</span><span style="font-family:Verdana;">ualitative community based research method was used involving 17 focus group discussions and 20 in-depth interviews with mothers, grandmothers, health professionals and religious leaders from three districts. Data from FGDs and interviews were transcribed and coded. The agreed upon codes were synthe</span><span style="font-family:Verdana;">sized and grouped into exhaustive categories. The categories were then merged</span><span style="font-family:Verdana;"> into themes representing the most common barriers on maternal and child feeding practice that emerged from the FGDs and interviews</span><i><span style="font-family:Verdana;">.</span></i><b> </b><span style="font-family:Verdana;">We found that traditional beliefs, myths, culture custodian influence, low accessibility and availability of nutritional foods, pattern and burden of other responsibilities, poor knowledge and health seeking behavior, perceived milk insufficiency as main barriers for optimal maternal and child feeding practices</span><i><span style="font-family:Verdana;">.</span></i><b> </b><span style="font-family:Verdana;">Barriers on optimal maternal and child feeding are very common in the study areas. More work needs to be done to strengthen community-based nutrition with </span><span style="font-family:Verdana;">strong social behavioral change communication with emphasis on age-specific</span><span style="font-family:Verdana;"> counselling on maternal and child nutrition at health facilities, during antenatal and early postnatal visits in the study areas through different media channels, particularly, Somali Region TV and FMs to promote optimal nutrition in the region. 展开更多
关键词 Barriers MATERNAL CHILD NUTRITION somali Region Eastern Ethiopia
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Crop Production Challenges Faced by Farmers in Somalia: A Case Study of Afgoye District Farmers
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作者 Mohamed Ibrahim Abdi-Soojeede 《Agricultural Sciences》 2018年第8期1032-1046,共15页
The objective of this article was to investigate existing challenges of crop production on farmers in Afgoye District lower Shabelle Somalia. The Focus was farmer’s attitude toward existing or not constraints to thei... The objective of this article was to investigate existing challenges of crop production on farmers in Afgoye District lower Shabelle Somalia. The Focus was farmer’s attitude toward existing or not constraints to their crop production and what the experts have seen and what are far from their perception. Sixty famers and academic experts were distributed questionnaires and interview about the constraints of crop production other than agricultural disciplines. This paper used survey descriptive research which facilitates easily connection between past constrains and challenges of crop production. Questionnaire was comprised in the following two parts;Part one;demographic variables and Part two;objective related questions. The study found both major and minor constraints are exists in the Somali farmers. The major constraints include unstable weather, water scarcity, pests damaging crops, and poor transportation, and minor constraints such as inability to access and use such as seed and fertilizers, lack of capital to buy, inadequate investment in irrigation which makes farmers very vulnerable to drought, and there is less knowledge and skill of all farmers. The finding with highest percentage that was challenged in Afgoye farmer was “there is fear of gunner and thieves in the farmers” and 75% of respondents strongly agreed and second question with highest score is “there is fear of conflict between rebels and government”, and 61.7% of them selected strongly agreed. 展开更多
关键词 CROP Production CHALLENGES somali
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Study on Management Practices and Constraints of Black Head Somali Sheep Reared in Awbarre District of Fafen Zone, Somali Region, Ethiopia
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作者 Abdi Abdilahi Mohammed Beyan +1 位作者 Sandip Banerjee Kawnin Abdimahad 《Open Journal of Animal Sciences》 CAS 2022年第3期493-505,共13页
The study was conducted to assess management practices and constraints of Black head Somali sheep in Awbarre district of Fafen zone, Somali regional state, Ethiopia. A total of 120 households were purposively selected... The study was conducted to assess management practices and constraints of Black head Somali sheep in Awbarre district of Fafen zone, Somali regional state, Ethiopia. A total of 120 households were purposively selected for this study using purposive sampling technique. The data were collected through the questionnaire, key informants interview, focus group discussions & field observations. The primary purpose of keeping sheep was for income generation followed by saving, meat production, milk, social and cultural functions. The main feeds for sheep during wet season were communal & private natural pastures. In dry season, communal natural pasture, crop residues & private natural pasture were used. The major source of water during wet season was dam/pond, whereas in the dry season spring & pipe water were used. The majority of the respondents (85.8%) used houses enclosed with thorn woody trees and houses enclosed with stone/brick fence were also reported. Majority of the respondents used controlled mating system and sheep are bred to lamb when forage is plentiful because they are less drought tolerant than goats and to avoid unwanted lambing in dry season. Majority (90%) of respondents own their breeding ram and those who have no breeding males used their neighbors’ rams and borrow from others. The breeding rams were born in the flock implying that animals within the flock are very closely related which leads to inbreeding. The most important health problems affecting sheep were circling disease, sheep pox, tick lameness (tick paralysis), Peste des Petits Ruminants (PPR), bloating, and Foot & mouth disease (FMD). The major constraints hindering sheep production in the study area were shortage of veterinary service, feed shortage, scarcity of water, predators, diseases, and marketing. Therefore, to improve and increase the productivity of sheep production in the study area, better management practices and establishing of veterinary service centers are necessary. 展开更多
关键词 Black Head somali Sheep Management Practice CONSTRAINTS Pastoral & Agro-Pastoral
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A Review of Autism Spectrum Disorder among the Somali Diaspora: Implications for Autism Care in Somalia
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作者 Zakaria Ahmed Mohamed Erick Thokerunga +2 位作者 Chunjiao Tang Ali Omar Jimale Jingyi Fan 《Open Journal of Psychiatry》 2022年第3期269-284,共16页
Despite the dramatic increase in autism spectrum disorders (ASD) globally, no research has been conducted in Somalia regarding ASD. However, research studies from Somali immigrants (diaspora) living in Sweden, the US,... Despite the dramatic increase in autism spectrum disorders (ASD) globally, no research has been conducted in Somalia regarding ASD. However, research studies from Somali immigrants (diaspora) living in Sweden, the US, the UK, etc., have been major contributors to the subject of ASD among people of Somali descent. In this review, we aimed to examine ASD among the Somali diaspora community in terms of its prevalence, possible causes, knowledge of the diseases among the diaspora community, and the challenges faced in raising ASD-affected children in a foreign country. These findings create a general picture of the magnitude of the burden of ASD diagnosis and management and the coping mechanisms adopted by the Somali diaspora community, which are vital lessons for policymakers, child health non-governmental organizations, and the professional medical bodies aiming to tackle ASD back home in Somalia. The study found that ASD is three to five times more prevalent among children of Somali descent than their peers from other backgrounds and that Somali children were generally diagnosed much later than their peers and often presented with lower intellectual abilities than their peers. Furthermore, Somali immigrants were found to have low levels of knowledge about autism, faced stigma and discrimination and often resorted to religion and a small tight circle of friends and family for social support. They faced a huge challenge of seeking access to healthcare and schools for their autistic children and have a mistrust of social services for fear of the government taking away their children. These findings raise the possibility that neglected ASD cases may be prevalent in Somalia and thus makes recommendations for future research, social policy development, and early intervention services for individuals with autism in Somalia. 展开更多
关键词 AUTISM ASD somali IMMIGRANTS DIASPORA
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MULTI-TIMESCALE VARIATIONS OF SOMALI JET AND ITS RELATION WITH PRECIPITATION IN CHINA
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作者 代玮 肖子牛 《Journal of Tropical Meteorology》 SCIE 2015年第2期185-193,共9页
Based on the ERA reanalysis winds data, the multi-time scale variations of Somali jet are analyzed synthetically. The jet's influences on rainfall in China on interannual, interdecadal and sub-monthly scales are a... Based on the ERA reanalysis winds data, the multi-time scale variations of Somali jet are analyzed synthetically. The jet's influences on rainfall in China on interannual, interdecadal and sub-monthly scales are also studied using correlation and composite analyses. The results demonstrate that the interdecadal variations of the jet are significant.The Somali jet became weaker in the 1960 s and became the weakest in the early 1970 s before enhancing slowly in the late 1970 s. Moreover, the relation between the Somali jet and summer precipitation in China is close, but varies on different timescales. Preliminary analysis shows that the intensity variations in May and June during the early days of establishment are well correlated with summer precipitation in China. The Somali jet intensity on the interdecadal scale is closely related with interdecadal variations of the precipitation in China. Regardless of leading or contemporaneous correlation, the correlations between the Somali jet intensity and the rainfall in northern and southern China show obvious interdecadal variations. Moreover, the link between the anomalies of the jet intensity in May-August and precipitation evolution on synoptic scale in China is further studied. China has more rainfall with positive anomalies of the Somali jet but less rainfall with negative anomalies during the active period of the jet. The influence of positive Somali jet anomalies on China precipitation is more evident. 展开更多
关键词 multi-timescale variations somali jet intensity precipitation in China
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Somalis Diasporic Transnational Life--From Placelessness to Placeness in Finnish Urban Environment
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作者 Johanna Malmi 《Sociology Study》 2012年第4期301-314,共14页
About 1.S million Somalis live in the diaspora and first Somali asylum seekers came to Finland in 1990. Then they were the first large refugee group in Finland. They have got integration problems with Finnish society ... About 1.S million Somalis live in the diaspora and first Somali asylum seekers came to Finland in 1990. Then they were the first large refugee group in Finland. They have got integration problems with Finnish society and from that perspective the author started to doubt that whether migrants adopted the same kinds of relationship with the local places and which kind of influence it would have on their integration. The author's aim for this study has been to explore their sense of belonging from transnational family and geographical perspectives. Relph argued that placelessness could be created either by individual itself or urban planning. With the content analyses the author analyzed 50 questions from seven respondents. The questionnaire includes the part of transnational contact keeping among kin members of transnational family, migration and respondents' sense toward urban surrounding where they lives. Emotional ties play a maior role in Finnish Somalis' diasporic life. Emotions intertwine around their life as members of transnational family and toward sense of place. Transnational family affects their perspectives toward western society and urban places. Placelessness is the first step toward integration and positive sense of place. With the integration placelessness turns to placeness. 展开更多
关键词 somalis transnational family placelessness INTEGRATION
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Possible Causes of the Interdecadal Transition of the Somali Jet Around the Late 1990s 被引量:4
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作者 肖子牛 石文静 杨萍 《Journal of Meteorological Research》 SCIE CSCD 2015年第2期214-227,共14页
This observational study demonstrates that the Somali jet(SMJ) experienced a notable interdecadal transition in not only its lower-level parts(〈 850 hP a) but also its higher-level parts(850-600 h Pa) in the la... This observational study demonstrates that the Somali jet(SMJ) experienced a notable interdecadal transition in not only its lower-level parts(〈 850 hP a) but also its higher-level parts(850-600 h Pa) in the late 1990 s. The results also show that the jet at higher level is more significantly related to East Asian monsoon rainfall than that at lower level. Thus, a new whole-layer SMJ(WSMJ) index which includes variations of the higher-level jet is defined based on the average meridional wind speed at five levels(1000-600 h Pa). The interdecadal transition of the SMJ can be mainly attributed to the meridional thermal contrast anomalies near the equator which are associated with the three-pole pattern of the southern Indian Ocean. 展开更多
关键词 interdecadal transition somali jet index Asian summer monsoon southern Indian Ocean sea surface temperature
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Somali Jet Changes under the Global Warming 被引量:1
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作者 林美静 范可 王会军 《Acta meteorologica Sinica》 SCIE 2008年第4期502-510,共9页
Somali Jet changes will influence the variability of Asian monsoon and climate. How would Somali Jet changes respond to the global warming in the future climate? To address this question, we first evaluate the abilit... Somali Jet changes will influence the variability of Asian monsoon and climate. How would Somali Jet changes respond to the global warming in the future climate? To address this question, we first evaluate the ability of IPCC-AR4 climate models and perform the 20th century climate in coupled models (20C3M) experiments to reproduce the observational features of the low level Somali Jet in JJA (June-July-August) for the period 1976 1999. Then, we project and discuss the changes of Somali Jet under the climate change of Scenario A2 (SRESA2) for the period 2005 2099. The results show that 18 IPCC-AR4 models have performed better in describing the climatological features of Somali Jet in the present climate simulations. Analysis of Somali Jet intensity changes from the multi-model ensemble results for the period 2005-2099 shows a weakened Somali Jet in the early 21st century (2010-2040), the strongest Somali Jet in the middle 21st century (2050 2060), as well as the weakest Somali Jet at the end of the 21st century (2070-2090). Compared with the period 1976-1999, the intensity of Somali Jet is weakening in general, and it becomes the weakest at the end of the 21st century. The results also suggest that the relationship between the intensity of Somali Jet in JJA and the increment of global mean surface air temperature is nonlinear, which is reflected differently among the models, suggesting the uncertainty of the IPCC-AR4 models. Considering the important role of Somali Jet in the Indian monsoon and East Asian monsoon and climate of China, the variability of Somali Jet and its evolvement under the present climate or future climate changes need to be further clarified. 展开更多
关键词 IPCC-AR4 models somali Jet changes global warming
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Effect of an educational intervention and parental vaccine refusal forms on childhood vaccination rates in a clinic with a large Somali population
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作者 Diane J.Madlon-Kay Emily R.Smith 《Family Medicine and Community Health》 2017年第3期188-192,共5页
Objective:The purpose of this study is to improve vaccination rates at a clinic with a large Somali population,and many vaccine hesitant parents.The study evaluated the effectiveness of some new materials for vaccine ... Objective:The purpose of this study is to improve vaccination rates at a clinic with a large Somali population,and many vaccine hesitant parents.The study evaluated the effectiveness of some new materials for vaccine hesitant parents.Methods:Educational sessions were given to providers and staff to give“talking points”and to introduce a vaccine refusal form.Chart reviews were done for notes from 50 random well child visits per month of children less than six years old for 7 months before and after the intervention.Results:Before the intervention,44% of Somali children who needed shots did not get them at their well child visit.Afterwards,34% of the Somali children did not get their needed shots.Of non-Somali children,16.8% did not get needed shots before the intervention,and 12.7% did not get needed shots after the intervention(P=0.07).The MMR was the most frequent vaccine omitted.After the intervention,29 parents signed the vaccine refusal form.Conclusion:The“talking points”and vaccine refusal form were associated with improve-ments in immunization rates in this challenging patient population that were not statistically signifi-cant.Refusal form use was not well documented,so its true value requires further study. 展开更多
关键词 Vaccination IMMUNIZATION MMR somali
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沿岸风和海洋波动在北向索马里流生成中的作用
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作者 储小青 彭启华 《热带海洋学报》 CAS CSCD 北大核心 2023年第2期1-8,共8页
基于同化资料和数值模式,文章研究了北向索马里流(norward Somali current,NSC)的季节特征和产生机制。NSC在5月开始出现,在8—9月向北延伸至近15°N,并形成一个强盛的反气旋式环流。10月下旬,NSC开始减弱,并于11月消失。NSC由局地... 基于同化资料和数值模式,文章研究了北向索马里流(norward Somali current,NSC)的季节特征和产生机制。NSC在5月开始出现,在8—9月向北延伸至近15°N,并形成一个强盛的反气旋式环流。10月下旬,NSC开始减弱,并于11月消失。NSC由局地沿岸风和东侧西传的海洋波动共同激发。在5—7月,在局地西南沿岸风的协助下,东非沿岸流(EACC)跨越赤道进入北印度洋,形成了NSC。在8—10月,即便无局地西南沿岸风,在来自阿拉伯海东边界的海洋波动和EACC共同作用下,依旧能形成NSC。研究表明,局地沿岸风虽能诱发近岸的环流结构,但NSC关联的影响范围较大的反气旋式环流结构则由西传的海洋波动所激发。 展开更多
关键词 北向索马里流 海洋波动 局地风场 季节变化 热带印度洋
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索马里海盆多金属结核中关键金属富集机制及古环境记录
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作者 程宇龙 徐勇航 +4 位作者 李东义 陈坚 李云海 林梵宇 尹希杰 《岩石学报》 SCIE EI CAS CSCD 北大核心 2023年第9期2778-2794,共17页
多金属结核富含Mn、Fe、Ni、Cu等元素以及Co和REY(稀土元素和钇)等关键金属,是重要的大洋矿产资源。为了探究西北印度洋索马里海盆结核中关键金属的富集机制及古环境记录,本文使用X射线衍射仪(XRD)分析了一个结核的矿物成分,并通过激光... 多金属结核富含Mn、Fe、Ni、Cu等元素以及Co和REY(稀土元素和钇)等关键金属,是重要的大洋矿产资源。为了探究西北印度洋索马里海盆结核中关键金属的富集机制及古环境记录,本文使用X射线衍射仪(XRD)分析了一个结核的矿物成分,并通过激光剥蚀电感耦合等离子体质谱仪(LA-ICPMS)和电子探针(EPMA)原位分析了该结核的微区元素组成。结果表明,研究区结核内层为柱状结构,中间为掌状,外层又变为柱状。结核主要由水成型富铁层构成,但外层中还存在薄的(100~200μm)成岩-混合型富锰层。富铁层MnO平均含量为25.1%,FeO为30.4%,Co为0.26%,Ni为0.24%,Cu为0.09%,ΣREY为1981×10^(-6)。富锰层MnO平均含量为52.0%,FeO为7.40%,Co为0.09%,Ni为2.45%,Cu为0.53%,ΣREY为719×10^(-6)。富铁层主要由含铁水羟锰矿构成,而富锰层主要由Ⅰ型布赛尔矿构成。Ni和Cu主要赋存于Ⅰ型布赛尔矿,Co和REY则主要赋存于含铁水羟锰矿中,并且Co存在一个“拐点”。富锰矿物(Ⅰ型布赛尔矿)相对更富集HREE,而含铁水羟锰矿中更富集LREE。从内到外,结核中ΣREY呈下降趋势,REY的变化主要受Ce影响。结核Mn/Fe比值与δCe不相关,但生长速率与δCe显著负相关,表明生长速率可能是控制Ce异常的主要因素,仅凭Ce异常不能区分结核微区的成因及氧化还原环境。根据Co经验公式估算,索马里海盆结核形成年龄为~1.46Ma。柱状结构的开始形成可能与早更新世晚期的古海洋环境转型有关。而掌状结构开始生长于~0.6Ma,中更新世气候转型之后风尘增加使得结核中Si和Al增加,并稀释了其他成矿元素。结核富锰层可能生长于末次间冰期的亚氧化底层水环境,且具有一定对称性和渐变性,指示了氧化还原环境的逐渐改变和恢复。 展开更多
关键词 索马里海盆 多金属结核 关键金属 富集机制 古环境记录
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索马里急流的年际变化及其对半球间水汽输送和东亚夏季降水的影响 被引量:111
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作者 王会军 薛峰 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2003年第1期18-25,共8页
利用美国国家环境预报中心和美国国家大气科学研究中心 (NCEP/NCAR)再分析月平均气候资料以及Xie和Arkin分析的月平均降水资料 ( 196 8~ 1998年 ) ,针对索马里低空急流 (SMJ)的年际变化及其对东亚夏季降水的影响问题展开了分析研究 .... 利用美国国家环境预报中心和美国国家大气科学研究中心 (NCEP/NCAR)再分析月平均气候资料以及Xie和Arkin分析的月平均降水资料 ( 196 8~ 1998年 ) ,针对索马里低空急流 (SMJ)的年际变化及其对东亚夏季降水的影响问题展开了分析研究 .结果揭示 ,SMJ作为最主要的越赤道气流 ,对两个半球间水汽输送起最关键的作用 ,它把水汽从冬半球输送到夏半球 .夏季SMJ的年际变化有全球范围内的环流异常与之相联系 ,特别是东亚沿岸的波列状异常分布、南亚高压以及澳大利亚以南的偶极型异常分布 ;它也同春季的北印度洋等海区的海温异常有密切关系 .研究还表明 ,春季SMJ的年际变化对东亚夏季降水和大气环流有显著影响 ,由于SMJ影响的超前性 ,因此它在东亚夏季气候预测上有重要意义 . 展开更多
关键词 年际变化 水汽输送 夏季 降水 索马里急流 大气环流
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云南2002年雨季偏早的环流特征分析 被引量:21
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作者 刘瑜 马振锋 +1 位作者 陶云 龙春华 《高原气象》 CSCD 北大核心 2003年第B10期102-109,共8页
1999—2002年云南处于雨季偏早、5月雨量偏多的气候背景下,2002年雨季连续第四年偏早,这种气候异常较罕见。利用雨季开始期资料,分析了云南雨季开始期变化的年代际特征。还对应分析了雨季开始偏早年及偏晚年1月及5月100、500hPa及SLP场... 1999—2002年云南处于雨季偏早、5月雨量偏多的气候背景下,2002年雨季连续第四年偏早,这种气候异常较罕见。利用雨季开始期资料,分析了云南雨季开始期变化的年代际特征。还对应分析了雨季开始偏早年及偏晚年1月及5月100、500hPa及SLP场距平合成场,并与2002年进行了比较,得到了一些对预测云南雨季开始期有指导性的结论。2002年云南雨季偏早开始与索马里急流建立,高层中低纬环流出现"突变"有直接原因。 展开更多
关键词 雨季 开始期 年代际 环流特征 索马里急流
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夏季索马里急流的建立及其影响机制 被引量:19
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作者 李晓峰 郭品文 +1 位作者 董丽娜 宇婧婧 《南京气象学院学报》 CSCD 北大核心 2006年第5期599-605,共7页
定义了夏季索马里急流(SSMJ)的建立指数,从而确定了1948—2002年的SSMJ建立日期,并以此为基础研究了SSMJ建立过程以及前冬海陆热力异常和冬季风异常对其建立早晚的影响。结果表明:SSMJ的建立是亚洲季风爆发的最早信号;其建立过程受到马... 定义了夏季索马里急流(SSMJ)的建立指数,从而确定了1948—2002年的SSMJ建立日期,并以此为基础研究了SSMJ建立过程以及前冬海陆热力异常和冬季风异常对其建立早晚的影响。结果表明:SSMJ的建立是亚洲季风爆发的最早信号;其建立过程受到马斯克林高压、中非低压以及阿拉伯高压等非洲—印度洋系统的影响,而印度低压的发展有利于SSMJ越过赤道后向东转向;夏季索马里急流建立时间的年际变化反映了北半球冬季海陆热力差异的年际异常;强(弱)东亚冬季风时,次年春季SSMJ建立偏迟(早)。 展开更多
关键词 夏季索马里急流 建立 东亚冬季风 年际变化
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非洲东海岸重点盆地油气资源潜力 被引量:36
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作者 周总瑛 陶冶 +1 位作者 李淑筠 丁文龙 《石油勘探与开发》 SCIE EI CAS CSCD 北大核心 2013年第5期543-551,共9页
基于对非洲东海岸沉积盆地区域构造演化阶段与沉积充填特征的分析,研究各盆地烃源岩、储集层及盖层条件等油气成藏地质条件的差异,分析盆地勘探潜力。非洲东海岸沉积盆地是在前寒武系基底基础上发育起来的叠合盆地,盆内依次充填了晚石... 基于对非洲东海岸沉积盆地区域构造演化阶段与沉积充填特征的分析,研究各盆地烃源岩、储集层及盖层条件等油气成藏地质条件的差异,分析盆地勘探潜力。非洲东海岸沉积盆地是在前寒武系基底基础上发育起来的叠合盆地,盆内依次充填了晚石炭世—早侏罗世陆内裂谷陆相沉积层序、中晚侏罗世—早白垩世陆内弱裂谷沉积层序和晚白垩世—新近纪被动大陆边缘海相沉积层序,3套沉积层序中发育不同生、储、盖组合,具有良好的油气勘探前景。通过对拉穆、索马里、坦桑尼亚、鲁伍马、莫桑比克和穆龙达瓦6个重点盆地油气成藏地质条件的综合对比分析,认为坦桑尼亚、鲁伍马和索马里3个盆地油气成藏地质条件优越,优质烃源岩发育,盖层和后期保存条件好,油气勘探潜力较大,莫桑比克盆地为较有利油气勘探盆地,拉穆、穆龙达瓦盆地为不利盆地。 展开更多
关键词 非洲东海岸 油气资源 成藏地质条件 勘探潜力 坦桑尼亚盆地 鲁伍马盆地 索马里盆地
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中国夏季降水对南印度洋偶极子的响应研究 被引量:41
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作者 杨明珠 丁一汇 《大气科学》 CSCD 北大核心 2007年第4期685-694,共10页
分析了春季印度洋海表温度(SST)与中国160个站夏季降水的关系,得到:印度洋全海盆的增温趋势与我国夏季降水的气候线性变化趋势是十分一致的。另外,热带外南印度洋出现西南印度洋为正(负)、其东北部出现(负)正海温异常的分布模态... 分析了春季印度洋海表温度(SST)与中国160个站夏季降水的关系,得到:印度洋全海盆的增温趋势与我国夏季降水的气候线性变化趋势是十分一致的。另外,热带外南印度洋出现西南印度洋为正(负)、其东北部出现(负)正海温异常的分布模态时,定义为正(负)南印度洋偶极子PSIOD(NSIOD)事件。SIOD事件对中国夏季降水具有重要影响,PSIOD年,5月份中国江南和西南以及长江中下游的降水偏多;6-8月份华北、东北区域、长江中游以及华南地区降水增多,华南与华北之间的区域降水偏少,即主要为两条雨带的分布。NSIOD年,5月份中国大部降水偏少;6-8月中国西南、江南地区以及黄淮地区降水偏多。不同时段SIOD所起的作用是不同的,5月,SIOD主要通过改变马斯克林局地环流的变化,影响印度洋低层越赤道的水汽通量输送;6-8月,通过改变海洋大陆下垫面SST热状态,改变其上空对流强度以及水汽输送方向,并间接影响西北太平洋副热带高压的强度和南北位置,进而对中国雨带的分布产生影响。 展开更多
关键词 印度洋海表温度 中国夏季降水 马斯克林高压 索马里急流 副热带高压
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