658 research outputs found

    The Chobe enclave : summary report

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    This summary report is the last in a serie of reports on the research programme conducted in the Communal First Development Area (CFDA) of the Chobe District, an area commonly known as the Chobe Enclave. This final report highlights the major findings of the study, summarizes the results of the land evaluation exercise (Chapter 2) and discusses options for rural development in the Chobe Enclave (Chapter 3). These options or recommendations logically reflect the results of the studies in the area. In this sense they provide a starting-point for the implementation of a rural development programme in the Chobe Enclave. It should be noted that the views presented in Chapter 3 are those of the research team of the University of Utrecht, and not necessarily those of the Government of Botswana

    Amicitia Christiana : Da Costa en Groen van Prinsterer in hun briefwisseling (1830 - 1860)

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    Balke, W. [Promotor]Bruijn, J. de [Promotor

    Motor sequence learning in older adults

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    The aging society calls for increased understanding of age-related cognitive and neural changes in motor learning. Why do healthy older adults have difficulties learning new motor skills, and how can we support them in their learning? The aim of this dissertation was to zoom in on the age-related differences in the cognitive processes underlying sequential motor skill, and explore avenues for enhancing motor learning in older adults. The experiments were all centered on motor sequence learning. Motor sequences are the building blocks of complex motor actions, this paradigm is often used to study the cognitive underpinnings of learning motor sequences. Three types of motor tasks were used. In the sequence-tapping task, the goal is to perform a sequence (e.g., ā€œ3 - 5 - 2 - 4 - 2ā€) that is continuously displayed on the screen as often as possible. The flexion-extension (FE) task requires participants to move a cursor on the screen as quickly and smoothly as possible to succeeding targets using elbow flexion-extension movements. Finally, in the discrete sequence production (DSP) task, participants perform a sequence by responding to series of succeeding cues as quick as possible. Chapter 2 examined whether older adults are able to develop and use the so-called effector-independent, visuospatial sequence representation that young adults have been shown to develop during the early stages of learning a motor sequence. This type of representation is thought to facilitate the flexible application of learned motor skills in new contexts. Therefore, it is relevant to know whether this mechanism is affected by advanced age. In the experiment, the older participants indeed displayed the ability to use sequence knowledge that was developed using FE movements in a test phase where the same sequence was to be performed using key-presses. However, when the practice phase consisted of key-presses and the ensuing test phase of FE movements, the older adults showed no benefit from practice while young participants did show slight transfer. We concluded that, although high age seems to affect the amount of transfer, the ability to apply sequence knowledge in a flexible manner seems to be largely preserved in older adults. Chapter 3 scrutinized older adultsā€™ ability to develop motor chunking behavior. Being able to develop and use motor chunks is important because it is associated with reduced attentional demands and thus frees capacity to focus on things besides controlling movement, like watching the road while shifting gears in a car. Chapter 3 complements Chapter 2 because this type of sequence representation is developed after the visuospatial representation. The results confirmed that the older participants are indeed able to develop chunking behavior, but just need more practice than their younger counterparts. Chapter 4 tested the hypothesis that the careful, error-averse way in which older adults perform motor tasks stimulates their reliance on external guidance and prevents them from developing more efficient, chunking based representations. The participant sample was divided into a speed group that received the instruction to perform the DSP task as fast as possible, and an accuracy group instructed to make as few errors as possible. The intervention sorted the expected effect with fast responses and relatively many errors in the speed group, and the opposite pattern in the accuracy group. However, our measure of chunking showed no group difference at any moment of practice. Furthermore, in the test phase, the speed group was not more successful in performing the sequences by heart than the accuracy group. Based on these results we concluded that speedy, error-rich performance during practice does not have a beneficial effect on the development of motor chunks in older adults. Chapter 5 explored the potential of transcranial direct current stimulation (tDCS) as a technique to enhance motor learning in older adults. While previous research suggested that tDCS indeed offers beneficial effects, the literature also calls for replications and incremental steps to add much-needed robustness to the existing results. We therefore tried to reproduce the results of a particular sequence learning study. In line with the results of that study, the replication condition in our study showed that tDCS indeed accelerates skill development in a simple but elegant sequence-tapping task. Importantly, we also showed for the first time that tDCS affected the development of sequence-specific skill, and not the general ability to perform such sequencing tasks. In general, the findings suggest that the cognitive processes underlying skill acquisition are largely the same for the age groups investigated. Older adults proved to be able to develop the visuospatial representation necessary for the flexible application of motor skill, and also showed the ability to develop motor chunks, albeit after extensive practice. Our attempt to speed up the development of motor chunks by motivating participants to practice sequences as fast as possible was not successful. On the contrary, non-invasive brain stimulation did improve motor learning, confirming the promise this technique brings for enhancing skill development in older adults

    Zdravstveni status i jestivost ribe iz tri hipertrofne akumulacije u južnoj Africi

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    Severozapadna oblast Južne Afrike je poznata po ekstenzivnim rudarskim i poljoprivrednim aktivnostima. Ove aktivnosti spiraju organska i neorganska jedinjenja iz zemljiÅ”ta i za posledicu imaju pogorÅ”anje kvaliteta vode u akumulacionim jezerima. Sledeće akumulacije iz severozapadne oblasti: Hartbeespoort Dam (HD), Klipvoor (KD) i Bospoort (BD) su poznate po visokim količinama nutrijenata i klasifikovana su kao hipertrofna jezera. Procena zdravlja riba i procena rizika po zdravlje ljudi čine važne komponente u uspostavljanju standarda kvaliteta vode i/ili dozvoljenih nivoa konzumiranja riba. Cilj ovog istraživanja bio je da se utvrdi: (1) da li su prisutni Å”tetni efekti na jedinkama Clarias gariepinus i Cyprinus carpio iz jezera HD, KD i BD (2) da li su prisutni efekti na ljudsko zdravlje ukoliko se ovakva riba konzumira. Rezultati su poređeni sa kontrolnom lokacijom - jezerom Marico-Bosveld Dam (MD). Voda, sediment i ribe (n=20) su uzorkovani iz HD, KD i BD. Uzorci vode i sedimenta su analizirani na prisustvo neorganskih i organskih molekula. Riba je izmerena, urađena je disekcija i pregled, uzeti su uzorci krvi i određena je starost svakog primerka. Organi koji su koriŔćeni za histoloÅ”ku procenu stanja su bili: Å”krge, jetra, bubreg, testisi i jajnici Urađena je kvalitativna i polukvantitativna histoloÅ”ka procena. MiÅ”ićno tkivo svakog primerka je uzorkovano i izvrÅ”ene su hemijske analize, koje su koriŔćene za procenu rizika po zdravlje ljudi. Makroskopskom analizom konstatovano je da je značajan broj riba iz jezera HD, KD i BD imao masnu degeneraciju i fokalnu promenu boje jetre, promene na koži i ozbiljnu infestaciju parazitima u visceralnoj Å”upljini. Vrednosti hematokrita su varirale od normalne do ispod i iznad normalnih vrednosti. Vrednosti leukokrita su bile u okvirima normalnih vrednosti, osim kod C. gariepinus iz jezera HD, koje su pokazivale viÅ”e vrednosti od normalnih. Vrednosti ukupnih proteina, factor kondicije i hepatosomatični indeks su bili u okviru normalnih vrednosti za obe vrste na svim ispitivanim lokacijama. Ribe iz jezera MD su bile starije od riba iz druga tri jezera. HistoloÅ”ke promene su primećene na jetri, bubregu i Å”krgama obe vrste, a jetra je pokazivala najviÅ”i stepen promena. pri klasifikaciji, bubreg i Å”krge su svrstane u grupu 1 (normalna struktura), dok je jetra svrstana u grupu 2 (struktura sa histoloÅ”kim promenama). Visoki nivoi aluminijuma, silicijuma i hroma su detektovani u miÅ”ićnom tkivu. Nivo hroma je bio iznad preporučenih vrednosti. Rezultati hemijske analize miÅ”ićnog tkiva su pokazali da je u obe vrste bio detektovan p,p,-DDE i to na svim lokacijama, pa i na kontrolnoj. C. gariepinus u jezeru HD pokazivao viÅ”e prosečne vrednosti p,p-DDD od propisanih 5Āµg/g/ jestivog dela ribe. Procena rizika po zdravlje ljudi je obuhvatala jestivi deo ribe (miÅ”iće). Svi nivoi opasnih materija i rizik od izazivanja kancera su bili niski, sa izuzetkom hroma, ali ni količine ovog elementa su bile takve da se ne predviđa pojava zdravstvenih problema kod ljudi ukoliko se riba svakodnevno konzumira

    Stromal cells in inflammatory bowel disease : perspectives of local mesenchymal stromal cell therapy

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    This thesis is about the role of stromal cells in inflammatory bowel disease (IBD) and to assess the therapeutic potential of local mesenchymal stromal cell (MSC)-therapy. First, we discuss the recent insights in the function of stromal cells in the healthy and inflamed gut and characterize fibroblasts in perianal fistulas from patients with IBD. Furthermore, we study the long-term effects of MSC-therapy for the treatment of perianal fistulas and the efficacy of locally injected MSCs in the inflamed intestines of in vivo IBD models. Lastly, we investigate the cytokine environment of inflamed tissue from IBD patients and how this could affect local MSC-therapy.LUMC / Geneeskund

    Die rol en funksies van die bedryfsmaatskaplike werker in Gauteng

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    M.A.Through experience and interviews held with industrial social workers and because of changes in the environment, it was found that the industrial social worker is unsure of what is expected of him/her and of the direction in which the profession is going. The future and priorities are vague and there is uncertainty regarding how to prepare for it. The aim of this study is to define the role and function of the industrial social worker as it currently exists in the industrial environment and to provide a future scenario for industrial social work ..
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