Next-generation organic blend semiconductors for high performance solution-processable field Effect Transistors

Ambitions for transparent, lightweight, flexible and inexpensive electronic technologies that can be printed over large area substrates have driven substantial advances in the field of organic/printed electronics in recent years. Amongst the various technologies investigated, solution-processed, organic thin-film transistors (OTFTs) have received extraordinary attention, primarily due to the enormous potential for simple, cost-effective manufacturing. Two exciting research areas relevant to OTFT development that offer tremendous potential are those of the small molecule/polymer organic semiconducting blends and the science and engineering of molecular doping. However, the lack of organic semiconducting blends that surpass the benchmark charge carrier mobility of 10 cm2/Vs, and the numerous challenges associated with the practical utilisation of molecular doping, have prevented adaptation of OTFTs as a viable technology for application in the emerging sector of plastic electronics. The work in this thesis focuses on an organic semiconducting system for OTFTs that addresses these two points. The first part of this thesis describes the development of advanced organic semiconducting blends, the so-called 3rd generation (3G) blend systems. Specifically, a new blend based on the small-molecule C8-BTBT and the conjugated polymer C16DT-BT is introduced. A third component, the molecular p-dopant, C60F48, is then added to the blend system and it is found to have remarkably positive effects on OTFT performance. The ternary blend system is then combined with a solvent-mixing approach, resulting in devices with an exceptional hole mobility value exceeding 13 cm2/Vs. Through the use of complementary characterisation techniques, it is shown that key to this achievement is the unusual three-component material distribution, hinting at the existence of an unconventional doping mechanism. Furthermore, by considering alternative processing techniques, the maximum mobility of the resulting OTFTs is improved further to a value in excess of 23 cm2/Vs. The second part of the thesis focuses on the impact of p-doping in the ternary C8 BTBT:C16IDT BT:C60F48 blend on other important operating characteristics of the OTFTs. The intentional and simple to implement doping process is shown to improve key device parameters such as bias-stress stability, parasitic contact resistance, threshold voltage and the overall device-to-device parameter variation (i.e. narrowing of the parameter spread). Importantly, the inclusion of the dopant is not found to adversely affect the nature of the C8 BTBT crystal packing at the OTFT channel. The final part of this thesis describes the incorporation of 3G blend-based OTFTs into fully functional logic electronic circuits. Hybrid inverter circuits (i.e. NOT gates) are fabricated at low temperatures from solution-phase by combining the high hole mobility C8-BTBT:C16IDT-BT:C60F48 blend OTFTs as the p-channel device and a novel In2O3/ZnO heterojunction metal oxide semiconducting system as the n-channel transistor. The resulting complementary inverters exhibit excellent signal gain and high noise margins, making this hybrid circuitry a promising contender for application in the emerging field of printed microelectronics.Open Acces

People, profits, and politics in the Eastern Cape chokka squid fishery: the socio-economics of an unstable resource

This study examines socio-economic issues confronting the chokka squid fishery in South Africa's Eastern Cape, particularly in the towns of St Francis Bay, Humansdorp and Jeffreys Bay. It examines the implications of two key issues challenging the industry: the volatility of chokka squid catches, and the government's recent proposal that, to further transformation, 25% of the sector's commercial rights should be reallocated to small-scale fishing cooperatives. It is argued that the socio-economic effects of catch volatility flow from the institutional structure of the fishery and the labour contracts in it, specifically the link between fishers' earnings and their catches. These are further linked to the local economy to which the fishery and its workers are closely tied. This thesis examines the ability of small-scale fishing co-operatives to participate efficiently in the sector and the potential impact of the proposed rights reallocation on the economic viability of existing firms. The primary data used was collected through personal communications with key sector participants. Possible solutions to the two issues examined are proposed. Alternative approaches to transformation and empowerment within the chokka sector are suggested

Partitioning space for range queries

It is shown that, given a set S of n points in R3, one can always find three planes that form an eight-partition of S, that is, a partition where at most n/8 points of S lie in each of the eight open regions. This theorem is used to define a data structure, called an octant tree, for representing any point set in R3. An octant tree for n points occupies O(n) space and can be constructed in polynomial time. With this data structure and its refinements, efficient solutions to various range query problems in 2 and 3 dimensions can be obtained, including (1) half-space queries: find all points of S that lie to one side of any given plane; (2) polyhedron queries: find all points that lie inside (outside) any given polyhedron; and (3) circular queries in R2: for a planar set S, find all points that lie inside (outside) any given circle. The retrieval time for all these queries is T(n)=O(na + m) where a= 0.8988 (or 0.8471 in case (3)) and m is the size of the output. This performance is the best currently known for linear-space data structures which can be deterministically constructed in polynomial time

Is pelvic floor morphology a predictor of successful pessary retention? Original research and review of the literature

BACKGROUND : Vaginal pessaries are known to be an effective treatment modality for pelvic organ prolapse (POP). Pessaries form an important part of the physician’s armamentarium in the treatment of POP, but currently many of the factors affecting their successful use are poorly understood. OBJECTIVES : To determine the association between pessary retention (PR) at 1 year, and functional pelvic floor morphology, i.e. levator hiatal distance and area, and levator avulsion. METHODS : This retrospective study reviewed the records of 73 patients with symptomatic POP at a tertiary urogynaecological centre. This multi-ethnic cohort had previously been studied for pelvic-floor morphology, had had 4D transperineal pelvic-floor ultrasound, and had opted for a vaginal pessary as a treatment option. RESULTS : Our population had a mean age of 59.4 (range 32 - 91) years, and mean body mass index of 29.4 (range 20 - 42) kg/m2, with a mean assessment of stage 3 in the Pelvic Organ Prolapse Quantifications System (POP-Q). The level of prolapse was found to be related to PR (p=0.077). We further explored this concept using symmetric measures of association (γ=–0.353), indicating that PR decreases with increasing prolapse severity. PR was also found to be inversely associated with prior pelvic reconstructive surgery (n=63; p=0.055; γ=–0.417). There was a strong correlation that failed, however, to achieve significance by a small margin (p=0.052) between hiatal distance on contraction and PR. CONCLUSION : This study found an inverse relationship between PR and hiatal distance on contraction, prior pelvic surgery and the severity of prolapse. This was a pilot study with a limited number of participants, and the authors plan a prospective study to further clarify the association between long-term PR and functional pelvic floor morphology.http://sajog.org.za/index.php/SAJOGam2019Obstetrics and Gynaecolog

Legally related religious challenges to public school materials, curricula, and instructional activities: The "Impressions" controversies, 1986-1994.

The increase and subsequent decline of challenges based on occult content coincided with a large number of challenges to Holt, Rinehart and Winston's Impressions reading series, the first whole language reading series and the most challenged set of curricular materials in American history. While Christian Right literature has tended to be critical of public school curriculum, Impressions was subject to more intense Christian Right opposition than any other textbook series. Overwhelmingly, individuals and groups that objected to Impressions did so after the series was adopted, and in almost all of these disputes the protestors sought to have the series removed. In the majority of cases, the protestors objected to the series on the grounds of its alleged occult content although other objections congruent with Christian Right issues were also raised. Five lawsuits were filed against Impressions; four of which went to trial. Two of these four cases involved alleged violations of the Establishment Clause and were ultimately decided in favor of the school districts by their respective federal courts of appeals.Surveys of challenges to public school materials in the 1960s, 1970s and early 1980s indicated that only a small percentage of the total number of challenges were on explicitly religious grounds. Beginning in 1983, the American Library Association and People for the American Way began issuing annual reports listing challenges and noting increases in Christian Right involvement in challenges. Reflecting major themes in Christian Right literature related to public education, explicitly religious objections can be divided into four main issues of concern: evolution, secular humanism, denigration of religion and occult content. The patterns of reported challenges from 1983 to 1996 indicate that activism related to secular humanism and occult content was, in some respects, an artificial construct of Christian Right leaders--artificial in the sense that activism on these issues was a product of focused, persuasive literature distributed to members of the movement. The activists' perceptions that public school materials and curricula endanger both school children and American society were heightened by books and materials published and distributed by Christian Right organizations

Approach to female urinary incontinence : Part 1 : Medical management

Urinary incontinence is defined as the involuntary loss of urine. It is a ubiquitous disorder, thought to occur more commonly than more familiar health issues such as hypertension, diabetes, and depression. It is a condition whose profile of affected patients includes women of all age groups and which transcends socioeconomic and cultural circumstance.2 Given the above, the social, emotional, and economic impact of the disease on individuals and communities is self-evident. The true prevalence of urinary incontinence world-wide, and in South Africa is essentially unknown. Community based studies have reported the prevalence as ranging between 14% and 67%, showing a large discrepancy from the estimates of physician-based studies, which show an estimated prevalence of between 0.5-5%. This disparity is thought to arise from a combination of underreporting, under-diagnosis, and under-treatment of the disease.http://www.journals.co.za/content/journal/medogam2019Obstetrics and Gynaecolog

Approach to female urinary incontinence : Part 2 : Surgical management

Part one of this article deals with the assessment and medical management of the disease. The following will delve into surgical techniques in the armamentarium of treatment for both urge and stress urinary incontinence.http://www.journals.co.za/content/journal/medogObstetrics and Gynaecolog

Absence of Brca2 causes genome instability by chromosome breakage and loss associated with centrosome amplification

AbstractWomen heterozygous for mutations in the breast-cancer susceptibility genes BRCA1 and BRCA2 have a highly elevated risk of developing breast cancer [1]. BRCA1 and BRCA2 encode large proteins with no sequence similarity to one another. Although involvement in DNA repair and transcription has been suggested, it is still not understood how loss of function of these genes leads to breast cancer [2]. Embryonic fibroblasts (MEFs) derived from mice homozygous for a hypomorphic mutation (Brca2Tr2014) within the 3′ region of exon 11 in Brca2[3], or a similar mutation (Brca2Tr) [4], proliferate poorly in culture and overexpress the tumour suppressor p53 and the cyclin-dependent kinase inhibitor p21Waf1/Cip1. These MEFs have intact p53-dependent DNA damage G1–S [3,4] and G2–M checkpoints [4], but are impaired in DNA double-strand break repair [3] and develop chromosome aberrations [4]. Here, we report that Brca2Tr2014/Tr2014 MEFs frequently develop micronuclei. These abnormal DNA-containing bodies were formed through both loss of acentric chromosome fragments and by chromosome missegregation, which resulted in aneuploidy. Absence of Brca2 also led to centrosome amplification, which we found associated with the formation of micronuclei. These data suggest a potential mechanism whereby loss of BRCA2 may, within subclones, drive the loss of cell-cycle regulation genes, enabling proliferation and tumourigenesis

Osteoblast differentiation of equine induced pluripotent stem cells.

Bone fractures occur in horses following traumatic and non-traumatic (bone overloading) events. They can be difficult to treat due to the need for the horse to bear weight on all legs during the healing period. Regenerative medicine to improve fracture union and recovery could significantly improve horse welfare. Equine induced pluripotent stem cells (iPSCs) have previously been derived. Here we show that equine iPSCs cultured for 21 days in osteogenic induction media on an OsteoAssay surface upregulate the expression of osteoblast associated genes and proteins, including COL1A1, SPARC, SPP1, IBSP, RUNX2 and BGALP We also demonstrate that iPSC-osteoblasts are able to produce a mineralised matrix with both calcium and hydroxyapatite deposition. Alkaline phosphatase activity is also significantly increased during osteoblast differentiation. Although the genetic background of the iPSC donor animal affects the level of differentiation observed after 21 days of differentiation, less variation between lines of iPSCs derived from the same horse was observed. The successful, direct, differentiation of equine iPSCs into osteoblasts may provide a source of cells for future regenerative medicine strategies to improve fracture repair in horses undergoing surgery. iPSC-derived osteoblasts will also provide a potential tool to study equine bone development and disease.Anne Duchess of Cambridge Charitable Trust, Paul Mellon Foundation, Cambridge Turs