The use of stereolithography and related technologies to produce short run tooling

ThesisWhere material properties are critical to a polymer part, rapid prototype (RP) models are inappropriate for evaluation purposes and actual parts moulded in a range of materials are required for evaluation. Conventional tool making processes have extremely long lead times considering that numerous iterations may be required. The aim of this project was to generate polymer parts, utilising various approaches to Rapid Tooling (RT) , including Stereolithography or related technologies, as part of the process. The objective was to establish decision-making criteria for deciding on the appropriateness of various processes and the risks involved to assist prospective users of these technologies. The first phase of the project focused on the process validation of utilising Stereolithography as a direct means to generate injection mould tooling inserts, which were fitted into an injection mould designed for the trial purposes. The objective was to obtain process information with regard to insert generation for Stereolithography. A three dimensional model of the part was generated with CAD and the associated mould was generated around the part. The insert halves were processed and solid epoxy inserts were generated with the 3D Systems SLA500 Stereolithography machine. These inserts were post-finished and fitted to the injection mould . Additional features were added to the inserts to test cooling and gating and wear resistance of the cavity material. The author attended the basic injection tool setting course of the Plastics Federation to enable him to contribute more directly to this process. This also highlighted some of the design issues to facilitate ease of production . Initial difficulties were experienced in finding optimal process parameters. A total of 70 parts were produced, with measurable insert degradation. During the author's training at 3D Systems in the USA, he obtained additional insight in current methods of insert modelling and insert generation. If these process problems could be overcome, it would be possible to produce in excess of a 100 parts with one set of inserts, assuming a tolerance specification of 0.2mm. The cost of producing the inserts was approximately 50% that of conventional tooling fabrication . The time lapse between growing of the inserts and production of parts was one week compared to 6 to 8 weeks tool manufacture time with conventional methods. The second phase of the project focused on methods to enhance the cavity surface. Electroplating of inserts and inserts generated from Aluminium filled epoxy were tested , to investigate the effects that plating has on tool life, dimensional accuracy, temperature distribution, and the cost implications for these subsequent process steps. Stereolithography inserts were generated, taking into account the design considerations. Aluminium filled epoxy inserts were subsequently cast from silicone moulds drawn off the Stereolithography master patterns. Two sets of Stereolithography inserts were plated with 20 ~m of electrolytic nickel plating. One set of aluminium filled epoxy inserts were plated with electrolytic copper followed by electroless nickel. The mould sets were subjected to the same injection moulding trials using Polypropylene. The third phase of the project evaluated the use of Stereolithography investment casting masters to produce tool steel inserts, through the QuickCast process. Porosity was evident, with substantial machining required to fit the inserts. Not all the detail was retained during the casting process. Thin rib features on the part were thus lost. Due to the porosity the cooling was changed to copper tubes fitted into the rear of the tool and back-filled with aluminium epoxy. As the Stereolithography patterns were not polished the metal inserts had to be hand finished. This was a time consuming process and skill is required to obtain a good finish. A cost comparison indicated that machining aluminium inserts would be more cost effective. The tool manufacture time and eventual cost is not significantly less than conventional machining . In fact, trials with aluminium High speed CNC machining proved to be more time, finish and cost effective. This is discussed as part of the trial examples. Wax injection into AIM tooling was investigated on behalf of a client, with good results . As ceramic and polymer injection are very similar, apart from the ceramic being far more abrasive, it is the author's opinion that AIM tooling would be applicable, taking into account that fewer parts may be achieved. The KelTool process was also investigated during the author's USA visit. The licensing fees and additional equipment are extremely costly due to the Rand IDollar exchange rate. Issues related to this process are documented in this report. Clearly the deciding factors remain the quantity of parts required and the complexity of form. Each manufacturing process has a certain level of risk involved. Accumulative risk not only sets manufactured parts at risk but could jeopardise project time scales and iterations of a process have significant impact on a project budget

Rehabilitate body, nature and architecture : sports rehabilitation centre Groenkloof campus

Man and nature...captured within a relational existence. Theoretically this document disputes the man-nature-relationship with the emphasis on architectural participation, in an at tempt to redefine their interdependency.Dissertation (MArch(Prof))--University of Pretoria, 2010.Architectureunrestricte

Orlistat treatment is safe in overweight and obese liver transplant recipients: a prospective, open label trial

Obesity is a frequent complication following liver transplantation and is insufficiently responsive to dietary and life style advice. We studied the safety of orlistat treatment in obese and overweight liver transplant recipients (n = 15) on a stable tacrolimus-based immunosuppressive regimen. For safety reasons, the treatment period was restricted (6 months 120 mg t.i.d., 3 months 120 mg daily). Three patients dropped out, tacrolimus dose was adjusted in six of 12 remaining patients (dose reduction in 4, increase in 2, P = N.S.). All dose adjustments occurred during the 6 months of orlistat 120 mg t.i.d. therapy. No drug intolerance, adverse events or episodes of rejection occurred during the study. Efficacy of orlistat treatment in this population could not be shown, because a formal control population was not included in this safety trial. Moreover, only a significant decrease of waist circumference (P < 0.01 versus start of the study), but not of weight or body mass index, was achieved in the treated group. Orlistat treatment is well tolerated in liver transplant recipients and can be started safely, provided immunosuppressive drug levels and dietary adherence are closely monitored

Association of Adipose tissue inflammation with histologic severity of nonalcoholic fatty liver disease

BACKGROUND & AIMS : The prevalence of nonalcoholic fatty liver disease (NAFLD) has increased with the obesity pandemic. We analyzed the transcriptional profiles of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT), and phenotypes and functional characteristics of adipocyte tissue macrophages (ATMs), in obese patients undergoing bariatric surgery. METHODS : We collected anthropometric data; plasma samples; and SAT, VAT, and liver tissues from 113 obese patients undergoing bariatric surgery at academic hospitals in Europe (Antwerp and Leuven) and South Africa. Based on clinical and histologic features, patients were assigned to the following groups: obese, NAFLD, nonalcoholic steatohepatitis (NASH), or NASH with fibrosis. Microarray analyses were performed to identify genes expressed differentially among groups. We measured levels of cytokines and chemokines in plasma samples and levels of RNAs in adipose tissues by quantitative reverse-transcription polymerase chain reaction. ATMs were isolated from patients and 13 lean individuals undergoing cholecystectomy (controls), analyzed by flow cytometry, and cultured; immunophenotypes and levels of cytokines and chemokines in supernatants were determined. RESULTS : We observed increased expression of genes that regulate inflammation in adipose tissues from patients with NAFLD and NASH; expression of these genes increased as disease progressed from NAFLD to NASH. We found 111 genes associated with inflammation that were expressed differentially between VAT and SAT. Serum levels of interleukin 8, chemokine (C-C motif) ligand 3, and tumor necrosis factor-a correlated with liver inflammation and NAFLD activity score. We developed 2 models that could be used to determine patients’ liver histology based on gene expression in VAT and SAT. Flow cytometry showed increased proportions of CD11cþCD206þ and CCR2þ macrophages in VAT from patients with NASH, and supernatants of cultured macrophages had increased levels of cytokines and chemokines compared with controls. CONCLUSIONS : VAT and SAT from patients with NAFLD and NASH have an increased expression of genes that regulate inflammation, and ATM produce increased levels of inflammatory cytokines, compared with adipose tissues from controls. We identified an expression profile of 5 genes in SAT that accurately predict liver histology in these patients. Transcript profiling: accession numbers: GSE58979 and GSE59045.Schalk van der Merwe, Chantal Mathieu, Frederik Nevens, David Cassiman, and Sven Francque are recipients of the Flanders fund for scientific research (FWO klinisch mandaat), and Hannelie Korf is a recipient of the FWO postdoctoral mandate. Research at the Department of Endocrinology, Diabetology and Metabolism and the Department of Gastroenterology and Hepatology of the Antwerp University Hospital (Belgium) was supported by the European Union: FP6 (HEPADIP contract LSHM-CT-2005-018734) and FP7-HEALTH (RESOLVE no. 305707). Supported by a fellowship from the South African Gastroenterology Association and a scholarship from the European Association for the Study of the Liver (J.d.P.). This research also was supported by a research grant from the Gastro foundation of South Africa. The authors specifically acknowledge the support of Dr. Chris Kassianides. Also funded in part by a grant from the Deutsche Forschungsgemeinschaft DFG-SFB 1052/1: Obesity Mechanisms (projects A04) and by the Helmholtz Alliance Imaging and Curing Environmental Metabolic Disease through the Initiative and Networking Fund of the Helmholtz Association (M.G.).http://www.journals.elsevier.com/gastroenterology2016-09-30hb2016Internal Medicin

Tacrolimus Drug Exposure Level and Smoking Are Modifiable Risk Factors for Early De Novo Malignancy After Liver Transplantation for Alcohol-Related Liver Disease

De novo malignancy (DNM) is the primary cause of mortality after liver transplantation (LT) for alcohol-related liver disease (ALD). However, data on risk factors for DNM development after LT are limited, specifically in patients with ALD. Therefore, we retrospectively analyzed all patients transplanted for ALD at our center before October 2016. Patients with a post-LT follow-up of &lt;12 months, DNM within 12 months after LT, patients not on tacrolimus in the 1st year post-LT, and unknown smoking habits were excluded. Tacrolimus drug exposure level (TDEL) was calculated by area under the curve of trough levels in the 1st year post-LT. 174 patients received tacrolimus of which 19 (10.9%) patients developed a DNM between 12 and 60 months post-LT. Multivariate cox regression analysis identified TDEL [HR: 1.710 (1.211–2.414); p = 0.002], age [1.158 (1.076–1.246); p &lt; 0.001], number of pack years pre-LT [HR: 1.021 (1.004–1.038); p = 0.014] and active smoking at LT [HR: 3.056 (1.072–8.715); p = 0.037] as independent risk factors for DNM. Tacrolimus dose minimization in the 1st year after LT and smoking cessation before LT might lower DNM risk in patients transplanted for ALD

Horizontal versus familial transmission of Helicobacter pylori.

Transmission of Helicobacter pylori is thought to occur mainly during childhood, and predominantly within families. However, due to the difficulty of obtaining H. pylori isolates from large population samples and to the extensive genetic diversity between isolates, the transmission and spread of H. pylori remain poorly understood. We studied the genetic relationships of H. pylori isolated from 52 individuals of two large families living in a rural community in South Africa and from 43 individuals of 11 families living in urban settings in the United Kingdom, the United States, Korea, and Colombia. A 3,406 bp multilocus sequence haplotype was determined for a total of 142 H. pylori isolates. Isolates were assigned to biogeographic populations, and recent transmission was measured as the occurrence of non-unique isolates, i.e., isolates whose sequences were identical to those of other isolates. Members of urban families were almost always infected with isolates from the biogeographic population that is common in their location. Non-unique isolates were frequent in urban families, consistent with familial transmission between parents and children or between siblings. In contrast, the diversity of H. pylori in the South African families was much more extensive, and four distinct biogeographic populations circulated in this area. Non-unique isolates were less frequent in South African families, and there was no significant correlation between kinship and similarity of H. pylori sequences. However, individuals who lived in the same household did have an increased probability of carrying the same non-unique isolates of H. pylori, independent of kinship. We conclude that patterns of spread of H. pylori under conditions of high prevalence, such as the rural South African families, differ from those in developed countries. Horizontal transmission occurs frequently between persons who do not belong to a core family, blurring the pattern of familial transmission that is typical of developed countries. Predominantly familial transmission in urban societies is likely a result of modern living conditions with good sanitation and where physical contact between persons outside the core family is limited and regulated by societal rules. The patterns observed in rural South African families may be representative of large parts of the developing world

SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe

Multi-mode antennas for hemispherical field-of-view coverage

Thesis ((PhD)--Stellenbosch University, 2015.ENGLISH ABSTRACT: This dissertation proposes a multi-mode antenna element excited through a multiconductor feed. It is shown that each of the orthogonal transverse electromagnetic modes supported by the antenna feed results in a unique radiated far-field pattern that collectively allow for nearhemispherical field-of-view coverage. Three multi-mode antenna designs are presented: a dual-mode antenna, integrating a single linearly polarised dipole antenna with a co-located monopole, as well as two quad-mode antenna designs integrating two dual-polarised dipole elements with a co-located monopole element. The dual-mode antenna is excited through a balanced transmission line feed supporting both differential- and common-mode signals that, respectively, result in typical dipole-over-ground and monopole radiated far-field patterns. The quad-mode antennas are each fed through a quadraxial transmission line allowing for excitation through four orthogonal transverse electromagnetic port modes. To characterise the multi-mode response of the multi-mode antennas, generalised transformations are derived by which the multi-mode S-parameters and radiated far-fields can be calculated from the S-parameters and far-fields corresponding to single-ended excitations. These transformations are implemented to validate the response of a dual-mode and quad-mode antenna design through measurements. An equivalent network representation for active multi-mode antennas is presented, including generalised transformations relating the multi-mode signal and noise response of the low-noise amplifiers to the two-port S-parameters and noise parameters of the low-noise amplifiers. Through the use of classical beamforming algorithms, the performance of an active dual-mode and quadmode antenna is presented. In the case of the active dual-mode antenna, it is shown that through the added use of common-mode signals, a variation in sensitivity of less than 50% is achieved in the E-plane. Similarly, the additional excitation modes supported by the active quad-mode antenna is shown to result in a significant improvement in the polarimetric capabilities over the field-of-view coverage.AFRIKAANSE OPSOMMING: Hierdie proefskrif stel ’n multimodale antenna element voor wat deur ’n multi-geleier transmissielyn gevoer word. Dit word gewys dat elk van die ortogonale transversale elektromagnetiese opwekkingsmodusse wat deur die antenna voer ondersteun word, ’n unieke vêrveld stralingspatroon skep, wat gesamentlik lei tot ’n hemisferiese gesigsveld. Drie multimodale antenna ontwerpe word voorgestel: ’n dubbelmodale antenna, waarin ’n enkel lineêrgepolariseerde dipool antenna en monopool mede-geleë word, asook twee viermodale antenna ontwerpe waarin twee dubbelgepolariseerde dipool elemente geïntegreer word met medegeleë monopool antenna elemente. Die dubbelmodale antenna word gevoer deur ’n gebalanseerde transmissielyn wat beide differensiële- en gemene-modus seine ondersteun, waar elk onderskeidelik dipool-oor-aardvlak en monopool stralingspatrone voortbring. Die viermodale antennas word elk gevoer deur vier-as transmissielyne wat vier ortogonale transversale elektromagnetiese opwekkingsmodusse ondersteun. Om die multimodale gedrag van die drie multimodale antennas te karakteriseer, word veralgemeende transformasies afgelei waardeur die multimodale strooiingsparameters asook die vêrveld stralingspatrone vanaf enkelpoort strooiingsparameters en vêrvelde bereken word. Hierdie transformasies word toegepas om die gedrag van ’n dubbel- en viermodale antenna ontwerp te karakteriseer deur metings. Ekwivalente netwerkvoorstellings vir aktiewe multimodale antennas word voorgestel, insluitend veralgemeende transformasies om die multimodale sein asook ruis gedrag van die lae-ruis versterkers betreklik te maak tot die tweepoort strooiingsparameters en ruisparameters van die laeruis versterkers. Deur gebruik te maak van klasieke bundelvormingsalgoritmes, word die gedrag van aktiewe dubbelmodale en viermodale antennas voorgestel. Vir die aktiewe dubbelmodale antenna word daar aangedui dat die gesamentlike gebruik van differensiële- en gemene-modus seine, ’n variasie in sensitiwiteit onder 50% tot gevolg het in die E-vlak. Soortgelyk word daar aangedui dat die addisionele opwekkingsmodusse wat deur die aktiewe viermodale antenna ondersteun word, tot ’n beduidende verbetering in die polarisasievermoë oor die gesigsveld lei