1,721,037 research outputs found
Correction: Corrigendum: Lipopolysaccharide-Induced Neutrophil Dysfunction Following Transjugular Intrahepatic Portosystemic Stent Shunt (TIPSS) Insertion is Associated with Organ Failure and Mortality
No full textScientific Reports 7: Article number: 40157; published online: 04 January 2017; updated: 28 April 2017 Schalk van der Merwe was omitted from the author list in the original version of this Article. This has been corrected in the PDF and HTML versions of the Article, as well as the Supplementary Information that now accompanies this Article.</jats:p
Universiteit Stellenbosch Eerste Bofbalspan, 1950
No full textDonated by J.H. Neethling.Back row: Elmer Downes, Teddy Evans, Jan Pickard, Johan Goosen. Middle: D. Visser, Schalk van der Merwe, Mr. Jannie Kriger (coach), Jan van Dijk (captain), Tom Barry. Front: W. Laubscher.Sepia photograph depicting Stellenbosch University's first baseball team
The Addams family - Aug 23'.mov
No full textThis recording forms part of my creative output research.</p
Abstract A26: The successful application of endoscopic ultrasound guided fine needle biopsy to establish pancreatic patient-derived tumor xenografts
No full textAbstract
Introduction: Pancreatic cancer is one of the most lethal cancer types with an overall 5-year survival rate of less than 5%. The vast majority of the patients are diagnosed late in their disease onset with already locally advanced setting or when metastasized to regional lymph nodes or other organs and are therefore excluded from surgery. Over the last decades no major advances have been made in the treatment of this disease, at least partly due to the lack of preclinical in vivo models reliably recapitulating the clinic. Patient-derived tumor xenografts (PDX) are currently used as reliable preclinical in vivo models to study tumor biology, accelerate biomarker discovery and preclinical drug screening. However, at present, large tumor biopsies obtained by invasive surgical approaches are still a prerequisite to successfully establish pancreatic PDXs thereby limiting this technique to patients that are eligible for surgery. The objective of the study was to establish pancreatic PDXs by transplanting tumor tissue acquired by endoscopic ultrasound (EUS) fine needle biopsies (FNB) and compare them to surgery-derived PDXs. Secondly, we aimed to demonstrate that EUS-derived PDXs of locally advanced or metastatic pancreatic cancer reflect the original tumors, at the histologic and genetic level.
Method: Biopsies of chemo-naive primary pancreatic carcinoma were collected at surgery and EUS. After localization of the tumor using a linear echoendoscope, a FNB on patients (n=10) with suspected malignant pancreas tumor was performed using a 22G needle. Concentration of the EUS-derived FNB occurred by centrifugation of the sample prior to engraftment. Surgical samples (n=4) on confirmed pancreatic adenocarcinoma were obtained at the time of tumor resection. Via a standardized aseptic technique transplantation was performed in nude mice upon propagation. To asses preservation of general tumor morphology and other tumor-specific characteristics as growth pattern and vascular-stromal composition, H&E and immunohistochemistry (cytokeratin-7, human-vimentin, CD31) were performed. To determine conservation of the mutation profile, copy number alterations and transcription profile, whole exome sequencing (WES), whole-genome low-coverage sequencing and RNA sequencing were executed.
Results: Using the adapted protocol of EUS-derived FNB, we achieved an engraftment rate of 60% whereas all surgical samples were successfully transplanted. Despite a decrease in desmoplastic stromal reaction, the general morphology of EUS-derived FNB PDXs, as assessed by histology, was conserved compared to that of the primary tumor. Also at the genetic level, there was no obvious difference compared to surgery-derived xenografts. In particular, despite some heterogeneity, somatic mutation and copy number profiles were largely shared between xenografts regardless of whether they were obtained by EUS or surgery.
Conclusion: We show that it is technically feasible to establish pancreatic PDXs from patients with locally advanced or metastatic disease by a minimal-invasive sampling technique such as EUS FNB. By acquiring a limited amount of tumor tissue, we demonstrated that tumor morphology, differentiation grade and genetic profile are largely maintained across the different passages suggesting that EUS-derived FNB xenografts may be useful to study pancreatic tumor biology and develop novel therapies in this patient population with a high clinical need. In addition, our approach could potentially be translated to establish PDXs in other unresectable tumor types.
Citation Format: Els Hermans, Schalk Van der Merwe, Jeroen Depreeuw, Jeroen Dekervel, Enrico Radaelli, Baki Topal, Diether Lambrechts, Frédéric Amant. The successful application of endoscopic ultrasound guided fine needle biopsy to establish pancreatic patient-derived tumor xenografts. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr A26.</jats:p
Multi-mode antennas for hemispherical field-of-view coverage
Full text linkThesis ((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.Doctora
Characterisation of L-band differential low noise amplifiers
Full text linkThesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: This thesis addresses the complications that are encountered when characterising the performance of differential
microwave LNAs. The predominant sources of noise in electronic circuits are introduced and equivalent
two-port noise models for active devices are derived. Correlation between noise generators are defined by
means of the noise correlation matrix and existing network theory is adapted to include noise analysis of twoport
and multi-port networks. Mixed-mode scattering parameters are introduced in order to define the signal
performance of differential and common-mode propagation in multi-port networks and, by applying the same
theory, the mixed-mode correlation matrix for a three-port dLNA is derived. Furthermore, an expression is derived
for de-embedding the differential noise figure of a three-port dLNA using two single ended measurements.
Two dLNA designs, both incorporating wideband 180°-Hybrid ring couplers, are discussed and the differential
signal and noise performance of the dLNAs are compared to that of their constituent single ended LNAs.AFRIKAANSE OPSOMMING: Hierdie tesis behandel die komplikasies wat ontwerpers in die gesig staar tydens die karakterisering van mikrogolf
differensiële laeruis versterkers. Die hoof ruisbronne in stroombane word bespreek en ekwivalente
tweepoortnetwerkmodelle vir aktiewe toestelle word afgelei. Korrelasie tussen ruisbronne word gedefnieer
deur middel van ruiskorrelasiematrikse en bestaande tweepoort- en multipoort-netwerkteorie word aangepas
om ruismodelle in te sluit. Weens die feit dat differensiële- en gemene-wyse voortplanting van seine voorkom
in multipoortnetwerke word gemengde-modus S-parameters behandel. Dieselfde teorie maak dit vervolgens
moontlik om die gemengde-modus ruiskorrelasiematriks van ’n drie-poort differensiële laeruis versterker af
te lei. Verder word daar ’n wyse voorgestel waarmee die differensiëleruissyfer van ’n drie-poort differensiële
laeruis versterker vanuit twee enkel ruissyfermetings bereken kan word. Twee differensiële laeruis versterker
ontwerpe, waarvan beide wyeband 180 -differensiaalkoppelaars implementeer, word bespreek en die
differensiëlesein- asook die differensiëleruis-werking word vergelyk met die werking van die omsluite ongebalanseerde
laeruis versterkers
Heat transfer modelling of semi-suspension biomass fired industrial watertube boiler at full- and part-load using CFD
No full textGhosts of the Popular: The Hidden Years Music Archive and the Interstices of South African Popular Music History
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