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Teses / dissertações sobre o tema "PH"

Autor: Grafiati
Publicado: 4 de junho de 2021
Última modificação: 29 de julho de 2024

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1

Chinnam, Krishna Chytanya. "Capacitive pH-Sensors using pH sensitive polymer". Thesis, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16279.

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This project aims in building a new experimental setup for capacitive measurements of a pH-Sensor. PAA-IOA (Poly Acrylic Acid co – Iso Octyl Acrylate) is the dielectric material over the in-plane interdigitated gold electrodes where PAA IOA acts as an H+ ion sensing layer. The changes in the capacitance of the sensor when the sensor is dipped into different pH solutions will be quantized accordingly. The dipping setup is built in such a way that the electrodes (containing the polymer layer) can be easily dipped into different pH liquids and to eliminate any contact between the polymer and set-up (e.g. pressure effects on the sensor). From the setup it is visible that the gold electrodes are not subjected to any external force as in the case of the setup used previously. Three phases of experiments have been used in this project to get a clear view on the working principle of the polymer. The effect of pH is only considered in this project, as we already have the evidences for the salt sensitiveness of PAA IOA from the work done in the past. The influence of various pH on polymer is observed as capacitance measurements. Response time is more than 5 minutes for PAA IOA. ∆C decreases with frequency and frequency choice depends on application/electronics. The degree of other ions influence is not clear but they have a minor influence in the resistance.

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2

Backhus, Ralf. "Hygienestatus frisch erlegter Fasanen (Phasianus colchicus, Ph. torquatus, Ph. mongolicus, Ph. versicolor) aus verschiedenen Revieren in Deutschland /". Hannover : [s.n.], 2000. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=009476449&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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3

Rueda, Javier Eduardo. "The Ph(t)/Ph(t)/s/c Queueing Model and Approximation". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9637.

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Time-dependent queueing models are important since most of real-life problems are time-dependent. We develop a numerical approximation algorithm for the mean, variance and higher-order moments of the number of entities in the system at time t for the Ph(t)/Ph(t)/s/c queueing model. This model can be thought as a reparameterization to the G(t)/GI(t)/s. Our approach is to partition the state space into known and identifiable structures, such as the M(t)/M(t)/s/c or M(t)/M(t)/1 queueing models. We then use the Polya-Eggenberger distribution to approximate certain unknown probabilities via a two-moment matching algorithm. We describe the necessary steps to validate the approximation and measure the accuracy of the model.
Master of Science
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4

Kulkarni, Aditya Umesh. "Approximating Deterministic Changes to Ph(t)/Ph(t)/1/c and Ph(t)/M(t)/s/c Queueing Models". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33460.

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A deterministic change to a time-varying queueing model is described as either changing the number of entities, the queue capacity, or the number of servers in the system at selected times. We use a surrogate distribution for N(t), the number of entities in the system at time t, to approximate deterministic changes to the Ph(t)/Ph(t)/1/c and the Ph(t)/M(t)/s/c queueing models. We develop a solution technique to minimize the number of state probabilities to be approximated.
Master of Science
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5

Rivinoja, A. (Antti). "Golgi pH and glycosylation". Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514292699.

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Abstract Glycans, as a part of glycoproteins, glycolipids and other glycoconjugates, are involved in many vital intra- and inter-cellular tasks, such as protein folding and sorting, protein quality control, vesicular trafficking, cell signalling, immunological defence, cell motility and adhesion. Therefore, their correct construction is crucial for the normal functioning of eukaryotic cells and organisms they form. Most cellular glycans are constructed in the Golgi, and abnormalities in their structure may derive, for instance, from alkalinization of the Golgi lumen. In this work we show that Golgi pH is generally higher and more variable in abnormally glycosylating, i.e. strongly T-antigen (Gal-β1,3-GalNAc-ser/thr) expressing cancer cells, than in non-T-antigen expressing cells. We also confirmed that the Golgi pH alterations detected in cancer cells have the potential to induce glycosylation changes. A mere 0.2 pH unit increase in Golgi pH is able to induce T-antigen expression and inhibit terminal N-glycosylation in normally glycosylating cells. The mechanism of inhibition involves mislocalization of the corresponding glycosyltransferases. We also studied potential factors that can promote Golgi pH misregulation in health and disease, and found that cultured cancer cells, despite variation and elevation in Golgi pH, are fully capable of acidifying the Golgi lumen under the normal Golgi pH. Moreover, we introduce a Golgi localized Cl-/HCO3- exchanger, AE2a, that participates in Golgi pH regulation by altering luminal bicarbonate concentration and thus also buffering capacity. Participation of AE2a in Golgi pH regulation is especially intriguing, because it also provides a novel mechanism for expelling protons from the Golgi lumen.
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6

Shin, John J. H. "Lipids as pH biosensors". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45704.

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7

Ighoroje, Ahbor Dolly Awani. "pH and vascular tone". Thesis, University of Glasgow, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293493.

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8

Marshall, Alexander James. "pH-sensitive holographic sensors". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615895.

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9

Barman, Dipti Narayan. "pH sensitive fluorescent sensors". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4972.

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Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 3, 2009) Includes bibliographical references.
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10

Shave, Evan Eric. "pH-biased isoelectric trapping separations". Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/4184.

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The classical isoelectric trapping (IET) technique, using the multicompartment electrolyzer (MCE), has been one of the most successful electrophoretic techniques in preparative-scale protein separations. IET is capable of achieving high resolution discrimination of proteins, by isolating proteins in between buffering membranes, in their isoelectric state. However, due to the inherent nature of the IET process, IET has suffered several shortcomings which have limited its applicability. During a classical IET separation, a protein gets closer and closer to its pI value, thus the charge of the protein gets closer and closer to zero. This increases the likelihood of protein precipitation and decreases the electrophoretic velocity of the protein, thus making the separation very long. Furthermore, the problems are aggravated by the fact that the instrumentation currently used for IET is not designed to maximize the efficiency of electrophoretic separations. To address these problems, a new approach to IET has been developed, pH-biased IET. By controlling the solution pH throughout the separation, such that it is not the same as the protein’s pI values, the problems of reduced solubility and low electrophoretic migration velocity are alleviated. The pH control comes from a novel use of isoelectric buffers (also called auxiliary isoelectric agents or pH-biasers). The isoelectric buffers are added to the sample solution during IET and are chosen so that they maintain the pH at a value that is different from the pI value of the proteins of interest. Two new pieces of IET instrumentation have been developed, resulting in major improvements in protein separation rates and energy efficiency. A variety of separations, of both small molecules and proteins, have been successfully performed using the pH-biased IET principle together with the new instrumentation.
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11

Trinh, Quang Thong. "Hydrogel based piezoresistive pH sensors". Dresden TUDpress, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2860048&prov=M&dok_var=1&dok_ext=htm.

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12

Stephen, John R. "pH regulation in enteric bacteria". Thesis, University of Aberdeen, 1997. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=130919.

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Escherichia coli mutants impaired in growth and survival at low external pH in minimal medium were selected and attempts made to identify the disrupted genes. This study suggested that clpX, encoding a heat-shock induced protease and molecular chaperone, was functional in survival of E. coli at pH 3.3. Promoter probe plasmid libraries of Salmonella typhimurium LT2 DNA were created in E. coli and screened for acid-inducible transcriptional elements, and transcriptionally active fragments of degradative amino-acid decarboxylase genes recovered. Chromosomal gene fusions to the reporter gene lacZ in E. coli generated by Mu DII 1734 insertion were screened in a similar way and suggested that the gene encoding adenylate cyclase (cya) could be induced by mild cytoplasmic acidification. The sequence of a gene known to be inducible by cytoplasmic acidification, inaA, became available during the course of this study. The 5' region of this gene was used to generate a set of plasmids carrying fragments of the acid-inducible promoter transcriptionally fused to a luciferase based reporter system. Elements of the sequence required for induction by cytoplasmic acidification were identified. One of these reporter constructs was used to screen an E. coli Tn10 chromosomal insertional mutant library for genes involved in the regulation of inaA. One such mutant had a multiple antibiotic resistant (mar) phenotype. The disrupted loci in 2 other mutants were identified by inverse PCR, sequence analysis and database searches. Both were known only as open reading frames (ORFs) discovered during the sequencing of the entire E. coli genome, and were tentatively identified as yddB (closely linked to gadB and gadC; required for glutamate dependent acid resistance) and f300 (closely linked to pldA; required for detergent resistance). The promoter of f300 was shown to be sensitive to cytoplasmic acidification. The inaA promoter was also demonstrated to be induced at the onset of stationary phase, and to be independent of the stationary phase and weak-acid inducible σ factor RpoS and also of cAMP levels.
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13

Bissell, Richard Alexander. "Luminescent sensing of microenvironmental pH". Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335570.

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14

Lynch, Patrick Lionel Mark. "Fluorescent molecular sensors for pH". Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317479.

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15

Pye, G. "Gastrointestinal pH and colorectal neoplasia". Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381466.

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16

Hynds, Peter John. "Thylakoidal delta pH driven translocation". Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325846.

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17

Alabdullah, Sahar Samir Mohammed. "pH measurements in ionic liquids". Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42877.

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Deep eutectic solvents (DESs) and ionic liquids (ILs) have been significantly used in a variety of applications and one of the challenges is to understand the behaviour of protons in these non-aqueous media. The aim of this study is to investigate pH scales in DESs and ILs and to use the values to understand processes which occur in these media. The first stage of the study involved the development of a spectroscopic analytical method for measuring effective proton activity in IL media. Its pKIn data for bromophenol blue as an indicator were obtained in DESs and ionic liquids and it was found that the pKIn was influenced by the amount of the salt in the system. The value of pKIn was lower in DESs and ILs than in water. pKIn values were used to obtain pKa values for different organic acid in variety of DESs and in two different imidazolium-based ILs containing different anions. The order of acidity is controlled by the element of the anion within it and it was found that F- > HSO4-> Cl-> Ac- suggesting some correlation with hydrogen bond strength. In the second stage of this study a glass membrane electrode was used for the first time in DESs and ILs. The investigation successfully measured the pH scales of different DESs. It was shown that the response of a glass electrode was almost Nernstian in a DES with minimal water incorporated. The Nernstian slope increased as more water was added to the DES. A new, non-aqueous glass electrode was also made using Ag/AgCl in Ethaline reference electrodes. It was shown that this also had a Nernstian response showing that the glass membrane could function with only the traces of water naturally incorporated in the DESs. In the final part of this study the pH values of DESs were used to investigate the solubility of metal oxides in different DESs and the solubility was found to correlate well with the pH of the liquid. The formation of polyaniline was invetgated in solutions of differing pH both with and without water. The data showed the effect of both pH and mass transport on the rate of film growth. It was found that pH was not directly related to polymer growth rate but it showed that polymer only grew when an emulsion of monomer formed in solution. This significant discovery was only enabled by quantification of solution pH.
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18

Schwartz, Jacob B. (Jacob Benjamin) 1975. "Eliminating intermediate lists in pH". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86511.

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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.
Includes bibliographical references (p. 89-92).
by Jacob B. Schwartz.
M.Eng.
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19

Allison, Stuart M. "Autotrophic nitrification at low pH". Thesis, University of Aberdeen, 1989. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU020926.

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The effect of low pH on autotrophic ammonia oxidation was to be investigated. Autotrophic ammonia oxidisers were successfully isolated from soils of low pH, from sites around Scotland, in an attempt to determine if acid tolerant or acidiphilic strains were responsible for nitrification in these soils. No acid tolerant bacteria were isolated and adaptation, of nitrifiers, to low pH was not found to have occurred during the maintenance of agricultural soil plots at low pH. Carbonate was found to be limiting at low pH, if sodium carbonate, alone, was used to adjust the pH of the medium. The pH minima for ammonia oxidation was not affected by additional carbonate. Recently isolated nitrifying bacteria, grown in liquid culture, were found to produce large amounts of exopolysaccharides at stationary phase, causing cell aggregation. Evidence suggested that this material offered protection against desiccation. Continuous flow columns were used to study surface attached N. europaea at low pH. It was demonstrated that surface attachment allowed nitrification to occur at 1.3 pH units lower than in liquid batch culture. This system also demonstrated a requirement for additional carbonate in medium of low pH. Evidence was found to indicate that ammonium is transported into the cell and that NH3 is not a limiting factor due to low pH. A nitrifying biofilm showed that attachment within a polysaccharide matrix offered significant persistence in a low pH environment and that activity occurred at a value lower than in liquid batch culture. The sensitivity of N. europaea to inhibition by PEX was found to increase in liquid batch culture. Continuous flow soil columns showed nitrapyrin to be more inhibitory at low pH. Nitrification occurred in columns at a pH value lower than in liquid batch culture. This culture system suggested that the bacteria were in a different physiological state than when grown in batch culture. Several strains of ammonia oxidisers, isolated from acid soils, were shown to possess a urease enzyme. A Nitrosospira sp exhibited limited growth on urea at pH 5.5.
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20

Burton, Simon Alexander Quentric. "Ureolytic nitrification at low pH". Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU052828.

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Laboratory studies of ureolytic nitrification were carried out to determine whether the ability of ammonia oxidisers to hydrolyse urea could explain their persistence and activity in acid soils. Ammonia oxidising bacteria were isolated from a number of acid soils, using previously described and novel techniques, and isolates tested for their ability to hydrolyse urea. None of the 17 isolated strains were found to be ureolytic, nor were they active below pH 7, indicating the persistence of neutrophilic ammonia oxidisers in acidic soils. The failure to isolate ureolytic and acidophilic strains suggested either their absence in these soils or inadequacies with the isolation procedure. Ten strains of ammonia oxidisers, previously isolated by other workers, were also tested for ureolytic activity and two were found to be ureolytic, Nitrosospira sp. (NPAV) and Nitrosospira sp. The growth of Nitrosospira sp. (NPAV) in liquid batch culture was studied in buffered and unbuffered media revealing that, in the presence of urea, growth and activity could be maintained in media with a pH value of 4-7 whereas growth on ammonium sulphate only occurred at or above pH 7. This suggested that ureolytic strains were capable of growth and activity in acidic conditions if urea was present, providing an explanation for the nitrification in acid soils. The oxidation of urea to nitrite by cultures was incomplete and ammonium accumulated. Growth appeared to inhibited at pH 8 in some media suggesting inhibition of growth by urea in these conditions. The growth and activity of Nitrosospira sp. (NPAV) was studied in continuous flow columns at low pH. Activity could be initiated in continuous flow columns by medium containing urea at pH 4 whereas ammonia was only oxidised at or above pH 6 when medium containing ammonium sulphate was supplied. When effluent nitrite production was constant and a steady state had been established, urea was completely hydrolysed by Nitrosospira sp., causing an increase in the pH, indicating the formation of NH3.
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21

Müller, Matthias. "pH-Regulation und Glukosestoffwechsel - Wirkung von Glut1-Überexpression, Serum und Dexamethason auf den zytosolischen pH". [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10733068.

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22

Silva, Maurício Chagas da. "Estudo teorico do mecanismo de acoplamento-cruzado envolvido na reação de formação da ligação Ph-Ph catalisada por paladio via PhB (OH)2 (Ph=C6H5)". [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248946.

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Orientador: Nelson Henrique Morgon
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-04T16:59:18Z (GMT). No. of bitstreams: 1 Silva_MauricioChagasda_M.pdf: 1448929 bytes, checksum: 5e8a626133912c0e72a209eeccbbfd34 (MD5) Previous issue date: 2005
Mestrado
Físico-Química
Mestre em Química
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23

Ferreira, José Olímpio. "Simulação de filas Gi/G/m e verificação de aproximações destas por filas Ph/Ph/m". Instituto Nacional de Pesquisas Espaciais, 1998. http://urlib.net/sid.inpe.br/iris@1913/2005/07.21.11.28.

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A avaliação de desempenho de um sistema de fila GI/G/m é um clássico problema difícil. Estes sistemas de filas com múltiplos servidores são notoriamente difíceis de serem analisados analiticamente, sendo que uma solução analítica exata somente é possível para casos especiais, tais como as filas M/M/m, M/D/m, M/K2 /m, GI/H2/m, GI/EK/m, GI/Ph/m, Ph/D/m e Ph/Ph/m. Os modelos de simulação por computadores, apesar de exigirem muitos recursos de hardware (memória de trabalho e de armazenagem de massa, velocidade de processamento da CPU) e de consumirem muito tempo na execução das rodadas da simulação, permitem considerações mais próximas das situações reais. Os modelos de simulação podem ser bastante úteis na checagem de suposições necessárias num modelo analítico e na checagem dos resultados do modelo analítico. Este trabalho trata da estimação de medidas de desempenho, em equilíbrio, de filas GI/G/m através de simulação. Também é tratada a verificação de aproximações de filas GI/G/m por filas Ph/Ph/m.
The performance evaluation of a GI/G/m queueing system is a classic hard problem. These multi-server queues are notoriously difficult to be evaluated analytically and, a analytic solutions is possible only for special cases, just as the queues M/M/m, M/D/m, M/K2 /m, GI/H2/m, GI/EK/m, GI/Ph/m, Ph/D/m e Ph/Ph/m. The computer simulation models, despite of requiring many hardware resources (work memory, storage memory, processing speed of the CPU) and consuming large amount of computer times in the execution of the simulation runs, allow the evaluation of more realistic models. The computer simulation models can be convenient enough to check the validity of assumptions needed in an analytic model and to check the results of the analytic model. This study deals with the estimation of steady-state (long-run) measures of performance for GI/G/m queueing systems through simulation models. It also checks the GI/G/m queues approximations by Ph/Ph/m queues.
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24

Nomura, Satoshi. "Development and Application of a Ligth-Scanning pH-Imaging Microscope Using a Flat Semiconductor pH Seneor". Kyoto University, 2000. http://hdl.handle.net/2433/151554.

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25

Monaco, Enzo. "pH Transients in Hydroxyapatite chromatography columns". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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Ceramic Hydroxyapatite (CHT), with empirical formula (Ca5(PO4)3OH)2, is a material used as ion exchange resin in chromatographic applications. The material, having both positive and negative charged sites, can be used in many different contexts encountered in the protein purification processes. Nevertheless, the resin shows an intrinsic limitation for this kind of applications: even if the material solubility in water is very low at pH values higher than 6.5, it sharply increases in more acidic environments, reducing the life of the material and increasing the operative costs of the process, making problematic the CHT application at these conditions. There is a further complication related to the CHT application: it is experimentally reported that the result of the resin interactions with salts is a pH transient occurring in the liquid phase of the chromatographic column. These pH variations are temporary but remarkable, they may influence in an important manner the material solubility, affecting the number of utilization cycle of the fixed bed and, eventually, the stability of the proteins involved in the separation process. In this work the principal aspects contributing at the selection of the operating pH and of the buffering specie are analyzed, discussing also the effect of the buffer itself on the material solubility. Then, it is reported a mathematical model useful for the description of the dynamic behavior of the column and it is proposed an interaction mechanism between the salts of the mobile phase and the stationary phase. In particular, it is emphasized the discussion regarding the different affinity shown by the stationary phase for the different counter-ions which may accompanies the buffering specie. Finally, a series of equations are developed at the scope to obtain a model useful to describe the observed pH transients.
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26

Schapiro, Florencia Beatriz. "pH homeostasis of the Golgi complex". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq58920.pdf.

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27

Nyberg, Lindborg Kristina. "Phagolysosomal pH measurements in alveolar macrophages /". Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4512-8/.

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28

Norbert, Waranakulaarachchiralalage D. J. A. "Metal complexes as potential pH sensors". Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336008.

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29

Hammond, Paul A. "A single-chip digital pH meter". Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401960.

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30

Fridd, Susan. "pH dependence of colicin P-domains". Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312027.

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31

Bourilkov, Jordan Todorov. "Electrical pH control in aqueous solutions". Thesis, City University London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418981.

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32

Griswold, Aaron A. (Aaron Alexander) 1981. "pH control in a miniaturized bioreactor". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32812.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (leaf 18).
A miniaturized bioreactor with a volume on the order of 100 [micro]l has been built with the aim of increasing the efficiency of the screening process for various microbial cultures. Unlike larger reactors currently in use, the current miniaturized design lacks a method of pH control. Without pH control, cell growth can be hindered or even stopped altogether when the growing medium becomes too acidic. Using technology already in place to optically measure the pH inside the reactor in conjunction with a valve and a base-filled reservoir, a simple closed-loop (feedback) control system has been developed. The volume of base injected into the reactor must be minimized because the reactor itself is so small. Data is recorded and control signals are outputted by a computer running LabView software. While the control system developed in this thesis shows promise, further development is needed before it can be put to good use.
by Aaron A. Griswold.
S.B.
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33

Trevor, Susie. "pH responsive chitosan based 'smart' materials". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613408.

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34

Faradji, Charly Andre. "Optically active ligands derived from PH₃". Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730899.

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35

Mihell, John Alexander. "Ruthenium dioxide thick film pH electrodes". Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/47133/.

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PH sensitive electrodes have been fabricated using thick film screen printing techniques. Powdered ruthenium dioxide hydrate was incorporated in a printable paste by mixing with an uncured polymer precursor. This paste was printed onto alumina tiles which had been previously patterned with conductive tracking which enabled connection to measurement circuitry. The liquid polymer was cured to a resistant solid using either temperature or ultraviolet light treatments. Large numbers of electrodes were fabricated in this way, using ruthenium dioxide with varying levels of hydration. Printed electrodes were tested for pH response using a number of fixed pH buffers. A commercial silver/silver chloride reference electrode was used to complete the potentiometric measurement cell. The response of electrodes was found to be comparable to that of commercial electrodes based upon a pH sensitive glass bulb. Electrodes were tested after prolonged soaking in various solutions, both acidic and alkali. Some types of printed electrode showed signs of chemical attack and failure after storage in acidic media. Charge was passed through electrodes to investigate the possible perturbation of electrochemical equilibria within the oxide. Electrodes were characterised by microscope examination of used and unused samples. The hydration level of the oxide powders used was investigated using thermogravimetric analysis techniques. The electrochemical mechanisms underlying the potentiometric pH response are speculated upon. The experimental evidence could indicate that an ion exchange mechanism involving hydroxide groups on the oxide surface is responsible for pH sensitivity. Results are discussed with respect to this and other mechanisms.
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Deng, Kangfa, Gerald Gerlach e Margarita Guenther. "Force-compensated hydrogel-based pH sensor". SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35185.

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This paper presents the design, simulation, assembly and testing of a force-compensated hydrogel-based pH sensor. In the conventional deflection method, a piezoresistive pressure sensor is used as a chemical-mechanical-electronic transducer to measure the volume change of a pH-sensitive hydrogel. In this compensation method, the pH-sensitive hydrogel keeps its volume constant during the whole measuring process, independent of applied pH value. In order to maintain a balanced state, an additional thermal actuator is integrated into the close-loop sensor system with higher precision and faster dynamic response. Poly (N-isopropylacrylamide) (PNIPAAm) with 5 mol% monomer 3-acrylamido propionic acid (AAmPA) is used as the temperature-sensitive hydrogel, while poly (vinyl alcohol) with poly (acrylic acid) (PAA) serves as the pH-sensitive hydrogel. A thermal simulation is introduced to assess the temperature distribution of the whole microsystem, especially the temperature influence on both hydrogels. Following tests are detailed to verify the working functions of a sensor based on pH-sensitive hydrogel and an actuator based on temperature-sensitive hydrogel. A miniaturized prototype is assembled and investigated in deionized water: the response time amounts to about 25 min, just half of that one of a sensor based on the conventional deflection method. The results confirm the applicability of the compensation method to the hydrogel-based sensors.
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37

Gorshkova, M. Yr, I. V. Volkova, E. S. Grigorian e V. A. Izumrudov. "Polyelectrolyte Nanocomplexes with pH-controlled Solubility". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35468.

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The prepared polyelectrolyte complexes of anionic copolymer of divinyl ester and maleic anhydride and cationic water soluble chitosan proved to be able to undergo reversible phase transition, in particular at physiological pH and ionic strength. Formation of either soluble or insoluble complexes occurred depending on pH value, charge ratio and degree of polymerization of the polymers. The stability of positively or negatively charged complexes against destruction action of the added salt drastically increased in acidic media presumably owing to H-bonds formation. According to light-scattering data, the size of the soluble complexes varied from 100 to 300 nm and remained virtually unchanged under storage after lyophilizing drying and resuspending in the same medium. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35468
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38

Wrobel, Magdalena. "pH-driven instabilities in chemical systems". Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/4380/.

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The main aim of my project is to find new feedback driven enzymatic systems and to develop new biochemical oscillators. Such systems help in the understanding of nonlinear behaviour in biological systems and may also find applications in, for example, drug delivery or material science. The first step was to obtain a clock behaviour and bistability in a new enzymatic system, the urea/urease/sulphuric acid reaction. A kinetic model has been proposed and compared with the experimental results. Secondly, front propagation has been also observed in space under specific range of conditions and the results have been analysed theoretically by expansion of the model into spatial dimension. Additionally irregular oscillations in the urea/urease/acetic acid system in flow were observed. Attempts to explain this behaviour theoretically have been made and discussed. In order to produce more robust, regular oscillations in the urea/urease reaction, literature and experimental investigations of reactions that could provide negative feedback were made. The most obvious strategy to obtain a pH oscillator is to find an H+ autocatalytic reaction, in which case the best candidates from organic reactions was hydrolysis of esters to produce a carboxylic acid. Simple general models have been proposed and several examples of esters have been investigated experimentally. Apparently one of the investigated esters, acetyl salicylic acid, exhibited very interesting behaviour from the perspective of chemical locomotion. The motion of aspirin has been analyzed qualitatively under different set of conditions.
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39

Zhang, Xiaomeng. "MRI OF TUMOR pH AND PERFUSION". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195293.

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In the early 1920s, Otto Warburg demonstrated that tumor cells have a capacity to convert glucose and other substrates into lactic acid instead of CO2 and water, even under aerobic conditions. Consequently, Warburg assumed that the intracellular pH (pHi) of tumor was acidic. However, later studies have shown that maintenance of pHi within a pH range of 7.0-7.2 is necessary for normal cellular proliferation and that the extracellular pH (pHe) is partially acidic in solid tumors. A low pHe may be an important factor inducing invasive behavior in tumor cells. Research into causes and consequences of this acid pH of tumors are highly dependent on accurate, precise and reproducible measurements. Techniques for measuring tissue pHi and pHe have undergone great changes since 1950s. From microelectrode and dye distribution studies, measurement of pH underwent a revolution with the advent of pH-sensitive dyes that could be loaded into the cytosol. Further significant advances have come from the measurement of cell and tissue pH in whole organisms by magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI) and pH-sensitive Positron Emission Tomography (PET) radiotracers.
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40

Wilson, Darren. "pH and vascular smooth muscle tone". Thesis, University of Bath, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362288.

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Sardarinejad, Ali. "Nano-engineered RuO2-based pH sensors". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1773.

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pH sensors are broadly used in chemical and biological applications. Example, Metal oxide-based pH sensors have many appealing features that include chemical resistance, insolubility, stability, outstanding mechanical strength, electrocatalyst and manufacturing technology. This thesis focuses on recent pH measurement techniques which incorporate miniaturization and optimization of the sensor and fabrication with super Nerstian pH sensitive materials. Such sensors have high sensitivity, fast response, excellent corrosion resistance, wide detection range, low hysteresis, long-term stability and good reversibility/reproducibility. The research validates the feasibility of developing a low-cost, rugged, miniaturized ruthenium oxide (RuO2) thin-film pH sensor comprising a RuO2 on platinum sensing electrode deposited using R.F. magnetron sputtered in conjunction with an integrated thick Ag/AgCl reference electrode. Ion diffusion condition (O2:Ar ratio), electrode film thickness (50-425 nm), sensing media temperature (1.5-50 °C) and working electrode area to reference electrode area ratio, are investigated for alumina and flexible substrates. Sensitivity values ranging from of 58.50 mV/pH to 84.50 mV/pH are attained with the developed sensors, for water quality, urease, biomedical application and standard buffer solutions of pH values 4.0 and 10.0. These results are in excellent agreement with the theoretical Nernstian response. The performance and characterization of the pH sensors with regards to sensitivity, response time, pH resolution, stability and reversibility are also investigated. A feasibility study for developing a ruthenium oxide (RuO2)-based pH sensor on a flexible substrate was also investigated. Moreover, the suitability of sensors demonstrate the concept of electrodes for monitoring engine oil acidity by adding nitric acid. Experimental results show a linear potential-versus-acid-concentration response for nitric acid concentration between 0 (fresh oil) to 400 ppm, thus demonstrating the accuracy of the RuO2 sensor in real-time operation, making it attractive for use in cars and industrial engines.
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42

Jansson, Jennie. "The influence of pH on fiber and paper properties : Different pH levels during beating and sheet forming". Thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-36514.

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The effect of pH on fiber and paper properties, during beating and sheet formation, was investigated for three different pulps. The pulps were pH adjusted to four different pH levels between 3 and 9. Isotropic laboratory sheet were made of both unbeaten and beaten pulps. The beaten neutral sulfite semi-chemical pulp and bleached softwood kraft pulp were affected by changes in pH; bleached softwood kraft pulp in a minor extent due to less fiber surface charges. Compared to the other pH levels, pH 3 showed a lower fiber surface charge, water retention value, tensile index, tensile stiffness index, compressive index and edge crush resistance index. SEM pictures showed a denser network at pH 9 than for pH 3. This was seen for both neutral sulphite semi-chemical and softwood kraft pulp. The unbeaten pulps and beaten bleached hardwood kraft pulp were not affected by changes in pH. SEM pictures showed no difference in the fiber network for bleached hardwood kraft pulp. A mill trial, with neutral sulphite semi-chemical pulp, at pH levels between pH 4.8 and pH 5.6 was completed. No significant difference was seen for any mechanical property.
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43

Ye, Xuemin. "The effect of water pH on swimming performance, blood pH, red cell pH, ion concentrations and catecholamine concentrations in plasma, and gill potential in rainbow trout (Salmo gairdneri)". Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26676.

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The effect of transferring fish from water at pH 7.0 to either more acid or more alkaline conditions was to reduce the maximum critical velocity of the fish. In water of pH 4.0, 5.0, and 10.0, the maximum critical velocity was only 54.5%, 66.5%, and 61% respectively of that recorded for fish in the water of pH 7.0. Thus, both acid and alkaline conditions in the water reduce the aerobic swimming capacity of trout. Exposure to acid conditions increased mucus secretion and this was associated with an increase in coughing and breathing frequency in resting fish. Coughing rate increased from 41/hr to 592/hr; and respiration frequency increased from 81/min to 104/min when fish were transferred from water at pH 7.0 to water at pH 4.0. In comparing fish exposed to acid and alkaline waters, the results indicates that fish have a greater capacity to regulate blood pH in acid than in alkaline conditions. The gill potential was strongly dependent on water pH, being negative in neutral water, but positive in acid water and more negative in alkaline solution. Catecholamine levels increased significantly during acid exposure, but were not altered during alkaline exposure. The increasing catecholamine levels appeared at different time periods in different fish during acid exposure and seemed to be associated with the death of the fish. Na⁺ and C1⁻ ion concentrations in plasma decreased significantly after 24hrs of acid exposure, but did not change significantly in alkaline water. This may indicate that ionoregulatory disturbance in plasma is one of the reasons for the decrease in the maximum critical velocity in acid water, but not in alkaline water.
Science, Faculty of
Zoology, Department of
Graduate
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44

Virvilaitė, Ilona. "Mėsos pH kitimo tyrimas technologinio proceso metu". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2007. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2007~D_20070420_100738-97922.

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The research of pH chantes in ripe smoke-dried sausvages during the whole technological process of production. The research is made at ŽŪB „Nematekas“ (agricultural company). The smoke-dried sausages were chosen as subject of research. One group of products was ripened for 7 days, the other one – for 13 days. The raw materials used for the production of all sausages were the same as follows: beef ham (I sort), beef (II sort), pork, pork or beef lard. The dynamics of pH and weight changes was researched. Following results were fixed: The biggest waste of weight – 25 % in 12 days were achieved by “Nerija”, “Karkle”, “Husarai” and “Airiska” sausages. The weight most dropped of in smoke-dried sausage “Nerija”, even 193 g and least in sausage “Kaimiska”, only 131 g. Remained part of smoke-dried products weight were various in scale from 190 to 155 g. The biggest alterations of smoke-dried sausages have happened in period of 2 days ripening. During that period most of production pH has reduced up to demanded 5,3 pH level. The biggest pH reduction were noticed in smoke-dried sausage “Airiska” – from 5,97 to 5,22, the smallest pH reduction were noticed in “Zemaitiskas Skilandis” – from 5,78 to 5,34. Remained specimens pH variations were from 5,42 to 5,29. Most significant pH alterations, noticed during first 2 days, were result of time, required for adaptation, for new microorganisms adaptation in new environment. In period of 5 -8 days because of reduced humidity microorganisms... [to full text]
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45

Bjaaland, Helen. "Ambivalens inför rutinmässigt navelsträngs-pH : Hur barnmorskor inom förlossningsvård resonerar kring det nyfödda barnets nytta av navelsträngs-pH". Thesis, Högskolan i Skövde, Institutionen för hälsa och lärande, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-16236.

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Bakgrund: Navelsträngs-pH tas rutinmässigt på nästan alla nyfödda barn i Sverige, det finns nu olika uppfattningar om navelsträngs-pH:ts nytta. Forskning visar att navelsträngs-pH har klinisk nytta för barn som föds vid högriskförlossningar, barnets nytta ses inte vid lågriskförlossningar. Själva provtagningsförfarandet ses inte utgöra några direkta risker för barnet. Det är viktigt att barnmorskors resonemang kring navelsträngs-pH synliggörs eftersom pH-provtagningen igår i barnmorskans ansvarsområde. Syfte: Att synliggöra hur barnmorskor inom förlossningsvård resonerar kring det nyfödda barnets nytta av navelsträngs-pH. Metod: Semistrukturerade intervjuer genomfördes med sex barnmorskor verksamma vid förlossningsavdelning. För dataanalys användes kvalitativ innehållsanalys. Resultat: Resultatet redovisas i tre kategorier: Navelsträngs-pH är till nytta för barn som föds medtagna; Navelsträngs-pH är inte till nytta för det friska barnet och Navelsträngs-pH tas (ändå) på alla barn. Ett Övergripande tema sammanlänkar kategorierna: Ambivalens inför rutinmässigt Navelsträngs-pH, vilket visar på den ambivalens barnmorskorna känner inför navelsträngs-pH på friska barn. Konklusion: Barnmorskorna följer rådande rutin och tar navelsträngs-pH på alla barn. Barnmorskorna lyfter att navelsträngs-pH har stor nytta för det medtagna barnet, då ger en inarbetad rutin trygghet. På det friska barnet önskar dock barnmorskorna få göra en individuell bedömning. För att kunna göra bedömningen på ett medicinskt säkert sätt behöver nya riktlinjer utarbetas.
Background: Umbilical-cord-pH is routinely tested at almost all births in Sweden, however views differ regarding the benefits. Studies show that umbilical-cord-pH gives clinical benefits in high-risk deliveries that are not found in low-risk deliveries. Umbilical-cord-pH is not viewed as a risk for the child. It is important to visualize midwives’ reasoning regarding the pH-sampling since it is their responsibility. Aim: To visualize how midwives in delivery care reason regarding the new-born child's benefit from umbilical-cord-pH. Method: Semi-structured interviews were conducted with six certified midwives who worked in a delivery ward. Qualitative content analysis was used. Results: The result is presented in three categories: Umbilical-cord-pH is useful for children born poorly; Umbilical-cord-pH does not benefit the healthy child and Umbilical-cord-pH is taken (anyway) on all children. An overall theme links these categories: Ambivalence to routinely take Umbilical-cord-pH, which shows the ambivalence the midwives feel regarding umbilical-cord-pH on healthy children. Conclusion: The midwives follow the established routine and test the umbilical-cord-pH of all children. They emphasize that the umbilical-cord-pH is of great benefit to the child who is born poorly, a well-established routine provides safety. Nevertheless, midwives wish to make individual assessments of the healthy children. New guidelines are needed if this is to be done in a medically secure manner.
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46

Weber, Johann Rudolf. "Messungen des extrazellulären pH und der pH-Differenz zwischen Intra- und Extrazellulärraum mittels Mikroelektroden am Ventrikelmyokard von Meerschweinchen /". [S.l : s.n.], 1987. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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47

Witzel, Dirk. "Pharmakologische Beeinflussung der pH-Regulation kardialer Fibroblasten". [S.l.] : [s.n.], 2003. http://archiv.ub.uni-marburg.de/diss/z2003/0424/.

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48

Schitthelm, Frank. "Amorphe diamantartige Kohlenstoffschichten für integrierte pH-Sensoren". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968691277.

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49

Olsson, Jan, e Åsa Sjödin. "Spermiers överlevnad i olika pH- och näringslösningar". Thesis, Högskolan Dalarna, Biologi, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:du-1548.

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The sperm in the seminal fluid is affected by various environmental factors, where one is the pH-value in the environment. An extremely low or high pH-value has been observed in other studies to be lethal to sperm cells, thus effecting the sperms capability to perform a conception. Addition of nutrion, such as glucose and fructose, also has been a factor contributing to the survival of the sperm.In this essay we found that the pH-value did not affect the lifespan of the sperm. Mainly due to the pH-value in the seminal fluid and the buffer capacity of the same, the different pH-solutions we used showed no significant effect on the sperm’s lifespan. Addition of nutrion (glucose or fructose) did however affect the time the sperm survived, adding hours to the lifespan. The best media for survival was the IVFTM nutrion solution used to perform so called ”swim up” tests, where the sperms get ”washed” and used without the seminal fluid’s content. The IVFTM improved the motility of the sperms and also made them longer living.
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50

Bou-Abboud, Elias. "Modulation by pH of sodium channel blockade". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35569.pdf.

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