169 research outputs found
Modifizierte Elektroden zum elektrochemischen Nachweis bioaktiver Stoffe
Katecholamine (Dopamin, Adrenalin, Noradrenalin) und Serotonin sind wichtige Monoamin-Neurotransmitter im menschlichen zentralen Nervensystem, deren quantitative Bestimmung von groĂem medizinischen Interesse ist, weil damit Aussagen zum Verlauf von Nervenkrankheiten und zur TumorgefĂ€hrdung des sympathoadrenalen bzw. neuroendokrinen Systems möglich sind. AscorbinsĂ€ure und HarnsĂ€ure finden sich in vielen KörperflĂŒssigkeiten. Ihre Bestimmung ist klinisch ebenfalls bedeutend, da deren Konzentration als Indikatoren bekannter Krankheitsbilder dienen.
Etablierte Standardmethoden, wie die HochleistungsflĂŒssigkeitschromatographie (HPLC) und immunologische Nachweisverfahren (ELISA) werden im klinischen Bereich zur Bestimmung der Neurotransmitter genutzt. Diese sind kostenintensiv und zeitaufwĂ€ndig und daher fĂŒr die Anwendung in den Arztpraxen, vor allem in EntwicklungslĂ€ndern nicht geeignet.
Elektrochemische Verfahren, insbesondere voltammetrische Messmethode haben den Vorteil, solche Bestimmungen in einfacher Weise zu ermöglichen. In der Literatur finden sich Angaben zu eingesetzten Elektroden auf Kohlenstoffbasis mit hoher SensitivitĂ€t fĂŒr die Katecholamine. Allerdings wurden diese Elektroden meist einzeln hergestellt. Der kommerzielle Durchbruch ist deshalb bisher, hauptsĂ€chlich infolge der mangelnden Reproduzierbarkeit der Elektrodeneigenschaften und der VerfĂŒgbarkeit einfacher elektronischer GerĂ€te ausgeblieben.
Es war daher Ziel dieser Arbeit, durch industrienahe Herstellungsverfahren Graphitelektroden mit reproduzierbaren Eigenschaften zu entwickeln und diese auf ihre Eignung fĂŒr den quantitativen Nachweis bioaktiver Stoffe zu erproben. Dazu waren Verfahrensschritte zu optimieren, die es erlauben, diese siebgedruckten Graphitelektroden reproduzierbar und kostengĂŒnstig zu fertigen und sie auf verschiedene Weise, z.B. durch halbleitende Polymere und nanoskalige Metalle zu modifizieren.
Neben den Neurotransmittern enthalten KörperflĂŒssigkeiten unter anderem AscorbinsĂ€ure und HarnsĂ€ure in hohen Konzentrationen. Daher waren zunĂ€chst Modellanalyten unter Verwendung dieser Stoffe herzustellen. Die voltammetrischen Methoden, wie die zyklische Voltammetrie (CV), die Differentielle Puls-Voltammetrie (DPV) und die Square-Wave-Voltammetrie (SWV) sollten auf ihre Eignung zum Nachweis der bioaktiven Substanzen erprobt werden. SchlieĂlich waren die Elektroden in realen Analyten zu testen. Insgesamt konnte in der vorliegenden Arbeit gezeigt werden, dass ausgewĂ€hlte Neurotransmitter, AscorbinsĂ€ure und HarnsĂ€ure sich mit differentiellen voltammetrischen Verfahren an industrienah hergestellten modifizierten Dickschichtelektroden bestimmen lassen. Es ist erstmalig gelungen, eine modifizierte Dickschichtelektrode zu entwickeln, mit der es möglich ist, Katecholamine unabhĂ€ngig von AscorbinsĂ€ure (3 mM) und HarnsĂ€ure (2 mM) quantitativ nachzuweisen. Damit eröffnen sich neue Wege fĂŒr den Einsatz von elektrochemischen Sensoren fĂŒr die einfache Bestimmung der Neurotransmitter vor Ort.
Die beschriebenen modifizierten Dickschichtelektroden sind ohne Verlust an elektrochemischer AktivitĂ€t an der Luft oder im Grundelektrolyten monatelang lagerfĂ€hig. Die Elektroden lassen sich im Gegensatz zu den in der Literatur beschriebenen Elektroden mit Einzelfertigung kostengĂŒnstig in groĂer StĂŒckzahl mit hoher Reproduzierbarkeit herstellen.:Inhaltsverzeichnis I
AbkĂŒrzungen V
1 Einleitung und Zielsetzung der Arbeit 1
2 Theoretischer Teil 5
2.1 Elektrochemische Verfahren in der Analytik 5
Klassifizierung elektroanalytischer Methoden 5
2.1.1 Voltammetrie 5
Cyclovoltammetrie (CV) 6
Differential-Puls-Voltammetrie (DPV) 9
Square-Wave-Voltammetrie (SWV) 10
2.1.2 Chronocoulometrie (ChrC) 11
2.1.3 Impedanzmessung (EIS) 12
2.1.4 Elektrochemische Quarzmikrowaage (EQCM) 14
2.2 Poly-3,4-Ethylendioxythiophen, ein leitfÀhiges Polymer 19
2.2.1 LeitfÀhige Polymere 19
2.2.2 Das Poly-3,4-ethylendioxythiophen 20
Elektrochemische Synthese und Dotierung 20
2.3 Bioaktive Stoffe 24
2.3.1 Katecholamine 24
Dopamin 25
Noradrenalin und Adrenalin 25
Abnorme Konzentration der Katecholamine 25
2.3.2 Serotonin 26
2.3.3 Interaktion von Katecholaminen und Serotonin 26
2.3.4 AscorbinsÀure und HarnsÀure 27
2.3.5 Elektrochemisches Verhalten der bioaktiven Stoffe 28
Katecholamine 28
Serotonin 30
AscorbinsÀure 30
HarnsÀure 30
3 Experimenteller Teil 32
3.1 Chemikalien 32
3.2 Lösungen 33
3.2.1 Ausgangslösungen 33
Grundelektrolyte 33
Lösungen der bioaktiven Stoffe 33
3.2.2 Lösungen fĂŒr Elektrodenmodifizierungen 33
EDOT-haltige Lösungen 33
Neurotransmitter-Lösungen 34
HAuCl4-Lösungen 34
Goldkolloide 34
Eisenhexacyanoferrat(II)-GoldsÀurehaltige Lösung 35
3.3 Elektrochemische Messmethoden 35
3.3.1 Voltammetrie, Chronocoulometrie und Impedanz 35
3.3.2 Elektrochemische Quarzmikrowaage 38
3.4 Elektroden und PrÀparation der Elektroden 39
3.4.1 Untersuchte Elektroden, deren Aktivierung und Konditionierung 39
3.4.3 Modifizierungen der Elektroden 41
Poly-3,4-Ethylendioxythiophen (PEDOT) 41
Goldnanopartikel 41
Komposite aus Goldnanopartikeln und PreuĂisch Blau (Au/PB) 42
Polymerfilme aus Monoamin-Neurotransmittern 42
3.5 PrĂ€paration der UP fĂŒr Untersuchungen in realen Medien 43
3.6 Spektroskopische Methoden 43
4 Ergebnisse und Diskussion 45
4.1 Unmodifizierte ElektrodenoberflÀchen 45
4.1.1 Einfluss der Aktivierung der ElektrodenoberflÀchen auf das Messverhalten 45
4.1.2 Bestimmung bioaktiver Stoffe an unmodifizierten Elektroden 48
Ermittlung des Peakpotenzials 48
Messeffekte an Gold- und Graphitelektroden in Neurotransmitter-Lösungen hoher Konzentrationen 50
Bestimmung bioaktiver Stoffe im Gemisch 52
4.2 Au- und Au/PB-modifizierte Elektroden 54
4.2.1 Abscheidung 54
4.2.2 Untersuchungen bioaktiver Stoffe an Au-modifizierten Elektroden 56
4.3 PEDOT-modifizierte Elektroden 58
4.3.1 Abscheidungen der PEDOT-Schichten 58
CV-Abscheidungen der PEDOT-Schichten 59
ChrC-Abscheidungen der PEDOT-Schichten 62
4.3.2 Voruntersuchungen an PEDOT-modifizierten Elektroden 66
Ermittlung des optimalen Potenzialbereiches fĂŒr voltammetrische Messungen an PEDOT-modifizierten Elektroden 66
Ermittlung der optimale PEDOT-Schichten fĂŒr die Bestimmung bioaktiver Stoffe 68
Peakpotenziale bioaktiver Stoffe 71
Einfluss des pH-Wertes des Elektrolyten und der Scangeschwindigkeit auf voltammetrische Messsignale bioaktiver Stoffe 72
Einfluss der Messmethoden auf die Messsignale bioaktiver Stoffe an PEDOT-modifizierten Elektroden 74
4.3.3 Bestimmung bioaktiver Stoffe an PEDOT-modifizierten Elektroden 78
Bestimmung der Neurotransmitter (Dopamin, Adrenalin, Noradrenalin und Serotonin) 78
Bestimmung von AscorbinsÀure und HarnsÀure 81
Bestimmung der Neurotransmitter mit Zusatz von AscorbinsÀure und HarnsÀure 82
StabiltitÀt der PEDOT-modifizierten Elektroden 83
Vergleich der Ergebnisse an PEDOT-Elektroden mit Literaturangaben 84
4.3.4 Spektroskopische Untersuchungen der PEDOT-OberflÀchen 85
4.3.5 Zusammenfassung der Ergebnisse an PEDOT-Elektroden 87
4.4 Au-PEDOT-modifizierte Elektroden 88
4.4.1 Abscheidungen der Goldnanopartikel auf PEDOT-OberflÀchen 88
Abscheidung der Goldnanopartikel durch Adsorption aus Goldkolloiden 88
Abscheidung der Goldnanopartikel auf PEDOT-modifizierten Elektroden mittels Cyclovoltammetrie 92
4.4.2 Bestimmung bioaktiver Stoffe an Au-PEDOT-Elektroden 94
Peakpotenziale bioaktiver Stoffe an Au-PEDOT-Elektroden 94
Bestimmung von Neurotransmittern in 0,1 M Phosphatpufferlösungen 96
Bestimmung von Neurotransmittern mit Zusatz von AscorbinsÀure und HarnsÀure 98
Bestimmung von AscorbinsÀure und HarnsÀure 99
StabilitÀt der SensitivitÀten und Reproduzierbarkeit der Elektrodenherstellung 102
Vergleich der Ergebnisse an Au-PEDOT-Elektroden mit Literaturangaben 102
4.4.3 Zusammenfassung der Ergebnisse an Au-PEDOT-Elektroden 104
4.5 Polymonoamin-modifizierte Elektroden bzw. PEDOT-Elektroden 105
4.5.1 Abscheidungen der Polymerschichten aus Monoaminen an Graphitelektroden 106
4.5.2 Abscheidungen der Polymerschichten aus Monoaminen an PEDOT-Elektroden 106
CV-Abscheidung 106
SWV-Abscheidung 108
4.5.3 Bestimmung bioaktiver Stoffe an Polyserotonin-modifizierte PEDOT-Elektroden 111
Peakpotenziale bioaktiver Stoffe 111
Bestimmung der Neurotransmitter 112
Bestimmung von AscorbinsÀure und HarnsÀure 114
Bestimmung der Neurotransmitter mit Zusatz von AS und HS 114
Bestimmung von HarnsÀure in Gegenwart von Dopamin 116
4.5.4 Möglicher Einsatz der 5-HT-PEDOT-Elektroden als pH-Elektroden 117
4.5.5 Zusammenfassung der Ergebnisse an Polyserotonin-PEDOT-Elektroden 118
4.6 Bestimmung bioaktiver Stoffe in UM 119
4.6.1 Bestimmung von HarnsÀure 119
Bestimmung von HarnsÀure im Modellanalyten 119
Bestimmung von HarnsÀure in prÀparierten UP 119
4.6.2 Bestimmung von Dopamin 120
DA-Bestimmung im Modellanalyten 120
Bestimmung von Dopamin in prÀparierten UP 121
5 Zusammenfassung und Ausblick 123
Zusammenfassung 123
Ausblick 126
Tabellenverzeichnis 127
Abbildungsverzeichnis 130
Anhang 138
Literaturverzeichnis 152
VERSICHERUNG 15
Factors affecting intention to purchase organic agriculture products among Vietnamese
Globally, customer intention to purchase has become the essential part of the product and organization's success in the market. More recently, the idea has captured the attention of academic and policymakers alike. Therefore, the current article analyses product quality features such as agreeableness, emotional stability conscientiousness, openness to experience and extroversion on the intention to purchase organic agricultural products in the context of Vietnam. The study also analyses the mediating role of customer satisfaction between the association of product quality features and intention to purchase organic products in Vietnam. The present study uses questionnaires to collect data pertaining to the health sector of Vietnam. The current study employs the smart-PLS to analyze the constructs and items' reliability as well as the association among constructs. The results show that product quality features except extroversion have a positive and significant association with intention to purchase organic products in Vietnam. The results also reveal that customer satisfaction significantly and positively mediates among the associations of product quality features and intention to purchase organic products in Vietnam. This study is suitable for policymakers while formulating policies that may directly or indirectly affect customers' intention to purchase organic agricultural products.Luong Thu Thuy (Faculty of Economics, Academy of Finance, Vietnam), Tran Thi Phuong Diu (Faculty of Economics, Academy of Finance, Vietnam), Nguyen Dinh Hoan (Faculty of Economics, Academy of Finance, Vietnam), Vu Viet Ninh (Faculty of Economics, Academy of Finance, Vietnam), Nguyen Thi Thuy Nga (Faculty of Economics, Academy of Finance, Vietnam)Includes bibliographical reference
Digital Transformation of the Banking Industry in Developing Countries
Purpose: Â The study's objective is to test the impact of digital transactions on banking performance. Based on the previous research and the actual situations, it has been recognized that the critical role of digital banking is in developing the banking industry, especially in developing countries.
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Theoretical framework: Â In the next section, the study presents background information to promote the research. The digital transformation has changed how customers use financial services. This has pushed banks to adapt more quickly to the wave of digital transformation if they don't want to lose their valuable customer base.
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Design/methodology/approach: Â the methodology applied uses POOL, FEM, REM, and FGLS models to examine the impact of banking transactions made by digital technology on the bank's deposit and lending revenue. This article studies banking operations on digital platforms from 2012 to 2019 in developing countries.
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Findings: The article's findings showed that digital banks' flexible products and services bring many benefits with a high level of interaction, such as supporting the relationship between customers and banks and improving operating revenue.
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Research, Practical & Social implications: Practical implications enhanced the development potential of digital banking is relatively large, stemming from the market demand development orientation of the banking industry.
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Originality/value: The paper's originality and value help banks invest in digital technology as the way forward to better serve their customers
DIVERSITY OF MICROORGANISMS IN SOME FAMOUS BAYS OF VIETNAM AND THEIR ABILITY TO USE IN AQUACULTURE
Joint Research on Environmental Science and Technology for the Eart
DISTRIBUTION OF USEFUL AND HARMFUL MICROORGANISMS IN SHRIMP AQUACULTURE WATER IN TIEN HAI COASTAL OF THAI BINH PROVINCE
Joint Research on Environmental Science and Technology for the Eart
Factors affecting to digital skills and adaptability of students in the context of digital transformation at the Ho Chi Minh city University of Technology and Education
The article focuses on analyzing the factors affecting students' digital skills and adaptability in the context of digital transformation. The study identified influencing factors: Environment, Behavior, Individuals, Teachers, Time of use, and access. However, the results of an online survey of 1.282 students of the Ho Chi Minh City University of Technology and Education (HCMUTE) with Cronbach's Alpha test method, EFA analysis, correlations, and regression analysis, showed that there are 3/5 factors identified in the hypothesis that affect digital skills and adaptability of HCMUTE students in the context of digital transformation, specifically: behavior (Beta = 0.177, Sig. = 0.000); individuals (Beta = 0.181, Sig. = 0.027); teacher (Beta = 0.547, Sig. = 0.000). Besides, the environment does not affect digital skills and adaptability (KNSKNTU) due to Beta = 0.017 and Sig.=0.384>0.05. Sig does not involve usage and access time factors. >0.05 in the table Correlations not be further analyzed in the regression model. The research results are expected to help provide a more objective view of the reality of digital adoption and student adaptability in the digital transformation context at HCMUTE
Factors affecting to digital skills and adaptability of students in the context of digital transformation at the Ho Chi Minh city University of Technology and Education
The article focuses on analyzing the factors affecting students' digital skills and adaptability in the context of digital transformation. The study identified influencing factors: Environment, Behavior, Individuals, Teachers, Time of use, and access. However, the results of an online survey of 1.282 students of the Ho Chi Minh City University of Technology and Education (HCMUTE) with Cronbach's Alpha test method, EFA analysis, correlations, and regression analysis, showed that there are 3/5 factors identified in the hypothesis that affect digital skills and adaptability of HCMUTE students in the context of digital transformation, specifically: behavior (Beta = 0.177, Sig. = 0.000); individuals (Beta = 0.181, Sig. = 0.027); teacher (Beta = 0.547, Sig. = 0.000). Besides, the environment does not affect digital skills and adaptability (KNSKNTU) due to Beta = 0.017 and Sig.=0.384>0.05. Sig does not involve usage and access time factors. >0.05 in the table Correlations not be further analyzed in the regression model. The research results are expected to help provide a more objective view of the reality of digital adoption and student adaptability in the digital transformation context at HCMUTE
Several prognosis factors of severe pertussis in children treated at Vietnam National Childrenâs Hospital (2019-2020)
A prospective, descriptive study was conducted on 382 pediatric patients diagnosed with pertussis at Vietnam National Childrenâs Hospital over a two-year period, from January 1st, 2019, to December 31st, 2020. Of all patients participating in this study, children with severe conditions accounted for 30.1% (115/382). Several factors were found to be associated with the risk of this condition with odds ratios (OR) and 95% confidence intervals (CI), including a decrease in the duration of the onset phase by 5 days [OR 1.53, 95% CI: 1.002-2.34], fever [2.49, 1.18-5.24], cyanosis [9.59, 2.9-31.7], pneumonia [14.45, 6.06-34.5], pulmonary hypertension [4.15, 1.02-16.83], an increase of 10 g/l in white blood cell (WBC) count in the full blood count (FBC) test [1.39, 1.05-1.84], a 5-cycle reduction in Cycle threshold (Ct) value in the pertussis real-time PCR test [1.36, 1.01-1.84], and superinfection [3.94, 1.84-8.48 times]. A WBC count in FBC of â„30 g/l could be used as a prognostic factor for the risk of severe illness condition (sensitivity 46.1%, specificity 90.6%), the requirement for mechanical ventilation (sensitivity 57.1%, specificity 88.5%), and mortality (sensitivity 100%, specificity 91%)
Communication activities of students with the social cultural environment during floods: A case study in Thua Thien Hue province, Vietnam
This study aims to explore the variances in communication behaviours among undergraduate students within the social-cultural context. A total of 104 participants (40 lecturers and six managers) were selected from two universities, namely Hue University of Science and Hue University of Education. The collected data was subsequently evaluated. The findings suggest that there are slight differences between male and female students. This study highlights significant differences in involvement among Kinh ethnic students and students from other ethnic groups. Furthermore, the geographical location and sociocultural environment of a region significantly influence the communication behaviors and preferences of students. Students demonstrate higher mean scores in diverse communication activities as compared to lecturers. The results highlight the significance of gender, ethnicity, geographic location and student status in influencing students' participation in communication. Recognizing and addressing these differences can help in the development of effective communication strategies, the development of inclusive environments and the encouragement of positive social interactions among various groups of students. The implications for students' well-being, academic success and intercultural competency might be explored in more detail in further studies by examining the fundamental variables that lead to these differences
Temporal fluctuation of multidrug resistant salmonella typhi haplotypes in the mekong river delta region of Vietnam.
BACKGROUND: typhoid fever remains a public health problem in Vietnam, with a significant burden in the Mekong River delta region. Typhoid fever is caused by the bacterial pathogen Salmonella enterica serovar Typhi (S. Typhi), which is frequently multidrug resistant with reduced susceptibility to fluoroquinolone-based drugs, the first choice for the treatment of typhoid fever. We used a GoldenGate (Illumina) assay to type 1,500 single nucleotide polymorphisms (SNPs) and analyse the genetic variation of S. Typhi isolated from 267 typhoid fever patients in the Mekong delta region participating in a randomized trial conducted between 2004 and 2005. PRINCIPAL FINDINGS: the population of S. Typhi circulating during the study was highly clonal, with 91% of isolates belonging to a single clonal complex of the S. Typhi H58 haplogroup. The patterns of disease were consistent with the presence of an endemic haplotype H58-C and a localised outbreak of S. Typhi haplotype H58-E2 in 2004. H58-E2-associated typhoid fever cases exhibited evidence of significant geo-spatial clustering along the SĂŽng H u branch of the Mekong River. Multidrug resistance was common in the established clone H58-C but not in the outbreak clone H58-E2, however all H58 S. Typhi were nalidixic acid resistant and carried a Ser83Phe amino acid substitution in the gyrA gene. SIGNIFICANCE: the H58 haplogroup dominates S. Typhi populations in other endemic areas, but the population described here was more homogeneous than previously examined populations, and the dominant clonal complex (H58-C, -E1, -E2) observed in this study has not been detected outside Vietnam. IncHI1 plasmid-bearing S. Typhi H58-C was endemic during the study period whilst H58-E2, which rarely carried the plasmid, was only transient, suggesting a selective advantage for the plasmid. These data add insight into the outbreak dynamics and local molecular epidemiology of S. Typhi in southern Vietnam
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