| 1. |
- Arslan, Muhammad, et al.
(författare)
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Impact of Varying Load Conditions and Cooling Energy Comparison of a Double-Inlet Pulse Tube Refrigerator
- 2020
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Ingår i: Processes. - : MDPI. - 2227-9717. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Modeling and optimization of a double-inlet pulse tube refrigerator (DIPTR) is very difficult due to its geometry and nature. The objective of this paper was to optimize-DIPTR through experiments with the cold heat exchanger (CHX) along the comparison of cooling load with experimental data using different boundary conditions. To predict its performance, a detailed two-dimensional DIPTR model was developed. A double-drop pulse pipe cooler was used for solving continuity, dynamic and power calculations. External conditions for applicable boundaries include sinusoidal pressure from an end of the tube from a user-defined function and constant temperature or limitations of thermal flux within the outer walls of exchanger walls under colder conditions. The results of the system's cooling behavior were reported, along with the connection between the mass flow rates, heat distribution along pulse tube and cold-end pressure, the cooler load's wall temp profile and cooler loads with varied boundary conditions i.e. opening of 20% double-inlet and 40-60% orifice valves, respectively. Different loading conditions of 1 and 5W were applied on the CHX. At 150 K temperature of the cold-end heat exchanger, a maximum load of 3.7 W was achieved. The results also reveal a strong correlation between computational fluid dynamics modeling results and experimental results of the DIPTR.
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| 2. |
- Basit, Abdul, et al.
(författare)
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Structural Modeling on the Determinants of Effectiveness of SOPs Containing COVID-19 in Mass Gatherings
- 2021
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The study is aimed to analyze the determinants of the effectiveness of SOPs in mass gatherings for containing COVID-19. The overall design of the study involves a literature review, data collection by field survey, structural modeling, and analysis. The study is built on the experts' opinion of a focus group (representing people who recently participated in and are responsible for mass gatherings). The study uses the discussion of the literature review to identify the determinants, interpretive structural modeling (ISM) for developing and analyzing a structural model, and Matrice d'Impacts Croises Multiplication Appliquée a un Classement (MICMAC) for corroboration of results of the ISM/classification of determinants. From the literature review, a list of determinants is generated and verified by a panel of experts. The results of the ISM revealed that the determinants “legal environment of the country,” “practicability of SOPs,” “perceived benefit of adapting SOPs,” and “possibilities of avoiding gathering” occupied the top of the model, therefore, they are less critical determinants, whereas “nature of gathering” occupied the bottom of the model, and is thus the most critical determinant. The remaining determinants form the middle of the model, and are therefore moderately severe. The results of MICMAC show that the determinant “perceived benefit of adapting SOPs” is dependent, “nature of gathering” is independent, and all others are linked. The results of MICMAC implicitly substantiate the findings of the ISM. The overall results of the study show that “nature of gathering” is the key determinant. This research does not require a priori theory since it is a theory-building study that uses an inductive approach. It is based on real data and it is useful for local authorities, organizers, participants (attendees/visitors) of mass gatherings, health officials/regulators, researchers, and the community at large. This study has fundamental importance for planning and preparing for such events while ensuring the minimum risk of COVID-19 transmission.
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| 3. |
- Nadeem, Aftab, et al.
(författare)
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Phosphatidic acid-mediated binding and mammalian cell internalization of the Vibrio cholerae cytotoxin MakA
- 2021
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Ingår i: PLoS Pathogens. - : Public Library of Science. - 1553-7366 .- 1553-7374. ; 17:3
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Tidskriftsartikel (refereegranskat)abstract
- Vibrio cholerae is a noninvasive intestinal pathogen extensively studied as the causative agent of the human disease cholera. Our recent work identified MakA as a potent virulence factor of V. cholerae in both Caenorhabditis elegans and zebrafish, prompting us to investigate the potential contribution of MakA to pathogenesis also in mammalian hosts. In this study, we demonstrate that the MakA protein could induce autophagy and cytotoxicity of target cells. In addition, we observed that phosphatidic acid (PA)-mediated MakA-binding to the host cell plasma membranes promoted macropinocytosis resulting in the formation of an endomembrane-rich aggregate and vacuolation in intoxicated cells that lead to induction of autophagy and dysfunction of intracellular organelles. Moreover, we functionally characterized the molecular basis of the MakA interaction with PA and identified that the N-terminal domain of MakA is required for its binding to PA and thereby for cell toxicity. Furthermore, we observed that the ΔmakA mutant outcompeted the wild-type V. cholerae strain A1552 in the adult mouse infection model. Based on the findings revealing mechanistic insights into the dynamic process of MakA-induced autophagy and cytotoxicity we discuss the potential role played by the MakA protein during late stages of cholera infection as an anti-colonization factor.
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| 4. |
- Sharafutdinov, Irshad, et al.
(författare)
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Campylobacter jejuni surface-bound protease HtrA, but not the secreted protease nor protease in shed membrane vesicles, disrupts epithelial cell-to-cell junctions
- 2024
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Ingår i: Cells. - : MDPI. - 2073-4409. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Fundamental functions of the intestinal epithelium include the digestion of food, absorption of nutrients, and its ability to act as the first barrier against intruding microbes. Campylobacter jejuni is a major zoonotic pathogen accounting for a substantial portion of bacterial foodborne illnesses. The germ colonizes the intestines of birds and is mainly transmitted to humans through the consumption of contaminated poultry meat. In the human gastrointestinal tract, the bacterium triggers campylobacteriosis that can progress to serious secondary disorders, including reactive arthritis, inflammatory bowel disease and Guillain–Barré syndrome. We recently discovered that C. jejuni serine protease HtrA disrupts intestinal epithelial barrier functions via cleavage of the tight and adherens junction components occludin, claudin-8 and E-cadherin. However, it is unknown whether epithelial damage is mediated by the secreted soluble enzyme, by HtrA contained in shed outer-membrane vesicles (OMVs) or by another mechanism that has yet to be identified. In the present study, we investigated whether soluble recombinant HtrA and/or purified OMVs induce junctional damage to polarized intestinal epithelial cells compared to live C. jejuni bacteria. By using electron and confocal immunofluorescence microscopy, we show that HtrA-expressing C. jejuni bacteria trigger efficient junctional cell damage, but not soluble purified HtrA or HtrA-containing OMVs, not even at high concentrations far exceeding physiological levels. Instead, we found that only bacteria with active protein biosynthesis effectively cleave junctional proteins, which is followed by paracellular transmigration of C. jejuni through the epithelial cell layer. These findings shed new light on the pathogenic activities of HtrA and virulence strategies of C. jejuni.
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| 5. |
- Ullah, Zia, et al.
(författare)
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Towards the development of sustainable tourism in pakistan : A study of the role of tour operators
- 2021
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Ingår i: Sustainability (Switzerland). - : MDPI AG. - 2071-1050. ; 13:9
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Tidskriftsartikel (refereegranskat)abstract
- The literature on sustainable tourism is scant, particularly in the least developed countries. Very few studies touch upon the concept and no holistic theoretical or conceptual frameworks around the idea of sustainable tourism have been formulated. This study aims at exploring the role of tour operators in developing sustainable tourism in Pakistan and how the tour operators (TOs) conceive their role in this regard. TOs were reached through phone calls, emails, and virtual sources as face-to-face interviews were not possible due to COVID-19 pandemic and restrictions on travel by the government. In-depth interviews were conducted to gather data. Results suggest that the TOs although realize the importance of social, environmental, and economic dimensions of tourism on the communities but have no management systems in place to cater accordingly. There are no incentives in place by the government facilitate TOs to design and implement such systems. The TOs do not select a destination based on Global Sustainable Tourism Council criterion, but rather the selection of destination is mostly demand-based and profit-oriented. The study suggests that corporate profit motive is the sole criterion for decision making and is one of the major causes impeding sustainable tourism in Pakistan. The role of TOs in developing sustainable tourism is vague as the TOs do not have any systems in place to implement sustainable models. The study recommends that efforts need to be put in place to incentivize sustainable tourism in Pakistan and proper laws should be set forth by the authorities to comply by the TOs. The role of TOs is important and understood, however, there is a need to put proper systems in place.
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