161 research outputs found
COVID-19 PANDEMIC: NEUROLOGICAL MANIFESTATIONS, COMPLICATIONS AND FUTURE PERSPECTIVE
No full textSyed Iftikhar Ur Hasaan*, Tooba Ali, Shafaq Taj, Fatema Tasnim, Warda Ali Naqvi, Moyosoreoluwa Onobun and Ahmed Al
ASYMPTOMATIC SPONTANEOUS BACTERIAL PERITONITIS IN PATIENTS WITH LIVER CIRRHOSIS
No full textDr. Marzia Ali*, Dr. Tooba Bukhari and Dr. Omer Qasi
Development of a non-living model system for cell membranes and investigation of its mechanical and tribological properties
No full textWhile our exposure to nanomaterials (NMs) has increased with advancements in nanotechnology, understanding harmful effects of such materials on humans is still wanting. Here we have proposed and developed a non-living model system for cell membranes which is suitable for elucidating interactions between NMs and living cells. In contrast to existing model systems for cell membranes, PAAm hydrogel was used as soft support for the lipid. Grafting of lipid with PAAm was achieved through layer by layer deposition of alternating poly(allylamine hydrochloride) (PAH)and poly(sodium 4-styrenesulfonate) (PSS) polyelectrolyte multilayers (PEM). Single step bilayer formation was observed under QCM on the PAAm-PEM support owing to high electrostatic interactions between the PEM and lipid vesicles with frequency and dissipation changes of ~-30 Hz and ~0.8x10-6, respectively. It is also shown that the PEM architecture is robust and reproducible on gels of different elastic modulus. AFM images confirm bilayer formation on top of PAAm-PEM supports with uniform bilayer patches of ~ 0.5 μm. AFM indentation experiments show significant differences in the elastic modulus and adhesion forces for systems with soft underlying supports compared to systems having a hard substrate. The physiological relevance of the developed system is clear from its mechanical characterization via AFM, where the system undergoes considerable deformation before and after bilayer rupture. This behavior is similar to behavior of real cells, in which deformation of cytoskeleton is dominant over that of the cell membrane. The model cell membrane system was also used to study shear forces at the interface of the lipid bilayer on hydrogel, which gave insights into the frictional behavior of the system and its mechanical interactions with nanoprobes.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-12-01The student, Tooba Shoaib, accepted the attached license on 2016-07-22 at 08:53.The student, Tooba Shoaib, submitted this Thesis for approval on 2016-07-22 at 10:40.This Thesis was approved for publication on 2016-07-22 at 15:06.DSpace SAF Submission Ingestion Package generated from Vireo submission #10071 on 2017-02-28 at 14:35:29Made available in DSpace on 2017-03-01T16:36:31Z (GMT). No. of bitstreams: 2
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Previous issue date: 2016-07-22Embargo set by: Seth Robbins for item 98552
Lift date: 2019-03-01T16:37:19Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 98552 on 2019-03-02T10:15:17Z
Softmatter tribology: Understanding the microstructure to property relationships of hydrogel-like materials
No full textBiological tribosystems are excellent examples of nature leveraging soft matter properties to achieve exceptional lubrication for prolonged periods of activity. In these systems, lubrication is provided by sparsely crosslinked, polymeric surface layers imbibed with an aqueous lubricant. A prominent biological tribosystem is the articular cartilage, an avascular tissue consisting of an extracellular matrix made of collagen fibrils and proteoglycans, with a small number of chondrocyte cells. However, in this tissue, there exists a gradient in the orientation of the collagen fibers and water content as a function of the distance from the bone, which emphasizes the importance of the microstructure in cartilage’s functionality, i.e. a load-bearing tissue that maintains low friction and wear. In fact, recent studies have shown that the cartilage’s articulating surface comprises of a network of highly hydrated mucins, polysaccharides, glycoproteins, and phospholipids, which play a key role in maintaining low friction in boundary lubrication. This has been evident in studies performed on multiple other biphasic, non-biological hydrogels as well, where a prominent effect of the interfacial microstructure is observed on their mechanical and tribological properties. Yet, not only there is a lack of knowledge but also wide discrepancy about the fundamental underlying mechanisms relating the dynamic and static frictional dissipation to the microstructure of these materials. Conversely, this fundamental gap in knowledge also limits progress in the design of functional replacements, based on hydrogel-like materials.
Our aim was to not only advance the existing knowledge about the frictional dissipation of hydrogels, by precisely correlating the role of microstructure to the tribological performance, but also, to establish design principles that can help combat some of the existing challenges related to their application as tribological biomaterials. In light of this, the doctoral work presented here has achieved the following specific goals:
I. Studied, modeled and quantified influence of the microstructure, crosslinking degree and stiffness of the polymer on the dynamic and static frictional response
II. Scrutinized the relation between friction force and interfacial rheology of hydrogels
III. Elucidated the pathways of network formation in double network hydrogels which lead to enhanced mechanical and frictional response
IV. Scrutinized mechanical and tribological response of biological hydrogels in physiologically relevant conditions
By combining powerful state-of-the-art experimental techniques such as the Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM) and extended surface forces apparatus (SFA), we have demonstrated that the main mechanisms behind the frictional dissipation of hydrogels arise directly from their biphasic nature – the polymeric network and the imbibing fluid. In the context of dynamic friction, the viscous-adhesive model developed here quantifies the hydrogel’s frictional response by considering an interplay of adhesive and viscous dissipation directly arising from the hydrogel’s microstructure. The model accounts for confinement effects, poroelastic deformation, and the influence of the polymer on the viscous friction force, and helps reconcile seemingly contradictory models proposed previously. The adhesive contribution was modeled as a combination of reversible, transient adhesive bonds between the hydrogel and the countersurface and the poroelastic deformation of the hydrogel during shear, while the role of viscous dissipation was revealed to be directly related to the rheological performance of the hydrogel’s interface. In the latter, the polymer and imbibed fluid, both dictated viscous dissipation. Scrutiny of the rheological behavior of hydrogel thin films in tandem with nanotribology was conducted to show that the effective viscosity measured in rheology agrees with the friction behavior, although it is not sufficient to capture the rich frictional response of hydrogels as a function of sliding velocity. In the context of static friction, the combined effects of microstructure, interfacial shear stresses, interfacial ageing, and temperature were all tied together into a conceptual phase diagram for the static friction of hydrogels. Feasibility of the models developed for the dynamic and static friction was validated by extending the concepts to other hydrogel systems such as physically crosslinked agarose and cartilage, thereby demonstrating the universality of the proposed mechanisms for biphasic soft materials.
The study was further extended to DN hydrogels and biological hydrogels. Systematic investigations of the DN hydrogels comprising of agarose and polyacrylamide hydrogels as independent, interpenetrating networks revealed the design limitations of achieving high strength and high lubricity, simultaneously. Lastly, the novel experimental study on the gel-like surface of the articular cartilage was conducted as a direct application of this research. The graded response of the cartilage’s gel-like articulating surface in elevated calcium concentrations was traced back to changes in the surface and sub-surface microstructure, which was reported to subsequently modulate the mechanical and tribological response of the material.
In summary, through its collective experimental studies and comprehensive models, this doctoral work provides the basic framework to understand lubrication mechanisms of hydrogel-like materials in light of their microstructure. Furthermore, it also helps provide the basic design principles for fabricating hydrogels capable of achieving low friction coefficients and augmented wear resistance through the precise control of their microstructure. Lastly, the novel methodologies and protocols stemming from this dissertation open up previously unexplored research avenues and hence can influence diverse areas of inquiries, not only limited to biolubrication and biomedical applications but soft robotics and microelectromechanical devices.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-08-01The student, Tooba Shoaib, accepted the attached license on 2021-07-14 at 11:30.The student, Tooba Shoaib, submitted this Dissertation for approval on 2021-07-14 at 11:37.This Dissertation was approved for publication on 2021-07-16 at 11:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #16930 on 2022-01-12 at 12:55:05Made available in DSpace on 2022-01-12T22:35:15Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-07-16Embargo set by: Seth Robbins for item 121121
Lift date: 2024-01-12T22:35:30Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Onl
Close Reduction of Supracondylar fracture of humerus in children by Gravity Method
No full textObjective: To evaluate the outcomes of employing a new technique, the gravity method, for the closed reduction of supracondylar humerus fractures (Gartland’s type II and III) in pediatric patients treated at the Trauma Center of Aziz Bhatti Shaheed Hospital Gujrat.
Methodology: This descriptive cross-sectional study was conducted at Aziz Bhatti Shaheed Hospital's Trauma Center from August 2022 to April 2023. Children under 12 years old, presenting within 48 hours of injury with closed supracondylar humerus fractures (Gartland’s Extension type II and III), were included. All patients underwent closed reduction and percutaneous pinning. Data analysis was performed using SPSS, employing means and standard deviations for quantitative variables, and frequency and percentage for qualitative variables.
Results: The mean age was 5.5 years (±1.5). Among 65 patients, there were 45 males and 20 females, with a male-to-female ratio of 1:0.4. The right humerus was affected in 28 patients (43%), while the left humerus was affected in 37 patients (57%). The gravity method successfully reduced 90% of fractures without the need for an assistant surgeon, resulting in a zero percent incidence of iatrogenic neurovascular injury. The average surgical duration was 20 minutes (ranging from 16 to 24 minutes), with an average of 7 images captured using the image intensifier. In cases where the gravity method failed, alternative closed reduction methods were employed for 10% of fractures; no open reduction was necessary.
Conclusion: The gravity method demonstrates safety and efficacy by providing accurate traction for reducing displaced supracondylar fractures without causing damage to the overlying skin or neurovascular structures around the elbow. Its applicability is particularly noteworthy in settings with a shortage of trained medical personnel and limited expertise in managing neurovascular complications
BRAND HUMOUR ADVERTISEMENTS ON A SOCIAL NETWORK PLATFORM AND ITS IMPACT ON ONLINE CONSUMER ENGAGEMENT: THE CASE OF INSTAGRAM
No full textPast studies on humour have predicted that the right kind of humour technique can attract attention and lead to organic engagement from the viewer. However, limited research has been conducted concerning the use of humour by brands on social media networks. Based on Speck's taxonomy of humour, this research aims to clarify whether online brand humour advertisements using comic wit or satirical humour technique have an impact on consumer engagement on a visual social media platform like Instagram. This thesis analyses the influence of comic wit and satire on product involvement, brand familiarity and gender, and their impact on online consumer engagement on the social network platform. A survey was developed and distributed online and a total of 216 participants from Qatar voluntarily filled out the questionnaire. The data was then analysed using SPSS and Structural Equation Modelling. Results provide evidence that both humour techniques have a significant impact on consumer engagement when product involvement is mediating their relationship. Managerial implications of the results and future research prospects were also discussed
Complete Classification of Cylindrically Symmetric Static Spacetimes and the Corresponding Conservation Laws
No full textIn this paper we find the Noether symmetries of the Lagrangian of cylindrically symmetric static spacetimes. Using this approach we recover all cylindrically symmetric static spacetimes appeared in the classification by isometries and homotheties. We give different classes of cylindrically symmetric static spacetimes along with the Noether symmetries of the corresponding Lagrangians and conservation laws
Metadiscourse Markers in English and Persian Scientific Texts
No full textMetadiscourse markers are aspects of a text which exclusively guide readers toward the meanings intended by the author. The present study aimed to investigate the organization of metadiscourse markers across scientific genre in Persian and English. It also attempted to explore the frequency of the two types of metadiscourse markers in English and Persian. The data for this study were supplied through different text types of scientific genre, such as biology, geology, chemistry, physics and mathematics. Out of the existing scientific textbooks in English and Persian, 20 books were randomly selected. The materials were originally written in English or Persian. In order to have ample instances of texts, 2 paragraphs of about 150 words were selected from each book. By analyzing the collected data, it was found that there is a relation between English and Persian in using metadiscourse markers. Both languages used high degree of metadiscourse markers, which contributed to their homogeneity in terms of metadiscourse usage. The findings also revealed that the average frequencies of the two types of metadiscourse are relatively different in Persian and English languages
Frequency of Nonalcoholic Fatty Liver Disease in Type 2 Diabetes Mellitus Patients
No full textNot Availabl
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