Mathematical models for heat and mass transfer in nanofluid flows.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.The behaviour and evolution of most physical phenomena is often best described using mathematical models in the form of systems of ordinary and partial differential equations. A typical example of such phenomena is the flow of a viscous impressible fluid which is described by the Navier-Stokes equations, first derived in the nineteenth century using physical approximations and the principles of mass and momentum conservation. The flow of fluids, and the growth of flow instabilities has been the subject of many investigations because fluids have wide uses in engineering and science, including as carriers of heat, solutes and aggregates. Conventional heat transfer fluids used in engineering applications include air, water and oil. However, each of these fluids has an inherently low thermal conductivity that severely limit heat exchange efficiency. Suspension of nanosized solid particles in traditional heat transfer fluids significantly increases the thermophysical properties of such fluids leading to better heat transfer performance. In this study we present theoretical models to investigate the flow of unsteady nanofluids, heat and mass transport in porous media. Different flow configurations are assumed including an inclined cylinder, a moving surface, a stretching cone and the flow of a polymer nanocomposite modeled as an Oldroyd-B fluid. The nanoparticles assumed include copper, silver and titanium dioxide with water as the base fluid. Most recent boundary-layer nanofluid flow studies assume that the nanoparticle volume fraction can be actively controlled at a bounding solid surface, similar to temperature controls. However, in practice, such controls present significant challenges, and may, in practice, not be possible. In this study the nanoparticle flux at the boundary surface is assumed to be zero. Unsteadiness in fluid flows leads to complex system of partial differential equations. These transport equations are often highly nonlinear and cannot be solved to find exact solutions that describe the evolution of the physical phenomena modeled. A large number of numerical or semi-numerical techniques exist in the literature for finding solutions of nonlinear systems of equations. Some of these methods may, however be subject to certain limitations including slow convergence rates and a small radius of convergence. In recent years, innovative linearization techniques used together with spectral methods have been suggested as suitable tools for solving systems of ordinary and partial differential equations. The techniques which include the spectral local linearization method, spectral relaxation method and the spectral quasiliearization method are used in this study to solve the transport equations, and to determine how the flow characteristics are impacted by changes in certain important physical and fluid parameters. The findings show that these methods give accurate solutions and that the speed of convergence of solutions is comparable with methods such as the Keller-box, Galerkin, and other finite difference or finite element methods. The study gives new insights, and result on the influence of certain events, such as internal heat generation, velocity slip, nanoparticle thermophoresis and random motion on the flow structure, heat and mass transfer rates and the fluid properties in the case of a nanofluid

Dietary habits, energy drink consumption, obesity, and physical activity in marginalised Palestinian schools in the West Bank: a cross-sectional study

Background Socioeconomic factors have been found to be related to adolescents’ dietary habits, physical activity, and body mass index (BMI). 50 schools in the West Bank that face socioeconomic and political challenges in terms of infrastructure, academic achievement, dropout rate, limited access, geography, and economic status were labelled as marginalised by the AMIDEAST School Support Program (SPP). This study aimed to describe and assess factors relating to dietary habits, energy drink consumption, BMI index, and physical activity in Palestinian adolescents attending marginalised schools. Methods Marginalised schools (n=50) were stratified by district and gender to select a random sample of 20 schools. All students in sixth or ninth grades in the targeted schools were interviewed one-to-one by one of 14 senior dental students who were trained and calibrated by a public health specialist. The schoolchildren were asked about their dietary habits, such as daily consumption of added sugar, carbonated drinks, sweetened juices, and energy drinks. Daily intake of milk, fruits, vegetables, nuts, and non-vegetarian food were also assessed. In addition, schoolchildren’s physical activity, father’s employment and mother’s education were recorded. Weight and height were measured, and BMI percentile was calculated. Parental informed consents were collected by the school administration. Ethics approval for the study was obtained from Al-Quds University Scientific Research Ethics Committee. Findings A total of 1282 students out of 1308 completed the questionnaire; a response rate of 98%. Of our sample, 6% (77 of 1282) were underweight (5th percentile or under) and 34% (436 of 1282) were overweight or obese (85th percentile or over). Among sixth graders, 43% (155 of 360) of the boys and 24% (59 of 247) of the girls were overweight or obese. The opposite was true for ninth graders; 20% (54 of 268) of the boys and 42% (158 of 377) of the girls were overweight or obese. Ninth graders had more added sugar in their diet than sixth graders (p=0·002), less milk consumption (p<0·0001), more energy drink consumption (p=0·001), and less physical activity (p<0·0001). Consumption of carbonated and sweetened drinks was associated with being overweight or obese (p=0·016, p=0·001). Consumption of carbonated drinks was higher among children of mothers with a high-school education than among children of mothers with college degrees (p<0·0001). In addition, children of mothers educated to high school level or below were associated with being underweight (p=0·05) Interpretation The results of this study suggest that dietary habits worsen between the ages of 12 years and 15 years. The mother’s level of education is an important factor in being overweight or underweight. Interventions to increase awareness of the importance of healthy diets and physical activity among adolescents and their mothers should start before the age of 12 years.Funding AMIDEAST School Support Program (SSP). Contributors SA contributed to the study design, literature review, data collection, and drafting of the Abstract. EK contributed to the study design, data collection, data analysis, and interpretation of data. AH contributed to data collection and data entry. FM contributed to the study design and data collection. All authors have seen and approved the final version of the Abstract for publication. Declaration of interests We declare no competing interests. Acknowledgments We thank the dental students of Al-Quds University who helped with the clinical screening of schoolchildren and data collection

A brief note from Pakistan: reflections from a British psychiatrist

A British general adult psychiatrist born and trained in the UK, who also considers himself Pakistani, had the opportunity to spend 2 weeks running a psychiatric clinic in a remote hospital in the Punjab province of Pakistan. In this article he offers some reflections on the unexpected culture shock he felt, on the hospital system, the patients he treated and their resilience in such a poor country

Strategi Pemulihan Usaha Kecil Dan Menengah Pasca Pandemi Covid-19 Pada Nasabah PT Bank Syariah Indonesia, Tbk. Regional Jakarta 1

Pandemi COVID-19 menyebabkan ketidakstabilan ekonomi, yang mempengaruhi usaha kecil dan menengah (UKM). Tujuan penelitian ini adalah (1) analisis kondisi nasabah UKM PT Bank Syariah Indonesia, Tbk (BSI) saat dan setelah pandemi Covid-19; (2) menentukan strategi pemulihan UKM setelah pandemi Covid-19 bagi nasabah BSI; dan (3) merumuskan strategi pemulihan UKM setelah pandemi Covid-19 bagi nasabah BSI. Penelitian dilakukan pada nasabah BSI Regional Jakarta 1 dan dilakukan Juli hingga Desember 2023. Metode analisis yang digunakan adalah analisis deskriptif, Analisis Dampak Bisnis (BIA), analisis SWOT, dan analisis AHP. Hasil menunjukkan pergerakan risiko dari tahun 2020 hingga 2023, dengan sektor pertanian berisiko rendah dan sektor transportasi berisiko tinggi. Alternatif strategi dari hasil SWOT yaitu (1) peningkatan layanan pembiayaan digital; (2) pelatihan bisnis berbasis teknologi dan program pendampingan; (3) peningkatan literasi keuangan melalui pendidikan berbasis teknologi; dan (4) Program Relaksasi Pembiayaan yang inklusif. Hasil analisis AHP adalah alternatif strategi relaksasi pembiayaan sebagai strategi utama untuk pemulihan UKM pasca-COVID-19 dengan bobot skor sebesar 0,565.The COVID-19 pandemic caused economic instability, affecting small and medium-sized businesses (SMEs). The aims of the study were (1) to analyze the real conditions of SMEs customers of PT Bank Syariah Indonesia, Tbk (BSI) during and after the Covid-19 pandemic; (2) to determine the SMEs recovery strategy after the Covid-19 pandemic for customers of BSI; and (3) to formulate the SMEs recovery strategy after the Covid-19 pandemic for customers of BSI. The study was conducted on customers of BSI Regional Jakarta 1. The research period from July to December 2023. The analysis methods used descriptive analysis, Business Impact Analysis, SWOT analysis, and Analytical Hierarchy Process (AHP). Results showed shifts in risk among SMEs from 2020 to 2023, with agriculture being low-risk and transportation high-risk. SWOT analysis provided alternative strategies namely (1) enhancing digital financing financing services; (2) offering technology-based business training and mentoring programs; (3) enhancing financial literacy through tech-based education; and (4) providing inclusive Financing Relaxation Programs. The AHP analysis emphasized the importance of targeted financing relaxation, assigning it a high weight score of 0,565 as the primary strategy for SMEs recovery post-COVID-19

Analysis, characterization and some properties of polyacrylamide-Ni(II) complexes

The complexation of polyarylamide (PAam) with Ni(II) metal ions at different concentrations was investigated. The metal complexes were characterized by fourier transform infrared spectroscopy (FTIR), UV-visible, differential scanning calorimeter (DSC) and atomic force microscope (AFM). FTIR spectroscopy was used to study the characteristic shifts of the absorbance bands of C=O and N-H2. UV-visible spectroscopy was used to follow the complex formation of PAam-Ni(II) and showed the appearance of a new band that was absent both in PAam and Ni(II) salt solutions. Thermal parameters, such as the glass transition temperature (Tg) and the melting point (Tm) of the polymer-metal complex have been measured by DSC. The variation of Tg and Tm with different Ni(II) concentrations was attributed to the complexation of the native polymer during the increasing of Ni(II) concentration. AFM was used to study the surface morphology of PAam films and its complexation with Ni(II) at different concentrations. The root mean square roughness increased as the Ni(II) concentration increases

Psychotic-like experiences with cannabis use predict cannabis cessation and desire to quit- A cannabis discontinuation hypothesis

Background Evidence suggests that cannabis-induced psychotic-like experiences may be a marker of psychosis proneness. The effect of such experiences on cannabis use has not systematically been examined.Methods We undertook a mixed-methods online survey of 1231 cannabis users (including 926 continued users) using the Cannabis Experiences Questionnaire. We examined the effect of psychotic-like and pleasurable experiences on cessation of cannabis and intention to quit. Socio-demographic variables, cannabis use parameters and substance misuse history were included as covariates. Free-text data explored subjective reasons for changes in use.Results Cessation of cannabis use was associated with greater psychotic-like experiences [p < 0.001, Exp(B) 1.262, 95% confidence interval (CI) 1.179-1.351], whilst continued cannabis users were more likely to report pleasurable experiences [p < 0.001, Exp(B) 0.717, 95% CI 0.662-0.776]. Intention to quit cannabis in continued users was associated with greater psychotic-like experiences [p < 0.003, Exp(B) 1.131, 95% CI 1.044-1.225], whilst intention to not quit was significantly associated with increased pleasurable experiences [p < 0.015, Exp(B) 0.892, 95% CI 0.814-0.978]. Whereas former users clearly ascribed cessation to negative experiences, continued users who expressed intention to quit less readily ascribed the intention to negative experiences.Conclusions Elucidation of psychotic-like experiences may form the basis of a therapeutic intervention for those who wish to quit. Cessation in those with cannabis-induced psychotomimetic experiences may offset the risk for the development of a psychotic disorder, in this higher risk group

Study on the morphology of polyacrylamide – silica fumed nanocomposite thin films

Silica fumed nanoparticles were dispersed in polyacrylamide thin films by direct mixing. Atomic Force Microscopy study was carried out in order to analyze the surface roughness. Height distribution of surface roughness changes from Gaussian like for polyacrylamide to skew asymmetric when increasing the silica concentration. The length of the distribution tail increases, indicating the formation of multi-scale features that increase in number and size, as the silica increase.The authors acknowledge the financial support of the German research foundation (DFG), French academy of sciences and French Ministry of Foreign Affairs, Prof. Philippe Meyer and the Meyer Foundation

Are researchers getting the terms used to denote different types of recreational cannabis right?-a user perspective

BACKGROUND: While current cannabis research has advanced our understanding into the effects of its individual components, there is a pressing need to identify simple terminology that is understood in the same way by researchers and users of cannabis. Current categorisation in research focuses on the two main cannabinoids: delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD); and two different species of cannabis: indica and sativa. Recreational cannabis has also been categorised by researchers as 'skunk' or 'hash'. Focusing on individuals who use cannabis frequently, this study aimed to identify views on current terms used to denote different types of cannabis and to identify terms validated by participants. These views were extracted from responses of the Cannabis Experiences Questionnaire (CEQ), a widely used instrument in the literature. METHODS: We qualitatively analysed 236 free-text responses from Question 23 of the CEQ survey (using Iterative Categorisation) relating to categorization and consumption methods. Data was used from a previous study (Sami et al., Psychol Med 49:103-12, 2019), which recruited a convenience sample of 1231 participants aged 18 years and above who had previously used cannabis. RESULTS: Regarding type of cannabis used, specific strain names (n = 130), concentrates (n = 37), indica/sativa (n = 22) and THC/CBD terms (n = 22) were mentioned. Other terms used were hybrids (n = 10), origins of specific strains (n = 17), edibles (n = 8), and herbal cannabis (n = 7). Regarding problems with specific terms, participants were skeptical about terms such as skunk and super skunk (n = 78) preferring terms like THC/CBD, indica/sativa, specific marketed strains and references to preparation methods. CONCLUSIONS: The results suggest a disparity between the common terms used by researchers in academia and those used by cannabis consumers. While there are advantages and limitations of using these terms to bridge views of researchers and individuals who use cannabis, this study underscores the importance of formally assessing chemical constituents rather than relying on self-report data and of incorporating cannabis user views on current terms used in research, potentially also incorporating descriptors of preparation and consumption methods

Cannabis Use Linked to Altered Functional Connectivity of the Visual Attentional Connectivity in Patients With Psychosis and Controls

Background: Both chronic cannabis use and psychotic disorders are associated with abnormalities in visual atten-tional processing. Using functional magnetic resonance imaging (fMRI), we sought to determine whether there would be a difference in functional connectivity in patients and controls with and without a history of cannabis use in the visual and dorsal attention networks. Methods: Resting-state fMRI data were acquired in patients with early psy-chosis with (EPC = 29) and without (EPNC = 25); and controls with (HCC = 16) and without (HCNC = 22) cannabis use. Results: There was a patient effect in both Visual-Dorsal Attention Internetwork (F(1,87) = 5.326, P = .023) and the Visual Network (F(1,87) = 4.044, P = .047) and a cannabis effect in the Dorsal Attention Network (F(1,87) = 4.773, P = .032). These effects were specific to the networks examined with no evidence for significant patient or cannabis effects in other canonical networks. Patients with a history of cannabis use showed increased connec-tivity in the Dorsal Attention Network (134%, P = .019) and Visual Dorsal Attention Internetwork (285%, P = .036) compared to non-using controls. In the EPC group con-nectivity of the Visual Network (ρ = 0.379, P = .042) and Visual-Dorsal Attention Internetwork (ρ = 0.421, P = .023) correlated with visual hallucinations which were significantly different from EPNC (P = .011). Dorsal attention network strength correlated with severity of dependence for cannabis (ρ = 0.215, P = .04). Conclusion: We demonstrate specific cannabis and patient effects in networks associated with visual attentional processing. There is a differential association with hallucinatory symptoms in patients with and without a history of cannabis use. This may indicate that dysconnectivity in these networks serves different roles in the context of cannabis use

Spectroscopic investigations of pentobarbital interaction with human serum albumin

The interaction between pentobarbital and human serum albumin has been investigated. The basic binding interaction was studied by UV-absorption and fluorescence spectroscopy. From spectral analysis pentobarbital showed a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constant (k) is estimated at 1.812 104 M 1 at 293 K. FT-IR spectroscopy with Fourier self-deconvolution technique was used to determine the protein secondary structure and drug binding mechanisms. The observed spectral changes of HSA–pentobarbital complex indicate a larger intensity decrease in the absorption band of a-helix relative to that of b-sheets. This variation in intensity is related indirectly to the formation of H-bonding in the complex molecules, which accounts for the different intrinsic propensities of a-helix and b-sheets.This work is supported by the German Research Foundation DFG Grant No. DR228/24-2