A group theory approach towards some rational difference equations

A full Lie point symmetry analysis of rational difference equations is performed. Non-trivial symmetries are derived and exact solutions using these symmetries are obtained.Comment: 19 page

Decentralised PI controller design based on dynamic interaction decoupling in the closed-loop behaviour of a flotation process

An enhanced method for design of decenralised proportional integral (PI) controllers to control various variables of flotation columns is proposed. These columns are multivariable processes characterised by multiple interacting manipulated and controlled variables. The control of more than one variable is not an easy problem to solve as a change in a specific manipulated variable affects more than one controlled variable. Paper proposes an improved method for design of decentralized PI controllers through the introduction of decoupling of the interconnected model of the process. Decoupling the system model has proven to be an effective strategy to reduce the influence of the interactions in the closed-loop control and consistently to keep the system stable. The mathematical derivations and the algorithm of the design procedure are described in detail. The behaviour and performance of the closed-loop systems without and with the application of the decoupling method was investigated and compared through simulations in MATLAB/Simulink. The results show that the decouplers - based closed-loop system has better performance than the closed-loop system without decouplers. The highest improvement (2 to 50 times) is in the steady-state error and 1.2 to 7 times in the settling and rising time. Controllers can easily be implemented

Improved outcomes for hepatic trauma in England and Wales over a decade of trauma and hepatobiliary surgery centralisation

Background: Over the last decade trauma services have undergone a reconfiguration in England and Wales. The objective is to describe the epidemiology, management and outcomes for liver trauma over this period and examine factors predicting survival. Methods: Patients sustaining hepatic trauma were identified using the Trauma Audit and Research Network database. Demographics, management and outcomes were assessed between January 2005 and December 2014 and analysed over five, 2-year study periods. Independent predictor variables for the outcome of liver trauma were analysed using multiple logistic regression. Results: 4368 Patients sustained hepatic trauma (with known outcome) between January 2005 and December 2014. Median age was 34 years (interquartile range 23–49). 81% were due to blunt and 19% to penetrating trauma. Road traffic collisions were the main mechanism of injury (58.2%). 241 patients (5.5%) underwent liver-specific surgery. The overall 30-day mortality rate was 16.4%. Improvements were seen in early consultant input, frequency and timing of computed tomography (CT) scanning, use of tranexamic acid and 30-day mortality over the five time periods. Being treated in a unit with an on-site HPB service increased the odds of survival (odds ratio 3.5, 95% confidence intervals 2.7–4.5). Conclusions: Our study has shown that being treated in a unit with an on-site HPB service increased the odds of survival. Further evaluation of the benefits of trauma and HPB surgery centralisation is warranted

The Effects of Angiotensin Converting Enzyme Inhibitors (ACE-I) on Human N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) Levels: A Systematic Review and Meta-Analysis

BACKGROUND: Tuberculous pericardial effusion is a pro-fibrotic condition that is complicated by constrictive pericarditis in 4% to 8% of cases. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a ubiquitous tetrapeptide with anti-fibrotic properties that is low in tuberculous pericardial effusion, thus providing a potential mechanism for the heightened fibrotic state. Angiotensin-converting enzyme inhibitors (ACE-I), which increase Ac-SDKP levels with anti-fibrotic effects in animal models, are candidate drugs for preventing constrictive pericarditis if they can be shown to have similar effects on Ac-SDKP and fibrosis in human tissues. Objective To systematically review the effects of ACE-Is on Ac-SDKP levels in human tissues. METHODS: We searched five electronic databases (1996 to 2014) and conference abstracts with no language restrictions. Two reviewers independently selected studies, extracted data and assessed methodological quality. The protocol was registered in PROSPERO. RESULTS: Four studies with a total of 206 participants met the inclusion criteria. Three studies (106 participants) assessed the change in plasma levels of Ac-SDKP following ACE-I administration in healthy humans. The administration of an ACE-I was associated with an increase in Ac-SDKP levels (mean difference (MD) 5.07 pmol/ml (95% confidence intervals (CI) 0.64 pmol/ml to 9.51 pmol/ml)). Two studies with 100 participants further assessed the change in Ac-SDKP level in humans with renal failure using ACE-I. The administration of an ACE-I was associated with a significant increase in Ac-SDKP levels (MD 8.94 pmol/ml; 95% CI 2.55 to 15.33; I 2 = 44%). CONCLUSION: ACE-I increased Ac-SDKP levels in human plasma. These findings provide the rationale for testing the impact of ACE-I on Ac-SDKP levels and fibrosis in tuberculous pericarditis

Web Information Seeking Behaviour of Undergraduate Students of Library and Information Studies at the University of Zululand

Web Information Seeking Behaviour of Undergraduate Students of Library and Information Studies at the University of ZululandBackground: In the 21st century, higher institutions of learning have completely transformed their teaching and learning by adopting the web and it related technologies due to the change of scenery in terms of information searching. Notably the new generation of students is highly dependent on the internet for their academic and personal activities. However, the internet contains a vast array of information, some of this information is not suitable for scholarly use. Thus it is crucial for new undergraduates to have necessary competences that will allow them to efficiently search and retrieve information online. Therefore, this transformation encouraged the examination of Web Information Seeking Behaviour of Undergraduate Students of Library and Information Studies at the University of Zululand. This research project aimed to enlighten curriculum designers about the importance of including more IT related modules on the first year students’ curriculum, furthermore it aimed at assisting academic libraries to realise challenges facing undergrads regarding using their services on the web. Methodology: The study employed a quantitative research approach using closeended questionnaire as a data collection tools. Results/findings: The study found that the web is the major source of information amongst library and information studies undergraduates’ students. The study also found that the web is used by students for academic purposes like: assignment completion, research and study purposes. Further findings indicate that the Google search engine was found to be the most used tool for information searching

Development of an IEC 61850 Standard-Based Busbar Protection Scheme

Communication systems of intelligent electronic devices play a huge role in the performance of busbar protection schemes. They determine the effectiveness of the protection scheme in terms of detecting and isolating busbar faults. A literature survey has revealed that multiple proposed algorithms of busbar protection schemes have encountered a common problem of achieving interoperability between intelligent electronic devices produced by different vendors. This affects the performance of busbar protection schemes. This paper focuses on achieving interoperability between IEC 61850 standard-based multi-vendor intelligent electronic devices “SEL and ABB”. This improves the performance of busbar protection schemes between multi-vendor devices, and at the same time increases the operational reliability. The investigation is conducted using a current differential busbar protection algorithm. The study is performed by implementing hardware-in-the-loop (HIL) testing using a real-time digital simulator (RTDS). A laboratory-scale test bench is developed to achieve interoperability between the IEDs SEL-487B and REF615. A fault condition is simulated, and the behaviour of the protection scheme is analysed. The hardware-in-the-loop results demonstrate the benefit of the proposed technique

Stability Evaluation of Non-ideal Grid-tied Photovoltaic on IEEE-9 Bus System

The integration of photovoltaic in power systems has proved its capability of being a viable source of power to be considered in grid-tied power systems. However, in some cases various electrical challenges may arise when high photovoltaic power is integrated into power systems at the time the voltage collapse caused by an increase in the load consumption. In case of non-ideal grid-tied photovoltaic due to inappropriate or absence of control strategies to regulate the power dispatch between the microgrid and the grid, the photovoltaic power may negatively further affect the grid voltage stability instead of restoring it to the stability level of the electrical grid. This paper investigates the challenge of solar power integration in the grid by demonstrating that due to its randomness and intermittent nature, the photovoltaic power is likely to be associated with voltage disturbance and low power quality that occurs on the electrical grid. Data from simulation of a non-ideal grid-tied photovoltaic are collected to demonstrate the characteristics and negative effects of high photovoltaic integration on the IEEE-9 bus system

Power Flow Analysis and Steady State Contingency of IEEE 9-bus System Using DigSilent

Power flow analysis and contingency states of a power system are fundamental tests of finding the real performance of an electrical network during power system planning and operation. Maintaining the system’s security is a challenging issue facing power system engineers. The system will be secure if it can run within system restrictions, such as limits of bus voltage magnitudes, current and power flow through the lines. in the case of a component failure, such as a generator or transmission line, contingency analysis is useful for increasing the power system’s resilience by examining the system’s vulnerability in case of components failure. Using an IEEE 9-bus system as benchmark, the analysis of power flow through contingency analysis is performed to identify the most critical component affected by voltage violation and critical loading condition. Using the one-by-one and two-by-two outages of generators and lines using DIgSILENT Power Factory software.  The results of the contingency analysis demonstrate how voltage on busbars can be critically affected when the power system is subject to some sort of unconditional phenomena during the operation of the electrical network

The occurrence of sequential oviposition in fig wasps and the implications for interpreting sex ratio data

DATA AVAILABILITY STATEMENT : All the counts on which this work is based and the calculations are available on figshare at 10.25403/UPresearchdata.24175050.Pollinating fig wasps are believed to adjust their sex ratios according to standard local mate competition (LMC) theory. Standard LMC theory assumes that all mothers ovipositing in a patch or fig does so simultaneously. However, it has been shown that fig wasps can oviposit sequentially. We counted the number of figs containing dead and living mothers in figs where mothers entered naturally to estimate the incidence of sequential and simultaneous oviposition. Single mothers were the norm in two wasp species, and multiple mothers the norm in the other two. However, contrary to LMC theory, in all four species, when multiple mothers occurred, sequential oviposition seems to occur more frequently than simultaneous oviposition. The sex allocation problem fig wasp mothers face is thus more complicated than the widely assumed simultaneous ovipositing situation, and it leads to several expectations. Single mother's sex ratios should increase as the probability of additional mothers increases. Naturally founded multi-mother figs should have more female-biased sex ratios than the standard LMC model predicts for the final number of mothers. This is because early-arriving mothers underestimate the number of mothers and lay more daughters than the final number of mothers would require and later-arriving mothers can lay fewer sons to be competitive against the first mothers' too female-biased clutches. Mothers must produce sex ratios that are optimised across a probabilistic range of foundress densities they experience.South African National Research Foundation.http://wileyonlinelibrary.com/journal/eenhj2024Biochemistry, Genetics and Microbiology (BGM)SDG-15:Life on lan

Patterns of disease on admission to children’s wards and changes during a COVID-19 outbreak in KwaZulu-Natal Province, South Africa

Background. Major causes of under-5 child deaths in South Africa (SA) are well recognised, and child mortality rates are falling. The focus of child health is therefore shifting from survival to disease prevention and thriving, but local data on the non-fatal disease burden are limited. Furthermore, COVID-19 has affected children’s health and wellbeing, both directly and indirectly.Objectives. To describe the pattern of disease on admission of children at different levels of care, and assess whether this has been affected by COVID-19.Methods. Retrospective reviews of children’s admission and discharge registers were conducted for all general hospitals in iLembe and uMgungundlovu districts in KwaZulu-Natal Province, SA, from January 2018 to September 2020. The Global Burden of Disease framework was adapted to create a data capture sheet with four broad diagnostic categories and 37 specific cause categories. Monthly admission numbers were recorded per cause category, and basic descriptive analysis was completed in Microsoft Excel.Results. Overall, 36 288 admissions were recorded across 18 hospital wards, 32.0% at district, 49.8% at regional and 18.2% at tertiary level. Communicable diseases, perinatal conditions and nutritional deficiencies (CPNs) accounted for 37.4% of admissions, non-communicable diseases (NCDs) for 43.5% and injuries for 17.1%. The distribution of broad diagnostic categories varied across levels of care, with CPNs being more common at district level and NCDs more common at regional and tertiary levels. Unintentional injuries represented the most common cause category (16.6%), ahead of lower respiratory tract infections (16.1%), neurological conditions (13.6%) and diarrhoeal disease (8.4%). The start of the local COVID-19 outbreak coincided with a 43.1% decline in the mean number of monthly admissions. Admissions due to neonatal conditions and intentional injuries remained constant during the COVID-19 outbreak, while those due to other disease groups (particularly respiratory infections) declined.Conclusions. Our study confirms previous concerns around a high burden of childhood injuries in our context. Continued efforts are needed to prevent and treat traditional neonatal and childhood illnesses. Concurrently, the management of NCDs should be prioritised, and evidence-based strategies are sorely needed to address the high injury burden in SA