Estimation of adjusted relative risks in log-binomial regression

**Problem statement:** For binary outcome data, the relative risk (RR) is an essential measure of association, which can be estimated directly for prospective studies. Calculating the odds ratio (OR) can overestimate and magnify the risk heavily, especially if dealing with a disease outcome of high incidence. In such cases OR should be avoided and RR can be used. The log-binomial model is a straightforward statistical approach in the case of risk adjustment and estimation, also it is much easier to interpret. However, the log-binomial model might fail or have difficulties maximizing log-likelihood function due to numerical instability, implicit parameter constraints, or naïve starting value, which leads to a dramatic increase of the required number of iterations therefore convergence failure. **Approach:** In this study, a modified Newton-type algorithm was developed for solving the maximum likelihood estimation problem under linear constraints. Moreover, a new system of linear inequality constraints on the number of covariates was imposed. In this approach, the log-likelihood function of the log-binomial regression model is maximized sequentially. The modified-newton-type algorithm proceeds iteratively by generating a sequence of estimates which solves the quadratic sub-problems obtained from a second-order Taylor approximation and converges under the linear inequality constraints. **Monte Carlo Simulation design:** For validation and evaluation purposes, a large full-factorial simulation study was conducted in order to study the behavior of the method "squadP" compared with other methods investigated in this research such as Fisher scoring, EM-type, BFGS, and Nelder-Mead. Assessment of coverage probability, model accuracy, and model bias were the primary objectives, while at the same time allowing for many different scenarios (varying number of events, sample size, and number of covariates). The 12 underlying covariates were generated via copula package in R with a specified correlation structure between all variables. In total, 104800 data sets were generated and analyzed for 108 scenarios. The complete simulation study including pseudo-random number generator using L'Ecuyer algorithm was conducted using parallel processing in R 3.5. Additionally, the running time of the six methods was computed. **Results:** The proposed modified Newton-type algorithm SquadP generally showed a significantly higher convergence rate than EM-type, Fisher-scoring, BFGS, and Nelder-Mead particularly in scenarios with small samples and small event probabilities. SquadP and Poisson(log) showed a similar convergence rate in most scenarios with significant excel of SquadP error measurements. EM-type and SquadP showed similar bias, coverage probabilities, and error measurements in most cases with an insignificant difference however EM-type had in most scenarios the smallest convergence rate. Furthermore, SquadP converged always faster than EM-type algorithm with a highly significant difference.**Problemstellung:** Für binäre Ergebnisdaten ist das relative Risiko (RR) ein wesentliches Assoziationsmaß, das für prospektive Studien direkt geschätzt werden kann. Die Berechnung des Odds Ratio (OR) kann das Risiko stark überschätzen und vergrößern, insbesondere wenn es sich um ein Krankheitsergebnis mit hoher Inzidenz handelt. In solchen Fällen sollte OR vermieden werden und RR kann verwendet werden. Das Log-Binomial-Modell ist ein einfacher statistischer Ansatz für die Risikoanpassung und -schätzung und auch viel einfacher zu interpretieren. Das Log-Binomial-Modell kann jedoch Schwierigkeiten haben und die Log-Likelihood-Funktion aufgrund numerischer Instabilität, impliziter Parameterbeschränkungen oder naiven Startwerts nicht maximieren, was zu einer dramatischen Zunahme der Anzahl der erforderlichen Iterationen führt, weshalb die Konvergenz fehlschlägt. **Ansatz:** In dieser Studie wurde ein modifizierter Newton-Algorithmus entwickelt, um das Problem der Schätzung der maximalen Wahrscheinlichkeit unter linearen Bedingungen zu lösen. Wir haben auch ein neues System linearer Ungleichheitsbeschränkungen für die Anzahl der Kovariaten eingeführt. Bei diesem Ansatz maximieren wir die Log-Wahrscheinlichkeit des log-binomialen Regressionsmodells nacheinander. Der Algorithmus vom modifizierten Newton-Typ geht iterativ vor, indem eine Folge von Schätzungen erzeugt wird, die die quadratischen Unterprobleme löst, die aus einer Taylor-Näherung zweiter Ordnung erhalten werden, und unter den linearen Ungleichungsbeschränkungen konvergiert. **Monte-Carlo-Simulationsdesign:** Zu Validierungs- und Bewertungszwecken wurde eine große vollfaktorielle Simulationsstudie durchgeführt, um das Verhalten der Methode (squadP) im Vergleich zu anderen in dieser Studie untersuchten Methoden wie Fisher Scoring, EM-type, BFGS und Nelder-Mead. Die Bewertung der Abdeckungswahrscheinlichkeit, der Modellgenauigkeit und der Modellverzerrung waren die Hauptziele, wobei gleichzeitig viele verschiedene Szenarien berücksichtigt wurden (unterschiedliche Anzahl von Ereignissen, Stichprobengröße und Anzahl von Kovariaten). Die 12 zugrunde liegenden Kovariaten wurden über ein Copula-Paket in R mit einer festgelegten Korrelationsstruktur zwischen allen Variablen generiert. Insgesamt wurden 104800 Datensätze generiert und für 108 Szenarien analysiert. Die vollständige Simulationsstudie einschließlich Zufallszahlengenerator unter Verwendung des L'Ecuyer-Algorithmus wurde unter Verwendung der Parallelverarbeitung in R 3.5 durchgeführt. Zusätzlich wurde die Laufzeit der sechs Methoden berechnet. **Ergebnisse:** Das vorgeschlagene modifizierte Newton-Algorithmus SquadP zeigte im Allgemeinen eine signifikant höhere Konvergenzrate als EM-Typ, Fisher-Scoring, BFGS und Nelder-Mead, insbesondere in Szenarien mit kleinen Stichproben und kleinen Ereigniswahrscheinlichkeiten. SquadP und Poisson(log) zeigten in den meis- ten Szenarien eine ähnliche Konvergenzrate mit einer signifikanten Überlegenheit der SquadP-Fehlermessungen. EM-Typ und SquadP zeigten in den meisten Fällen ähnliche Verzerrungen, Abdeckungswahrscheinlichkeiten und Fehlermessungen mit unbedeutendem Unterschied, jedoch hatte EM-Typ in den meisten Szenarien die geringste Konvergenzrate. Darüber hinaus konvergierte SquadP immer schneller als ein EM-Algorithmus mit einem sehr signifikanten Unterschied

Phenotypic and Genotypic Characterization of Nosocomial Isolates of Staphylococcus aureus with Reference to Methicillin Resistance

Purpose: To investigate the occurrence, species prevalence, antibacterial resistance, and molecular characteristics of S. aureus isolates from different wards located in a university hospital.Methods: A total of one hundred and fifty S. aureus isolates were  recovered from various clinical specimens. The isolates were tested phenotypically by conventional methods and genotypically by polymease chain reaction (PCR) for direct detection of femB and mecA genes.Results: Thirty one isolates (20.7 %) of these were identified as  methicillin-resistant Staphylococcus aureus (MRSA) by oxacillin agar screen test and 124 (82.7 %) of the isolates were β-lactamase producers. The prevalence of MRSA strains among S. aureus isolates was 20.7 %. The overall resistance of MRSA to a variety of antibiotics tested was linezolid, 48.7 %; ciprofloxacin, 15.3 %; sulfamethoxazole/trimethoprim (TMS), 14.0 %; gentamicin, 12.7 %; and rifampicin, 6.7 %. All MRSA isolates were positive for femB and mecA genes; one MSSA carried mecA gene.Conclusion: Since S. aureus isolates are commonly associated with wound infections, skin and soft tissue infections and blood stream infections, glycopeptides, mupirocin, and quinupristin/dalfopristin (Q/D) would be the most effective antibiotics for the treatment of MRSA infections.Keywords: Staphylococcus aureus, mecA, femB, Antibiotics, Staphylococcal infections, Methicillin resistanc

Is the Arab audience willing to pay for online news? Predictors of their paying intent

Recently several newspapers considered paid content strategies to substitute advertising and government subsidy. This study examines to what extent Arab audiences are willing to support these strategies, and what factors influence their willingness to pay (WTP) for online news, using a survey of 530 adults. The study found most of the public is not willing to pay for online newspapers, but are willing to pay for entertainment services. Most of them are not subscribing to printed or online newspapers. They do not have a real intent to help the newspapers in their digital transformation. Most of the public did not experience the paywall yet. Age and income influence the likelihood of paying for online news and to a lesser extent, gender and education. Age and income were predictors for WTP for entertainment services. Age and education were predictors for using online sources

"Threads of the Orientalist/Procolonial discourse in John Updike's novel The Coup"

This paper is an attempt to point out how John Updike’s novel The Coup (1978) conforms to the traditional Western notions and conventions about Africa and Africans. The methodology of this paper involves a textual analysis of The Coup whereby significant passages from the novel are cited and elucidated with regard to the ideas of Orientalism as a discourse to reveal how Updike employs such a discourse to render a distorted image of Africa and African cultures as he draws heavily on stereotypes and traditional prejudices as embodiment of the darker side of the human psyche. At the same time, this paper is meant to point out the seemingly authoritative stance of Updike through the sources he consults and the techniques he utilizes to endow his negative discourse with a tone of authority, knowledge, and expertise. This seemingly authentic stance provides Updike with the means to adopt a superior, Western voice of power in the creation of truth with regard to Africa as a nation and to the East/West relationship as a dichotomy. As the novel relates, Updike not only justifies the American intervention in Africa, but he does injustice to the humanity of the African personality which he diminished through racist stereotyping. It is, therefore, through utilizing this Orientalist/postcolonial approach and relevant data that this paper concludes that Updike displays absolutely no insight into the characters involved in this novel. Instead, he weaves African colonialism, Islam, the Cold War, socialism, capitalism, and exploitation of every variety into a novel with a few too many characters that are explored just enough to make them into two-dimensional cartoons of real human beings. As such, Updike's The Coup is no more than an attempt to assert the authority of the West, specifically the United States, as a superpower that surpasses the Soviet Union in its control over Africa and African resources

Keratin: dissolution, extraction and biomedical application

Keratinous materials such as wool, feathers and hooves are tough unique biological co-products that usually have high sulfur and protein contents. A high cystine content (7–13%) differentiates keratins from other structural proteins, such as collagen and elastin. Dissolution and extraction of keratin is a difficult process compared to other natural polymers, such as chitosan, starch, collagen, and a large-scale use of keratin depends on employing a relatively fast, cost-effective and time efficient extraction method. Keratin has some inherent ability to facilitate cell adhesion, proliferation, and regeneration of the tissue, therefore keratin biomaterials can provide a biocompatible matrix for regrowth and regeneration of the defective tissue. Additionally, due to its amino acid constituents, keratin can be tailored and finely tuned to meet the exact requirement of degradation, drug release or incorporation of different hydrophobic or hydrophilic tails. This review discusses the various methods available for the dissolution and extraction of keratin with emphasis on their advantages and limitations. The impacts of various methods and chemicals used on the structure and the properties of keratin are discussed with the aim of highlighting options available toward commercial keratin production. This review also reports the properties of various keratinbased biomaterials and critically examines how these materials are influenced by the keratin extraction procedure, discussing the features that make them effective as biomedical applications, as well as some of the mechanisms of action and physiological roles of keratin. Particular attention is given to the practical application of keratin biomaterials, namely addressing the advantages and limitations on the use of keratin films, 3D composite scaffolds and keratin hydrogels for tissue engineering, wound healing, hemostatic and controlled drug release.info:eu-repo/semantics/publishedVersio

Innovative foods : the future food supply, nutrition and health

In the coming decades, feeding the growing world population is going to become a global food-supply challenge for our existing food systems. At present, the global food-supply chain has been severely affected due to disruptions caused by the COVID-19 pandemic, climate change, and political conflicts. These disruptions have led to substantial increases in food prices (e.g., FAO cereal Price Index increased by about 25 points and vegetable oil Price Index increased by more than 60 points in March 2022, https://www. statista.com/chart/20165/un-global-food-price-index/, accessed on 22 February 2023). The global food-production crisis and lack of sustenance affordability can create further regional food-security and political disruptions and trigger further socioeconomical injustice among various nations. Innovations to reshape global food systems through improving local food-production capabilities, enabling infrastructure for agricultural innovation, and facilitating knowledge flow as well as technology dissemination are necessary to curb food shortages and security. Developing and applying new and emerging technologies, including synthetic biology and artificial intelligence, to modernize food production and processing would strengthen efforts to overcome supply challenges in the future

Improvement and enhancement of clavulanic acid production in Streptomyces clavuligerus using vegetable oils

Clavulanic acid (CA) is a potent inhibitor of β-lactamases. Oil can be used as a source of carbon and energy in CA production. To develop a policy for enhanced production of CA, the selection of a production medium and an optimum pH, different vegetable oils as carbon source have been used. The effects of different medium containing vegetable oil on cell growth and CA yield production during the fermentation of Streptomyces clavuligerus ATCC 27064 were demonstrated. In this study, three out of eight tested oils supported CA production. Medium containing olive oil showed two-fold higher CA yield than glycerol containing medium. The highest productivity was obtained at initial pH 7. We concluded that using olive oil as a sole source of carbon and energy for cultivation of S. clavuligerus is a promising strategy for CA production. It has several scientific advantages and economic benefits that lead to increased antibiotic titre and can be considered as a cheaper alternative compared to carbohydrates. The results of this study can be applied for the efficient production of β-lactamase inhibitory antibiotics.Key words: Clavulanic acid, enzymes, β-lactamases, vegetable oils, Streptomyces clavuligerus