Search Results (26)

The Student’s t-distribution provides a thematic connection between the historical and technical elements of this paper. The historical section offers a brief account of the early contributions of Chris Heyde and his collaborations with Madan and Seneta in the development of financial mathematics. The technical section focuses on hypothesis testing, motivated by the observation that, in a setting with pairwise exchangeable dependence for test statistics, the cutoff methods proposed by Sarkar and colleagues in 2016 can be viewed as a first iteration of the classical approach developed by Holm in 1979. These methods had already been refined earlier by Seneta and Chen in their work from 1997 and 2005, which laid the foundation for further improvements. Building on this, a new iteration of the Seneta-Chen method is presented, offering enhancements over the Sarkar approach. Numerical and graphical comparisons are provided, focusing on equal tails testing within the multivariate t-distribution framework. While the tabulated results clearly show improvements with the new procedure, the simulated family-wise error rates across varying correlations reveal only minor practical differences between the iterative methods. This suggests that, under suitable conditions, a single iteration suffices in practice. The paper concludes with personal reflections from the first author, sharing memories of Joe Gani and Chris Heyde, in keeping with the commemorative nature of this issue. Full article

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with a highly variable expression of phenotypes (restricted interest or activity and repetitive behavior in communication and social interactions), genes (mutation), markers (alteration of transcription) and pathways. Loss of function of the CC2D1A gene appears to primarily affect the brain, leading to a range of behavioral problems in humans. In our study published in 2020, we found that the expressions of miR-19a-3p, miR-361-5p, miR-150-5p, miR-3613-3p, miR-126-3p and miR-499a-5p were downregulated in the serum samples of autistic patients, their families and mouse models (Cc2d1a +/− and valproic acid treated males). Here, acquired non-Mendelian hereditary character in a genetically defined mouse model of autism (Cc2d1a +/−) correlates with the transcriptional alteration of five miRNAs. We seek to test the hypothesis that miRNA levels vary by changes in RNA/DNA structure during development, thereby creating transcription alteration and cell memory. Behavioral tests were conducted on the offspring of Cc2d1a (+/−) mutant and control mice, such as novel object, social interaction, marble burying and tail suspension behavior. Two RNA fractions were isolated from mouse hippocampal tissues and sperm cells via standard TRIzol extraction: free RNA and the fraction of RNA bound to DNA in the form of a DNA/RNA hybrid (R-loop). The expression levels of miR-19a-3p, miR-361-5p, miR-150-5p, miR-126-3p and miR-499a-5p were investigated by quantitative real-time RT-PCR. We report differences in the distribution of five miRNAs in the hippocampus between male and female mice, particularly in colonies of Cc2d1a (+/−) mice. Furthermore, the number of miRNAs engaged in the DNA/RNA hybrid fraction is generally higher in the mutant pedigree than in the control group. On the other hand, in sperm, both fractions are at lower levels than in controls. R-loops contribute to the physiology and pathology of organisms including human disease. Here, we report a variation in five miRNA levels between gender and tissue. Our results suggest that the transcription levels of these five miRNAs are directly regulated by their RNA. Full article

Satellite DNA (satDNA) consists of sequences of DNA that form tandem repetitions across the genome, and it is notorious for its diversity and fast evolutionary rate. Despite its importance, satDNA has been only sporadically studied in reptile lineages. Here, we sequenced genomic DNA and PCR-amplified microdissected W chromosomes on the Illumina platform in order to characterize the monomers of satDNA from the Henkel’s leaf-tailed gecko U. henkeli and to compare their topology by in situ hybridization in the karyotypes of the closely related Günther’s flat-tail gecko U. guentheri and gold dust day gecko P. laticauda. We identified seventeen different satDNAs; twelve of them seem to accumulate in centromeres, telomeres and/or the W chromosome. Notably, centromeric and telomeric regions seem to share similar types of satDNAs, and we found two that seem to accumulate at both edges of all chromosomes in all three species. We speculate that the long-term stability of all-acrocentric karyotypes in geckos might be explained from the presence of specific satDNAs at the centromeric regions that are strong meiotic drivers, a hypothesis that should be further tested. Full article

Introduction: Toxocariasis is an infection caused in canines, felines, humans, and other vertebrates by species of the genus Toxocara, such as T. canis and T. cati. The embryonated eggs of these parasites are the primary means of acquiring the infection for both definitive hosts, dogs and cats, respectively, and for intermediates, such as humans and other vertebrates. When deposited on park soils, environmental contamination becomes a risk to environmental, human, and animal health. Objective: To determine the global prevalence of Toxocara cati in cats (Felis catus). Methods: A systematic review of the literature was carried out in six databases (Scopus, PubMed, ScienceDirect, SciELO and Google Scholar) to evaluate the global prevalence of Toxocara cati in cats, defined by coproparasitological, histological, and molecular techniques. A meta-analysis was performed using a random effects model to calculate pooled prevalence and 95% confidence intervals (95% CI). A two-tailed 5% alpha level was used for hypothesis testing. Results: Two hundred and eighty-nine studies were included. The global pooled prevalence of Toxocara cati in cats using coproparasitological methods was 17.0% (95.0% CI: 16.2–17.8%). In the subgroup analysis according to country, Nepal had the highest prevalence of T. cati infection (94.4%; 95% CI 89.7–99.2%). The pooled prevalence of T. cati infection by PCR in four studies was 4.9% (95.0% CI: 1.9–7.9%). Conclusions: This systematic review underscores the need for preventive action against toxocariasis due to its widespread prevalence. The interplay between animal and human health should be emphasised, necessitating measures like deworming cats, hygiene practices, and public education to mitigate risks. Safeguarding feline health can also reduce human transmission, benefiting both species. Full article

We propose a two-sample testing procedure for high-dimensional time series. To obtain the asymptotic distribution of our ${\ell }_{\infty }$-type test statistic under the null hypothesis, we establish high-dimensional central limit theorems (HCLTs) for an $\alpha$-mixing sequence. Specifically, we derive two HCLTs for the maximum of a sum of high-dimensional $\alpha$-mixing random vectors under the assumptions of bounded finite moments and exponential tails, respectively. The proposed HCLT for $\alpha$-mixing sequence under bounded finite moments assumption is novel, and in comparison with existing results, we improve the convergence rate of the HCLT under the exponential tails assumption. To compute the critical value, we employ the blockwise bootstrap method. Importantly, our approach does not require the independence of the two samples, making it applicable for detecting change points in high-dimensional time series. Numerical results emphasize the effectiveness and advantages of our method. Full article

This paper investigates the properties of the change in persistence detection for observations with infinite variance. The innovations are assumed to be in the domain of attraction of a stable law with index $\kappa \in (0,2]$. We provide a new test statistic and show that its asymptotic distribution under the null hypothesis of non-stationary $I\left(1\right)$ series is a functional of a stable process. When the change point in persistence is not known, the consistency is always given under the alternative, either from stationary $I\left(0\right)$ to non-stationary $I\left(1\right)$ or vice versa. The proposed tests can be used to identify the direction of change and do not over-reject against constant $I\left(0\right)$ series, even in relatively small samples. Furthermore, we also consider the change point estimator which is consistent and the asymptotic behavior of the test statistic in the case of near-integrated time series. A block bootstrap method is suggested to determine critical values because the null asymptotic distribution contains the unknown tail index, which results in critical values depending on it. The simulation study demonstrates that the block bootstrap-based test is robust against change in persistence for heavy-tailed series with infinite variance. Finally, we apply our methods to the two series of the US inflation rate and USD/CNY exchange rate, and find significant evidence for persistence changes, respectively, from $I\left(0\right)$ to $I\left(1\right)$ and from $I\left(1\right)$ to $I\left(0\right)$. Full article

The COVID-19 pandemic and the resulting public health crisis had an enormous impact on the global economy and its sectors. Most components were adversely affected, especially the tertiary industry (the part of a country’s economy that provides services), with different types and sizes of businesses suffering to varying degrees. Reports on the impact on agriculture are not lacking, and the crisis was perceived and responded to differently from the supply chain to the household level. The research question proposed in this paper concerns the impact of the early restrictions induced by COVID-19, namely the lockdown period from March to June 2020, on Romanian agriculture and more precisely Western Romanian crop production. Two counties in the West were selected: the county Timis for its highly favourable agricultural production and the county Caras Severin for its integrative agricultural production centred on mixed farms, where crop production is integrated with animal production towards a higher added value. Using secondary data from the National Agency for Payments and Interventions in Agriculture allowed the disaggregation of data at the level of each municipality for 2019 and 2020. The choice of this dataset was related to the level of precision, as the beneficiaries of direct payments in the respective areas are verified each year for both areas and crops. The paired two-tailed t-test was used to test the data for each LAU 2 municipality in each of the selected counties; as the crops sown in 2019 could not be affected by the COVID lockdown period in spring 2020 (March to June), the most important spring crops in terms of area in 2020 were selected and tested against the 2019 datasets. The results show that there is not enough evidence to conclude a significant statistical difference between the two years, and therefore, we cannot reject the null hypothesis and conclude that the pandemic lockdown did not affect the spring crops during their most restrictive period in spring 2020; thus, the overall influence of the COVID-19 lockdown on crop production in Western Romania was insignificant, observed only at the level of primary production. Spring crop production could have been severely affected by the restrictions imposed by the health crisis on access to certain inputs, freedom of movement for field work, and other activities closely linked to agricultural production, leading to early disruptions along the food chain. Full article

Financing has been identified as a major stumbling block to the effective launch and long-term success of SMEs, particularly in emerging economies. However, little is known about the impact of capital startups on SMEs’ performance in South Africa. Thus, the aim of this article is to compare differences in business success for three different levels of Capital startups and to determine the impact of capital startups on SMEs’ performance. The analysis was premised on a two-tail hypothesis test that the average weights of the three groups are different. The Cronbach Alpha test and the test–re-test reliability approach on the survey instrument indicated values of 0.70 and 0.875, respectively. A one-way between-groups analysis of variance was conducted startup. There was a statistically significant difference at the p < 0.05 level in scores for the three groups (F (2, 477) = 12.967 p = 0.0000). Post hoc comparisons using the Tukey HSD test indicated that the mean scores for Group 1 (M = 19.93, SD = 6.343) were significantly different from Group 2 (M = 20.94, SD = 2.309) and Group 3 (M = 21.73, SD = 2.880). Despite reaching statistical significance, the actual difference in mean scores between the groups was quite small. The one-way ANOVA approach indicates that finance (startup capital) remains a significant impediment to the effective launch of service-providing SMEs. It is recommended that SMEs who want to raise startup capital must create a solid business plan or build a prototype to sell the idea. This will assist them in discussions with venture capitalists, angel investors, banks, or other financial institutions. Full article

Many studies have pointed out that the Performance Evaluation Matrix (PEM) is a convenient and useful tool for the evaluation, analysis, and improvement of service operating systems. All service items of the operating system can collect customer satisfaction and importance through questionnaires and then convert them into satisfaction indices and importance indices to establish PEM and its evaluation rules. Since the indices have unknown parameters, if the evaluation is performed directly by the point estimates of the indices, there will be a risk of misjudgment due to sampling error. In addition, most of the studies only determine the critical-to-quality (CTQ) that needs to be improved, and do not discuss the treatment rules in the case of limited resources nor perform the confirmation after improvement. Therefore, to address similar research gaps, this paper proposed the unbiased estimators of these two indices and determined the critical-to-quality (CTQ) service items which need to be improved through the one-tailed statistical hypothesis test by building a PEM method of the satisfaction index. In addition, through the one-tailed statistical hypothesis test method of the importance index, the improvement priority of service items was determined under the condition of limited resources. Confirmation of the effect on improvement is an important step in management. Thus, this paper adopted a statistical two-tailed hypothesis test to verify whether the satisfaction of all the CTQ service items that need to be improved was enhanced. Since the method proposed in this paper was established through statistical hypothesis tests, the risk of misjudgment due to sampling error could be reduced. Obviously, reducing the misjudgment risk is the advantage of the method in this paper. Based on the precondition, utilizing the model in this study may assist the industries to determine CTQ rapidly, implement the most efficient improvement under the condition of limited resources and also confirm the improvement effect at the same time. Finally, a case study of computer-assisted language learning system (CALL System) was used to illustrate a way to apply the model proposed in this paper. Full article

We evaluate the use of generalized empirical likelihood (GEL) estimators in portfolio efficiency tests for asset pricing models in the presence of conditional information. The use of conditional information is relevant to portfolio management as it allows for checking whether asset allocations are efficiently exploiting all the information available in the market. Estimators from the GEL family present some optimal statistical properties, such as robustness to misspecifications and better properties in finite samples. Unlike generalized method of moments (GMM) estimators, the bias for GEL estimators does not increase with the number of moment conditions included, which is expected in conditional efficiency analysis. Due to these better properties in finite samples, our main hypothesis is that portfolio efficiency tests using GEL estimators may have better properties in terms of size, power, and robustness. Using Monte Carlo experiments, we show that GEL estimators have better performance in the presence of data contaminations, especially under heavy tails and outliers. Extensive empirical analyses show the properties of the estimators for different sample sizes and portfolio types for two asset pricing models. Full article

The study aimed to evaluate the prevalence, characteristics and outcomes of patients affected by Charcot neuro-arthropathy (CN) and peripheral arterial disease (PAD) compared to CN without PAD. Consecutive patients presenting with an acute CN were included. The sample size was calculated by the power analysis by adopting the two-tailed tests of the null hypothesis with alfa = 0.05 and a value of beta = 0.10 as the second type error and, therefore, a test power equal to 90%. Seventy-six patients were identified. Twenty-four patients (31.6%) had neuro-ischaemic CN; they were older (66 vs. 57yrs), p = 0.03, had a longer diabetes duration (19 vs. 14yrs), p < 0.001, and more cases of end-stage-renal-disease (12.5 vs. 0%), p = 0.04 and ischaemic heart disease (58.3 vs. 15.4%), p < 0.0001 than neuropathic CN. Fifty patients (65.8%) had concomitant foot ulcers, 62.5% and 67.3% (p = 0.3), respectively, in CN with and without PAD. Neuro-ischaemic CN show arterial lesions of 2.9 vessels, and PAD was located predominantly below-the-knee (75%) but not below-the-ankle (16.7%). The outcomes for neuro-ischaemic and neuropathic CN patients were, respectively: wound healing (86.7 vs. 94.3%), p = 0.08; minor amputation (25 vs. 7.7%), p = 0.003; major amputation (8.3 vs. 1.9%), p = 0.001; hospitalization (75 vs. 23%), p = 0.0001. The study showed a frequent association between CN and PAD, leading to a neuro-ischaemic Charcot foot type. Neuro-ischaemic CN leaded to an increased risk of minor and major amputation and hospitalization, compared to neuropathic CN. Full article

The fat tail is a phenotype that divides indigenous Iranian sheep genetic resources into two major groups. The objective of the present study is to refine the map location of candidate regions associated with fat deposition, obtained via two separate whole genome scans contrasting thin and fat tail breeds, and to determine the nature of the selection occurring in these regions using a hitchhiking approach. Zel (thin tail) and Lori-Bakhtiari (fat tail) breed samples that had previously been run on the Illumina Ovine 50 k BeadChip, were genotyped with a denser set of SNPs in the three candidate regions using a Sequenom Mass ARRAY platform. Statistical tests were then performed using different and complementary methods based on either site frequency (F_ST and Median homozygosity) or haplotype (iHS and XP-EHH). The results from candidate regions on chromosome 5 and X revealed clear evidence of selection with the derived haplotypes that was consistent with selection to near fixation for the haplotypes affecting fat tail size in the fat tail breed. An analysis of the candidate region on chromosome 7 indicated that selection differentiated the beneficial alleles between breeds and homozygosity has increased in the thin tail breed which also had the ancestral haplotype. These results enabled us to confirm the signature of selection in these regions and refine the critical intervals from 113 kb, 201 kb, and 2831 kb to 28 kb, 142 kb, and 1006 kb on chromosome 5, 7, and X respectively. These regions contain several genes associated with fat metabolism or developmental processes consisting of TCF7 and PPP2CA (OAR5), PTGDR and NID2 (OAR7), AR, EBP, CACNA1F, HSD17B10,SLC35A2, BMP15, WDR13, and RBM3 (OAR X), and each of which could potentially be the actual target of selection. The study of core haplotypes alleles in our regions of interest also supported the hypothesis that the first domesticated sheep were thin tailed, and that fat tail animals were developed later. Overall, our results provide a comprehensive assessment of how and where selection has affected the patterns of variation in candidate regions associated with fat deposition in thin and fat tail sheep breeds. Full article

Due to the COVID-19 pandemic, there was an urgent need to move to online teaching and develop innovative teaching techniques to ensure that student learning outcomes (SOs) were fulfilled. This paper tries to answer the important question of whether an established teaching strategy through a multi-course project-based learning (MPL) approach, along with online assessment techniques, helps in the effective achievement of SOs in a senior-level electrical engineering (EE) course. The authors have developed a course project for attaining the objectives of a senior and a capstone course, where students are registered at the same time. In addition, the course conducts assessments online. The paper reports the effect of the two approaches on the attainment of the SOs of the two courses, along with testing the programming and problem-solving abilities of the students. It is known that the MPL approach enhances the critical thinking capacity of students, which is also a major outcome of Sustainable Development Education (ESD). It was ensured that the project that was used to test the fulfillment of a series of SOs were concentrated on soft engineering and project management skills. The difficulty of adopting the MPL method for the senior-level courses is in the scheduling of the course materials to help the student advance to the final project while also aligning the project towards fulfilling the learning outcomes of the individual course. The study also provides the students with feedback on online assessment techniques incorporated within the MPL. Besides this, the effect of the innovative teaching approaches was compared with the same senior course taught using conventional methods in an earlier semester. Based on the feedback from teachers and students from a previously conducted case study, it was concluded that the MPL approach had supported the student learning. The results of the statistical analysis (Chi-square, two-tailed T statistics and hypothesis testing using a z-test) show that an MPL approach and online assessment improved the attainment of the SOs despite the constraints posed by the pandemic. Full article

Many studies in the literature have presented multiple remote sensing techniques for defect inspection of paintings. At present, however, papers on defect inspection and restoration of oriental architectural arts—such as door god paintings—are still rare. If an aged and damaged door god painting needs a restoration, then following the style and treatment skill of the original artist as much as possible is important for the restoration. Unfortunately, it is usually difficult to access the original artists for some of the aged door god paintings. This paper considers the texture features of auspicious patterns of armors on warrior door gods as useful information to recognize styles of door god paintings by unknown artists. First, a two-level two-dimensional discrete wavelet transform coupled with co-occurrence matrix calculation was adopted to analyze the texture features, based on the descriptors of angular second moment (ASM), entropy (ENT), contrast (CON), homogeneity (HOM), dissimilarity (DIS), correlation (COR), and cluster tendency (CLU), in the four orientations of 0° (horizontal), 45° (vertical), and 90° and 135° (double diagonal). Second, a two-tailed t-test based on the analyzed texture features was introduced into the hypothesis testing for demonstrating the master and apprentice relationships between the surveyed artists, and for recognizing the door god painting styles of unknown artists as well. The experimental results show that the proposed method effectively describes the texture features of the auspicious patterns of the surveyed door god paintings, and is able to determine the useful co-occurrence features for recognizing unknown artists’ painting styles. Full article

Nitric oxide (NO) is a powerful vasodilator in different vascular beds and NO-donors are widely used in clinical practice. Early data suggested that NO and NO-donors activate vascular smooth muscle high-conductance, calcium-activated potassium channels (BK channels). There exist two hypotheses explaining the effect of NO and NO-donors on BK channels—one stating that protein kinase G (PKG) mediates the effect of NO, and the other one stating that NO acts directly on the channel. Thus, the degree of contribution of PKG to the NO-induced activation of the BK channel is still not completely clear. This study tested the hypothesis that the sodium nitroprusside (SNP)-induced activation of vascular smooth muscle BK channels is fully mediated by PKG. This hypothesis was investigated using the patch-clamp technique and freshly isolated smooth muscle cells from rat tail artery. In whole-cell experiments, SNP considerably increased the outward current compared with the addition of the bath solution. SNP did not alter the current in the presence of iberiotoxin, the specific blocker of BK channels, during co-application with hydroxocobalamin, an NO-scavenger, and in the presence of Rp-8-Br-PET-cGMPS, the specific PKG-inhibitor. In inside-out patches, the activity of BK channels was increased by SNP, SNAP, and DEA-NO. However, these effects did not differ from the effect of the application of drug-free bath solution. Furthermore, a similar increase in single BK channel activity was induced by Rp-8-Br-PET-cGMPS, Rp-8-Br-PET-cGMPS together with SNP, hydroxocobalamin, and hydroxocobalamin together with SNP or DEA-NO. Finally, the activity of excised BK channels did not change in the absence of any application but was considerably increased by PKG compared with the addition of drug-free bath solution. These results suggest that NO released from NO-donors stimulates the BK current only through activation of PKG. Full article