Statistically-significant Relationships Research Articles

Board Characteristics and Quality of Integrated Reporting of Firms Listed Nairobi Securities Exchange

Companies that opt for integrated reporting are in a favorable position to enhance a range of benefits,whether internal or external in nature. It encompasses improvements in resource allocation, shareholderengagement, and reputation. On the other hand, external advantages pertain to investors who rely ongovernance disclosure, as well as compliance with regulations, frameworks, standards, and guidelines setby stock exchanges. The expansion and adoption of integrated reporting are broadening its scope, with anincreasing number of companies showing willingness to adopt this approach. The diffusion and adoptionof reporting practices stem from diffusion theory, which has evolved from institutional theory,encompassing institutional factors that influence organizational behavior. The positive and statisticallysignificant relationships between board characteristics highlight how crucial it is for publicly tradedcorporations to work to improve the independence of their boards of directors while also includingmembers with financial expertise to facilitate the disclosure of both financial and non‐financial information.The findings are significant especially in the implementation of board decisions, strategic planning, and inmanaging corporate governance attributes in the attempts to enhance information disclosure through theimplementation of integrated reporting.

An observational study of gastric contents in pediatric patients with long bone fracture using gastric ultrasound.

The retention of gastric contents at surgery presentation is a risk factor for perioperative aspiration. A preoperative fasting (nil per os; NPO) interval is widely used to reduce this risk, but this approach is based on assumptions about the prevalence of typical gastric emptying rates. We assessed NPO guidelines' reliability with ultrasound (US) imaging and suction in pediatric patients presenting for single long-bone fracture repair after appropriate NPO intervals, when nearly all should have had empty stomachs. This prospective cross-sectional observational study comprised 200 pediatric surgical patients. As their NPO times varied by food/drink type, we defined "weighted NPO units" as the lowest multiple of elapsed recommended NPO times between consumption and surgery for each type of food or drink. We used US to image the stomach and its contents before anesthesia induction, followed by gastric suction. We evaluated the relationships between weighted NPO units, US gastric contents grade, opioid analgesic dosage and timing, and suctioned volume. Despite meeting typical NPO standards (median 14 h fasting), many patients retained nontrivial quantities of gastric contents at surgery. Weighted NPO units did not exhibit statistically-significant relationships with either suctioned volume or US grade. However, suctioned volume did correspond well to US grade. NPO status may be a less reliable predictor of gastric contents at anesthesia induction in this patient population than has been assumed. Bedside US screening appears to provide more useful information for the planning of airway management.

Effect of nasendoscopy procedure on acoustic features of voice and speech

Nasendoscopy procedure enables direct visualization of voice and speech anatomy. The procedure passes a flexible scope transnasally to observe velopharyngeal mechanism or the larynx during speech and phonation. This imaging technique is commonly used simultaneously with audio recordings. Studies have identified important statistically-significant relationships between imaging-based and acoustic measures related to voice and speech quality. However, the effect of the nasendoscopy procedure itself on specific acoustic features is rarely being considered. Nasendoscopy is likely to cause some speakers to deviate from their typical vocal function by inducing stress and tension during recordings. Furthermore, the flexible nasendoscope can also change the sound and airflow behavior inside the vocal tract. The current study attempts to quantify how nasendoscopy influences acoustic features using a physical model based on a child's vocal tractduring a sibilant sound. An electrolarynx was used to provide a constant sound source with the input airflow to the model. Audio recordings were captured while retracting the nasendoscope from the level of the hypopharynx. Results show that compared to the same data taken without nasendoscopy, the scope can change measures of signal-to-noise and cepstral-peak-prominence by 15% and 7%, respectively. The nasendoscope had a minimal effect (<3%) on the SPL measure.

The Effect of Lifestyle on Primary Dysmenorrhea

Introduction: Dysmenorrhea, also known as painful periods, is a common gynaecological diagnosis faced by most women of fertile age. Dysmenorrhea is still a misunderstood condition and most women accept it as a normal part of their menstrual cycle. The pain has a strong impact on well being and can severely affect quality of life. Methods: An online questionnaire was administered to female subjects between May and July 2020. Shapiro-Wilk, Mann-Whitney and Kruskal-Wallis tests were used, non-para-medical statistical analyses using Spearman correlation coefficient. Statistical significance was set at p 0.05. Results: The sample consisted of 774 women. It can be seen that the respondents who have already given birth have statistically significantly less menstrual pain (MR = 270.36; VR = 67859.50) than the respondents who have not given birth (MR = 402.06; VR = 184545.50). On average, respondents who experience orgasm less than 1x/week (MR = 346.93) have the least menstrual pain, and respondents who experience orgasm daily or 4-6x/ week have the most menstrual pain (MR = 427.18). Respondents who go to bed at 1am or later have the highest mean pain response score (MR = 433.65) and the lowest among those who go to bed before 10pm (MR = 346.30). The highest mean menstrual pain response score is among respondents who have negative attitude towards menstruation (MR = 557.54) and the lowest is among respondents who have neutral attitude (MR = 268.82). Conclusions: The results confirm statistically significant relationships between sleep, sexuality, stress, menstrual perception and menstrual pain.

Towards a medical school curriculum for uncertainty in clinical practice

ABSTRACT Uncertainty abounds in the clinical environment. Medical students, however, are not explicitly prepared for situations of uncertainty in clinical practice, which can cause anxiety and impact well-being. To address this gap, we sought to capture how students felt in various clinical scenarios and identify programs they found helpful as they worked through uncertainty in their clerkships to better inform curriculum that prepares them to acknowledge and navigate this uncertainty. This is an observational cross-sectional study of third-year medical students surveyed at the end of core clerkships. The survey consisted of the General Self-Efficacy (GSE) Scale and Intolerance of Uncertainty Scale (IUS). Items asked students to rate preparedness, confidence, and comfort with uncertainty in clinical practice. Items on curricular programs asked students to identify training that prepared them for uncertainty in clerkships, and examined correlations with specific clinical practice uncertainty domains (CPUDs). Spearman’s rank-order correlation, Chi-Square, and ANOVA were used to analyze quantitative data. Open responses were analyzed using Braun and Clarke’s Framework. Response rate was 98.9% (287/290). GSE was inversely correlated with IUS (p < 0.001). GSE was positively correlated with all CPUDs (p < 0.005). IUS had an inverse correlation with all CPUDs (p < 0.005). Pedagogies with statistically-significant relationships with preparing students for uncertainty, communicating and building relationships with patients during times of uncertainty, and overall well-being included: team debriefs, role plays, case- and team-based learning, story slams, and sharing narratives with peers and faculty (p < 0.05). Qualitatively, students appreciated storytelling, role-modeling of communication strategies, debriefing, and simulations. Strategically immersing specific educational formats into formal curriculum may help cultivate skills needed to prepare students for uncertainty. Clinical debriefs, interprofessional role plays, simulations, communications skills training, instructor emotional vulnerability, storytelling, and peer-to-peer conversations may have the most impact. Further study is required to evaluate their longitudinal impact.

Academic Librarians’ Teaching Identities and Work Experiences: Exploring Relationships to Support Perspective Transformation in Information Literacy Instruction

Academic library leaders have a vested interest in quality library instruction, but strategies to ensure this happens can vary across environments. In this study, the author analyzed data collected using King’s Learning Activities Survey to consider how work demographics impacted instruction librarians’ teaching identity development. Through one-way analyses of variance and cross-tabulation analyses, she found several statistically-significant relationships between how academic librarians’ institution types and times at their institution differently inform their teaching identity development. These relationships offer opportunities for library leaders to offer intentional, data-driven support for academic librarians in developing teaching identities while offering high-quality instruction for learners.

The role of antioxidants and 25-hydroxyvitamin D during pregnancy in the development of allergic diseases in early school-age children ‐ Polish Mother and Child Cohort Study

Purpose: Based on the available data, alterations of the antioxidant defense as well as the vitamin status in mothers may affect the prenatal process of lung and immune system development as a pathophysiological background of increased prevalence of allergic diseases. The primary aim of the current study was to assess the associations among cord blood concentrations of zinc (Zn); copper (Cu); selenium (Se); β-carotene; and vitamin A, E, and D, and the occurrence of atopic dermatitis, food allergy, allergic rhinitis, and asthma in early school-age children. Methods: We evaluated 211 children, 7-9 years old, from the Polish Mother and Child Cohort Study. the women were interviewed during pregnancy to collect demographic and socioeconomic data, and the medical and reproductive history. At delivery, umbilical cord blood plasma was sampled. Seven to nine years after the birth, the child's exposure and health status (including skin-prick test and spirometry for allergy assessment and urine sample for cotinine level) were examined. In the analyses, a multivariable model was applied. Results: Statistically significant relationships were found among Zn; Cu; Se; and vitamin A, E, and D concentrations in cord blood; and the prevalence of food allergy, allergic rhinitis, atopic dermatitis, and asthma in children ages 7-9 years after adjustment for several confounders. Conclusion: We showed an imbalance in the antioxidant defense system in cord blood, which may lead to the occurrence of allergic diseases later in life. The maternal diet may have substantial potential to modify immune tolerance and, consequently, the development of allergic disease in the offspring.Clinical trial NCT01861548, <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.clinicaltrials.gov">www.clinicaltrials.gov</ext-link>.

Comparison of dose statistics for bladder wall and rectum wall vs whole organs for VMAT prostate treatment

Dose-wall histograms (DWHs) have been used as alternatives to dose-volume histograms (DVHs) for hollow organs, with the rationale that the dose delivered to the interior of a hollow organ would be unrelated to the level of radiation damage. The purpose of this study is to conduct a statistical comparison of dose statistics for both walled and solid structure contours for both bladder and rectum in the treatment of intermediate risk prostate cancer with volumetric arc therapy (VMAT). Ten intermediate risk prostate cases were randomly selected. Rectum and bladder were first contoured as solid structures, and then the corresponding wall structures were generated using either a slice-by-slice cropping (2D method), or with a full 3D cropping tool (3D method). Each case was then inverse planned using a 2-arc VMAT technique. Two plans per case were created, 1 with a hypofractionated treatment and 1 with a standard fractionated treatment. DVHs were calculated for solid structure contours, and DWHs were calculated for the walled structure contours generated using 2D and 3D contouring tools. A nonparametric Spearman statistic correlation test was used to compare a large number of relevant dose histogram points, and to establish the relationship between dose statistics for walled and solid structures. Several notable relationships were observed. Maximum rectal dose was strongly correlated between the solid structure and both the 2D-generated (Spearman's correlation rs = 0.988, p < 0.01) and 3D-generated (rs = 0.952 p< 0.01) wall structures. This indicates that the rectal hot spot occurred in or near the wall for all cases, suggesting that both structure types give similar maximum dose information for rectum. Maximum bladder dose was not significantly correlated between solid structures and the 2D (rs = 0.596, p= 0.069) and 3D-generated (rs = 0.681, p= 0.03) counterparts. This suggests that the maximum dose is not consistently in or near the bladder wall. This favors the use of bladder wall contours when considering bladder toxicity, with the maximum dose to the wall potentially being more relevant radiobiologically. This analysis was extended to many other relevant points on the rectum and bladder histogram curves. Where correlations are strong, equations of best-fit are presented. This work establishes several statistically-significant relationships between bladder and rectum DVHs and DWHs for VMAT irradiation of intermediate-risk prostate cancer. This information may be used to inform contouring requirements for clinical trial design as well as for standard patient care.

Risco de olho seco e ressecamento ocular em terapia intensiva: estudo transversal

verify the relationship between risk factors and clinical datawith the nursing diagnosis of dry eye risk and ocular dryness in adult patients admittedto the intensive care unit (ICU). Method: it is a cross-sectional pilot study performed atthe ICU of a public hospital between October and December 2015. Results: Statisticallysignificant relationships with the nursing diagnosis under study and the following riskfactors and clinical data were observed: therapy with mechanical ventilation,neurological lesions with sensory loss, motor reflex, Schirmer test and length of hospitalstay. Burns,use of vasoactive drugs, Schirmer test and days of hospitalization alsoshowed a significant relation with ocular dryness. Conclusion: the results suggest thatsome risk factors and certain clinical data may present a greater relationship in the ICU environment. Practical implications: the knowledge provided can support the planning ofinterventions aimed at avoiding visual impairments.

Relationship between the Organizational Climate and Occurrences of Workaholism in Enterprises Employing Knowledge Workers

A competent employee is nowadays a dominant value in enterprises (Juchnowicz, 2010). That is why some enterprises positively perceive employees addicted to work. In fact, a workaholic is working constantly in a rush, can make mistakes and expresses a high need to control (Lipka, Waszczak, 2013). Some organizations stimulate workaholism by shaping the organizational climate. Research was carried out among knowledge workers (N = 600) and the relationship between the intensity of workaholism and organizational climate dimensions was analyzed. The climate was assessed using the Polish adaptation of the Organizational Climate Questionnaire developed by L. Rosenstiel and R. Bögel. To analyze the level of workaholism the Polish version of the DUWAS-10 developed by W. Schaufeli and T. Taris was used. The results show the existence of statistically significant relationships between variables.

Inferior alveolar nerve injury: Correlation between indicators of risk on panoramic radiographs and the incidence of tooth and mandibular canal contact on cone-beam computed tomography scans in a Western Australian population.

The aim of the present study was to assess risks prior to third molar removal. A 2-D panoramic radiograph or a 3-D cone-beam computed tomography (CBCT) scan can be used to visualize the proximity of the third molar to the mandibular canal. We aimed to correlate panoramic indicators of risk with the incidence of contact between these two structures on CBCT scans. Patients were selected from a Western Australian population if they had a panoramic radiograph that illustrated signs of risk of inferior alveolar nerve injury and had a CBCT scan on file. Statistically-significant relationships between the relative position and distance between the mandibular canal and third molar were investigated using χ2 -test and Fisher's exact test in Stata version 13. Within the Western Australian sample (N=100), of six possible panoramic indicators of risk, two were significantly associated with contact between the tooth and mandibular canal on CBCT: (a) interruption of the radiographic white line of the canal; and (b) darkening of the root(s). Two panoramic radiograph risk signs are significantly more likely to indicate contact on the CBCT scans: interruption of the white line and darkening of the root(s). Further research is required to develop CBCT prescription guidelines for surgical planning.

MortalityPredictors.org: a manually-curated database of published biomarkers of human all-cause mortality.

Biomarkers of all-cause mortality are of tremendous clinical and research interest. Because of the long potential duration of prospective human lifespan studies, such biomarkers can play a key role in quantifying human aging and quickly evaluating any potential therapies. Decades of research into mortality biomarkers have resulted in numerous associations documented across hundreds of publications. Here, we present MortalityPredictors.org, a manually-curated, publicly accessible database, housing published, statistically-significant relationships between biomarkers and all-cause mortality in population-based or generally healthy samples. To gather the information for this database, we searched PubMed for appropriate research papers and then manually curated relevant data from each paper. We manually curated 1,576 biomarker associations, involving 471 distinct biomarkers. Biomarkers ranged in type from hematologic (red blood cell distribution width) to molecular (DNA methylation changes) to physical (grip strength). Via the web interface, the resulting data can be easily browsed, searched, and downloaded for further analysis. MortalityPredictors.org provides comprehensive results on published biomarkers of human all-cause mortality that can be used to compare biomarkers, facilitate meta-analysis, assist with the experimental design of aging studies, and serve as a central resource for analysis. We hope that it will facilitate future research into human mortality and aging.

Does brand posting behaviour influence follower engagement on Instagram?

Abstract The Instagram application captured the attention of hundreds of millions of users. The goal of this paper was to study whether there is a statistically significant relationship between the posting behaviour of corporate retail brands on Instagram and follower engagement. The proxy variables used to describe the posting behaviour were: number of days with posts, number of posts and existence of calls to action within posts. The proxy variables for engagement were the number of likes, as well as the sum of likes and comments for each post. The study referred to the Instagram activity of the top fifty global specialty retailers. Lately, the researchers’ interest in social media grew substantially. In contrast, the studies relative to the posting behaviour of companies on Instagram are rather scarce. At present, scientific research on this topic is in an preliminary state. In addition, there are no published findings of scientific research on the use of Instagram by top global specialty retailers. The paper aimed to answer the following research questions: (a) “Is posting on Instagram a common behaviour of the top fifty global specialty retailers?”; (b) “How active are these companies in posting own photo and video content?”; (c) “Are there statistically significant relationships between the variables describing the posting behaviour and those reflecting the follower engagement?”. The data were collected by monitoring verified badge Instagram accounts of the top fifty global specialty retailers. The t test was applied on data from the online study of 612 posts. Findings reveal statistical significant relationships between the analysed variables. There is a strong correlation between the number of posts and engagement. To the best of our knowledge, this article is the first to approach this topic. As a direct implication for retailers, an intense posting activity may lead to an increased engagement of followers.

MODIS vegetation products as proxies of photosynthetic potential along a gradient of meteorologically and biologically driven ecosystem productivity

Abstract. A direct relationship between gross ecosystem productivity (GEP) estimated by the eddy covariance (EC) method and Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation indices (VIs) has been observed in many temperate and tropical ecosystems. However, in Australian evergreen forests, and particularly sclerophyll and temperate woodlands, MODIS VIs do not capture seasonality of GEP. In this study, we re-evaluate the connection between satellite and flux tower data at four contrasting Australian ecosystems, through comparisons of GEP and four measures of photosynthetic potential, derived via parameterization of the light response curve: ecosystem light use efficiency (LUE), photosynthetic capacity (Pc), GEP at saturation (GEPsat), and quantum yield (α), with MODIS vegetation satellite products, including VIs, gross primary productivity (GPPMOD), leaf area index (LAIMOD), and fraction of photosynthetic active radiation (fPARMOD). We found that satellite-derived biophysical products constitute a measurement of ecosystem structure (e.g. leaf area index – quantity of leaves) and function (e.g. leaf level photosynthetic assimilation capacity – quality of leaves), rather than GEP. Our results show that in primarily meteorological-driven (e.g. photosynthetic active radiation, air temperature, and/or precipitation) and relatively aseasonal ecosystems (e.g. evergreen wet sclerophyll forests), there were no statistically significant relationships between GEP and satellite-derived measures of greenness. In contrast, for phenology-driven ecosystems (e.g. tropical savannas), changes in the vegetation status drove GEP, and tower-based measurements of photosynthetic activity were best represented by VIs. We observed the highest correlations between MODIS products and GEP in locations where key meteorological variables and vegetation phenology were synchronous (e.g. semi-arid Acacia woodlands) and low correlation at locations where they were asynchronous (e.g. Mediterranean ecosystems). However, we found a statistical significant relationship between the seasonal measures of photosynthetic potential (Pc and LUE) and VIs, where each ecosystem aligns along a continuum; we emphasize here that knowledge of the conditions in which flux tower measurements and VIs or other remote sensing products converge greatly advances our understanding of the mechanisms driving the carbon cycle (phenology and climate drivers) and provides an ecological basis for interpretation of satellite-derived measures of greenness.

Rosenberg Self-Esteem Scale Greek Validation on Student Sample

This paper presents the standardization of the Rosenberg Self-Esteem Scale (RSES) in the Greek population. Self-esteem is defined as the positive or negative reflection that the individual has for himself/herself and the belief of being able to cope with the basic challenges of life. The RSES was completed by university students with a mean age of 19. Along with the RSES we administered the Health Locus of Control Scale, the Perceived Stress Scale (PSS), the Stress and Personality Self Test and the self-esteem questionnaire (Darviri & Varvogli). The results on the reliability and validity of the RSES were satisfactory as the internal reliability index crombach a was .80 and the RSES had positive statistical significant relationship with the second questionnaire of self-esteem. We also found statistically significant relationships with stress levels, health locus of control and personality types. It seems that when people attribute their good health to others, they have increased self-esteem in relation to people who attributed their good health to themselves. Furthermore our study showed that women have higher levels of self-esteem than men, an opposite outcome to the one of previous validations. The RSES Greek version is a tool that can be used for the measurement of Self-Esteem in the Greek Population.

The relationship between emotional intelligence and leadership styles in the South African petrochemical industry

Orientation: Although research on emotional intelligence in the context of leadership has remained a recurrent area of interest in theory and practice during the past decade, ongoing debate continues regarding the contribution of emotional intelligence to the understanding of leadership.Research purpose: The aim of this study was to determine the relationship between self-reported emotional intelligence and leadership styles in a South African context and to determine whether emotional intelligence can predict an effective leadership style.Motivation for the study: Research is needed in order to determine a more detailed relationship between emotional intelligence and leadership in the dynamic and globalising South African petrochemical context.Research design, approach and method: The study was conducted in terms of a positivist paradigm, using quantitative research instruments. Leaders (N = 161) were selected from a business unit in a South African petrochemical organisation. Self-reports from the emotional quotient inventory and the Multifactor Leadership Questionnaire (MLQ Form 5X, Version 2009) were analysed. Correlation analyses indicated statistically-significant relationships between emotional intelligence and transformational and laissez-faire leadership.Main findings: Findings indicated positive correlations between self-reported emotional intelligence (specifically adaptability) and transformational leadership. Negative correlations were obtained between emotional intelligence (specifically intrapersonal skills) and laissez-faire leadership. The research also showed differences between specific demographic variables.Practical/managerial implications: This study provides valuable significance for organisations’ endeavours in improving, training and identifying alternative selection and assessment procedures for evaluating leaders’ strengths.Contribution/value-add: This research contributes to the South African research on emotional intelligence and leadership styles and thereby adds context-specific value to the topic within a specific cultural and organisational context.

Statistical and Domain Analytics Applied to PV Module Lifetime and Degradation Science

A better understanding of the degradation modes and rates for photovoltaic (PV) modules is necessary to optimize and extend the lifetime of these modules. Lifetime and degradation science (L&DS) is used to understand degradation modes, mechanisms and rates of materials, components and systems to predict lifetime of PV modules. A PV module lifetime and degradation science (PVM L&DS) model is an essential component to predict lifetime and mitigate degradation of PV modules using reproducible open data science. Previously published accelerated testing data from Underwriter Laboratories on PV modules with fluorinated polyester backsheets, which included eight modules that were exposed up to 4000 hrs of damp heat (85% relative humidity at 85°C) and eight exposed up to 4000 hrs of ultraviolet light (80 W/m2 of 280-400 nm wavelengths at 60°C) (UV preconditioning) were used to determine statistically significant relationships between the applied stresses and measured responses. There were 15 different variables tracking aspects of system performance, degradation mechanisms, component metrics and time. Modules were analyzed for three system performance metrics (fill factor, peak power, and wet insulation). The results were statistically analyzed to identify variable transformations, statistically significant relationships (SSRs) and to develop the PVM L&DS model informed by a generalization of structural equation modeling techniques. The SSRs and significant model coefficients, combined with domain analytics, incorporating materials science, chemistry, and physics expertise, produced a pathway diagram ranking the variables' impact on the system performance, which were iteratively examined using sound statistical analysis and diagnostics. The SSRs determined from the damp heat exposure for the system response of Pmax corresponded to the degradation pathway of polyester terephthalate (PET) and ethylene vinyl acetate (EVA) hydrolysis. A linear change point for the damp heat exposure with the system response of Pmax was determined to be 1890 hrs. The UV preconditioning exposure did not induce sufficient degradation shown by the quality of the R2 values for many of the best fitting models. This exemplifies the development of a methodology to determine rank ordered lifetime and degradation pathways present in modules and their effects on module performance over lifetime.

Beyond Individualism-Collectivism and Conflict Style: Considering Acculturation and Media Use

Opportunities for individuals from varied cultural backgrounds to interact, and therefore conflict, are inherently greater because the technologies, economies, and livelihoods of people of many countries are increasingly interdependent. In light of globalization, it is ever more valuable to understand how culture influences the way people manage conflict. The purpose of this study was to examine factors influencing people's individualistic-collectivistic culture tendencies and conflict styles, and whether or not acculturation is a moderating factor between individualism-collectivism and conflict style among foreign nationals living within the United States. In addition to acculturation, researchers also measured media use. The data revealed statistically-significant relationships for media-use and acculturation on individualism-collectivism and conflict styles, and supported the idea that acculturation is a moderating factor between individualism-collectivism and conflict style, although this relationship was only significant among those who preferred the dominating conflict style.

The influence of aza-substitution on azole aromaticity

A homogeneous set of values for the aromaticity indices ASE (Aromatic Stabilisation Energy), HOMA (Harmonic Oscillator Model of Aromaticity) and NICS(1) (Nucleus-Independent Chemical Shift) for azoles has been investigated using multiple linear regression analysis. Statistically-significant relationships were found between the aromaticity indices and the number of nitrogen atoms at positions 2/5 and 3/4 of the ring. Aza-derivatives of pyrrole, furan and thiophene all gave similar relationships. For all three indices aza-substitution at positions 2 and/or 5 increases aromaticity. However, aza-substitution at positions 3 and/or 4 decreases classical aromaticity (ASE and HOMA) but increases magnetic aromaticity (NICS(1)). These indices appear to be measuring different properties of the azoles. The influence of aza-substitution on these different aspects of aromaticity is tentatively rationalized in terms of either bond length equalization or uniformity of π electron distribution.

Threshold selection in gene co-expression networks using spectral graph theory techniques

BackgroundGene co-expression networks are often constructed by computing some measure of similarity between expression levels of gene transcripts and subsequently applying a high-pass filter to remove all but the most likely biologically-significant relationships. The selection of this expression threshold necessarily has a significant effect on any conclusions derived from the resulting network. Many approaches have been taken to choose an appropriate threshold, among them computing levels of statistical significance, accepting only the top one percent of relationships, and selecting an arbitrary expression cutoff.ResultsWe apply spectral graph theory methods to develop a systematic method for threshold selection. Eigenvalues and eigenvectors are computed for a transformation of the adjacency matrix of the network constructed at various threshold values. From these, we use a basic spectral clustering method to examine the set of gene-gene relationships and select a threshold dependent upon the community structure of the data. This approach is applied to two well-studied microarray data sets from Homo sapiens and Saccharomyces cerevisiae.ConclusionThis method presents a systematic, data-based alternative to using more artificial cutoff values and results in a more conservative approach to threshold selection than some other popular techniques such as retaining only statistically-significant relationships or setting a cutoff to include a percentage of the highest correlations.