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Childhood trauma is a well-established risk factor for psychosis, paranoia, and substance use, with cannabis being a modifiable environmental factor that exacerbates these vulnerabilities. This study examines the interplay between childhood trauma, cannabis use, and paranoia using standard tetrahydrocannabinol (THC) units as a comprehensive measure of cannabis exposure.
Methods
Data were derived from the Cannabis&Me study, an observational, cross-sectional, online survey of 4,736 participants. Childhood trauma was assessed using a modified Childhood Trauma Screen Questionnaire, while paranoia was measured via the Green Paranoid Thoughts Scale. Cannabis use was quantified using weekly standard THC units. Structural equation modeling (SEM) was employed to evaluate direct and indirect pathways between trauma, cannabis use, and paranoia.
Results
Childhood trauma was strongly associated with paranoia, particularly emotional, and physical abuse (β = 16.10, q < 0.001; β = 16.40, q < 0.001). Cannabis use significantly predicted paranoia (β = 0.009, q < 0.001). Interactions emerged between standard THC units and both emotional abuse (β = 0.011, q < 0.001) and household discord (β = 0.011, q < 0.001). SEM revealed a small but significant indirect effect of trauma on paranoia via cannabis use (β = 0.004, p = 0.017).
Conclusions
These findings highlight childhood trauma as a primary driver of paranoia, with cannabis use amplifying its effects. While trauma had a strong direct impact, cannabis played a significant mediating role. Integrating standard THC units into psychiatric research and clinical assessments may enhance risk detection and refine intervention strategies, particularly for childhood trauma-exposed individuals.
As historic drought conditions become more common in western North America, Late Quaternary hydroclimate records become vital for putting present anthropogenic conditions into a longer-term context. Here, we establish a high-resolution record of drought for the eastern Sierra Nevada (California) using lacustrine carbonates from well-dated sediment cores. We used oxygen and carbon stable-isotope ratios, combined with high-resolution scanning X-ray fluorescence counts of calcium (Ca) and titanium (Ti), to reconstruct the drought record over the last 4600 years in June Lake. We found elevated δ18O and δ13C carbonate isotope values coinciding with peaks in both total inorganic carbon and Ca/Ti, suggesting enhanced carbonate precipitation in response to evaporative concentration of lake water. At least six intervals of prolonged (centennial-scale) carbonate deposition were identified, including three pulses during the Late Holocene Dry Period (LHDP; ~3500–2000 cal yr BP), the Medieval Climate Anomaly (~1200–800 cal yr BP), and the Current Warm Period, which began around 100 cal yr BP. This record highlights the complexities of the LHDP, an interval that was more variable at June Lake than has been previously described in regional records.
The association between cannabis and psychosis is established, but the role of underlying genetics is unclear. We used data from the EU-GEI case-control study and UK Biobank to examine the independent and combined effect of heavy cannabis use and schizophrenia polygenic risk score (PRS) on risk for psychosis.
Methods
Genome-wide association study summary statistics from the Psychiatric Genomics Consortium and the Genomic Psychiatry Cohort were used to calculate schizophrenia and cannabis use disorder (CUD) PRS for 1098 participants from the EU-GEI study and 143600 from the UK Biobank. Both datasets had information on cannabis use.
Results
In both samples, schizophrenia PRS and cannabis use independently increased risk of psychosis. Schizophrenia PRS was not associated with patterns of cannabis use in the EU-GEI cases or controls or UK Biobank cases. It was associated with lifetime and daily cannabis use among UK Biobank participants without psychosis, but the effect was substantially reduced when CUD PRS was included in the model. In the EU-GEI sample, regular users of high-potency cannabis had the highest odds of being a case independently of schizophrenia PRS (OR daily use high-potency cannabis adjusted for PRS = 5.09, 95% CI 3.08–8.43, p = 3.21 × 10−10). We found no evidence of interaction between schizophrenia PRS and patterns of cannabis use.
Conclusions
Regular use of high-potency cannabis remains a strong predictor of psychotic disorder independently of schizophrenia PRS, which does not seem to be associated with heavy cannabis use. These are important findings at a time of increasing use and potency of cannabis worldwide.
The general public and scientific community alike are abuzz over the release of ChatGPT and GPT-4. Among many concerns being raised about the emergence and widespread use of tools based on large language models (LLMs) is the potential for them to propagate biases and inequities. We hope to open a conversation within the environmental data science community to encourage the circumspect and responsible use of LLMs. Here, we pose a series of questions aimed at fostering discussion and initiating a larger dialogue. To improve literacy on these tools, we provide background information on the LLMs that underpin tools like ChatGPT. We identify key areas in research and teaching in environmental data science where these tools may be applied, and discuss limitations to their use and points of concern. We also discuss ethical considerations surrounding the use of LLMs to ensure that as environmental data scientists, researchers, and instructors, we can make well-considered and informed choices about engagement with these tools. Our goal is to spark forward-looking discussion and research on how as a community we can responsibly integrate generative AI technologies into our work.
Previous research established that white matter hyperintensities (WMH), a biomarker of small vessel cerebrovascular disease, are strong predictors of cognitive function in older adults and associated with clinical presentation of Alzheimer’s disease (AD), particularly when distributed in posterior brain regions. Secondary prevention clinical trials, such as the Anti-Amyloid Treatment in Asymptomatic Alzheimer’s (A4) study, target amyloid accumulation in asymptomatic amyloid positive individuals, but it is unclear the extent to which small vessel cerebrovascular disease accounts for performance on the primary cognitive outcomes in these trials. The purpose of this study was to examine the relationship between regional WMH volume and performance on the Preclinical Alzheimer Cognitive Composite (PACC) among participants screened for participation in the A4 trial. We also determined whether the association between WMH and cognition is moderated by amyloid positivity status.
Participants and Methods:
We assessed demographic, amyloid PET status, cognitive screening, and raw MRI data for participants in the A4 trial and quantitated regional (by cerebral lobe) WMH volumes from T2-weighted FLAIR in amyloid positive and amyloid negative participants at screening. Cognition was assessed using PACC scores, a z-score sum of four cognitive tests: The Mini-Mental State Examination (MMSE), the Free and Cued Selective Reminding Test, Logical Memory Test, and Digit Symbol Substitution Test. We included 1329 amyloid positive and 329 amyloid negative individuals (981 women; mean age=71.79 years; mean education=16.58 years) at the time of the analysis. The sample included Latinx (n=50; 3%), non-Latinx (n=1590; 95.9%), or unspecified ethnicity (n=18; 1.1%) individuals who identified as American Indian/Alaskan Native (n=7; 0.4%), Asian (n=38; 2.3%), Black/African American (n=41; 2.5%), White (n=1551 ; 93.5%), or unspecified (n=21; 1.3%) race. We first examined the associations of total and regional WMH volume and amyloid positivity on PACC scores (the primary cognitive outcome measure for A4) using separate general linear models and then determined whether amyloid positivity status and regional WMH statistically interacted for those WMH regions that showed significant main effects.
Results:
Both increased WMH, in the frontal and parietal lobes particularly, and amyloid positivity were independently associated with poorer performance on the PACC, with similar magnitude. In subsequent models, WMH volume did not interact with amyloid positivity status on PACC scores.
Conclusions:
Regionally distributed WMH are independently associated with cognitive functioning in typical participants enrolled in a secondary prevention clinical trial for AD. These effects are of similar magnitude to the effects of amyloid positivity on cognition, highlighting the extent to which small vessel cerebrovascular disease potentially drives AD-related cognitive profiles. Measures of small vessel cerebrovascular disease should be considered explicitly when evaluating outcomes in trials, both as potential effect modifiers and as possible targets for intervention or prevention. The findings from this study cannot be generalized widely, as the participants are not representative of the overall population.
Childhood adversity and cannabis use are considered independent risk factors for psychosis, but whether different patterns of cannabis use may be acting as mediator between adversity and psychotic disorders has not yet been explored. The aim of this study is to examine whether cannabis use mediates the relationship between childhood adversity and psychosis.
Methods
Data were utilised on 881 first-episode psychosis patients and 1231 controls from the European network of national schizophrenia networks studying Gene–Environment Interactions (EU-GEI) study. Detailed history of cannabis use was collected with the Cannabis Experience Questionnaire. The Childhood Experience of Care and Abuse Questionnaire was used to assess exposure to household discord, sexual, physical or emotional abuse and bullying in two periods: early (0–11 years), and late (12–17 years). A path decomposition method was used to analyse whether the association between childhood adversity and psychosis was mediated by (1) lifetime cannabis use, (2) cannabis potency and (3) frequency of use.
Results
The association between household discord and psychosis was partially mediated by lifetime use of cannabis (indirect effect coef. 0.078, s.e. 0.022, 17%), its potency (indirect effect coef. 0.059, s.e. 0.018, 14%) and by frequency (indirect effect coef. 0.117, s.e. 0.038, 29%). Similar findings were obtained when analyses were restricted to early exposure to household discord.
Conclusions
Harmful patterns of cannabis use mediated the association between specific childhood adversities, like household discord, with later psychosis. Children exposed to particularly challenging environments in their household could benefit from psychosocial interventions aimed at preventing cannabis misuse.
While cannabis use is a well-established risk factor for psychosis, little is known about any association between reasons for first using cannabis (RFUC) and later patterns of use and risk of psychosis.
Methods
We used data from 11 sites of the multicentre European Gene-Environment Interaction (EU-GEI) case–control study. 558 first-episode psychosis patients (FEPp) and 567 population controls who had used cannabis and reported their RFUC.
We ran logistic regressions to examine whether RFUC were associated with first-episode psychosis (FEP) case–control status. Path analysis then examined the relationship between RFUC, subsequent patterns of cannabis use, and case–control status.
Results
Controls (86.1%) and FEPp (75.63%) were most likely to report ‘because of friends’ as their most common RFUC. However, 20.1% of FEPp compared to 5.8% of controls reported: ‘to feel better’ as their RFUC (χ2 = 50.97; p < 0.001). RFUC ‘to feel better’ was associated with being a FEPp (OR 1.74; 95% CI 1.03–2.95) while RFUC ‘with friends’ was associated with being a control (OR 0.56; 95% CI 0.37–0.83). The path model indicated an association between RFUC ‘to feel better’ with heavy cannabis use and with FEPp-control status.
Conclusions
Both FEPp and controls usually started using cannabis with their friends, but more patients than controls had begun to use ‘to feel better’. People who reported their reason for first using cannabis to ‘feel better’ were more likely to progress to heavy use and develop a psychotic disorder than those reporting ‘because of friends’.
Illicit substance use is dangerous in both acute and chronic forms, frequently resulting in lethal poisoning, addiction, and other negative consequences. Similar to research in other psychiatric conditions, whose ultimate goal is to enable effective prevention and treatment, studies in substance use are focused on factors elevating the risk for the disorder. The rapid growth of the substance use problem despite the effort invested in fighting it, however, suggests the need in changing the research approach. Instead of attempting to identify risk factors, whose neutralization is often infeasible if not impossible, it may be more promising to systematically reverse the perspective to the factors enhancing the aspect of liability to disorder that shares the same dimension but is opposite to risk, that is, resistance to substance use. Resistance factors, which enable the majority of the population to remain unaffected despite the ubiquity of psychoactive substances, may be more amenable to translation. While the resistance aspect of liability is symmetric to risk, the resistance approach requires substantial changes in sampling (high-resistance rather than high-risk) and using quantitative indices of liability. This article provides an overview and a practical approach to research in resistance to substance use/addiction, currently implemented in a NIH-funded project. The project benefits from unique opportunities afforded by the data originating from two longitudinal twin studies, the Virginia Twin Study of Adolescent and Behavioral Development and the Minnesota Twin Family Study. The methodology described is also applicable to other psychiatric disorders.
This study provides the first focused investigation of rudist bivalves from the Upper Cretaceous of the Gulf Coastal Plain (GCP) in the southern US and previously undescribed specimens from the Flor de Alba Limestone Member of the Pozas Formation in Puerto Rico. Identified rudists from the GCP comprise the Monopleuridae, including Gyropleura, as well as Radiolitidae, including Biradiolites cardenasensi, Durania maxima, Guanacastea jamaicensis, Radiolites acutocostata, and Sauvagesia. Integrating rudist occurrences within well-established GCP biostratigraphy allows for extension of upper ranges of D. maxima and R. acutocostata into the late Campanian, and extension of the lower ranges of B. cardenasensis and G. jamaicensis into the early Campanian. Identified rudists from Puerto Rico comprise the Hippuritidae and include Barrettia monilifera, which supports the age of the Flor de Alba Limestone Member of the Pozas Formation as middle Campanian. Combined taxonomic, biostratigraphic, and paleobiogeographic analyses indicate there is no rudist fauna endemic to the GCP, and the region marks the northeastern range of the Caribbean genera Biradiolites, Durania, Guanacastea, Gyropleura, Radiolites, and Sauvagesia during the Campanian and Maastrichtian. The new occurrences help inform future updates of Late Cretaceous sea surface-current reconstructions for the Caribbean and Western Interior Seaway, USA.
To investigate a cluster of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in employees working on 1 floor of a hospital administration building.
Methods:
Contact tracing was performed to identify potential exposures and all employees were tested for SARS-CoV-2. Whole-genome sequencing was performed to determine the relatedness of SARS-CoV-2 samples from infected personnel and from control cases in the healthcare system with coronavirus disease 2019 (COVID-19) during the same period. Carbon dioxide levels were measured during a workday to assess adequacy of ventilation; readings >800 parts per million (ppm) were considered an indication of suboptimal ventilation. To assess the potential for airborne transmission, DNA-barcoded aerosols were released, and real-time polymerase chain reaction was used to quantify particles recovered from air samples in multiple locations.
Results:
Between December 22, 2020, and January 8, 2021, 17 coworkers tested positive for SARS-CoV-2, including 13 symptomatic and 4 asymptomatic individuals. Of the 5 cluster SARS-CoV-2 samples sequenced, 3 were genetically related, but these employees denied higher-risk contacts with one another. None of the sequences from the cluster were genetically related to the 17 control sequences of SARS-CoV-2. Carbon dioxide levels increased during a workday but never exceeded 800 ppm. DNA-barcoded aerosol particles were dispersed from the sites of release to locations throughout the floor; 20% of air samples had >1 log10 particles.
Conclusions:
In a hospital administration building outbreak, sequencing of SARS-CoV-2 confirmed transmission among coworkers. Transmission occurred despite the absence of higher-risk exposures and in a setting with adequate ventilation based on monitoring of carbon dioxide levels.
Numerous theories posit different core features to borderline personality disorder (BPD). Recent advances in network analysis provide a method of examining the relative centrality of BPD symptoms, as well as examine the replicability of findings across samples. Additionally, despite the increase in research supporting the validity of BPD in adolescents, clinicians are reluctant to diagnose BPD in adolescents. Establishing the replicability of the syndrome across adolescents and adults informs clinical practice and research. This study examined the stability of BPD symptom networks and centrality of symptoms across samples varying in age and clinical characteristics.
Methods
Cross-sectional analyses of BPD symptoms from semi-structured diagnostic interviews from the Collaborative Longitudinal Study of Personality Disorders (CLPS), the Methods to Improve Diagnostic Assessment and Service (MIDAS) study, and an adolescent clinical sample. Network attributes, including edge (partial association) strength and node (symptom) expected influence, were compared.
Results
The three networks were largely similar and strongly correlated. Affective instability and identity disturbance emerged as relatively central symptoms across the three samples, and relationship difficulties across adult networks. Differences in network attributes were more evident between networks varying both in age and in BPD symptom severity level.
Conclusions
Findings highlight the relative importance of affective, identity, and relationship symptoms, consistent with several leading theories of BPD. The network structure of BPD symptoms appears generally replicable across multiple large samples including adolescents and adults, providing further support for the validity of the diagnosis across these developmental phases.
To evaluate whether incorporating mandatory prior authorization for Clostridioides difficile testing into antimicrobial stewardship pharmacist workflow could reduce testing in patients with alternative etiologies for diarrhea.
Design:
Single center, quasi-experimental before-and-after study.
Setting:
Tertiary-care, academic medical center in Ann Arbor, Michigan.
Patients:
Adult and pediatric patients admitted between September 11, 2019 and December 10, 2019 were included if they had an order placed for 1 of the following: (1) C. difficile enzyme immunoassay (EIA) in patients hospitalized >72 hours and received laxatives, oral contrast, or initiated tube feeds within the prior 48 hours, (2) repeat molecular multiplex gastrointestinal pathogen panel (GIPAN) testing, or (3) GIPAN testing in patients hospitalized >72 hours.
Intervention:
A best-practice alert prompting prior authorization by the antimicrobial stewardship program (ASP) for EIA or GIPAN testing was implemented. Approval required the provider to page the ASP pharmacist and discuss rationale for testing. The provider could not proceed with the order if ASP approval was not obtained.
Results:
An average of 2.5 requests per day were received over the 3-month intervention period. The weekly rate of EIA and GIPAN orders per 1,000 patient days decreased significantly from 6.05 ± 0.94 to 4.87 ± 0.78 (IRR, 0.72; 95% CI, 0.56–0.93; P = .010) and from 1.72 ± 0.37 to 0.89 ± 0.29 (IRR, 0.53; 95% CI, 0.37–0.77; P = .001), respectively.
Conclusions:
We identified an efficient, effective C. difficile and GIPAN diagnostic stewardship approval model.
Several reports have recently highlighted the close association between anxiety disorders and bipolar disorder. These reports have indicated a worse course for patients with such comorbidity, including more severe symptoms and poorer outcomes. Fewer studies, however, have closely looked at how social anxiety in particular impacts the clinical presentation and treatment-seeking behavior of people with bipolar disorder. The present report addresses this question using data from the Methods to Improve Diagnostic Assessment and Services (MIDAS) project, one of the largest ongoing clinical epidemiology studies in the United States with over 2,500 participants enrolled to date. Participants were outpatients seeking psychiatric treatment, all of whom underwent an extensive assessment via semi-structured interviews by highly trained diagnosticians. Patients with bipolar disorder and social anxiety (n = 85) were compared to patients with bipolar disorder alone (n = 150) on a series of clinical characteristics, including comorbidity, to determine how social anxiety impacts the clinical presentation of bipolar disorder. Results indicate that comorbid social anxiety is associated with a more severe clinical presentation. Follow-up analyses explored the extent to which this was due to social anxiety specifically versus comorbidity in general. Discussion focuses on how differences in presentation due to comorbid social anxiety and bipolar disorder are likely to impact treatment.
A recent systematic review found a high prevalence of violence and mental distress among women trafficked for sexual exploitation; no data were identified for trafficked men and children.
Objectives:
To describe the clinical characteristics of trafficked people in contact with a large inner city mental health service compared with a non-trafficked cohort.
Aims:
To investigate whether, compared with a non-trafficked cohort, trafficked people would be significantly more likely to have co-morbid disorders and have significantly smaller improvements in functioning at the end of an episode of care.
Methods:
Study population: mental health service users who had been trafficked for exploitation and a non-trafficked service user cohort matched for gender and age. Data source: The South London and Maudsley NHS Trust (SLaM) Biomedical Research Centre Case Register Interactive Search (CRIS) database of anonymised full patient records (2006–2012).
Results:
We identified case records of 135 people who had been trafficked. 104 (77%) were female; age at first SLaM contact ranged from 8 to 49 years (mean 23.6, SD 8.0). 38 (28%) of the trafficked service users received psychiatric care from an emergency department. Depression (28.1%, n = 38), PTSD (19.3%, n = 26), non-affective psychoses (12.6%, n = 17) were the most frequently recorded diagnoses among trafficked service users. Further analysis is in progress and scheduled for completion by March 2013.
Conclusions:
Significant numbers of trafficked people were seen in an inner-city mental health service; services therefore need to understand their complex needs.
Preoperative mechanical ventilation is associated with morbidity and mortality following CHD surgery, but prior studies lack a comprehensive analysis of how preoperative respiratory support mode and timing affects outcomes.
Methods:
We retrospectively collected data on children <18 years of age undergoing cardiac surgery at an academic tertiary care medical centre. Using multivariable regression, we examined the association between modes of preoperative respiratory support (nasal cannula, high-flow nasal cannula/noninvasive ventilation, or invasive mechanical ventilation), escalation of preoperative respiratory support, and invasive mechanical ventilation on the day of surgery for three outcomes: operative mortality, postoperative length of stay, and postoperative complications. We repeated our analysis in a subcohort of neonates.
Results:
A total of 701 children underwent 800 surgical procedures, and 40% received preoperative respiratory support. Among neonates, 243 patients underwent 253 surgical procedures, and 79% received preoperative respiratory support. In multivariable analysis, all modes of preoperative respiratory support, escalation in preoperative respiratory support, and invasive mechanical ventilation on the day of surgery were associated with increased odds of prolonged length of stay in children and neonates. Children (odds ratio = 3.69, 95% CI 1.2–11.4) and neonates (odds ratio = 8.97, 95% CI 1.31–61.14) on high-flow nasal cannula/noninvasive ventilation had increased odds of operative mortality compared to those on room air.
Conclusion:
Preoperative respiratory support is associated with prolonged length of stay and mortality following CHD surgery. Knowing how preoperative respiratory support affects outcomes may help guide surgical timing, inform prognostic conversations, and improve risk stratification models.
A sense of competency and confidence in disaster management is linked to response willingness and efficacy. This study assessed current health-care student disaster competency curricula and resultant confidence.
Methods:
A survey was sent to students and administrators in nurse practitioner (NP), master of public health (MPH), and medical/osteopathic schools (MD/DO), assessing curriculum coverage of 15 disaster management competencies (1-4, total 15-60), and confidence in performing 15 related behaviors (1-7, total 15-105). One-way analysis of variance with Tukey’s post-hoc and Mann-Whitney U-tests were used to examine group differences.
Results:
A total of 729 students and 72 administrators completed the survey. Low coverage of all topics was reported by both students and administrators (mean 24.4; SD 9.6). Among students, NP students (21.66 ± 8.56) scored significantly lower than MD/DO (23.32 ± 8.19; P < 0.001) and MPH students (26.58 ± 9.06; P < 0.001) on curriculum coverage. Both administrators and students expressed low confidence in competence, with students significantly lower (P < 0.001). NP students scored higher (63.12 ± 20.69; P < 0.001) than both MPH (54.85 ± 17.82) and MD/DO (51.17 ± 19.71; P < 0.001) students.
Conclusions:
Health-care students report low coverage of topics considered to be necessary disaster response competencies, as well as their confidence to execute functions. This may negatively impact willingness and ability of these professionals to respond effectively in a disaster.
Human trafficking is a crime and a human rights violation that involves various and simultaneous traumatic events (sexual and physical violence, coercion). Yet, it is unknown how the patterning of violence and coercion affects the mental health of female and male trafficking survivors.
Methods
We conducted a cross-sectional study using a sample of 1015 female and male survivors of trafficking who received post-trafficking assistance services in Cambodia, Thailand or Vietnam. We assessed symptoms of anxiety and depression with the Hopkins Symptoms Checklist and symptoms of post-traumatic stress disorder (PTSD) with the Harvard Trauma Questionnaire. Violence was measured with questions from the World Health Organization International Study on Women's Health. Latent class analysis (LCA) was used to identify distinct patterns of violence and coercion in females and males. Novel multi-step mixture modelling techniques were employed to assess the association of the emergent classes with anxiety, depression and PTSD in females and males.
Results
LCA identified two distinct classes of violence and coercion experiences in females (class I: severe sexual and physical violence and coercion (20%); class II: sexual violence and coercion (80%)) and males (class I: severe physical violence and coercion (41%); class II: personal coercion (59%)). Females in class I had a two-fold increase in the odds of anxiety (OR = 2.10; 95% CI: 1.57–2.81) and PTSD (OR = 2.07; 95% CI: 1.03–4.17) compared with females in class II, but differences in the prevalence of anxiety, depression and PTSD were not significant when comparing males in class I to class II.
Conclusions
Specific patterns of violence and coercion provide a more in-depth understanding of the role of gender in the experience of violence and coercion and its association with mental health in survivors of trafficking. This information could be useful to target comprehensive mental health services for female and male trafficking survivors.
Conodont fossils are highly valuable for Paleozoic biostratigraphy and for interpreting evolutionary change, but identifying and describing conodont morphologies, and characterizing gradual shape variation remain challenging. We used geometric morphometric (GM) analysis to conduct the first landmark-based morphometric analysis of the biostratigraphically useful conodont genus Neognathodus. Our objective is to assess whether previously defined morphotype groups are reliably distinct from one another. As such, we reevaluate patterns of morphologic change in Neognathodus P1elements, perform maximum-likelihood tests of evolutionary modes, and construct novel, GM-based biozonations through a Desmoinesian (Middle Pennsylvanian) section in the Illinois Basin. Our GM results record the entire spectrum of shape variability among Neognathodus morphotypes, thus alleviating the problem of documenting and classifying gradual morphologic transitions between morphotypes. Statistically distinct GM groups support previously established classifications of N. bassleri, N. bothrops, and N. roundyi. Statistically indistinct pairs of GM groups do not support literature designations of N. medadultimus and N. medexultimus, and N. dilatus and N. metanodosus, and we synonymize each pair. Maximum-likelihood tests of evolutionary modes provide the first statistical assessment of Neognathodus evolutionary models in the Desmoinesian. The most likely evolutionary models are an unbiased random walk or a general random walk. We name four distinct biozones through the Desmoinesian using GM results, and these align with previous biozonation structure based on the Neognathodus Index (NI), illustrating that Neognathodus-based biostratigraphic correlations would not change between GM or NI methods. The structural similarity between both biozonations showcases that determining GM-based biozones is not redundant, as this comparison validates using landmark-based GM work to construct viable biozonations for subsequent stratigraphic correlations. Although this study is limited to the Illinois Basin, our quantitative methodology can be applied broadly to test taxonomic designations of additional genera, interpret statistically robust evolutionary patterns, and construct valid biozones for this significant chordate group.
Fluid flow through a two-dimensional fracture network has been simulated using a discrete fracture model. The computed field-scale permeabilities were then compared to those obtained using an equivalent continuum approach in which the permeability of each grid block is first obtained by performing fine-scale simulations of flow through the fracture network within that region. In the equivalent continuum simulations, different grid-sizes were used, corresponding to N by N grids with N = 10, 40, 100 and 400. The field-scale permeabilities found from the equivalent continuum simulations were generally within 10% of the values found from the discrete fracture simulations. The discrepancies between the two approaches seemed to be randomly related to the grid size, as no convergence was observed as N increased. An interesting finding was that the equivalent continuum approach gave accurate results in cases where the grid block size was clearly smaller than the 'representative elementary volume'.