Intelligent electroactive material systems with self-adaptive mechanical memory and sequential logic.

By synthesizing the requisite functionalities of intelligence in an integrated material system, it may become possible to animate otherwise inanimate matter. A significant challenge in this vision is to continually sense, process, and memorize information in a decentralized way. Here, we introduce an approach that enables all such functionalities in a soft mechanical material system. By integrating nonvolatile memory with continuous processing, we develop a sequential logic-based material design framework. Soft, conductive networks interconnect with embedded electroactive actuators to enable self-adaptive behavior that facilitates autonomous toggling and counting. The design principles are scaled in processing complexity and memory capacity to develop a model 8-bit mechanical material that can solve linear algebraic equations based on analog mechanical inputs. The resulting material system operates continually to monitor the current mechanical configuration and to autonomously search for solutions within a desired error. The methods created in this work are a foundation for future synthetic general intelligence that can empower materials to autonomously react to diverse stimuli in their environment.

An improved pathway for autonomous bioluminescence imaging in eukaryotes.

The discovery of the bioluminescence pathway in the fungus Neonothopanus nambi enabled engineering of eukaryotes with self-sustained luminescence. However, the brightness of luminescence in heterologous hosts was limited by performance of the native fungal enzymes. Here we report optimized versions of the pathway that enhance bioluminescence by one to two orders of magnitude in plant, fungal and mammalian hosts, and enable longitudinal video-rate imaging.

The Dubai Definition and Diagnostic Criteria of Laryngopharyngeal Reflux: The IFOS Consensus.

OBJECTIVE: The objective of this work was to gather an international consensus group to propose a global definition and diagnostic approach of laryngopharyngeal reflux (LPR) to guide primary care and specialist physicians in the management of LPR. METHODS: Forty-eight international experts (otolaryngologists, gastroenterologists, surgeons, and physiologists) were included in a modified Delphi process to revise 48 statements about definition, clinical presentation, and diagnostic approaches to LPR. Three voting rounds determined a consensus statement to be acceptable when 80% of experts agreed with a rating of at least 8/10. Votes were anonymous and the analyses of voting rounds were performed by an independent statistician. RESULTS: After the third round, 79.2% of statements (N = 38/48) were approved. LPR was defined as a disease of the upper aerodigestive tract resulting from the direct and/or indirect effects of gastroduodenal content reflux, inducing morphological and/or neurological changes in the upper aerodigestive tract. LPR is associated with recognized non-specific laryngeal and extra-laryngeal symptoms and signs that can be evaluated with validated patient-reported outcome questionnaires and clinical instruments. The hypopharyngeal-esophageal multichannel intraluminal impedance-pH testing can suggest the diagnosis of LPR when there is >1 acid, weakly acid or nonacid hypopharyngeal reflux event in 24 h. CONCLUSION: A global consensus definition for LPR is presented to improve detection and diagnosis of the disease for otolaryngologists, pulmonologists, gastroenterologists, surgeons, and primary care practitioners. The approved statements are offered to improve collaborative research by adopting common and validated diagnostic approaches to LPR. LEVEL OF EVIDENCE: 5 Laryngoscope, 134:1614-1624, 2024.

Outcomes Among Malnourished Patients With Crohn's Disease Undergoing Elective Ileocecectomy: A Nationwide Analysis.

BACKGROUND: Crohn's patients' nutritional status can be suboptimal given disease pathophysiology; the effect of a malnourished state prior to elective surgery on post-operative outcomes remains to be more clearly elucidated. This study aims to characterize the effect of malnutrition on post-operative outcomes and readmission patterns for Crohn's patients undergoing elective ileocecectomy using a nationally representative cohort. METHODS: The colectomy-targeted National Surgical Quality Improvement Program Database (2016-2020) was used to identify patients with Crohn's disease without systemic complications who underwent elective ileocecectomy; emergency surgeries were excluded. Malnourished status was defined as pre-operative hypoalbuminemia <3.5 g/dL, weight loss >10% in 6 months, or body mass index <18.5 kg/m2 prior to surgery. RESULTS: Of 1464 patients (56% female) who met inclusion criteria, 1137 (78%) were well-nourished and 327 (22%) were malnourished. Post-operatively, malnourished patients had more organ space surgical site infections (SSI) (9% vs 4% nourished groups, P < .001) and more bleeding events requiring transfusion (9% vs 3% nourished, P < .001). 30-day unplanned readmission was higher in the malnourished group (14% vs 9% nourished, P = .032). Index admission length of stay was significantly longer in the malnourished group (4 days [3-7 days] vs the nourished cohort: 4 days [3-5 days], P < .001). DISCUSSION: Poor nutritional status is associated with organ space infections and bleeding as well as longer hospitalizations and more readmissions in Crohn's patients undergoing elective ileocecectomy. A detailed nutritional risk profile and nutritional optimization is important prior to elective surgery.

Disrupting the Repeat Domain of Premelanosome Protein (PMEL) Produces Dysamyloidosis and Dystrophic Ocular Pigment Reflective of Pigmentary Glaucoma.

Pigmentary glaucoma has recently been associated with missense mutations in PMEL that are dominantly inherited and enriched in the protein's fascinating repeat domain. PMEL pathobiology is intriguing because PMEL forms functional amyloid in healthy eyes, and this PMEL amyloid acts to scaffold melanin deposition. This is an informative contradistinction to prominent neurodegenerative diseases where amyloid formation is neurotoxic and mutations cause a toxic gain of function called "amyloidosis". Preclinical animal models have failed to model this PMEL "dysamyloidosis" pathomechanism and instead cause recessively inherited ocular pigment defects via PMEL loss of function; they have not addressed the consequences of disrupting PMEL's repetitive region. Here, we use CRISPR to engineer a small in-frame mutation in the zebrafish homolog of PMEL that is predicted to subtly disrupt the protein's repetitive region. Homozygous mutant larvae displayed pigmentation phenotypes and altered eye morphogenesis similar to presumptive null larvae. Heterozygous mutants had disrupted eye morphogenesis and disrupted pigment deposition in their retinal melanosomes. The deficits in the pigment deposition of these young adult fish were not accompanied by any detectable glaucomatous changes in intraocular pressure or retinal morphology. Overall, the data provide important in vivo validation that subtle PMEL mutations can cause a dominantly inherited pigment pathology that aligns with the inheritance of pigmentary glaucoma patient pedigrees. These in vivo observations help to resolve controversy regarding the necessity of PMEL's repeat domain in pigmentation. The data foster an ongoing interest in an antithetical dysamyloidosis mechanism that, akin to the amyloidosis of devastating dementias, manifests as a slow progressive neurodegenerative disease.

Implicit Assessment of Non-Suicidal Self-Injury: Group Differences in Temporal Stability of the Self-Injury Implicit Association Test (SI-IAT).

OBJECTIVE: We examine differences on the Self-Injury Implicit Association Test (SI-IAT) by history of non-suicidal self-injury (NSSI), in a test-retest design, to examine short-term temporal stability of SI-IAT scores. METHOD: Treatment-seeking participants (N = 113; 58% female; 89% White; Mage = 30.57) completed the SI-IAT and self-report measures at two time points (MTimeframe = 3.8 days). RESULTS: Data suggested NSSI (51% of the sample endorsed lifetime NSSI) was related to Time 1 (T1) identity and attitude, and affected stability of scores. T1 and T2 SI-IAT identity and attitude were more strongly related for participants with NSSI history. NSSI characteristics (recency; number of methods) affected stability. CONCLUSIONS: The short-term test-retest reliability of the SI-IAT is strong among those with NSSI history from T1 to T2. However, the SI-IATs use with participants without a history of NSSI was not supported beyond its established ability to differentiate between groups by NSSI history. This test may provide clinically-relevant assessment among those with a history of NSSI.

Participants with vs. without NSSI history respond differently on the SI-IATTemporal stability of SI-IAT performance is strong in a short timeframeResults supported the test-retest reliability of the SI-IAT in the target group.

Kinematics and energetics of foraging behavior in Rice's whales of the Gulf of Mexico.

Rorqual foraging behavior varies with species, prey type and foraging conditions, and can be a determining factor for their fitness. Little is known about the foraging ecology of Rice's whales (Balaenoptera ricei), an endangered species with a population of fewer than 100 individuals. Suction cup tags were attached to two Rice's whales to collect information on their diving kinematics and foraging behavior. The tagged whales primarily exhibited lunge-feeding near the sea bottom and to a lesser extent in the water-column and at the sea surface. During 6-10 min foraging dives, the whales typically circled their prey before executing one or two feeding lunges. Longer duration dives and dives with more feeding-lunges were followed by an increase in their breathing rate. The median lunge rate of one lunge per dive of both animals was much lower than expected based on comparative research on other lunge-feeding baleen whales, and may be associated with foraging on fish instead of krill or may be an indication of different foraging conditions. Both animals spent extended periods of the night near the sea surface, increasing the risk for ship strike. Furthermore, their circling before lunging may increase the risk for entanglement in bottom-longline fishing gear. Overall, these data show that Rice's whale foraging behavior differs from other lunge feeding rorqual species and may be a significant factor in shaping our understanding of their foraging ecology. Efforts to mitigate threats to Rice's whales will benefit from improved understanding of patterns in their habitat use and fine-scale ecology.

Critically endangered Rice's whales (Balaenoptera ricei) selectively feed on high-quality prey in the Gulf of Mexico.

Determining the drivers of prey selection in marine predators is critical when investigating ecosystem structure and function. The newly recognized Rice's whale (Balaenoptera ricei) is one of the most critically endangered large whales in the world and endemic to the industrialized Gulf of Mexico. Here, we investigated the drivers of resource selection by Rice's whales in relation to prey availability and energy density. Bayesian stable isotope (δ13C, δ15N) mixing models suggest that Rice's whales feed primarily on a schooling fish, Ariomma bondi (66.8% relative contribution). Prey selection using the Chesson's index revealed that active prey selection was found to be positive for three out of the four potential prey identified in the mixing model. A low degree of overlap between prey availability and diet inferred from the mixing model (Pianka Index: 0.333) suggests that prey abundance is not the primary driver of prey selection. Energy density data suggest that prey selection may be primarily driven by the energy content. Results from this study indicate that Rice's whales are selective predators consuming schooling prey with the highest energy content. Environmental changes in the region have the potential to influence prey species that would make them less available to Rice's whales.

An examination of theory-based suicidal ideation risk factors in college students with multiple marginalized identities.

Social marginalization increases the risk of suicidal ideation (SI) among individuals with diverse identities, yet research examining the effects of marginalization has focused on one identity. Emerging adulthood is a critical period of identity development and the age group with the highest rates of SI. Considering the challenges of living in potentially heterosexist, cissexist, racist, and sizeist environments, we tested whether possessing multiple marginalized identities was associated with severity of SI through factors proposed in the interpersonal-psychological theory (IPT) and the three-step theory (3ST) of suicide and if mediation paths were moderated by sex. A sample of 265 college students completed a cross-sectional online survey assessing SI and constructs related to IPT and 3ST. The number of marginalized identities was generated by adding minoritized sexual orientation, race/ethnicity other than non-Hispanic White, body mass index >25 kg/m2, sexual attraction to same sex but identified as heterosexual, and gender-fluid identity. In IPT multiple mediation analyses, possessing more marginalized identities was associated with SI severity through burdensomeness and hopelessness, but not belonging. Indirect paths through burdensomeness and belonging were moderated by sex. For 3ST, possessing more marginalized identities was associated with SI severity through hopelessness and psychological pain, but not social connection or meaning in life. Future research should consider intersecting social identities and test mechanisms by which multiply marginalized college students develop resilience to SI risk factors, such as support within their marginalized groups, to inform suicide assessment and intervention efforts on college campuses. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

An optimized bioluminescent substrate for non-invasive imaging in the brain.

Bioluminescence imaging (BLI) allows non-invasive visualization of cells and biochemical events in vivo and thus has become an indispensable technique in biomedical research. However, BLI in the central nervous system remains challenging because luciferases show relatively poor performance in the brain with existing substrates. Here, we report the discovery of a NanoLuc substrate with improved brain performance, cephalofurimazine (CFz). CFz paired with Antares luciferase produces greater than 20-fold more signal from the brain than the standard combination of D-luciferin with firefly luciferase. At standard doses, Antares-CFz matches AkaLuc-AkaLumine/TokeOni in brightness, while occasional higher dosing of CFz can be performed to obtain threefold more signal. CFz should allow the growing number of NanoLuc-based indicators to be applied to the brain with high sensitivity. Using CFz, we achieve video-rate non-invasive imaging of Antares in brains of freely moving mice and demonstrate non-invasive calcium imaging of sensory-evoked activity in genetically defined neurons.

Application of the Three-Step Ideation-to-Action Theory to Passive and Active Suicidal Ideation in College Students.

Background: Few studies have tested the three-step theory of suicide (3ST), particularly in college students, who have unique developmental experiences of connectedness and high rates of suicidal ideation (SI). This study tested if factors purported in the 3ST distinguish undergraduate students with no SI, passive SI, and active SI using two conceptualizations of connectedness: social connection and meaning in life. Methods: A sample of undergraduate students aged 18-26 from an urban university completed an online survey (n=265). Results: Results showed some support for the 3ST. Greater psychological pain increased likelihood of passive SI (OR=3.74, p<.001); the model accurately identified 36% of students with passive SI. Greater pain (OR=2.74, p=.01) and hopelessness (OR=17.17, p<.05) differentiated students with active SI from those without SI in social connection models. In meaning models, greater pain relative to meaning in life differentiated students with passive SI (OR=2.29, p<.01) and active SI (OR=1.81, p<.05) relative to no SI. Each model accurately identified 68% of students with active SI. No 3ST factors differentiated students with passive SI from those with active SI. Conclusions: There was limited applicability for 3ST in differentiating college students with passive SI from those with no SI or active SI, with better differentiation of students with active SI relative to no SI. Interventions for college students with passive and active SI could target psychological pain, foster hope, and cultivate meaning.

The inner junction protein CFAP20 functions in motile and non-motile cilia and is critical for vision.

Motile and non-motile cilia are associated with mutually-exclusive genetic disorders. Motile cilia propel sperm or extracellular fluids, and their dysfunction causes primary ciliary dyskinesia. Non-motile cilia serve as sensory/signalling antennae on most cell types, and their disruption causes single-organ ciliopathies such as retinopathies or multi-system syndromes. CFAP20 is a ciliopathy candidate known to modulate motile cilia in unicellular eukaryotes. We demonstrate that in zebrafish, cfap20 is required for motile cilia function, and in C. elegans, CFAP-20 maintains the structural integrity of non-motile cilia inner junctions, influencing sensory-dependent signalling and development. Human patients and zebrafish with CFAP20 mutations both exhibit retinal dystrophy. Hence, CFAP20 functions within a structural/functional hub centered on the inner junction that is shared between motile and non-motile cilia, and is distinct from other ciliopathy-associated domains or macromolecular complexes. Our findings suggest an uncharacterised pathomechanism for retinal dystrophy, and potentially for motile and non-motile ciliopathies in general.

Development of a rapid, simple, and sensitive point-of-care technology platform utilizing ternary NanoLuc.

Point-of-care tests are highly valuable in providing fast results for medical decisions for greater flexibility in patient care. Many diagnostic tests, such as ELISAs, that are commonly used within clinical laboratory settings require trained technicians, laborious workflows, and complex instrumentation hindering their translation into point-of-care applications. Herein, we demonstrate the use of a homogeneous, bioluminescent-based, split reporter platform that enables a simple, sensitive, and rapid method for analyte detection in clinical samples. We developed this point-of-care application using an optimized ternary, split-NanoLuc luciferase reporter system that consists of two small reporter peptides added as appendages to analyte-specific affinity reagents. A bright, stable bioluminescent signal is generated as the affinity reagents bind to the analyte, allowing for proximity-induced complementation between the two reporter peptides and the polypeptide protein, in addition to the furimazine substrate. Through lyophilization of the stabilized reporter system with the formulated substrate, we demonstrate a shelf-stable, all-in-one, add-and-read analyte-detection system for use in complex sample matrices at the point-of-care. We highlight the modularity of this platform using two distinct SARS-CoV-2 model systems: SARS-CoV-2 N-antigen detection for active infections and anti-SARS-CoV-2 antibodies for immunity status detection using chemically conjugated or genetically fused affinity reagents, respectively. This technology provides a simple and standardized method to develop rapid, robust, and sensitive analyte-detection assays with flexible assay formatting making this an ideal platform for research, clinical laboratory, as well as point-of-care applications utilizing a simple handheld luminometer.

Simple, Rapid Chemical Labeling and Screening of Antibodies with Luminescent Peptides.

Sensitive and selective detection assays are essential for the accurate measurement of analytes in both clinical and research laboratories. Immunoassays that rely on nonoverlapping antibodies directed against the same target analyte (e.g., sandwich enzyme-linked immunosorbent assays (ELISAs)) are commonly used molecular detection technologies. Use of split enzyme reporters has simplified the workflow for these traditionally complex assays. However, identifying functional antibody pairs for a given target analyte can be cumbersome, as it generally involves generating and screening panels of antibodies conjugated to reporters. Accordingly, we sought a faster and easier reporter conjugation strategy to streamline antibody screening. We describe here the development of such a method that is based on an optimized ternary NanoLuc luciferase. This bioluminescence complementation system is comprised of a reagent-based thermally stable polypeptide (LgTrip) and two small peptide tags (ß9 and ß10) with lysine-reactive handles for direct conjugation onto antibodies. These reagents enable fast, single-step, wash-free antibody labeling and sensitive functional screening. Simplicity, speed, and utility of the one-pot labeling technology are demonstrated in screening antibody pairs for the analyte interleukin-4. The screen resulted in the rapid development of a sensitive homogeneous immunoassay for this clinically relevant cytokine.

Acoustic localization, validation, and characterization of Rice's whale calls.

The recently named Rice's whale in the Gulf of Mexico is one of the most endangered whales in the world, and improved knowledge of spatiotemporal occurrence patterns is needed to support their recovery and conservation. Passive acoustic monitoring methods for determining spatiotemporal occurrence patterns require identifying the species' call repertoire. Rice's whale call repertoire remains unvalidated though several potential call types have been identified. This study uses sonobuoys and passive acoustic tagging to validate the source of potential call types and to characterize Rice's whale calls. During concurrent visual and acoustic surveys, acoustic-directed approaches were conducted to obtain visual verifications of sources of localized sounds. Of 28 acoustic-directed approaches, 79% led to sightings of balaenopterid whales, of which 10 could be positively identified to species as Rice's whales. Long-moan calls, downsweep sequences, and tonal-sequences are attributed to Rice's whales based on these matches, while anthropogenic sources are ruled out. A potential new call type, the low-frequency downsweep sequence, is characterized from tagged Rice's whale recordings. The validation and characterization of the Rice's whale call repertoire provides foundational information needed to use passive acoustic monitoring for better understanding and conservation of these critically endangered whales.

The distribution of manta rays in the western North Atlantic Ocean off the eastern United States.

In 2018, the giant manta ray was listed as threatened under the U.S. Endangered Species Act. We integrated decades of sightings and survey effort data from multiple sources in a comprehensive species distribution modeling (SDM) framework to evaluate the distribution of giant manta rays off the eastern United States, including the Gulf of Mexico. Manta rays were most commonly detected at productive nearshore and shelf-edge upwelling zones at surface thermal frontal boundaries within a temperature range of approximately 20-30 °C. SDMs predicted highest nearshore occurrence off northeastern Florida during April, with the distribution extending northward along the shelf-edge as temperatures warm, leading to higher occurrences north of Cape Hatteras, North Carolina from June to October, and then south of Savannah, Georgia from November to March as temperatures cool. In the Gulf of Mexico, the highest nearshore occurrence was predicted around the Mississippi River delta from April to June and again from October to November. SDM predictions will allow resource managers to more effectively protect manta rays from fisheries bycatch, boat strikes, oil and gas activities, contaminants and pollutants, and other threats.

Central Executive Network and Executive Function in Patients With Alzheimer's Disease and Healthy Individuals: Meta-Analysis of Structural and Functional MRI.

OBJECTIVE: The neural architecture of executive function is of interest given its utility as a transdiagnostic predictor of adaptive functioning. However, a gap exists in the meta-analytic literature assessing this relationship in neuropsychiatric populations, concordance between structural and functional architecture, and the relationship with neuropsychological assessment of executive function. Given the importance of the central executive network (CEN) in Alzheimer's disease, this population may be useful in understanding this relationship in Alzheimer's disease pathology. METHODS: A meta-analysis of studies (k=21) was conducted to elucidate the relationship between executive function and CEN for structural architecture (k=10; N=1,027) among patients with Alzheimer's disease (k=6; N=250) and healthy control subjects (HCs) (k=4; N=777) and for functional architecture (k=11; N=522) among patients with Alzheimer's disease (k=6; N=306) and HCs (k=5; N=216). Random-effects modeling was used to increase accuracy of conclusions about population means. RESULTS: Analyses revealed a positive brain-behavior relationship (pr=0.032, 95% CI=0.07, 0.54), although there was a lack of statistically significant heterogeneity between functional and structural neuroimaging (Q=9.89, p=0.971, I2=0.00%) and between the Alzheimer's and HC groups in functional (Q=8.18, p=0.612, I2=0.00%) and structural (Q=1.60, p=0.996, I2=0.00%) neuroimaging. Similarly, a lack of statistically significant heterogeneity was revealed between functional and structural neuroimaging among patients with Alzheimer's disease (Q=3.59, p=0.980, I2=0.00%) and HCs (Q=3.67, p=0.885, I2=0.00%). CONCLUSIONS: Structural and functional imaging in the CEN are predictive of executive function performance among patients with Alzheimer's disease and HCs. Regardless of how the CEN is affected, behavior is correlated to the degree to which the CEN is affected. Findings are significant in the context of methodological decisions in multimodal neuroimaging research.

Autosomal dominant non-syndromic hearing loss maps to DFNA33 (13q34) and co-segregates with splice and frameshift variants in ATP11A, a phospholipid flippase gene.

Sequencing exomes/genomes have been successful for identifying recessive genes; however, discovery of dominant genes including deafness genes (DFNA) remains challenging. We report a new DFNA gene, ATP11A, in a Newfoundland family with a variable form of bilateral sensorineural hearing loss (SNHL). Genome-wide SNP genotyping linked SNHL to DFNA33 (LOD = 4.77), a locus on 13q34 previously mapped in a German family with variable SNHL. Whole-genome sequencing identified 51 unremarkable positional variants on 13q34. Continuous clinical ascertainment identified several key recombination events and reduced the disease interval to 769 kb, excluding all but one variant. ATP11A (NC_000013.11: chr13:113534963G>A) is a novel variant predicted to be a cryptic donor splice site. RNA studies verified in silico predictions, revealing the retention of 153 bp of intron in the 3' UTR of several ATP11A isoforms. Two unresolved families from Israel were subsequently identified with a similar, variable form of SNHL and a novel duplication (NM_032189.3:c.3322_3327+2dupGTCCAGGT) in exon 28 of ATP11A extended exon 28 by 8 bp, leading to a frameshift and premature stop codon (p.Asn1110Valfs43Ter). ATP11A is a type of P4-ATPase that transports (flip) phospholipids from the outer to inner leaflet of cell membranes to maintain asymmetry. Haploinsufficiency of ATP11A, the phospholipid flippase that specially transports phosphatidylserine (PS) and phosphatidylethanolamine (PE), could leave cells with PS/PE at the extracellular side vulnerable to phagocytic degradation. Given that surface PS can be pharmaceutically targeted, hearing loss due to ATP11A could potentially be treated. It is also likely that ATP11A is the gene underlying DFNA33.

Metacognitive beliefs about uncontrollability relate most strongly to health anxiety among US-based non-Latinx White primary care patients: Comparing strength of relations with US-based non-Latinx Black and Latinx primary care patients.

Metacognitive beliefs have emerged as important to health anxiety, particularly beliefs that health-related thoughts are uncontrollable. Preliminary research examining generalized worry indicates uncontrollability beliefs relate more strongly to anxiety among US-based self-identifying White relative to Black college students. The present study sought to extend that line of research by examining if metacognitive beliefs about the uncontrollability of health-related thoughts differentially relate to health anxiety among self-identifying non-Latinx Black (n = 123), Latinx (n = 104) and non-Latinx White (n = 80) US-based primary care patients. As predicted, although positive associations were seen across all three groups, beliefs that health-related thoughts are uncontrollable more strongly related to health anxiety among White patients compared to both Black and Latinx patients. Those differential relations held in multivariate analyses while statistically controlling for positive depression screening status, generalized anxiety symptom severity and medical morbidity. Although the effect size surrounding the differential relations was small in magnitude, the present results further support the notion that metacognitive beliefs about uncontrollability relate less strongly to anxiety among US-based ethnoracial minorities compared to White individuals. Potential reasons for the differential relations are discussed, along with additional areas for future research.