Analysis of Genome Architecture during SCNT Reveals a Role of Cohesin in Impeding Minor ZGA.

Somatic cell nuclear transfer (SCNT) can reprogram a somatic nucleus to a totipotent state. However, the re-organization of 3D chromatin structure in this process remains poorly understood. Using low-input Hi-C, we revealed that, during SCNT, the transferred nucleus first enters a mitotic-like state (premature chromatin condensation). Unlike fertilized embryos, SCNT embryos show stronger topologically associating domains (TADs) at the 1-cell stage. TADs become weaker at the 2-cell stage, followed by gradual consolidation. Compartments A/B are markedly weak in 1-cell SCNT embryos and become increasingly strengthened afterward. By the 8-cell stage, somatic chromatin architecture is largely reset to embryonic patterns. Unexpectedly, we found cohesin represses minor zygotic genome activation (ZGA) genes (2-cell-specific genes) in pluripotent and differentiated cells, and pre-depleting cohesin in donor cells facilitates minor ZGA and SCNT. These data reveal multi-step reprogramming of 3D chromatin architecture during SCNT and support dual roles of cohesin in TAD formation and minor ZGA repression.

Organization of Chromosomal DNA by SMC Complexes.

Structural maintenance of chromosomes (SMC) complexes are key organizers of chromosome architecture in all kingdoms of life. Despite seemingly divergent functions, such as chromosome segregation, chromosome maintenance, sister chromatid cohesion, and mitotic chromosome compaction, it appears that these complexes function via highly conserved mechanisms and that they represent a novel class of DNA translocases.

Clamping of DNA shuts the condensin neck gate.

SignificanceDNA needs to be compacted to fit into nuclei and during cell division, when dense chromatids are formed for their mechanical segregation, a process that depends on the protein complex condensin. It forms and enlarges loops in DNA through loop extrusion. Our work resolves the atomic structure of a DNA-bound state of condensin in which ATP has not been hydrolyzed. The DNA is clamped within a compartment that has been reported previously in other structural maintenance of chromosomes (SMC) complexes, including Rad50, cohesin, and MukBEF. With the caveat of important differences, it means that all SMC complexes cycle through at least some similar states and undergo similar conformational changes in their head modules, while hydrolyzing ATP and translocating DNA.

Randomized trial of two maintenance doses of vitamin D in children with chronic kidney disease.

BACKGROUND: Correction of nutritional vitamin deficiency is recommended in children with chronic kidney disease (CKD). The optimal daily dose of vitamin D to achieve or maintain vitamin D sufficiency is unknown. METHODS: We conducted a phase III, double-blind, randomized trial of two doses of vitamin D3 in children ≥ 9 years of age with CKD stages 3-5 or kidney transplant recipients. Patients were randomized to 1000 IU or 4000 IU of daily vitamin D3 orally. We measured 25-hydroxvitamin D (25(OH)D) levels at baseline, 3 months and 6 months. The primary efficacy outcome was the percentage of patients who were vitamin D replete (25(OH)D ≥ 30 ng/mL) at 6 months. RESULTS: Ninety-eight patients were enrolled: 49 randomized into each group. Eighty (81.6%) patients completed the study and were analyzed. Baseline plasma 25(OH)D levels were ≥ 30 ng/mL in 12 (35.3%) and 12 (27.3%) patients in the 1000 IU and 4000 IU treatment groups, respectively. At 6 months, plasma 25(OH)D levels were ≥ 30 ng/mL in 33.3% (95% CI: 18.0-51.8%) and 74.4% (95% CI: 58.8-86.5%) in the 1000 IU and 4000 IU treatment groups, respectively (p = 0.0008). None of the patients developed vitamin D toxicity or hypercalcemia. CONCLUSIONS: In children with CKD, 1000 IU of daily vitamin D3 is unlikely to achieve or maintain a plasma 25(OH)D ≥ 30 ng/mL. In children with CKD stages 3-5, a dose of vitamin D3 4000 IU daily was effective in achieving or maintaining vitamin D sufficiency. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01909115.

The practice of participatory action research: Complicity, power and prestige in dialogue with the 'racialised mad'.

Mental health service users in the UK have become increasingly involved in research over the last 2 decades partly as a consequence of research governance. Ethnic minority service users, however, point to power imbalances stemming from marginalisation and discrimination creating barriers to knowledge co-production (Kalathil, J. (2013). Hard to reach? Racialised groups and mental health service user involvement.). Heavily influenced by Freire's liberatory education, participatory action research (PAR) repoliticises participation where those most affected by injustice are central in both producing knowledge about injustice and implementing solutions. Ethnic minority people with lived experience of 'severe mental illness' ('the racialised mad') were appointed as coresearchers to work with academic researchers on a qualitative study exploring ethnic inequalities in 'severe mental illness'. Drawing on Foucault's notion of power as relational, we focus on three key aspects of productive power: (1) relational engagement and reciprocity, (2) positioning coresearchers as authentic researchers and (3) adopting an ethic of care, to explore complicity and resistance in reproducing hierarchies of knowledge and power when attempting to create and sustain a PAR process for collective analysis, action and solidarity. We utilise retrospective and recorded reflections over the course of the project. Finally, we discuss the ethical and methodological implications for contemporary sociological research into health and illness.

Thermal Conductivity Enhancement in Ion-Irradiated Hydrogenated Amorphous Carbon Films.

Amorphous solids are traditionally assumed to set the lower bound to the vibrational thermal conductivity of a material due to the high degree of structural disorder. Here, were demonstrate the ability to increase the thermal conductivity of amorphous solids through ion irradiation, in turn, altering the bonding network configuration. We report on the thermal conductivity of hydrogenated amorphous carbon implanted with C+ ions spanning fluences of 3 × 1014-8.6 × 1014 cm-2 and energies of 10-20 keV. Time-domain thermoreflectance measurements of the films' thermal conductivities reveal significant enhancement, up to a factor of 3, depending upon the preirradiation composition. Films with higher initial hydrogen content provide the greatest increase, which is complemented by an increased stiffening and densification from the irradiation process. This enhancement in vibrational transport is unique when contrasted to crystalline materials, for which ion implantation is known to produce structural degradation and significantly reduced thermal conductivities.

Automated Dispensing Cabinet Functionality Expansion to Reduce Controlled Substance Inventory Discrepancies.

Background: Automated dispensing cabinets have the potential to create technology-induced errors that can arise during controlled substance medication dispensing. Despite enhancements made to the medication use process, the impact of ADC functionality on technology-induced controlled substance discrepancies have yet to be described. Objective: To evaluate the impact of ADC functionality expansion on technology-induced errors such as controlled substance discrepancies created during "blind inventory counts" and cassette dispensing errors. Methods: This quasi-experimental study was conducted over 18 months that evaluated the expanded use of dispensing cassettes within 8 ADCs at the University of Chicago Medicine. Unit-dose controlled substances with high usage were directed for inventory reassignment to cassettes. Controlled substance dispenses, blind inventory counts discrepancies and cassette dispensing errors were evaluated before and after cassette expansion. ADC discrepancy and Cassette Dispensing Error rates were calculated using 1-week segments across the study period. Results: Of the 64 040 dispenses during the study period, the proportion of cassette dispenses increased from 16% to 72% after cassette expansion. Controlled substance discrepancies decreased from 11 to 7 discrepancies for every 1000 dispenses (P < .0001). After cassette expansion, cassette dispensing errors increased to roughly 28 errors for every 1000 dispenses (P < .0001). Conclusion: Expansion of ADC functionality created opportunities for reduced technology-induced controlled substance discrepancy rates at the expense of increased cassette dispensing errors.

Identifying evidence of effectiveness in the co-creation of research: a systematic review and meta-analysis of the international healthcare literature.

BACKGROUND: To investigate and address the evidence gap on the effectiveness of co-creation/production in international health research. METHODS: An initial systematic search of previous reviews published by 22 July 2017 in Medline, Embase, PsycINFO, Scopus and Web of Science. We extracted reported aims, elements and outcomes of co-creation/production from 50 reviews; however, reviews rarely tested effectiveness against intended outcomes. We therefore checked the reference lists in 13 included systematic reviews that cited quantitative studies involving the public/patients in the design and/or implementation of research projects to conduct meta-analyses on their effectiveness using standardized mean difference (SMD). RESULTS: Twenty-six primary studies were included, showing moderate positive effects for community functions (SMD = 0.56, 95%CI = 0.29-0.84, n = 11) and small positive effects for physical health (SMD = 0.25, 95%CI = 0.07-0.42, n = 9), health-promoting behaviour (SMD = 0.14, 95%CI = 0.03-0.26, n = 11), self-efficacy (SMD = 0.34, 95%CI = 0.01-0.67, n = 3) and health service access/receipt (SMD = 0.36, 95%CI = 0.21-0.52, n = 12). Non-academic stakeholders that co-created more than one research stage showed significantly favourable mental health outcomes. However, co-creation was rarely extended to later stages (evaluation/dissemination), with few studies specifically with ethnic minority groups. CONCLUSIONS: The co-creation of research may improve several health-related outcomes and public health more broadly, but research is lacking on its longer term effects.

Where next for understanding race/ethnic inequalities in severe mental illness? Structural, interpersonal and institutional racism.

In this article we use the example of race/ethnic inequalities in severe mental illness to demonstrate the utility of a novel integrative approach to theorising the role of racism in generating inequality. Ethnic minority people in the UK are at much greater risk than White British people of being diagnosed with a severe - psychosis related - mental illness, and this is particularly the case for those with Black Caribbean or Black African origins. There is entrenched dispute about how we might understand the drivers of this inequality. To address this dispute we build on, and to a certain extent refine, established approaches to theorising structural and institutional racism, and integrate this within a theoretical framework that also incorporates racist/discriminatory interactions (interpersonal racism). We argue that this provides a conceptually robust and thorough analysis of the role of inter-related dimensions of racism in shaping risks of severe mental illness, access to care, and policy and practice responses. This analysis carries implications for a broader, but integrated, understanding of the fundamental drives of race/ethnic inequalities in health and for an anti-racism public health agenda.

Use of Medicare Claims Data for the Identification of Myocardial Infarction: The Reasons for Geographic And Racial Differences in Stroke Study.

OBJECTIVES: Assess the validity of Medicare claims for identifying myocardial infarction (MI). METHODS: We used data from 9951 Medicare beneficiaries 65 years and above in the Reasons for Geographic And Racial Differences in Stroke study. Between 2003 and 2012, 669 participants had an MI identified and adjudicated through study procedures (ie, the gold standard), and 552 had an overnight inpatient claim with a code for MI (ICD-9 code 410.x0 or 410.x1) in any discharge diagnosis position. RESULTS: Using Medicare claims with a discharge diagnosis code for MI in any position, the positive predictive value (PPV) was 84.3% [95% confidence interval (CI), 80.9%-87.3%] and the sensitivity was 49.0% (95% CI, 44.9%-53.1%). Sensitivity was lower for men (45.8%) versus women (55.1%), microsize MIs (13.7%) versus other MIs (64.7%), type 2 (30.9%), and 4-5 MIs (11.1%) versus type 1 MIs (76.6%), and MIs occurring in-hospital (28.8%) versus out-of-hospital (66.7%). Using Medicare claims with a code for MI in the primary discharge diagnosis position, the PPV was 89.7% (95% CI, 86.3%-92.5%) and sensitivity was 40.1% (95% CI, 36.1%-44.2%). The sensitivity of claims with a code for MI in the primary discharge diagnosis position was lower for microsize versus other MIs, type 2 and 4-5 MIs versus type 1 MIs and MIs occurring in-hospital versus out-of-hospital. Hazard ratios for MI associated with participant characteristics were similar using adjudicated MIs identified through study procedures or claims for MI without further adjudication. CONCLUSIONS: Medicare claims have a high PPV but low sensitivity for identifying MI and can be used to investigate individual-level characteristics associated with MI.

Methods of Responsibly Managing End-of-Life Foams and Plastics Containing Flame Retardants: Part II.

This is Part II of a review covering the wide range of issues associated with all aspects of the use and responsible disposal of foam and plastic wastes containing toxic or potentially toxic flame retardants. We identify basic and applied research needs in the areas of responsible collection, pretreatment, processing, and management of these wastes. In Part II, we explore alternative technologies for the management of halogenated flame retardant (HFR) containing wastes, including chemical, mechanical, and thermal processes for recycling, treatment, and disposal.

Methods of Responsibly Managing End-of-Life Foams and Plastics Containing Flame Retardants: Part I.

Flame retardants (FRs) are added to foams and plastics to comply with flammability standards and test requirements in products for household and industrial uses. When these regulations were implemented, potential health and environmental impacts of FR use were not fully recognized or understood. Extensive research in the past decades reveal that exposure to halogenated FRs, such as those used widely in furniture foam, is associated with and/or causally related to numerous health effects in animals and humans. While many of the toxic FRs have been eliminated and replaced by other FRs, existing products containing toxic or potentially toxic chemical FRs will remain in use for decades, and new products containing these and similar chemicals will permeate the environment. When such products reach the end of their useful life, proper disposal methods are needed to avoid health and ecological risks. To minimize continued human and environmental exposures to hazardous FR chemicals from discarded products, waste management technologies and processes must be improved. This review discusses a wide range of issues associated with all aspects of the use and responsible disposal of wastes containing FRs, and identifies basic and applied research needs in the areas of responsible collection, pretreatment, processing, and management of these wastes.

Copovidone-related Cutaneous Response in the Dog.

A cutaneous response (localized swelling and/or erythema of the skin) has been noted in dog toxicology studies in which multiple, unrelated compounds were administered orally with copovidone as a vehicle. The response has been noted in studies with 6 different test items that are structurally unrelated and span several different therapeutic indications spanning an approximate 6-year period (2009-2015). A factor common among the studies is the formulation-a copovidone amorphous solid dispersion (ASD). Cutaneous responses have not been observed in dogs administered non-ASD formulations of the same test items but have occasionally been noted in placebo (copovidone control) dogs. Polyvinylpyrrolidone (a polymer of one of the primary components of copovidone) has been reported to result in similar findings in dogs when administered by the intravenous route. Considerations for the role of copovidone and the potential role of histamine in the cutaneous changes are outlined.

Effect of team rank and player classification on activity profiles of elite wheelchair rugby players.

The aim of the current study was to establish which indicators of mobility are associated with successful wheelchair rugby performance and determine whether these indicators differed across classification. Data were collected from 11 international teams during 30 matches (353 match observations) using a radio-frequency-based, indoor tracking system across two tournaments. Players (n = 111) were first grouped by team rank as determined by their International Wheelchair Rugby Federation (IWRF) world ranking (LOW, MID, HIGH) and then into one of four groups based on their IWRF classification: Group I (0.5), Group II (1.0-1.5), Group III (2.0-2.5) and Group IV (3.0-3.5). The volume of activity (relative distance and mean speed), peak speed and time spent within classification-specific arbitrary speed zones were calculated for each individual. Although no differences were identified in the volume of activity, playing time was significantly reduced in LOW (34:51 ± 8:35) compared to MID (48:54 ± 0:51) and HIGH (45:38 ± 9:53), which was further supported by the greater number of substitutions performed by LOW. HIGH achieved greater peak speeds (3.55 ± 0.40 m · s-(1)) than LOW (3.27 ± 0.42 m · s(-1)) and MID (3.45 ± 0.41 m · s(-1)). Peak speed was further shown to be classification-dependent (P ≤ 0.005), whereby HIGH Groups III and IV players achieved greater peak speeds than LOW and MID. The time spent performing high-intensity activities was also greater in HIGH compared to LOW and MID, whilst further influenced by classification (P ≤ 0.0005). To conclude, peak speed and the ability to perform a greater number of high-intensity activities were associated with successful performance in wheelchair rugby.

The validity and reliability of a novel indoor player tracking system for use within wheelchair court sports.

The aim of the current study was to investigate the validity and reliability of a radio frequency-based system for accurately tracking athlete movement within wheelchair court sports. Four wheelchair-specific tests were devised to assess the system during (i) static measurements; (ii) incremental fixed speeds; (iii) peak speeds; and (iv) multidirectional movements. During each test, three sampling frequencies (4, 8 and 16 Hz) were compared to a criterion method for distance, mean and peak speeds. Absolute static error remained between 0.19 and 0.32 m across the session. Distance values (test (ii)) showed greatest relative error in 4 Hz tags (1.3%), with significantly lower errors seen in higher frequency tags (<1.0%). Relative peak speed errors of <2.0% (test (iii)) were revealed across all sampling frequencies in relation to the criterion (4.00 ± 0.09 m · s-(1)). Results showed 8 and 16 Hz sampling frequencies displayed the closest-to-criterion values, whilst intra-tag reliability never exceeded 2.0% coefficient of variation (% CV) during peak speed detection. Minimal relative distance errors (<0.2%) were also seen across sampling frequencies (test (iv)). To conclude, the indoor tracking system is deemed an acceptable tool for tracking wheelchair court match play using a tag frequency of 8 or 16 Hz.

Validity and reliability of an inertial sensor for wheelchair court sports performance.

The purpose of the current study was to determine the validity and reliability of an inertial sensor for assessing speed specific to athletes competing in the wheelchair court sports (basketball, rugby, and tennis). A wireless inertial sensor was attached to the axle of a sports wheelchair. Over two separate sessions, the sensor was tested across a range of treadmill speeds reflective of the court sports (1.0 to 6.0 m/s). At each test speed, ten 10-second trials were recorded and were compared with the treadmill (criterion). A further session explored the dynamic validity and reliability of the sensor during a sprinting task on a wheelchair ergometer compared with high-speed video (criterion). During session one, the sensor marginally overestimated speed, whereas during session two these speeds were underestimated slightly. However, systematic bias and absolute random errors never exceeded 0.058 m/s and 0.086 m/s, respectively, across both sessions. The sensor was also shown to be a reliable device with coefficients of variation (% CV) never exceeding 0.9 at any speed. During maximal sprinting, the sensor also provided a valid representation of the peak speeds reached (1.6% CV). Slight random errors in timing led to larger random errors in the detection of deceleration values. The results of this investigation have demonstrated that an inertial sensor developed for sports wheelchair applications provided a valid and reliable assessment of the speeds typically experienced by wheelchair athletes. As such, this device will be a valuable monitoring tool for assessing aspects of linear wheelchair performance.

Breathlessness Predicts Mortality in Adults: A Systematic Review and Meta-Analysis.

Breathlessness is a commonly encountered symptom, and although its relationship with mortality is well established for many conditions, less clear is this relationship in healthy adults. This systematic review and meta-analysis examines whether breathlessness is associated with mortality in a general population. This is important in understanding the impact of this common symptom on a patient's prognosis. This review was registered with PROSPERO (CRD42023394104). Medline, EMBASE, CINAHL and EMCARE were searched for the terms 'breathlessness' and 'survival' or 'mortality' on January 24, 2023. Longitudinal studies of >1,000 healthy adults comparing mortality between breathless and non-breathless controls were eligible for inclusion. If an estimate of effect size was provided, studies were included in the meta-analysis. Eligible studies underwent critical appraisal, data extraction and risk of bias assessment. A pooled effect size was estimated for the relationship between the presence of breathlessness and mortality and levels of severity of breathlessness and mortality. Of 1,993 studies identified, 21 were eligible for inclusion in the systematic review and 19 for the meta-analysis. Studies were of good quality with a low risk of bias, and the majority controlled for important confounders. Most studies identified a significant relationship between the presence of breathlessness and increased mortality. A pooled effect size was estimated, with the presence of breathlessness increasing the risk of mortality by 43% (risk ratio (RR): 1.43, 95% confidence interval (CI): 1.28-1.61). As breathlessness severity increased from mild to severe, mortality increased by 30% (RR: 1.30, 95% CI: 1.21-1.38) and 103%, respectively (RR: 2.03, 95% CI: 1.75-2.35). The same trend was seen when breathlessness was measured using the modified Medical Research Council (mMRC) Dyspnoea Scale: mMRC grade 1 conferred a 26% increased mortality risk (RR: 1.26, 95% CI: 1.16-1.37) compared with 155% for grade 4 (RR: 2.55, 95% CI: 1.86-3.50). We conclude that mortality is associated with the presence of breathlessness and its severity. The mechanism underlying this is unclear and may reflect the ubiquity of breathlessness as a symptom of many diseases.

What stroke symptoms tell us: association of risk factors and individual stroke symptoms in the REasons for Geographic And Racial Differences in Stroke (REGARDS) study.

BACKGROUND: Stroke symptoms are common among people without a history of stroke or transient ischemic attack; however, it is unknown if particular attention should be focused on specific symptoms for subgroups of patients. METHODS: Using baseline data from 26,792 REasons for Geographic And Racial Differences in Stroke (REGARDS) participants without a history of transient ischemic attack or stroke, we assessed the association between age, sex, race, current smoking, hypertension, and diabetes and the 6 stroke symptoms in the Questionnaire for Verifying Stroke-Free Status. RESULTS: The mean age of participants was 64.4 ± 9.4 years, 40.7% were black, and 55.2% were women. After multivariable adjustment, older persons more often reported an inability to understand (odds ratio [OR] 1.16 per 10 years older age; 95% confidence interval [CI] 1.07-1.25) and unilateral vision loss (OR 1.09; 95% CI 1.01-1.18) and less often reported numbness (OR 0.83; 95% CI 0.79-0.87) and weakness (OR 0.85; 95% CI 0.80-0.90). Women reported difficulty communicating more often than men (OR 1.36; 95% CI 1.19-1.56). The OR for blacks compared to whites for each of the 6 stroke symptoms was increased, markedly so for unilateral numbness (OR 1.97; 95% CI 1.81-2.16), unilateral weakness (OR 1.96; 95% CI 1.76-2.18), and inability to understand (OR 1.87; 95% CI 1.61-2.18). Current smoking, hypertension, and diabetes were associated with higher ORs for each stroke symptom. CONCLUSIONS: The association of risk factors with 6 individual stroke symptoms studied was not uniform, suggesting the need to emphasize individual stroke symptoms in stroke awareness campaigns when targeting populations defined by risk.

Creating Custom Digital Assistants for the Scientific Laboratory using the HelixAI Platform.

Voice technology and fully virtual digital assistants are becoming increasingly prevalent in many industries, including the scientific laboratory. This environment can greatly benefit from the use of hands-free digital assistants due to the fact that scientists regularly need access to tools and information while performing bench work. The use of a digital assistant in this environment has the potential to streamline laboratory work and reduce the chances of human error due to contamination and the context switching involved in moving between experiments and information storage media. Because the particular protocols and reagents used by each laboratory are often different, there is a need to create custom digital assistants for individual laboratories. In this technical brief we describe a custom software and web application, referred to as the HelixAI platform, that can be used to create digital assistants for individual scientific laboratories. Digital assistants created with this platform can be accessed through any Alexa-enabled smart speaker device. Here we describe the process by which labs can use this platform to create their own digital assistants, along with a description of the underlying technology. An assistant containing information from the scientific company New England Biolabs (NEB) has been created using this software and will serve as an example throughout this paper.

Medication discrepancy rates and sources upon nursing home intake: A prospective study.

BACKGROUND: Medication discrepancies at nursing home intake increase the risk of drug-related adverse events. Measuring discrepancy incidence rates and locating the origins of discrepancies can assist in identifying information exchange deficits for high-risk medications. OBJECTIVE: To determine class-specific discrepancy rates, to determine discordance between medication lists, and to explore patient and system-level factors associated with medication discrepancies discovered between the first and second medication reconciliations conducted at nursing home intake. METHODS: Medication discrepancy data were prospectively collected from four long-term care facilities over a 9-month period. Medication discrepancies were defined as mismatched prescribing orders between at least two medication history lists. Discrepancy locations were defined as the pairs or triads of facilities between which medication history lists were discordant. Unadjusted logistic regressions were used to identify medication classes with the highest discrepancy rates and patient factors significantly associated with any medication discrepancy. RESULTS: 40.8% of newly admitted or re-admitted residents and 6.3% of medications reviewed had at least one medication discrepancy discovered during the second medication reconciliation conducted at nursing home intake. Residents prescribed fewer than 14 medications were at less risk of discrepancies. Residents with Charlson Comorbidity Index of 5, COPD, HF, anemia or HTN were at greater risk of discrepancies. Respiratory and analgesic medications were twice as likely as other medication classes to be discrepant (OR = 2.2, 95% CI 1.2-4.4; OR = 2.2, 95% CI 1.3-3.5). Most discrepancies occurred between hospital and nursing home lists (44.9%), or between the hospital, nursing home, and community pharmacy lists (39.3%) CONCLUSIONS: Given the higher risk of discrepancies within respiratory or analgesics, transitions of care teams need to prioritize residents with respiratory conditions or pain. Although re-admitted residents' increased discrepancy risk is likely due to poorer health status, miscommunications across the nursing home, hospital and community pharmacy require further research to clarify system failures.