Contact Investigation Research Articles

High Tuberculosis Preventive Treatment Uptake and Completion Rates Using a Person-Centered Approach among Tuberculosis Household Contact in Yogyakarta.

Coverage of tuberculosis preventive treatment (TPT) in Indonesia is inadequate, and persons who start TPT often do not complete treatment. In 2020, Zero TB Yogyakarta implemented person-centered contact investigation and shorter TPT regimen provision in collaboration with primary health care centers. Between 1 January 2020 and 31 August 2022, we assessed eligibility for TPT among household contacts of persons with bacteriologically confirmed TB (index cases) and offered them a 3-month TPT regimen (3RH or 3HP). A dedicated nurse monitored contacts on TPT for treatment adherence and side effects every week in the first month and every two weeks in the next months. Contacts were also able to contact a nurse by phone or ask for home visits at any point if they had any concerns. A total of 1016 contacts were eligible for TPT: 772 (78.8%) started short regimen TPT with 706 (91.5%) completing their TPT. Side effects were reported in 26 (39%) of the non-completion group. We conclude that high rates of TPT uptake and completion among contacts assessed as eligible for TPT can be achieved through person-centered care and the use of shorter regimens. Side-effect monitoring and management while on TPT is vital for improving TPT completion.

Active close contact investigation of tuberculosis through computer-aided detection and stool Xpert MTB/RIF among people living in Oromia Region, Ethiopia (CADOOL Study): protocol for a prospective, cross-sectional study

IntroductionPulmonary tuberculosis (TB) is an infectious disease with high incidence in low-income countries (LICs); it remains one of the infectious diseases with the highest mortality in the world, especially in...

Preparation of the Thermoelement Surfaces and Investigation of Ohmic Film Contacts Formed on Them by Different Methods

Preparation of the Thermoelement Surfaces and Investigation of Ohmic Film Contacts Formed on Them by Different Methods

1882. Contact Investigation of Congenital Tuberculosis in a Neonatal Intensive Care Unit in South Korea

Abstract Background Congenital tuberculosis (TB) is uncommon and difficult to detect in neonates due to its nonspecific symptoms. We conducted a contact investigation of infants and healthcare workers (HCWs) exposed to a neonate with congenital TB in a neonatal ICU (NICU) in Korea. Methods A premature infant born was admitted to NICU on September 16, 2022. On October 24, the infant's mother was diagnosed with miliary TB, and infant’s sputum AFB stain showed 4 positive results. All NICU infants and HCWs during the same period were screened for active pulmonary TB using chest radiography (CXR) immediately. Exposed infants were evaluated with a TST and CXR three months after exposure. Interferon-Gamma Release Assay (IGRA) testing was performed on those with a positive TST or abnormal CXR finding. Prophylactic rifampin was provided to the exposed infants for 3 months, as index had isoniazid-resistant M. tuberculosis infection. Exposed HCWs underwent IGRA testing immediately after exposure (1st IGRA) and at 8 to 10 weeks post-exposure (2nd IGRA), and CXR was performed 6 months after exposure. Results Five out of 82 exposed infants had positive TST (≥ 10 mm) results, while all 31 infants who underwent IGRA testing had negative results. All five with positive TST had received BCG vaccination a median 105 days before. Of the 119 exposed HCWs, three had a conversion; two had negative results (on annual IGRA testing performed according to the national TB prevention Act) before exposure and positive at 1st IGRA test, and one had negative 1st IGRA test then positive 2nd IGRA test. None had active TB during 6-month follow-up. Conclusion We found that 6% of exposed infants had positive TST results and 0% had positive IGRA, while 2.5% of exposed HCWs had conversion. Considering the possibility of false positive TST results due to prior BCG vaccination, the chance of transmission to the infants would be 0%; otherwise, it would be 6.1%. Disclosures All Authors: No reported disclosures

Genomic transmission clusters and circulating lineages of Mycobacterium tuberculosis among refugees residing in refugee camps in Ethiopia

BackgroundUnderstanding the transmission dynamics of Mycobacterium tuberculosis (Mtb) could benefit the design of tuberculosis (TB) prevention and control strategies for refugee populations. Whole Genome Sequencing (WGS) has not yet been used to document the Mtb transmission dynamics among refugees in Ethiopia. We applied WGS to accurately identify transmission clusters and Mtb lineages among TB cases in refugee camps in Ethiopia. Method and designWe conducted a cross-sectional study of 610 refugees in refugee camps in Ethiopia presenting with symptoms of TB. WGS data of 67 isolates was analyzed using the Maximum Accessible Genome for Mtb Analysis (MAGMA) pipeline; iTol and FigTree were used to visualize phylogenetic trees, lineages, and the presence of transmission clusters. ResultsMtb culture-positive refugees originated from South Sudan (52/67, 77.6%), Somalia (9/67, 13.4%). Eritrea (4/67, 6%), and Sudan (2/67, 3%). The majority (52, 77.6%) of the isolates belonged to Mtb lineage (L) 3, and one L9 was identified from a Somalian refugee. The vast majority (82%) of the isolates were pan-susceptible Mtb, and none were multi-drug-resistant (MDR)-TB. Based on the 5-single nucleotide polymorphisms cutoff, we identified eight potential transmission clusters containing 23.9% of the isolates. Contact investigation confirmed epidemiological links with either family or social interaction within the refugee camps or with neighboring refugee camps. ConclusionFour lineages (L1, L3, L4, and L9) were identified, with the majority of strains being L3, reflecting the Mtb L3 dominance in South Sudan, where the majority of refugees originated from. Recent transmission among refugees was relatively low (24%), likely due to the short study period. The improved understanding of the Mtb transmission dynamics using WGS in refugee camps could assist in designing effective TB control programs for refugees.

Investigation of sub-stoichiometric MoOx hole-selective contacts for rear junction passivating contact silicon solar cells

Carrier-selective contacts play a crucial role in improving the performance of silicon solar cells by reducing recombination losses. This study explores the use of sub-stoichiometric molybdenum oxide (MoOx) as a hole-selective contact material deposited via thermal evaporation. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) analysis reveal diverse Mo–O bonding configurations and a low work function of ∼5.02 eV for the MoOx film. The passivation properties of a cell-like structure with local MoOx contact are found to be comparable to those of a structure with a full front passivation layer, as evidenced by an implied open-circuit voltage (iVoc) of 703.2 mV. However, the conversion efficiency of the solar cell with MoOx contact is limited to 16.5 %, with reduced external quantum efficiency (EQE) at UV and visible wavelengths. The study proposes that optimizing the MoOx front contact's work function and passivation characteristics could improve the solar cell's efficiency to 21.8 %. This research demonstrates the potential of sub-stoichiometric MoOx as a promising hole-selective contact for silicon solar cells, highlighting the factors influencing its performance.

First contact investigations and compliance to treatment in patients with uveitis.

To ascertain the pattern of investigations at first contact in uveitic patients and evaluate compliance to treatment. An observational study comprised of 201 uveitic patients presenting for the first time to our centre from January 2019 to June 2020. Detailed information regarding systemic investigations undertaken by specialists at the time of first contact and the cost of these investigations were reviewed on the first visit to our centre. Compliance with the treatment was determined and reasons behind non-compliance were evaluated on the first follow-up in patients who had no improvement in clinical signs and symptoms. The mean age of the study group was 35.35±14.1y and gender composition was 59.7% males and 40.3% females. Anterior uveitis was observed in 45.3% of patients, intermediate uveitis in 31.8% of patients, posterior uveitis in 14.9% of patients and panuveitis in 8.0% of patients. Association with a systemic disease was evident in 17.9% of patients. When compared with standard guidelines and uveitis patterns, systemic investigations were identified to be relevant only in 38.3% of patients. Non-compliance to treatment was documented in 22.4% of patients. Common reasons for non-compliance were inadequate counselling by the treating physician about treatment in 26.7% of patients and a busy schedule at work/school in 22.2% of patients. Significant number of investigations performed at first contact is found to be contrary to standard guidelines and are not contributory to the care. About a quarter of patients in this study are found to be non-compliant with the treatment. Compliance is more challenging to achieve in school-going children and working adults. The availability of comprehensive, periodically updated, evidence-based guidelines on the role of investigations and the use of trained counsellors may help to channelize proper evaluation and improve compliance to treatment, respectively, in patients with uveitis.

State Reporting Requirements for Involuntary Holds, Court-Ordered Guardianship, and the US National Firearm Background Check System

Firearm violence is a leading cause of death in the US. There is broad public agreement that individuals at high risk of perpetrating violence should not be allowed to purchase or possess firearms. The National Instant Criminal Background Check System (NICS) is a national system intended to stop firearm purchases or possession by prohibited persons, but there is heterogeneity in how states interact with and report data to NICS. To examine variability in state requirements for NICS reporting for mental health prohibitions. This cross-sectional study in the US reviewed current statutes for all 50 states and the District of Columbia (enacted through the 2021 legislative session) regarding reporting mental health prohibitions to NICS or state systems. Data were analyzed from October 2022 to April 2023. For each state, the following were recorded: reliance on Federal Bureau of Investigation vs state point of contact for NICS checks; regulation requiring or allowing reporting to NICS for 3 hypothetical cases; and details on reporting responsibility and time frame. The number of NICS listings for adjudicated mental health reasons was obtained, and state rates per 1000 population were calculated. To compare states, we developed 3 hypothetical cases of individuals with risk of firearm violence, whether possibly temporary (involuntary commitment for decompensated psychosis, or involuntary short-term psychiatric hold for suicidal ideation) or chronic and progressive (court-appointed guardianship for dementia). A total of 39 states required and 5 allowed reporting to NICS for court-ordered, involuntary psychiatric hospitalization. Thirteen states required and 5 allowed reporting to NICS when a court determines an individual is mentally incompetent to manage their affairs (with or without guardianship). Two states required NICS reporting for short-term emergency psychiatric holds. Five states and the District of Columbia had no legislation explicitly requiring or allowing NICS reporting in the 3 scenarios. In this cross-sectional study of state laws, there was substantial heterogeneity in NICS reporting requirements and lack of clarity around processes. This raises questions about the ability of NICS to be used to block firearm purchases or possession by individuals with court-identified high risk of perpetrating violence toward themselves or others.

EPIDEMIOLOGICAL CONTACT (EPICONTACT) INVESTIGATION OF COVID-19 AT ISLAMIC BOARDING SCHOOLS IN KUNINGAN REGENCY, INDONESIA

Introduction: COVID-19 has spread throughout the world with more than 61, 27 million patients infected, including in education clusters that implement boarding schools. Contact investigations on the cluster are necessary to control the spread of the virus. Aims: To describe the epidemiological contact pattern of investigation results in the Islamic Boarding School cluster in Kuningan Regency. Methods: The design of this study is descriptive with epidemiological approach. The population is all students of Pondok Pesantren X, as many as 164 students, a sample of 157 students who are positive for COVID-19, and research instrument for the COVID-19 outbreak is investigation form, the variables studied included age, gender, symptoms, duration of contact, number of contacts, number of contact groups and place of contact. Result: Univariate data analysis with epi-contact analysis show: sex: 33.3% male, 60.03% female, average age 15.05 years, the average number of contacts 3.25 people, the average number of male contacts 2.62 and female 3.39, number of male contact groups 41, number of female contact groups 91. Age of value p=0.037. Conclusions: Contact pattern conclusions are mostly in female with the number of contacts between 3-4 people and age is related to the number of contacts. Limiting contact when there is suspicion is necessary to prevent transmission.

Transmissibility and severity of COVID-19 in a humanitarian setting: First few X investigation of cases and contacts in Juba, South Sudan, 2020.

The first few 'X' (FFX) studies provide evidence to guide public health decision-making and resource allocation. The adapted WHO Unity FFX protocol for COVID-19 was implemented to gain an understanding of the clinical, epidemiological, virological and household transmission dynamics of the first cases of COVID-19 infection detected in Juba, South Sudan. Laboratory-confirmed COVID-19 cases were identified through the national surveillance system, and an initial visit was conducted with eligible cases to identify all close contacts. Consenting cases and close contacts were enrolled between June 2020 and December 2020. Demographic, clinical information and biological samples were taken at enrollment and 14-21 days post-enrollment for all participants. Twenty-nine primary cases and 82 contacts were included in the analyses. Most primary cases (n= 23/29, 79.3%) and contacts (n= 61/82, 74.4%) were male. Many primary cases (n= 18/29, 62.1%) and contacts (n= 51/82, 62.2%) were seropositive for SARS-CoV-2 at baseline. The secondary attack rate among susceptible contacts was 12.9% (4/31; 95% CI: 4.9%-29.7%). All secondary cases and most (72%) primary cases were asymptomatic. Reported symptoms included coughing (n= 6/29, 20.7%), fever or history of fever (n= 4/29, 13.8%), headache (n= 3/29, 10.3%) and shortness of breath (n= 3/29, 10.3%). Of 38 cases, two were hospitalised (5.3%) and one died (2.6%). These findings were used to develop the South Sudanese Ministry of Health surveillance and contract tracing protocols, informing local COVID-19 case definitions, follow-up protocols and data management systems. This investigation demonstrates that rapid FFX implementation is critical in understanding the emerging disease and informing response priorities.

Effectiveness of a community-based approach for the investigation and management of children with household tuberculosis contact in Cameroon and Uganda: a cluster-randomised trial

Globally, the uptake of tuberculosis-preventive treatment (TPT) among children with household tuberculosis contact remains low, partly due to the necessity of bringing children to health facilities for investigations. This study aimed to evaluate the effect on TPT initiation and completion of community-based approaches to tuberculosis contact investigations in Cameroon and Uganda. We did a parallel, cluster-randomised, controlled trial across 20 clusters (consisting of 25 district hospitals and primary health centres) in Cameroon and Uganda, which were randomised (1:1) to receive a community-based approach (intervention group) or standard-of-care facility-based approach to contact screening and management (control group). The community-based approach consisted of symptom-based tuberculosis screening of all household contacts by community health workers at the household, with referral of symptomatic contacts to local facilities for investigations. Initiation of TPT (3-month course of rifampicin-isoniazid) was done by a nurse in the household, and home visits for TPT follow-up were done by community health workers. Index patients were people aged 15 years or older with bacteriologically confirmed, drug-susceptible, pulmonary tuberculosis diagnosed less than 1 month before inclusion and who declared at least one child or young adolescent (aged 0-14 years) household contact. The primary endpoint was the proportion of declared child contacts in the TPT target group (those aged <5 years irrespective of HIV status, and children aged 5-14 years living with HIV) who commenced and completed TPT, assessed in the modified intention-to-treat population (excluding enrolled index patients and their contacts who did not fit the eligibility criteria). Descriptive cascade of care assessment and generalised linear mixed modelling were used for comparison. This study is registered with ClinicalTrials.gov (NCT03832023). The study included nine clusters in the intervention group (after excluding one cluster that did not enrol any index patients for >2 months) and ten in the control group. Between Oct 14, 2019 and Jan 13, 2022, 2894 child contacts were declared by 899 index patients with bacteriologically confirmed tuberculosis. Among all child contacts declared, 1548 (81·9%) of 1889 in the intervention group and 475 (47·3%) of 1005 in the control group were screened for tuberculosis. 1400 (48·4%) child contacts were considered to be in the TPT target group: 941 (49·8%) of 1889 in the intervention group and 459 (45·7%) of 1005 in the control group. In the TPT target group, TPT was commenced and completed in 752 (79·9%) of 941 child contacts in the intervention group and 283 (61·7%) of 459 in the control group (odds ratio 3·06 [95% CI 1·24-7·53]). A community-based approach using community health workers can significantly increase contact investigation coverage and TPT completion among eligible child contacts in a tuberculosis-endemic setting. Unitaid. For the French translation of the abstract see Supplementary Materials section.

Tuberculosis Case Detection and Guideline Adherence among Child Contacts in Switzerland: A Retrospective Observational Study

Background: Children exposed to a tuberculosis (TB) index case are at risk of TB infection and disease. Objectives: The aim of this study was to describe the proportion of child contacts who developed TB infection or disease after exposure and to assess the diagnostic pathways and adherence to current guidelines. Methods: Retrospective observational study including children ≤16 years of age who had contact to a TB index case between January 2019 and July 2021. Analysis was stratified by age groups 0–4, 5–11, and 12–16 years. Results: Of 401 TB-exposed children, data were available for 380 (95%). Of those, 7 (2%) were diagnosed with TB disease and 35 (9%) with TB infection. We identified several deviations in the management compared to recommendations in national Swiss guidelines: In the children aged 0–4 years, only 82% were examined with an immunodiagnostic test or a chest radiography within 2 weeks after last contact. Recommended prophylactic treatment was prescribed in 66% of the children only. In the children aged 5–11 years, 64% were tested with an immunodiagnostic test in a first examination and 75% in a second examination, 2 weeks and 2 months after last contact, respectively. Conclusions: Contact investigations of children exposed to a TB index case identified a significant proportion of children with TB infection and disease in a low TB incidence setting. We observed significant deviations from the guidelines in the contact investigations suggesting the need for improved implementation.

Strategi Intervensi untuk Mengeliminasi Kasus Tuberkulosis

This study aims to analyze tuberculosis intervention strategies in Southeast Asia. The method used is a systematic review. The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) as a guide and The Joanna Briggs Institute (JBI) were used to conduct quality assessment. Data were born in the Scopus, Science Direct, and Pubmed databases on articles published in the last five years. In the final review, ten papers were included. The research results show that the intervention strategy is divided into three categories: community-based support through health cadres, nutritional status support, and investigation of household contacts and early detection. In conclusion, efforts to eliminate TB cases require a full-scale strategy with evidence-based interventions in identifying risk factors, contact investigation, and successful treatment.&#x0D; &#x0D; Keywords: Southeast Asia, TB Elimination, İntervention, Strategy, Tuberculosis

Outcome of Candida auris contact investigations conducted in a 6 month period at a New York City hospital

Candida auris is a multidrug-resistant fungus that has led to health care-associated outbreaks globally. Contact investigations for new cases of Candida auris are a recommended infection prevention practice; however, there is limited knowledge and experience with such investigations. We describe our institution's experience from June 2018 through January 2019.

Investigation of dynamic contact between cold spray particles and substrate based on 2D SPH method

In cold spray, the study of the dynamic contact between the particle and the substrate in the high-velocity impact is essential during particle deposition. To entirely reveals the dynamic contact process, the SPH (Smoothed Particle Hydrodynamics) method is applied to virtual experiments to avoid the time-consuming and high costs in real experiments due to scale. In particular, an interface force model is proposed to completely describe the dynamic contact between the cold spray particles (CS particles) and substrate, which has the ability to eliminate the unphysical SPH particle penetration, rebounding phenomenon, and insufficient momentum transfer. The variation of the steady mean temperature of the CS particle surface with the initial velocity is analyzed and the critical velocity of particle deposition is successfully predicted. Furthermore, the effect of particle shapes on the deposition is discussed, which shows that the circular particles are more favourable to be deposited than the elliptical ones. The cold spray SPH model with the novel dynamic contact developed in this paper is in favor of understanding the mechanism of CS particles deposition and guiding the cold spray processes in a certain extent.

Modelling and experimental investigation of capsule-tumour contact for early bowel cancer detection

Tissue’s mechanical properties, such as stiffness, are critical biomarkers that could be utilised to detect early stages of malignant transformation and distinguish between healthy and abnormal tissues. This paper studied a new method by using a capsule robot to evaluate the stiffness of bowel tumour for early bowel cancer detection and staging. Hertz contact theory was used to model capsule-tumour contact in an intestinal environment. Both lateral and vertical contacts were performed with finite element (FE) and experimental validations. Young’s moduli of bowel tumours obtained by the proposed models were applied to FE models and then generated force–displacement curves to compare with experiments. Our comparative analyses show that FE results are in good agreement with experimental results. The proposed method can be potentially used in real time for detecting early bowel cancer by using a capsule robot when self-propelling in the bowel.

The Impact of Preventive Treatment for Multidrug- and Rifampin-Resistant Tuberculosis Exceeds Trial-Based Estimates.

Several clinical trials of tuberculosis preventive treatment (TPT) for household contacts of patients with multidrug- or rifampin-resistant tuberculosis (MDR/RR-TB) are nearing completion. The potential benefits of delivering TPT to MDR/RR-TB contacts extend beyond the outcomes that clinical trials can measure. We developed an agent-based, household-structured TB and MDR/RR-TB transmission model, calibrated to an illustrative setting in India. We simulated contact investigation in households of patients with MDR/RR-TB, comparing an MDR/RR-TPT regimen (assuming 6-month duration, 70% efficacy) and associated active case finding against alternatives of contact investigation without TPT or no household intervention. We simulated the TB and MDR/RR-TB incidence averted relative to placebo over 2 years, as measurable by a typical trial, as well as the incidence averted over a longer time horizon, in the broader population, and relative to no contact investigation. Observing TPT and placebo recipients for 2 years as in a typical trial, MDR/RR-TPT was measured to prevent 72% (interquartile range, 45%-100%) of incident MDR/RR-TB among recipients; the median number needed to treat (NNT) to prevent 1 MDR/RR-TB case was 73, compared to placebo. This NNT decreased to 54 with 13-18 years of observation, to 27 when downstream transmission effects were also considered, and to 12 when the effects of active TB screening were included by comparing to a no-household-contact-intervention scenario. If forthcoming trial results demonstrate efficacy, the long-term population impact of TPT for MDR/RR-TB-including the large effect of increased active TB detection among MDR/RR-TB contacts-could be much greater than suggested by trial outcomes alone.

Pediatric multi-drug-resistant tuberculosis in Germany – diagnostic and therapeutic challenges of an “orphan disease”

Delay in diagnosing multidrug-resistant tuberculosis (MDR-pTB) in children prolongs time to effective treatment. Data on risk factors for pediatric MDR from low-incidence countries are scarce. Retrospective nationwide case–control study to analyze MDR-pTB cases in Germany between 2010 and 2020 in comparison to a drug-susceptible (DS)-pTB group. We included 52 MDR cases (24 tuberculosis (TB), 28 TB infection (TBI); mean age 7.3 years) and 56 DS cases (31 TB, 26 TBI; mean age 7.9 years). Groups were similar for sex, household size, and migration background. Compared to the DS group, more children with MDR were born in the Commonwealth of Independent States (CIS) (22% MDR-pTB vs. 13% DS-pTB, n.s.) and had more MDR index cases (94% MDR-pTB, 5% DS-pTB, p < 0.001). The interval between first healthcare contact and initiation of effective therapy was significantly longer in MDR-pTB (47 days) than in DS-pTB (11 days, p < 0.001), correlating with disease progression. Treatment for MDR-pTB was successful in 74%, but 22% experienced long-term adverse effects (e.g., hepatopathy, hearing loss).Conclusions: Close contact to MDR cases or birth in MDR-TB-high-incidence countries are risk factors for MDR-pTB. Early identification of potential MDR index cases by contact investigation, and susceptibility testing in children from high-burden MDR-TB countries are essential for timely diagnosis and treatment, reducing the severity of disease and treatment side effects.Trial Registration: Deutsches Register Klinischer Studien (https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00023817), DRKS00023817, 2020–09-08.What is Known:•Management of children with MDR-TB remains challenging due to difficulties in diagnosing MDR-TB (lack of information on MDR index case, lack of microbiological confirmation in paucibacillary disease).•Choice of treatment regimen and monitoring of side effects.What is New:•Children with an MDR-TB index or born in a MDR-TB-high-incidence country are at higher risk of developing MDR-TB in a low incidence country.•The time lag to initiate treatment in MDR-TB is longer than in DS-TB and MDR-TB treatment involves a higher risk of adverse effects in longer treatment regimens especially with injectables.

A descriptive study on the potential transmission of COVID-19 to hospitalized patients from a nursery school affiliated with it

IntroductionDuring the epidemic of the Omicron variant of SARS-CoV-2, nosocomial transmissions from healthcare workers (HCWs) to patients occur frequently. The influence of COVID-19 on hospitalized patients from nursing schools affiliated with the hospitals is a concern but it had not been well studied. MethodsWe here describe COVID-19 outbreaks at the nursery school affiliated with an acute-care hospital, during the surges of the Omicron variants on the transmission of SARS-CoV-2 children as well as for the patients who were judged to be the close contacts of patients of COVID-19 by contact investigation by PCR testing. ResultsA total of 36 children and five caregivers were diagnosed with COVID-19 during the study period. Of the 206 preschoolers who had close contact with the infected persons, only 16 became positive (7.6%). Secondary transmission from the 36 preschool children to the parents as HCWs occurred in 19 (61%) out of 31 parents. Three hospitalized patients were judged to have unsafe contact with the infected HCWs but this did not result in their infections, making a total of zero transmission from the nursery school to the hospital. ConclusionsChildren at the nursery school are potential reservoirs for nosocomial transmissions at the affiliated hospital, but multiple practical measures might have prevented them to occur.

Nonlinear dynamic behaviors of angular contact ball bearing with waviness based on a synthetical multi-degree-of-freedom mathematical modelling

This paper proposes a synthetical multi-degree-of-freedom mathematical modelling for analyzing the dynamic characteristics of angular contact ball bearing with waviness subjected to the external load working conditions. The above multi-degree-of-freedom mathematical modelling is established based on nonlinear elastic Hertz contact theory and inner raceway control theory by employing improved Newton–Raphson iteration method; the validation of the established mathematical modelling is verified by comparing the presented results with the existing literature results. The above mathematical modelling has considered raceway waviness, ball waviness, bearing clearance, centrifugal force, gyroscopic moment, external loads, and rotating speed comprehensively. Firstly, the effects of waviness order and waviness amplitude on time-varying contact and stiffness characteristics of angular contact ball bearing are investigated systematically. Then, the influences of bearing clearance, rotating speed, axial force, radial force, and torque on the dynamic contact and stiffness characteristics of angular contact ball bearing with waviness are analyzed thoroughly. The main results show that the solution results of mathematical modelling have converged, respectively, when raceway waviness order increases to 25 and ball waviness order increases to 5; The variation tendencies of time-varying contact angle, contact force, and stiffness of angular contact ball bearing with waviness are aperiodic; The amplitudes of time-varying contact angle, contact force, and stiffness of angular contact ball bearing increase evidently with waviness amplitude increased; The bearing clearance has important influence on the contact angle and contact force of outer raceway and inner raceway, respectively; The effects of radial force and torque on contact and stiffness characteristics are consistent basically in the corresponding direction; The influences of axial force and rotating speed on the contact and stiffness characteristics are more remarkable compared with other factors. The investigations of contact and stiffness characteristics of angular contact ball bearing with waviness are helpful for the designation and manufacture of high precision angular contact ball bearing.