Last data update: Apr 22, 2024. (Total: 46599 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Rishi K [original query] |
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Two rotavirus outbreaks caused by genotype G2P[4] at large retirement communities: cohort studies.
Cardemil CV , Cortese MM , Medina-Marino A , Jasuja S , Desai R , Leung J , Rodriguez-Hart C , Villarruel G , Howland J , Quaye O , Tam KI , Bowen MD , Parashar UD , Gerber SI . Ann Intern Med 2012 157 (9) 621-31 BACKGROUND: Outbreaks of rotavirus gastroenteritis in elderly adults are reported infrequently but are often caused by G2P[4] strains. In 2011, outbreaks were reported in 2 Illinois retirement facilities. OBJECTIVE: To implement control measures, determine the extent and severity of illness, and assess risk factors for disease among residents and employees. DESIGN: Cohort studies using surveys and medical chart abstraction. SETTING: Two large retirement facilities in Cook County, Illinois. PATIENTS: Residents and employees at both facilities and community residents with rotavirus disease. MEASUREMENTS: Attack rates, hospitalization rates, and rotavirus genotype. RESULTS: At facility A, 84 of 324 residents (26%) were identified with clinical or laboratory-confirmed rotavirus gastroenteritis (median age, 84 years) and 11 (13%) were hospitalized. The outbreak lasted 7 weeks. At facility B, 90 case patients among 855 residents (11%) were identified (median age, 88 years) and 19 (21%) were hospitalized. The facility B outbreak lasted 9.3 weeks. Ill employees were identified at both locations. In each facility, attack rates seemed to differ by residential setting, with the lowest rates among those in more separated settings or with high baseline level of infection control measures. The causative genotype for both outbreaks was G2P[4]. Some individuals shed virus detected by enzyme immunoassay or genotyping reverse transcription polymerase chain reaction for at least 35 days. G2P[4] was also identified in 17 of 19 (89%) samples from the older adult community but only 15 of 40 (38%) pediatric samples. LIMITATION: Medical or cognitive impairment among residents limited the success of some interviews. CONCLUSION: Rotavirus outbreaks can occur among elderly adults in residential facilities and can result in considerable morbidity. Among older adults, G2P[4] may be of unique importance. Health professionals should consider rotavirus as a cause of acute gastroenteritis in adults. PRIMARY FUNDING SOURCE: None. |
Comparison of nanocomposite dispersion and distribution for several melt mixers
Veigel D , Rishi K , Okoli U , Beaucage G , Galloway JA , Campanelli H , Ilavsky J , Kuzmenko I , Fickenscher M . Polymer 2023 269 Breakup (dispersion) and distribution of nanoparticles are the chief hurdles towards taking advantage of nanoparticles in polymer nanocomposites for reinforcement, flame retardancy, conductivity, chromaticity, and other properties. Microscopy is often used to quantify mixing, but it has a limited field of view, does not average over bulk samples, and fails to address nano-particle hierarchical structures. Ultra-small-angle X-ray scattering (USAXS) can provide a macroscopic statistical average of nanoscale dispersion (breakup) and emergent hierarchical structure, as well as the distribution on the nanoscale. This work compares several common mixer geometries for carbon black-polystyrene nanocomposites. Two twin-screw extruder geometries, typical for industrial processing of melt blends, are compared with a laboratory-scale single screw extruder and a Banbury mixer. It is found that for a given mixer, nanoscale distribution increases following a van der Waals function using accumulated strain as an analogue for temperature while macroscopic distribution/dispersion, using microscopy, does not follow this dependency. Breakup and aggregation in dispersive mixing follow expected behavior on the nanoscale. Across these drastically different mixing geometries an unexpected dependency is observed for nanoscale distributive mixing (both nano and macroscopic) as a function of accumulated strain that may reflect a transition from distributive turbulent to dispersive laminar mixing as the mixing gap is reduced. © 2023 Elsevier Ltd |
Dispersion of modified fumed silica in elastomeric nanocomposites
Okoli Ugochukwu , Rishi Kabir , Beaucage Gregory , Kammler Hendrik K , McGlasson Alex , Chauby Michael , Narayanan Vishak , Grammens James , Kuppa Vikram K . Polymer 2023 264 125407 In polymer nanocomposites, surface modification of silica aggregates can shield Coulombic interactions that inhibit agglomeration and formation of a network of agglomerates. Surface modification is usually achieved with silane coupling agents although carbon-coating during pyrolytic silica production is also possible. Pyrogenic silica with varying surface carbon contents were dispersed in styrene-butadiene (SBR) rubber to explore the impact on hierarchical dispersion, the emergence of meso-scale structures, and the rheological response. Pristine pyrogenic silica aggregates at concentrations above a critical value (related to the Debye screening length) display correlated meso-scale structures and poor filler network formation in rubber nanocomposites due to the presence of silanol groups on the surface. In the present study, flame synthesized silica with sufficient surface carbon monolayers can mitigate the charge repulsion thereby impacting network structural emergence. The impact of the surface carbon on the van der Waals enthalpic attraction, a∗, is determined. The van der Waals model for polymer nanocomposites is drawn through an analogy between thermal energy, kBT, and the accumulated strain, γ. The rheological response of the emergent meso-scale structures depends on the surface density of both carbon and silanol groups. |
A scattering function for correlated lamellae
Camara M , Rishi K , Beaucage G , Sukumaran SK . Polymer 2021 237 Melt crystallized polymers display an emergent, multi-hierarchical, ordered structure made up of stacked lamellar single crystals that form fibrous or other meso structures which, in turn, form macroscopic crystallites. A dominant feature of small-angle scattering from these complex assemblies is a correlation peak associated with the stacking period. A new model-based function is proposed for small-angle scattering data from such correlated lamellar multi-hierarchical structures. Generally, routine use of scattering data has been limited to a 1-d analysis to determine the long period from Lorentz corrected data (I(q)q2 versus q). Fourier transforms of the data are sometimes used to determine the 1-d pairwise correlation function for the electron-density distribution which has been further analyzed in terms of the structure of these materials. A simple 1-d fitting model limited to infinite width 2-d sheets was introduced by Hermans (1944; Hosemann, 1950) [1,2] in the 1940s with some success. A new approach, the Unified Born-Green Function (UBG), is proposed that uses the Unified Function as adapted to correlated lamellar structures and incorporates a Born-Green description of one-dimensional correlations. The UBG fit allows quantification of the average lamellar aspect ratio, the local degree of crystallinity within a stack, quantification of the stacking versus non-stacking amorphous, and two types of disorder in addition to the stacking period and lamellar thickness. UBG can account for higher levels of structure such as crystalline domains in block copolymers and convoluted lamellar structure. The UBG fit is compared to the Hermans (1944; Hosemann, 1950) [1,2] and a hybrid-Hermans function. Fits to data sets from a wide range of polyethylene are shown ranging from molecular weight standard samples that are isothermally crystallized, to commercial HDPE quenched from the melt and a metallocene blown film sample. Several other examples from the literature are explored. It is shown that the Unified fit allows for new understanding of the impact of thermal and mechanical history, chain structure, fillers, nucleating agents, and additives on the crystalline structure and the resulting physical properties. Limitations of the UBG approach are noted. © 2021 Elsevier Ltd |
Severe outcomes are associated with genogroup 2 genotype 4 norovirus outbreaks: a systematic literature review.
Desai R , Hembree CD , Handel A , Matthews JE , Dickey BW , McDonald S , Hall AJ , Parashar UD , Leon JS , Lopman B . Clin Infect Dis 2012 55 (2) 189-93 BACKGROUND: Noroviruses are the most common cause of epidemic gastroenteritis, however, the relative impact of individual factors underlying severe illness are poorly understood. This report reviews published norovirus outbreak reports to quantify hospitalization and mortality rates and assess their relationship with outbreak setting, transmission route, and strain. METHODS: Between January 1993 and June 2011, 2435 non-duplicate articles were identified in PubMed, EMBASE, and Web of Knowledge using a string of terms related to "norovirus" and "outbreak". Inclusion criteria included outbreaks with a minimum of two ill persons with a common exposure and at least one RT-PCR-confirmed case of norovirus disease. Univariate analyses were performed and multivariable models were fitted to estimate the independent effect of each factor. RESULTS: 843 norovirus outbreaks reported in 233 published articles from 45 countries were analyzed. Based upon 71,724 illnesses, 501 hospitalizations, and 45 deaths, overall hospitalization and mortality rates were 0.54% and 0.06%, respectively. In multivariate analysis, genogroup II genotype 4 (GII.4) norovirus strains were associated with higher hospitalization (IRR: 9.4, 95% CI: 6.1 - 14.4, p < 0.001) and mortality rates (IRR: 3.1, 95% CI: 1.3 - 7.6, p=0.013); deaths were much more likely to occur in outbreaks occurring in healthcare facilities (IRR: 60, 95% CI: 6 - 109, p=0.013). CONCLUSIONS: Our review suggests that hospitalizations and deaths were more likely in outbreaks associated with GII.4 viruses, independent of other factors, and underscores the importance of developing vaccines against GII.4 viruses to prevent severe disease outcomes. |
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