Flow-Induced Crystallization in Polyethylene: Effect of Flow Time on Development of Shish-Kebab

The flow-induced formation and relaxation of the representative oriented shish-kebab structure were studied with synchrotron small-angle X-ray scattering (SAXS) method. The flow duration was varied from 2 to 6 s at an identical strain rate to reveal the effect of flow time on stability and dimension of formed shish. It was found that the short flow time of 2 s was able to generate shish during flow, which, however, relaxed during the isothermal process after cessation of flow. An increase in flow time can improve the shish stability and the long flow time of 6 s can generate the stable shish that nucleate the growth of kebab lamellae. In addition, the quantitative analysis of SAXS results showed that with increasing flow time from 2 to 6 s, the shish length increased from 242 to 574 nm, while the shish diameter remained around 34 nm. This detailed information of the formed shish-kebab structure can be used to shed light on their evolution that occurred during flow from 2 to 6 s, where shish grew at a longitudinal speed of around 80 nm/s, and there was an improvement in the stability and nucleation capability for kebab lamellae.

Intrauterine SARS-CoV-2 infection – a case confirming transplacental transmission followed by divergence of the viral genome

Pregnant women and their newborns may be at particular risk for poor outcomes due to the coronavirus (COVID-19) pandemic. Intrauterine SARS-CoV-2 transmission has been suggested but most reports have not ruled out postpartum infection. We demonstrate a confirmed case of transplacental transmission of SARS-CoV-2 in a neonate born to a mother infected in the third trimester. Comprehensive virological, pathological and genetic investigations establish that intrauterine SARS-CoV-2 transmission occurred via the following chain of events; I) maternal viremia in a seemingly mildly symptomatic patient, II) high viral load in the placenta with massive perivillous fibrin deposition, acute intervillositis in areas with strong positivity for SARS-CoV-2 and chorangiosis in the areas less affected by infection and inflammation, III) intrauterine fetal distress with pathological cardiotocography and acidemia in validated umbilical cord blood gases and IV) mild neonatal COVID-19. Whole genome sequencing of isolates from the mother and placenta revealed a single variant of the virus. Interestingly, the neonate displayed a mixed SARS-CoV-2 population, harboring both an identical strain to the mother as well as a population with one single-nucleotide polymorphism difference, indicating intrapatient genetic drift.

Clusters of nontuberculous mycobacteria linked to water sources at three Veterans Affairs medical centers

Objective:To characterize nontuberculous mycobacteria (NTM) associated with case clusters at 3 medical facilities.Design:Retrospective cohort study using molecular typing of patient and water isolates.Setting:Veterans Affairs Medical Centers (VAMCs).Methods:Isolation and identification of NTM from clinical and water samples using culture, MALDI-TOF, and gene population sequencing to determine species and genetic relatedness. Clinical data were abstracted from electronic health records.Results:An identical strain of Mycobacterium conceptionense was isolated from 41 patients at VA Medical Centers (VAMCs A, B, and D), and from VAMC A’s ICU ice machine. Isolates were initially identified as other NTM species within the M. fortuitum clade. Sequencing analyses revealed that they were identical M. conceptionense strains. Overall, 7 patients (17%) met the criteria for pulmonary or nonpulmonary infection with NTM, and 13 of 41 (32%) were treated with effective antimicrobials regardless of infection or colonization status. Separately, a M. mucogenicum patient strain from VAMC A matched a strain isolated from a VAMC B ICU ice machine. VAMC C, in a different state, had a 4-patient cluster with Mycobacterium porcinum. Strains were identical to those isolated from sink-water samples at this facility.Conclusion:NTM from hospital water systems are found in hospitalized patients, often during workup for other infections, making attribution of NTM infection problematic. Variable NTM identification methods and changing taxonomy create challenges for epidemiologic investigation and linkage to environmental sources.

History-dependent perturbation response in limb muscle

1AbstractMuscle mediates movement but movement is typically unsteady and perturbed. Muscle is known to behave non-linearly and with history dependent properties during steady locomotion, but the importance of history dependence in mediating muscles function during perturbations remains less clear. To explore muscle’s capacity to mitigate perturbations, we constructed a series of perturbations that varied only in kinematic history, keeping instantaneous position, velocity and time from stimulation constant. We discovered that muscle’s perturbation response is profoundly history dependent, varying by four fold as baseline frequency changes, and dissipating energy equivalent to ~ 6 times the kinetic energy of all the limbs (nearly 2400 W Kg−1). Muscle’s energy dissipation during a perturbation is predicted primarily by the force at the onset of the perturbation. This relationship holds across different frequencies and timings of stimulation. This history dependence behaves like a viscoelastic memory producing perturbation responses that vary with the frequency of the underlying movement.Summary StatementThe response of muscles to rapid, identical strain perturbations is history dependent, but is captured by a viscoelastic model with memory. Muscle function during perturbations therefore depends on locomotor frequency.

Salmonella enterica Serotype Panama: An exceptionally virulent cause of illness in children?

Salmonella enterica serotype Panama accounts for <1% of all reported cases of Salmonellosis. Previous reports suggest that it may be unusually virulent in children. We report the case of a family, five of six of whom developed a diarrheal illness due to this organism following exposure during a trip to Costa Rica. Included among these patients were three children, all of whom developed clinical shock requiring aggressive fluid resuscitation, and all of whom ultimately recovered. DNA fingerprinting, using pulsed-field gel electrophoresis, demonstrated that all three children were infected with an identical strain of Salmonella. Moreover, this strain was unique among strains recovered in Nebraska. Clinicians should be aware of the propensity of Salmonella enterica serotype Panama to cause especially severe disease in children; laboratory personnel should be aware of the unique need for thiourea buffering when attempting to perform pulsed-field gel electrophoresis analysis on such strains.

Complete Genome Sequence of a CTX-M-15-Producing Escherichia coli Strain from the H 30Rx Subclone of Sequence Type 131 from a Patient with Recurrent Urinary Tract Infections, Closely Related to a Lethal Urosepsis Isolate from the Patient’s Sister

We report here the complete genome sequence, including five plasmid sequences, of Escherichia coli sequence type 131 (ST131) strain JJ1887. The strain was isolated in 2007 in the United States from a patient with recurrent cystitis, whose caregiver sister died from urosepsis caused by a nearly identical strain.

Recent Progress in Full Scale Fatigue Test of PZL-130 "Orlik" TC-II Structure

This article presents preparation of the Full Scale Fatigue Test of the PZL-130 "Orlik" TC-II. After completing the flight load acquisition stage [1] a load block representing 200 Simulated Flight Hours in 194 flights was developed. This load block was further modified in order to introduce fatigue markers on the crack surface [2] visible during Quantitative Fractography, planned to take place during the Teardown Inspection of the structure after completion of the test. Meanwhile, the test rig along with the loading system and the test specimen were prepared at Výzkumný a Zkušební Letecký Ústav (VZLU, Prague, Czech Republic). The test specimen, consisting of the overhauled fuselage, modernized wings and the landing gear, was instrumented with the identical strain gauge measuring system as presented in [3], which was calibrated before the commencement of fatigue testing. Finally, some preliminary issues encountered during the fatigue test startup were highlighted and the outline for future work was described

Strain Measurement in Semiconductor Heterostructures by Scanning Transmission Electron Microscopy

This article deals with the measurement of strain in semiconductor heterostructures from convergent beam electron diffraction patterns. In particular, three different algorithms in the field of (circular) pattern recognition are presented that are able to detect diffracted disc positions accurately, from which the strain in growth direction is calculated. Although the three approaches are very different as one is based on edge detection, one on rotational averages, and one on cross correlation with masks, it is found that identical strain profiles result for an InxGa1−xNyAs1−y/GaAs heterostructure consisting of five compressively and tensile strained layers. We achieve a precision of strain measurements of 7–9·10−4 and a spatial resolution of 0.5–0.7 nm over the whole width of the layer stack which was 350 nm. Being already very applicable to strain measurements in contemporary nanostructures, we additionally suggest future hardware and software designs optimized for fast and direct acquisition of strain distributions, motivated by the present studies.