A novel method for the analysis of particle coating behaviour via contact spreading in a tumbling drum: Effect of coating liquid viscosity

Spray coating is a common method of distributing liquids over powders, especially in the pharmaceutical, detergent and food industries. During this process, liquid drops are deposited on the surface of particles. Liquid is then transferred between particles via particle collisions, in a process called liquid contact spreading. This contact spreading process facilitates inter-particle coating, in which wetting, de-wetting, mixing and drying are occurring simultaneously. This work presents the first experimental study of the mechanism of liquid contact spreading. In this work, a novel experimental method has been developed to investigate the mechanism of contact spreading, incorporating a newly developed image analysis technique, based on colourimetric measurements, to quantitatively determine coating behaviour via contact spreading. Here, experiments designed to isolate the contact spreading coating mechanism were performed in a tumbling drum using a model material system; alumina particles and dyed polyethylene glycol solutions of varying viscosities. The coating uniformity was quantified by the variation in inter-particle coating; the coefficient of variation (CoV). For all systems, the uniformity of the coating increased with time until the CoV decreased to an asymptotic value. The rate of the decrease in the CoV was successfully fitted using an exponential decay function. The viscosity of the coating solution had a significant effect on the rate of liquid transfer; the lower the viscosity the faster the contact spreading process. This effect is attributed to differences in the formation and stability of liquid bridges between the particles, influencing the extent of liquid transfer. The results also show that in most cases examined here, viscous forces play a main role in the contact spreading process, and the contribution of capillary forces are minimal. This understanding could assist the design and scale up for the wet coating processes

Estrous Cyclicity in Mice During Simulated Weightlessness

Hindlimb unloading (HU) is a rodent model system used to simulate weightlessness experienced in space. However, some effects of this approach on rodent physiology are under-studied, specifically the effects on ovarian estrogen production which drives the estrous cycle. To resolve this deficiency, we conducted a ground-based validation study using the HU model, while monitoring estrous cycles in 16-weeks-old female C57BL6 mice. Animals were exposed to HU for 12 days following a 3 day HU cage acclimation period, and estrous cycling was analyzed in HU animals (n=22), normally loaded HU Cage Pair-Fed controls (CPF; n=22), and Vivarium controls fed ad libitum (VIV; n=10). Pair feeding was used to control for potential nutritional deficits on ovarian function. Vaginal cells were sampled daily in all mice via saline lavage. Cells were dried and stained with crystal violet, and the smears evaluated using established vaginal cytology techniques by two individuals blinded to the animal treatment group. Estrous cyclicity was disrupted in nearly all HU and CPF mice, while those maintained in VIV had an average normal cycle length of 4.8+/- 0.5 days, with all stages in the cycle visibly observed. CPF and HU animals arrested in the diestrous phase, which precedes the pre-ovulatory estrogen surge. Additionally, infection-like symptoms characterized by vaginal discharge and swelling arose in several HU animals, which we suspect was due to an inability of these mice to properly groom themselves, and/or due to the change in the gravity vector relative to the vaginal opening, which prevented drainage of the lavage solution. Pair-feeding resulted in similar weight gains of HU and CPF (1.5% vs 3.0%, respectively). The current results indicate that pair-feeding controlled weight gain and that the HU cage alone influenced estrous cyclicity. Thus, longer acclimation needs to be tested to determine if and when normal estrous cycling resumes in non-loaded mice in HU cages prior to HU testing. Future studies might also examine whether modifications to the vaginal lavage procedure might prevent the onset of the infection-like symptoms, and allow estrous cyclicity to be measured in this model system. Research supported by NNX15AB48G to JST

Collapse of superconductivity in a hybrid tin-graphene Josephson junction array

When a Josephson junction array is built with hybrid superconductor/metal/superconductor junctions, a quantum phase transition from a superconducting to a two-dimensional (2D) metallic ground state is predicted to happen upon increasing the junction normal state resistance. Owing to its surface-exposed 2D electron gas and its gate-tunable charge carrier density, graphene coupled to superconductors is the ideal platform to study the above-mentioned transition between ground states. Here we show that decorating graphene with a sparse and regular array of superconducting nanodisks enables to continuously gate-tune the quantum superconductor-to-metal transition of the Josephson junction array into a zero-temperature metallic state. The suppression of proximity-induced superconductivity is a direct consequence of the emergence of quantum fluctuations of the superconducting phase of the disks. Under perpendicular magnetic field, the competition between quantum fluctuations and disorder is responsible for the resilience at the lowest temperatures of a superconducting glassy state that persists above the upper critical field. Our results provide the entire phase diagram of the disorder and magnetic field-tuned transition and unveil the fundamental impact of quantum phase fluctuations in 2D superconducting systems.Comment: 25 pages, 6 figure

Primary rat sertoli and interstitial cells exhibit a differential response to cadmium

Two cell types central to the support of spermatogenesis, the Sertoli cell and the interstitial (Leydig) cell, were isolated from the same cohort of young male rats and challenged with cadmium chloride to compare their susceptibility to the metal. Both cell types were cultured under similar conditions, and similar biochemical endpoints were chosen to minimize experimental variability. These endpoints include the uptake of 109 Cd, reduction of the vital tetrazolium dye MTT, incorporation of 3 H-leucine, change in heat-stable cadmium binding capacity, and production of lactate. Using these parameters, it was observed that the Sertoli cell cultures were adversely affected in a dose-and time-dependent manner, while the interstitial cell cultures, treated with identical concentrations of CdCl 2 , were less affected. The 72-hr LC 50 's for Sertoli cells and interstitial cells were 4.1 and 19.6 μM CdCl 2 , respectively. Thus, different cell populations within the same tissue may differ markedly in susceptibility to a toxicant. These in vitro data suggest that the Sertoli cell, in relation to the interstitium, is particularly sensitive to cadmium. Because the Sertoli cell provides functional support for the seminiferous epithelium, the differential sensitivity of this cell type may, in part, explain cadmium-induced testicular dysfunction, particularly at doses that leave the vascular epithelium intact.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42554/1/10565_2004_Article_BF00135027.pd

Characterization of the extended-spectrum β-lactamases and determination of the virulence factors of uropathogenic Escherichia coli strains isolated from children

BACKGROUND AND AIM: The aim of the study was to characterize ESBL-producing uropathogenic Escherichia coli (UPEC) strains isolated in children. That included the investigation of virulence factors and the analysis of the types of β-lactamases at the molecular genetic level. ----- MATERIAL AND METHODS: During the 2-year study period, 77 ESBL-producing E. coli strains were recovered from urine samples of febrile children with significant bacteriuria hospitalized at one Croatian hospital. Susceptibility of isolates to bactericidal serum activity was tested by Shiller and Hatch method, while adhesin expression was determined by agglutination methods. Characterization of ESBLs was performed by PCR with specific primers for ESBLs and by sequencing of bla (ESBL) genes. Genotyping of the E. coli isolates was performed by pulsed-field gel electrophoresis (PFGE). ----- RESULTS: Twenty-seven (35.1 %) and 50 (64.9 %) ESBL-producing UPEC strains were isolated in neonates and infants, respectively. Of 70 strains investigated for the presence of virulence factors, adhesins were detected in 48.6 % strains (8.6 % in the neonate and 40 % in the infants group) giving a statistically significant difference in adhesin expression between the two groups (p < 0.01). Hemolysin was produced by 84.3 %, whereas 70 % of strains were serum-resistant. The bla (TEM) gene was detected in 22 (28 %) and bla (SHV) gene in 57 strains (74 %), whereas bla (CTX-M) gene was detected in only two isolates (2.5%). In ten isolates, bla (TEM) and bla (SHV) were simultaneously detected. Sequencing of bla (SHV) genes revealed that SHV-5 β-lactamase was by far the most prevalent and was found in 51 strains (66 %). The strains were clonally related as demonstrated by PFGE and assigned into ten clusters. ----- CONCLUSIONS: Infection control measures should be employed and the consumption of expanded-spectrum cephalosporins in the hospital should be restricted