Microphysical and Polarimetric Radar Modeling of Hydrometeor Refreezing

A unique polarimetric radar signature indicative of hydrometeor refreezing during ice pellet events has been documented in several recent studies, yet the underlying microphysical causes remain unknown. The signature is characterized by enhancements in differential reflectivity (ZDR), specific differential phase (KDP), and linear depolarization ratio (LDR), and a reduction in co-polar correlation coefficient (ρhv) within a layer of decreasing radar reflectivity factor at horizontal polarization (ZH). In previous studies, the leading hypothesis for the observed radar signature is the preferential refreezing of small drops. Here, a simplified, one-dimensional, explicit bin microphysics model is developed to simulate the refreezing of fully melted hydrometeors, and coupled with a polarimetric radar forward operator to quantify the impact of preferential refreezing on simulated radar signatures. The modeling results demonstrate that preferential refreezing is insufficient by itself to produce the observed signatures. In contrast, simulations considering an ice shell growing asymmetrically around a freezing particle (i.e., emulating a thicker ice shell on the bottom of a falling particle) produce realistic ZDR enhancements, and also closely replicate observed features in ZH, KDP, LDR, and ρhv. Simulations that assume no increase in particle wobbling with freezing produce an even greater ZDR enhancement, but this comes at the expense of reducing the LDR enhancement. It is suggested that the polarimetric refreezing signature is instead strongly related to both the distribution of the unfrozen liquid portion within a freezing particle, and the orientation of this liquid with respect to the horizontal.

Physicochemical and Antimicrobial Properties of Thermosensitive Chitosan Hydrogel Loaded with Fosfomycin

Thermosensitive chitosan hydrogels—renewable, biocompatible materials—have many applications as injectable biomaterials for localized drug delivery in the treatment of a variety of diseases. To combat infections such as Staphylococcus aureus osteomyelitis, localized antibiotic delivery would allow for higher doses at the site of infection without the risks associated with traditional antibiotic regimens. Fosfomycin, a small antibiotic in its own class, was loaded into a chitosan hydrogel system with varied beta-glycerol phosphate (β-GP) and fosfomycin (FOS) concentrations. The purpose of this study was to elucidate the interactions between FOS and chitosan hydrogel. The Kirby Bauer assay revealed an unexpected concentration-dependent inhibition of S. aureus, with reduced efficacy at the high FOS concentration but only at the low β-GP concentration. No effect of FOS concentration was observed for the planktonic assay. Rheological testing revealed that increasing β-GP concentration increased the storage modulus while decreasing gelation temperature. NMR showed that FOS was removed from the liquid portion of the hydrogel by reaction over 12 h. SEM and FTIR confirmed gels degraded and released organophosphates over 5 days. This work provides insight into the physicochemical interactions between fosfomycin and chitosan hydrogel systems and informs selection of biomaterial components for improving infection treatment.

Unraveling the leaf-dropping behavior behind bat folivory: do bats use biological control against roost parasites?

Folivory in bats, the behavior of chewing bites of leaves to extract the liquid portion and discard the fiber as oral pellets, is seen as a strategy that might provide vitamins, micronutrients and proteins not always available in fruits, and even secondary metabolites (hormonal precursors) that stimulate/inhibit reproductive processes. While examining chewed leaves, we noticed an important amount of completely intact leaves below the roosts of Artibeus amplus and Artibeus lituratus, and decided to systematically quantify them during a year. We recovered 639 intact leaves from six plant species and found that both species are constantly feeding on leaves, but invariably leaving 26–78% of these intact, dropping them on the floor just below their roosting sites. These large proportions of dropped, intact leaves suggest a completely different, novel, non-nutritional use by bats. Several studies in birds have revealed that fresh leaves are effectively used in nests to control diverse organisms that include blood suckling ectoparasites, protozoans, fungus and bacteria. We report for the first time this biological control behavior performed by bats by selecting, bringing and dropping intact leaves below their roosting sites. The chemical properties of the leaves need to be investigated to reveal those active components against specific pathogens.

Modernization of continuous casting machines with the purpose of increasing of finished product quality

To prevent formation or suppress development of crystallization,shrink and liquating defects different methods of physical impact on setting melt are used. For technology selection in every case economy, efficiencyand ecological norms should be considered first of all.Methods of physical impact on crystallizable billet considered: electro-hydro impulse impact, gas-impulse stirring, modifier input, inoculator input, consumable coolers input, ultrasonic impact, “soft” reduction, electromagnetic stirring (EMS).Due to authors’ opinion, EMS of liquid portion of a CC billet is the most effective method ofactive impact on crystallization process of a CC billet directly during casting resulted in a guarantee possibility to control the process of structure formation. At present in world practice the EMS of liquid metal at CC machines became an integral part of advanced technology of high quality billets obtaining. The requirements increase to products qualityand development of effective methods and means of melts electromagnetic processing resulted in a requirement of obligatory EMS usage when producing products of high quality steels.It was shown, that for a number of CC bullet macrostructure defects, arising from crystallization process, shrinkage and liquating phenomena, which can not be eliminated completely even at optimal CC machinesdesign features and rational technology parameters of CC process, additional methods of physical impact on the liquid metal setting needed. The method to be used depends on the CC technology and existing CC machines equipment.

Financial Constraints and the Response of Business Investment to Monetary Policy Shocks

In this study I investigate what impact monetary policy shocks have on firms’ fixed investment, the less liquid portion of gross investment that requires more planning. I account for firms facing financial constraints firms by utilizing a common measure of asset size, which is used in previous literature. I use two exogenous, continuous series of monetary policy shocks to show that constrained firms have statistically different responses to policy than unconstrained firms. Specifically, I find that constrained firms’ fixed investment significantly responds more to monetary policy shocks than unconstrained firms.

Nanoclay addition to a conventional glass ionomer cements: Influence on physical properties

ABSTRACT Objective: The objective of the present study is to investigate the reinforcement effect of polymer-grade montmorillonite (PGN nanoclay) on physical properties of glass ionomer cement (GIC). Materials and Methods: The PGN nanoclay was dispersed in the liquid portion of GIC (HiFi, Advanced Healthcare, Kent, UK) at 1%, 2% and 4% (w/w). Fourier-transform infrared (FTIR) spectroscopy was used to quantify the polymer liquid of GICs after dispersion of nanoclay. The molecular weight (Mw) of HiFi liquid was determined by gel permeation chromatography. The compressive strength (CS), diametral-tensile strength, flexural strength (FS) and flexural modulus (Ef) of cements (n = 20) were measured after storage for 1 day, 1 week and 1 month. Fractured surface was analyzed by scanning electron microscopy. The working and setting time (WT and ST) of cements was measured by a modified Wilson's rheometer. Results: The FTIR results showed a new peak at 1041 cm−1 which increased in intensity with an increase in the nanoclay content and was related to the Si-O stretching mode in PGN nanoclay. The Mw of poly (acrylic acid) used to form cement was in the range of 53,000 g/mol. The nanoclay reinforced GICs containing <2% nanoclays exhibited higher CS and FS. The Ef cement with 1% nanoclays was significantly higher. The WT and ST of 1% nanoclay reinforced cement were similar to the control cement but were reduced with 2% and 4% nanoclay addition. Conclusion: The dispersion of nanoclays in GICs was achieved, and GIC containing 2 wt% nanoclay is a promising restorative materials with improved physical properties.

Effect of Nanoclay Dispersion on the Properties of a Commercial Glass Ionomer Cement

Objective.The reinforcement effect of polymer-grade montmorillonite (PGV and PGN nanoclay) on Fuji-IX glass ionomer cement was investigated.Materials and Method.PGV and PGV nanoclays (2.0 wt%) were dispersed in the liquid portion of Fuji-IX. Fourier-transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) were used to quantify acid-base reaction and the liquid portion of GIC. The mechanical properties (CS, DTS, FS, andEf) of cements (n= 20) were measured at 1 hour, 1 day, and 1 month. The microstructure was examined by cryo-SEM and TEM.Results. FTIR shows that the setting reaction involves the neutralisation of PAA by the glass powder which was linked with the formation of calcium and aluminium salt-complexes. The experimental GICs (C-V and C-N) exhibited mechanical properties in compliance to ISO standard requirement have higher values than Fuji-IX cement. There was no significant correlation of mechanical properties was found between C-V and C-N. The average Mw of Fuji-IX was 15,700 and the refractive index chromatogram peak area was 33,800. TEM observation confirmed that nanoclays were mostly exfoliated and dispersed in the matrix of GIC.Conclusion. The reinforcement of nanoclays in GICs may potentially produce cements with better mechanical properties without compromising the nature of polyacid neutralisation.

Pressure-temperature-fluid constraints for the Emmaville-Torrington emerald deposit, New South Wales, Australia: Fluid inclusion and stable isotope studies

The Emmaville-Torrington emeralds were first discovered in 1890 in quartz veins hosted within a Permian metasedimentary sequence, consisting of meta-siltstones, slates and quartzites intruded by pegmatite and aplite veins from the Moule Granite. The emerald deposit genesis is consistent with a typical granite-related emerald vein system. Emeralds from these veins display colour zonation alternating between emerald and clear beryl. Two fluid inclusion types are identified: three-phase (brine+vapour+halite) and two-phase (vapour+liquid) fluid inclusions. Fluid inclusion studies indicate the emeralds were precipitated from saline fluids ranging from approximately 33 mass percent NaCl equivalent. Formational pressures and temperatures of 350 to 400 °C and approximately 150 to 250 bars were derived from fluid inclusion and petrographic studies that also indicate emerald and beryl precipitation respectively from the liquid and vapour portions of a two-phase (boiling) system. The distinct colour zonations observed in the emerald from these deposits is the first recorded emerald locality which shows evidence of colour variation as a function of boiling. The primary three-phase and primary two-phase FITs are consistent with alternating chromium-rich ‘striped’ colour banding. Alternating emerald zones with colourless beryl are due to chromium and vanadium partitioning in the liquid portion of the boiling system. The chemical variations observed at Emmaville-Torrington are similar to other colour zoned emeralds from other localities worldwide likely precipitated from a boiling system as well.