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Multicaloric materials show thermal changes that can be driven simultaneously or sequentially by more than one type of external field. The use of more than one driving field can induce larger thermal changes, with smaller field magnitudes, over wider ranges of operating temperature, and can also eliminate hysteresis in one control parameter by transferring it to another. The thermodynamics behind multicaloric effects is well established, but only a small number of multicaloric materials have been experimentally studied to date. Here, we describe the fundamentals of multicaloric effects and discuss the performance of representative multicaloric materials. Exploiting multicaloric effects could aid the future development of cooling devices, where key challenges include energy efficiency and the span of the operating temperature.
For more than a century, humankind has achieved refrigeration by exploiting volatile gases that harm the environment when released to the atmosphere. More recently, the observation of electrocaloric effects in commercial multilayer capacitors has inspired the possibility of environmentally friendly cooling. In this article, we describe electrocaloric effects in multilayer capacitors for cooling applications, compare the electrocaloric performance of existing multilayer capacitors, and discuss the improvements required for practical cooling devices.
Documentation of antibiotic indication provides helpful information for antimicrobial stewardship, but accuracy is not understood. Review of 396 antibiotic orders in a pediatric ICU and adult medicine step-down unit found 90% agreement between provider-selected indication and independent review. Prompts to enter antibiotic indication during order entry provide largely accurate information.
We report new laboratory experiments of a flow accelerating from an initially turbulent state following the opening of a valve, together with large eddy simulations of the experiments and extended Stokes first problem solutions for the early stages of the flow. The results show that the transient flow closely resembles an accelerating laminar flow superimposed on the original steady turbulent flow. The primary consequence of the acceleration is the temporal growth of a boundary layer from the wall, gradually leading to a strong instability causing transition. This extends the findings of previous direct numerical simulations of transient flow following a near-step increase in flow rate. In this interpretation, the initial turbulence is not the primary characteristic of the resulting transient flow, but can be regarded as noise, the evolution of which is strongly influenced by the development of the boundary layer. We observe the spontaneous appearance of turbulent spots and discontinuities in the velocity signals in time and space, revealing rich detail of the transition process, including a striking contrast between streamwise and wall-normal fluctuating velocities.
Theoretically determined vertical excitation energies of C5 and C7 molecules have been shown to agree with the strongest diffuse interstellar band at 4430Å. Several other weak diffuse bands can be identified with vibrational transitions, if 4430Å band is taken as 0-3 transition and vibrational constant have a value of 2190cm−1. The vertical excitation energy of a second electronic transition of C7 molecule agrees with diffuse band at 6177Å. This electronic band system may account for diffuse bands at 5778Å, 6660Å and other bands near them.
A significant reservoir of potential energy in hot astrophysical plasmas exists in multiply charged positive ions. Inelastic collisional processes involving such ions govern the ionization and energy balance in such plasmas. Although inelastic processes such as, charge transfer, have been widely investigated, there remains a paucity of knowledge about charge changing processes where both reactions and products are state-diagnosed. We have applied high-resolution translational energy gain/loss spectroscopy to investigate state-diagnosed collisions between Kr2+ and H2 leading to single electron capture into specific electronic states of Kr+ at collision energies in the range 1–6 keV.
Prematurity is a risk factor for hypertension, vascular stiffness, nephron deficit and adult onset cardiorenal disease. The vascular tree and kidneys share morphogenic drivers that promote maturation in utero before 36 weeks of gestation. Vascular elastin accrual terminates after birth leaving collagen to promote vascular stiffness. Our objective was to determine if the histomorphometry of the umbilical artery, an extension of the aorta, parallels nephron mass across gestational age groups. From a cohort of 54 newborns, 32 umbilical cord specimens were adequate for evaluation. The umbilical cord was sectioned, stained with trichrome, and digitalized. Muscular and collagenous areas of the umbilical artery were measured in pixels using the Image J 1.48q software. Total kidney volume was measured by ultrasound and factored by body surface area (TKV/BSA). The umbilical artery total area was significantly greater in term v. preterm infants (9.3±1.3 v. 7.0±2.0 mm2; P<0.05) and increased with gestational age; while the percent muscular and collagen areas were independent of gestational age (R2=0.04; P=ns). Percent muscular area correlated positively with TKV/BSA (r=0.53; P=0.002); while an increase in collagen correlated inversely with kidney mass (r=−0.53; P=0.002). In conclusion, an enhanced % muscular area and presumed vascular elasticity was associated with increased renal mass in all infants. Umbilical artery histomorphometry provides a link between the intrauterine environment, vascular and kidney development.
Low birth weight is associated with adverse health outcomes. If birth weight records are not available, studies may use recalled birth weight. It is unclear whether this is reliable. We performed a systematic review and meta-analysis of studies comparing recalled with recorded birth weights. We followed the Meta-Analyses of Observational Studies in Epidemiology (MOOSE) statement and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched MEDLINE, EMBASE and Cumulative Index to Nursing and Allied Health Literature (CINAHL) to May 2015. We included studies that reported recalled birth weight and recorded birth weight. We excluded studies investigating a clinical population. Two reviewers independently reviewed citations, extracted data, assessed risk of bias. Data were pooled in a random effects meta-analysis for correlation and mean difference. In total, 40 studies were eligible for qualitative synthesis (n=78,997 births from 78,196 parents). Agreement between recalled and recorded birth weight was high: pooled estimate of correlation in 23 samples from 19 studies (n=7406) was 0.90 [95% confidence interval (CI) 0.87–0.93]. The difference between recalled and recorded birth weight in 29 samples from 26 studies (n=29,293) was small [range −86–129 g; random effects estimate 1.4 g (95% CI −4.0–6.9 g)]. Studies were heterogeneous, with no evidence for an effect of time since birth, person reporting, recall bias, or birth order. In post-hoc subgroup analysis, recall was higher than recorded birth weight by 80 g (95% CI 57–103 g) in low and middle income countries. In conclusion, there is high agreement between recalled and recorded birth weight. If birth weight is recalled, it is suitable for use in epidemiological studies, at least in high income countries.
Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000–2000 yr younger than the enclosing peat. We suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies a potentially large supply of old carbon gases in peatlands that should be considered in global carbon models of the terrestrial biosphere.
The Medium-l Program of the Michelson Doppler Imager (MDI) instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to ∼ 300. The initial results show that the noise in the Medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. In a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer.
We have developed a new method for controlling the size, crystallinity, and polydispersity of 100–2000 nm tetrafluoride phosphor particles. Five polyol-based deep eutectic solvents (DESs) were downselected out of a set of more than 130 candidates. We analyzed their benefits in synthesizing phosphor matrix particles of β-NaYF4, β-NaYbF4, and β-NaGdF4. We produced green (λmax = 540 nm) and blue/UV (λmax = 450 nm) upconverting phosphors in DES using Yb,Er and Yb,Tm codopants, respectively. The blue/UV phosphor reaction was scaled the up to 25 L, yielding nearly 400 g of high-quality, bright photoluminescent, β-phase product under mild conditions. We conclude that polyol-based DES systems offer a uniquely specialized and useful toolkit for phosphor synthesis.
Semiconductor photocatalysis has emerged as an interesting area of research since the discovery of Honda-Fujishima effect. In this study, TiO2/MoO2/graphene composites have been prepared by a solar radiation-assisted co-reduction method, wherein ammonium tetrathiomolybdate salt and graphite oxide are reduced to MoO2 and graphene respectively along with TiO2. The method involved the utilization of focused pulses of natural sunlight using a simple convex lens, thereby eliminating the need for harmful reducing agents. The compound was characterized by XRD and SEM for phase identification and morphology. The TiO2/MoO2/graphene composite exhibits superior photocatalytic water splitting activity without using a co-catalyst. In addition, we demonstrate the electrocatalytic hydrogen production using this earth abundant catalyst, which shows high current density (60 mA/cm2) and low Tafel slope (47 mV/dec). The hydrogen evolved during photocatalysis was detected by gas chromatography.
As the need for smaller data storage devices in the market continues to grow, the study of new combinations of self-assembled magnetic nanoparticles/films is greatly needed. In this research, Fe50-Ni50 films were synthesized using a Pulsed Laser Deposition technique. The films were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and physical properties measurement system (PPMS). Films were deposited from Fe-Ni alloy target (50%-50% composition), deposition was conducted in vacuum, at substrate temperatures varying from liquid nitrogen temperature -196°C to 600°C. The films were annealed in a vacuum chamber at 600°C for 1 hour. The study reveals that the substrate temperature has significant effect on the structure of the films and their magnetic properties. It was shown that additional thermal treatment improved the quality of films in terms of narrow grain size distribution. Magnetic properties were also found to improve significantly after post annealing process.
Due to the rapid advance of the emergence of resistant microorganisms to different antibiotics, there is a need to create new antimicrobial agents. It is possible that Nanotechnology has a great impact in this area since the nanoparticles can improve the antimicrobial effect of the antibiotics. In this study we used three different metal oxides nanoparticles, the MgO, ZnO and CuO. These nanoparticles were selected because their interactions leading to cell death and their optical properties. The aim of this study is to develop new methods that are more effective against resistance bacteria, developing antibacterial agents using different nanoparticles against Escherichia coli (ATCC 10536), Pseudomonas aeruginosa (ATCC 10145), and Staphylococcus aureus (ATCC BAA-1026). This study was conducted to evaluate the antibacterial effects of a combination of nanoparticles together with different concentrations of three antibiotics, Gentamicin, Cephalexin and Co-Trimoxazole. The results showed that some nanoparticles are effective to inhibit growth in these microorganisms by increasing the effectiveness of the antibiotic. Therefore, the present study indicates that the combination of the nanoparticles with antibiotics may be applicable as a new antimicrobial agent.
The present work focuses on the synthesis and evaluation of the antimicrobial activity of ZnxMg1-xO solid solutions. ZnxMg1-xO solid solutions were synthesized through the thermal decomposition of ZnMg-precursor synthesized in aqueous and ethanol solutions via a two-steps process. The antimicrobial activity of ZnxMg1-xO solid solution against E. coli was evaluated using the spread plate method in presence of ZnxMg1-xO powder of different contents of Zn species, ‘x’. The powder concentrations evaluated were 500, 1000, and 1500 ppm. Zn0.10Mg0.90O powders exhibited a bacterial growth inhibition between 38% and 100% when the powder concentration increased from 500 up to 1500 ppm, respectively. A decreasing trend was observed for x = 0.30 and above; the corresponding bacterial growth inhibition was 12%, 6%, and 5% when the particles concentration was, respectively, 500, 1000, and 1500 ppm. X-Ray diffraction analyses suggested the incorporation of Zn ions into the MgO lattice for ‘x’ values below 0.10, enhancing the antimicrobial activity; the formation of two isolated oxide phases observed at larger ‘x’ values (e.g. x = 0.30 and x = 0.50 Zn), could explain the detected inhibition of the corresponding antimicrobial activity.
This paper describes the organometallic synthesis of pure rhenium nanoparticles (Re NPs) and their characterization by a combination of state-of-the art techniques (TEM, HAADF-STEM, EDX, WAXS, EA, FT-IR). The Re NPs synthesis is achieved by reducing the [Re2(C3H5)4] complex in solution under a dihydrogen atmosphere and in the presence of hexadecylamine or polyvinylpyrrolidone as stabilizing agents. The so-obtained Re NPs are monodisperse with a mean size of 1.1 nm (0.3) nm and display a spherical shape with a disordered hcp structure.
As a promising transition metal dichalcogenide (TMDC), molybdenum disulfide (MoS2) has recently attracted a lot of attention due to its graphene-liked two dimensional layer structure, which leads to potential applications in electronic and optoelectronic devices. However, the fabrication of mono- or few-layer MoS2 is limited to ether liquid exfoliation or CVD, and the chemical solution deposition is limited to ammonium thiomolybdate-based precursor. In this paper, hydrazine-based dimensional reduction technique is applied in the chemical solution deposition of MoS2 thin-film, and a larger area uniform thin-film is obtained from bulk powder MoS2. This solution-based process could be applied with a variety coating techniques and lead to wafer level MoS2 thin film production.
The organometallic approach was successfully applied to synthesize water-soluble ruthenium nanoparticles displaying interesting catalytic properties in hydrogenation of unsaturated model-substrates. Nanocatalyst synthesis was performed by hydrogenation of the complex [Ru(COD)(COT)] in the presence of sulfonated diphosphines and cyclodextrins as protective agents providing very small ruthenium nanoparticles (ca. 1.2-1.5 nm) with narrow size distribution and high stability. Catalysis results in water evidenced a control of the surface properties of these novel ruthenium nanocatalysts at a supramolecular level.