Electrically induced liquid-liquid phase transition in water at room temperature.

In this work we expand on findings previously reported [Wexler et al., Phys. Chem. Chem. Phys., 2016, 18, 16281] on the experimental observation of a phase transition in a hydrogen bonded liquid manifesting in long range dipole-dipole interactions. The studied system, liquid water stressed by an electric field, exhibits collective oscillations brought about through spontaneous breakdown of symmetry. Raman spectroscopy identifies the primary excitation of the emergent phase as transverse optically active phonon-like sidebands that appear on the hydrogen bonded asymmetric stretch mode. The phase transition is observed throughout the entire volume of liquid. The system also exhibits a self-similarity relation between the scattered Raman intensity and the electric field strength which further supports the conclusion that collective behavior persists against thermal disruption. The experimental findings are discussed in terms of a quantum field theory for macroscopic quantum systems.

Possibilities for Groundwater Flow Sensing with Fiber Bragg Grating Sensors.

An understanding of groundwater flow near drinking water extraction wells is crucial when it comes to avoiding well clogging and pollution. A promising new approach to groundwater flow monitoring is the deployment of a network of optical fibers with fiber Bragg grating (FBG) sensors. In preparation for a field experiment, a laboratory scale aquifer was constructed to investigate the feasibility of FBG sensors for this application. Multiparameter FBG sensors were able to detect changes in temperature, pressure, and fiber shape with sensitivities influenced by the packaging. The first results showed that, in a simulated environment with a flow velocity of 2.9 m/d, FBG strain effects were more pronounced than initially expected. FBG sensors of a pressure-induced strain implemented in a spatial array could form a multiplexed sensor for the groundwater flow direction and magnitude. Within the scope of this research, key technical specifications of FBG interrogators for groundwater flow sensing were also identified.

Dynamic Consolidation Measurements in a Well Field Using Fiber Bragg Grating Sensors.

Currently available groundwater flow prediction tools and methods are limited by insufficient spatial resolution of subsurface data and the unknown local heterogeneity. In this field study, fiber Bragg grating (FBG) sensors were installed in an extraction well field to investigate its potential to measure groundwater flow velocity. Reference in-situ pore pressure and temperature measurements were used to identify possible sources of FBG responses. FBG strain sensors were able to detect soil consolidation caused by groundwater extraction from 250 m distance. The results show that FBG responses were influenced by interface friction between soil and FBG packaging. FBG packaging slipped in soil and the effect was more pronounced during higher groundwater flow around a nearby well. These FBG fibers could be applied for indirect flow monitoring that does not require any tracer and provide real-time and long-term data during regular operation of extraction wells.

Non-equilibrium thermodynamics and collective vibrational modes of liquid water in an inhomogeneous electric field.

In this experiment liquid water is subject to an inhomogeneous electric field (∇(2)Ea≈ 10(10) V m(2)) using a high voltage (20 kV) point-plane electrode system. Using interferometry it was found that the application of a strong electric field gradient to water generates local changes in the refractive index of the liquid, polarizes the surface and creates a downward moving electro-convective jet. A maximum temperature difference of 1 °C is measured in the immediate vicinity of the point electrode. Raman spectroscopy performed on water reveals an enhancement of the vibrational collective modes (3250 cm(-1)) as well as an increase in the local mode (3490 cm(-1)) energy. This bimodal enhancement indicates that the spectral changes are not due to temperature changes. The intense field gradient thus establishes an excited subpopulation of vibrational oscillators far from thermal equilibrium. Delocalization of the collective vibrational mode spatially expands this excited population beyond the microscale. Hindered rotational freedom due to electric field pinning of molecular dipoles retards the heat flow and generates a chemical potential gradient. These changes are responsible for the observed changes in the refractive index and temperature. It is demonstrated that polar liquids can thus support local non-equilibrium thermodynamic transient states critical to biochemical and environmental processes.

Identification and quantification of 16 inorganic ions in water by Gaussian curve fitting of near-infrared difference absorbance spectra.

This study shows two novel fitting strategies applied to differential absorbance spectra for identification and quantification of electrolytes. The effects of 16 dissolved salts were investigated in the wavelength range from 14000 to 9091 wavenumbers (714-1100 nm) by linear fits of the differential absorbance values (Y(υ,c)=offset(υ)+b(υ)×c) recorded for each wavenumber (υ) and concentration (c) ranges from 500 to 30 mM. The slopes (b) of these fits resulted in clear fingerprints of the electrolytes. A narrow bandwidth (10754-9618 wavenumbers) sensor can be created using truth tables resulting from the Gaussian curve fitting method.

Ultrafast vibrational energy relaxation of the water bridge.

We report the energy relaxation of the OH stretch vibration of HDO molecules contained in an HDO:D(2)O water bridge using femtosecond mid-infrared pump-probe spectroscopy. We found that the vibrational lifetime is shorter (~630 ± 50 fs) than for HDO molecules in bulk HDO:D(2)O (~740 ± 40 fs). In contrast, the thermalization dynamics following the vibrational relaxation are much slower (~1.5 ± 0.4 ps) than in bulk HDO:D(2)O (~250 ± 90 fs). These differences in energy relaxation dynamics strongly indicate that the water bridge and bulk water differ on a molecular scale.

Nuclear Magnetic Relaxation Mapping of Spin Relaxation in Electrically Stressed Glycerol.

This work discusses nuclear magnetic relaxation effects in glycerol subject to a strong electric field. The methods used are 1.5 T magnetic resonance imaging (MRI), referenced by 9.4 T nuclear magnetic resonance (NMR). While MRI allows a glycerol probe to be sampled with a high voltage (HV) of 16 kV applied to the probe, NMR provides precise molecular data from the sample, but the sample cannot be tested under HV. Using MRI, the recording of magnetic relaxation times was possible while HV was applied to the glycerol. NMR spectroscopy was used to confirm that MRI provides a reasonably accurate estimation of temperature. The applied HV was observed to have a negligible effect on the spin-lattice relaxation time T 1, which represents the energy release to the thermal bath or system enthalpy. In contrast to that, the spin-spin relaxation time T 2, which does represent the local entropy of the system, shows a lower response to temperature while the liquid is electrically stressed. These observations point toward a proton population in electrically stressed glycerol that is more mobile than that found in the bulk, an observation that is in agreement with previously published results for water.

The cost of reaching the 90-90-90 targets: are current investments enough?

PURPOSE OF REVIEW: The 90-90-90 targets were launched with the aim of reaching specific milestones by 2020. To support these targets, modeling has shown that additional resources are needed. This review examines what is known about current investments for HIV in low and middle-income countries, resource needs, and the potential for additional investment. RECENT FINDINGS: Reaching the 90-90-90 targets would place the global community on track to end the AIDS epidemic by 2030, significantly improving health outcomes and reducing future spending needs. Recent analyses indicate, however, that funding has slowed and there is a significant gap in resources needed to reach targets. While some studies have modeled the potential for additional HIV spending based on normative and theoretical benchmarks, there are limitations to such approaches. Others have looked at the potential to increase efficiencies. Even if spending continues at recent rates, there would still be a gap of $6.4 billion in 2020. SUMMARY: There is a significant gap in resources needed to reach the 90-90-90 targets by 2020. It may be possible to reduce the gap through more efficient allocation of resources. In addition, there are efforts underway to mobilize more investment. Ultimately, any gap that remains has implications for health outcomes and future spending.

Potential for additional government spending on HIV/AIDS in 137 low-income and middle-income countries: an economic modelling study.

BACKGROUND: Between 2012 and 2016, development assistance for HIV/AIDS decreased by 20·0%; domestic financing is therefore critical to sustaining the response to HIV/AIDS. To understand whether domestic resources could fill the financing gaps created by declines in development assistance, we aimed to track spending on HIV/AIDS and estimated the potential for governments to devote additional domestic funds to HIV/AIDS. METHODS: We extracted 8589 datapoints reporting spending on HIV/AIDS. We used spatiotemporal Gaussian process regression to estimate a complete time series of spending by domestic sources (government, prepaid private, and out-of-pocket) and spending category (prevention, and care and treatment) from 2000 to 2016 for 137 low-income and middle-income countries (LMICs). Development assistance data for HIV/AIDS were from Financing Global Health 2018, and HIV/AIDS prevalence, incidence, and mortality were from the Global Burden of Disease study 2017. We used stochastic frontier analysis to estimate potential additional government spending on HIV/AIDS, which was conditional on the current government health budget and other finance, economic, and contextual factors associated with HIV/AIDS spending. All spending estimates were reported in 2018 US$. FINDINGS: Between 2000 and 2016, total spending on HIV/AIDS in LMICs increased from $4·0 billion (95% uncertainty interval 2·9-6·0) to $19·9 billion (15·8-26·3), spending on HIV/AIDS prevention increased from $596 million (258 million to 1·3 billion) to $3·0 billion (1·5-5·8), and spending on HIV/AIDS care and treatment increased from $1·1 billion (458·1 million to 2·2 billion) to $7·2 billion (4·3-11·8). Over this time period, the share of resources sourced from development assistance increased from 33·2% (21·3-45·0) to 46·0% (34·2-57·0). Care and treatment spending per year on antiretroviral therapy varied across countries, with an IQR of $284-2915. An additional $12·1 billion (8·4-17·5) globally could be mobilised by governments of LMICs to finance the response to HIV/AIDS. Most of these potential resources are concentrated in ten middle-income countries (Argentina, China, Colombia, India, Indonesia, Mexico, Nigeria, Russia, South Africa, and Vietnam). INTERPRETATION: Some governments could mobilise more domestic resources to fight HIV/AIDS, which could free up additional development assistance for many countries without this ability, including many low-income, high-prevalence countries. However, a large gap exists between available financing and the funding needed to achieve global HIV/AIDS goals, and sustained and coordinated effort across international and domestic development partners is required to end AIDS by 2030. FUNDING: The Bill & Melinda Gates Foundation.

Behavioral study of selected microorganisms in an aqueous electrohydrodynamic liquid bridge.

An aqueous electrohydrodynamic (EHD) floating liquid bridge is a unique environment for studying the influence of protonic currents (mA cm-2) in strong DC electric fields (kV cm-1) on the behavior of microorganisms. It forms in between two beakers filled with water when high-voltage is applied to these beakers. We recently discovered that exposure to this bridge has a stimulating effect on Escherichia coli.. In this work we show that the survival is due to a natural Faraday cage effect of the cell wall of these microorganisms using a simple 2D model. We further confirm this hypothesis by measuring and simulating the behavior of Bacillus subtilis subtilis, Neochloris oleoabundans, Saccharomyces cerevisiae and THP-1 monocytes. Their behavior matches the predictions of the model: cells without a natural Faraday cage like algae and monocytes are mostly killed and weakened, whereas yeast and Bacillus subtilis subtilis survive. The effect of the natural Faraday cage is twofold: First, it diverts the current from passing through the cell (and thereby killing it); secondly, because it is protonic it maintains the osmotic pressure in the cell wall, thereby mitigating cytolysis which would normally occur due to the low osmotic pressure of the surrounding medium. The method presented provides the basis for selective disinfection of solutions containing different microorganisms.

A Quasi-Elastic Neutron Scattering Study of the Dynamics of Electrically Constrained Water.

We have measured the quasi-elastic neutron scattering (QENS) of an electrohydrodynamic liquid bridge formed between two beakers of pure water when a high voltage is applied, a setup allowing to investigate water under high-voltage without high currents. From this experiment two proton populations were distinguished: one consisting of protons strongly bound to oxygen atoms (immobile population, elastic component) and a second one of quasi-free protons (mobile population, inelastic component) both detected by QENS. The diffusion coefficient of the quasi-free protons was found to be D = (26 ± 10) × 10(-5) cm(2) s(-1) with a jump length lav ∼ 3 Å and an average residence time of τ0 = 0.55 ± 0.08 ps. The associated proton mobility in the proton channel of the bridge is ∼9.34 × 10(-7) m(2) V(-1) s(-1), twice as fast as diffusion-based proton mobility in bulk water. It also matches the so-called electrohydrodynamic or "apparent" charge mobility, an experimental quantity which so far has lacked molecular interpretation. These results further corroborate the proton channel model for liquid water under high voltage and give new insights into the molecular mechanisms behind electrohydrodynamic charge transport phenomena and delocalization of protons in liquid water.

The preparation of electrohydrodynamic bridges from polar dielectric liquids.

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Contraction-Induced Changes in Hydrogen Bonding of Muscle Hydration Water.

Protein-water interaction plays a crucial role in protein dynamics and hence function. To study the chemical environment of water and proteins with high spatial resolution, synchrotron radiation-Fourier transform infrared (SR-FTIR) spectromicroscopy was used to probe skeletal muscle myofibrils. Observing the OH stretch band showed that water inside of relaxed myofibrils is extensively hydrogen-bonded with little or no free OH. In higher-resolution measurements obtained with single isolated myofibrils, the water absorption peaks were relatively higher within the center region of the sarcomere compared to those in the I-band region, implying higher hydration capacity of thick filaments compared to the thin filaments. When specimens were activated, changes in the OH stretch band showed significant dehydrogen bonding of muscle water; this was indicated by increased absorption at ∼3480 cm-1 compared to relaxed myofibrils. These contraction-induced changes in water were accompanied by splitting of the amide I (C=O) peak, implying that muscle proteins transition from α-helix to ß-sheet-rich structures. Hence, muscle contraction can be characterized by a loss of order in the muscle-protein complex, accompanied by a destructuring of hydration water. The findings shed fresh light on the molecular mechanism of muscle contraction and motor protein dynamics.

Persisting water droplets on water surfaces.

Droplets of various liquids may float on the respective surfaces for extended periods of time prior to coalescence. We explored the features of delayed coalescence in highly purified water. Droplets several millimeters in diameter were released from a nozzle onto a water surface. Results showed that droplets had float times up to hundreds of milliseconds. When the droplets did coalesce, they did so in stepwise fashion, with periods of quiescence interspersed between periods of coalescence. Up to six steps were noted before the droplet finally vanished. Droplets were released in a series, which allowed the detection of unexpected abrupt float-time changes throughout the duration of the series. Factors such as electrostatic charge, droplet size, and sideways motion had considerable effect on droplet lifetime, as did reduction of pressure, which also diminished the number of steps needed for coalescence. On the basis of present observations and recent reports, a possible mechanism for noncoalescence is considered.

Effect of buffers on aqueous solute-exclusion zones around ion-exchange resins.

Interaction between charged surfaces in aqueous solution is a fundamental feature of colloid science. Theoretically, surface potential falls to half its value at a distance equal to a Debye length, which is typically on the order of tens to hundreds of nanometers. This potential prevents colloids from aggregating. On the other hand, long-range surface effects have been frequently reported. Here we report additional long-range effects. We find that charged latex particles in buffer solutions are uniformly excluded from several-hundred-micron-thick shells surrounding ion-exchange beads. Exclusion is observed whether the beads are charged similarly or oppositely to the particles. Hence, electrostatic interactions between bead and microsphere do not cause particle exclusion. Rather, exclusion may be the consequence of water molecules re-orienting to produce a more ordered structure, which then excludes the particles.