Density depletion and enhanced fluctuations in water near hydrophobic solutes: identifying the underlying physics

We investigate the origin of the density depletion and enhanced density fluctuations that occur in water in the vicinity of an extended hydrophobic solute. We argue that both phenomena are remnants of the critical drying surface phase transition that occurs at liquid-vapor coexistence in the macroscopic planar limit, ie. as the solute radius $R_s\to\infty$. Focusing on the density profile $\rho(r)$ and a sensitive spatial measure of fluctuations, the local compressibility profile $\chi(r)$, we develop a scaling theory which expresses the extent of the density depletion and enhancement in compressibility in terms of $R_s$, the strength of solute-water attraction $\varepsilon_s$, and the deviation from liquid-vapor coexistence $\delta\mu$. Testing the predictions against results of classical density functional theory for a simple solvent and Grand Canonical Monte Carlo simulations of a popular water model, we find that the theory provides a firm physical basis for understanding how water behaves at a hydrophobe.Comment: 5 pages, 4 figures. To appear in Phys. Rev. Let

Understanding the physics of hydrophobic solvation

Simulations of water near extended hydrophobic spherical solutes have revealed the presence of a region of depleted density and accompanying enhanced density fluctuations.The physical origin of both phenomena has remained somewhat obscure. We investigate these effects employing a mesoscopic binding potential analysis, classical density functional theory (DFT) calculations for a simple Lennard-Jones (LJ) solvent and Grand Canonical Monte Carlo (GCMC) simulations of a monatomic water (mw) model. We argue that the density depletion and enhanced fluctuations are near-critical phenomena. Specifically, we show that they can be viewed as remnants of the critical drying surface phase transition that occurs at bulk liquid-vapor coexistence in the macroscopic planar limit, i.e.~as the solute radius $R_s\to\infty$. Focusing on the radial density profile $\rho(r)$ and a sensitive spatial measure of fluctuations, the local compressibility profile $\chi(r)$, our binding potential analysis provides explicit predictions for the manner in which the key features of $\rho(r)$ and $\chi(r)$ scale with $R_s$, the strength of solute-water attraction $\varepsilon_{sf}$, and the deviation from liquid-vapor coexistence of the chemical potential, $\delta\mu$. These scaling predictions are confirmed by our DFT calculations and GCMC simulations. As such our theory provides a firm basis for understanding the physics of hydrophobic solvation.Comment: 18 page

Ante-Autobiography and the Archive of Childhood

This essay examines the concept of children’s autobiography via several autobiographical extracts written by the author as a child. Although only a small proportion of people will compose and publish a full-length autobiography, almost everyone will, inadvertently, produce an archive of the self, made from public records and private documents. Here, such works are seen as providing access to writing both about and by children. The essay explores the ethics and poetics of children’s writing via the key debates in life writing; in particular, the dynamic relationship between adults and children, both as distinct stages of life and dual parts of one autobiographical identity. The term “ante-autobiography” is coined to refer to these texts which come before or instead of a full-length narrative. They are not read as less than or inadequate versions of autobiography, but rather as transgressive and challenging to chronological notions of the genre

Light-space

The works which comprise my thesis show are oil paintings and drawings done directly from life. The subjects of the works are either still life objects with plants, the human figure with plants and some objects without plant material. The paintings explore a number of the myriad possibilities of light and space offered by direct painting in a particular environment. The still life situations used for my work generally include objects on hand and a variety of plant material. Most of the plants selected are large with a varied leaf or stem structure. The backgrounds include some drapery, white paper and the walls and partitions of the studio area. While a number of objects may be used in any given painting, they are generally dispersed in open arrangements permitting free visual movement from one to the other, corresponding to my intention of treating them as elements of a spatial continuum rather than as distinct entities. The objects themselves are unimportant as subject matter. While exploring what light and space does to objects in a particular environment, I discovered that light can make objects as light or heavy as the negative light-space which surrounds them. A leaf need not appear to be floating if its space and light are such to give it the weight of the leaf's container. The light-space of the environment gives substance to the objects or figures within it. I have also found that light can intensify space, creating a greater or lesser tension or pull between the objects. I discovered that this same activity often carried the movement into the surrounding space

Using smartwatches to observe changes in activity during recovery from critical illness following COVID-19:a 1 year multi-centre observational study

BACKGROUND: As a sequela of the COVID-19 pandemic, a large cohort of critical illness survivors have had to recover in the context of ongoing societal restrictions. OBJECTIVE: We aimed to use smartwatches (Fitbit Charge 3; Fitbit LLC) to assess changes in the step counts and heart rates of critical care survivors following hospital admission with COVID-19, use these devices within a remote multidisciplinary team (MDT) setting to support patient recovery, and report on our experiences with this. METHODS: We conducted a prospective, multicenter observational trial in 8 UK critical care units. A total of 50 participants with moderate or severe lung injury resulting from confirmed COVID-19 were recruited at discharge from critical care and given a smartwatch (Fitbit Charge 3) between April and June 2020. The data collected included step counts and daily resting heart rates. A subgroup of the overall cohort at one site—the MDT site (n=19)—had their smartwatch data used to inform a regular MDT meeting. A patient feedback questionnaire and direct feedback from the MDT were used to report our experience. Participants who did not upload smartwatch data were excluded from analysis. RESULTS: Of the 50 participants recruited, 35 (70%) used and uploaded data from their smartwatch during the 1-year period. At the MDT site, 74% (14/19) of smartwatch users uploaded smartwatch data, whereas 68% (21/31) of smartwatch users at the control sites uploaded smartwatch data. For the overall cohort, we recorded an increase in mean step count from 4359 (SD 3488) steps per day in the first month following discharge to 7914 (SD 4146) steps per day at 1 year (P=.003). The mean resting heart rate decreased from 79 (SD 7) beats per minute in the first month to 69 (SD 4) beats per minute at 1 year following discharge (P<.001). The MDT subgroup’s mean step count increased more than that of the control group (176% increase vs 42% increase, respectively; +5474 steps vs +2181 steps, respectively; P=.04) over 1 year. Further, 71% (10/14) of smartwatch users at the MDT site and 48% (10/21) of those at the control sites strongly agreed that their Fitbit motivated them to recover, and 86% (12/14) and 48% (10/21), respectively, strongly agreed that they aimed to increase their activity levels over time. CONCLUSIONS: This is the first study to use smartwatch data to report on the 1-year recovery of patients who survived a COVID-19 critical illness. This is also the first study to report on smartwatch use within a post–critical care MDT. Future work could explore the role of smartwatches as part of a randomized controlled trial to assess clinical and economic effectiveness. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.12968/ijtr.2020.010

The Vehicle, November 1960, Vol. 3 no. 1

CONTENTS To the ReaderStaffpage 2 N’ = N : 1Donald C. Blairpage 3 ConsistencyDonald C. Blairpage 3 Unto MeLinda Kay Campbellpage 4 The Meek Shall InheritE. J. B. page 5 The Infinite QuestLarry W. Dudleypage 6 Dreamer’s DawnMike Hindmanpage 7 BirthNancy Coepage 7 The Lost DutchmanDonald C. Blairpage 8 W. E. Noonan IRobert S. Hodgepage 8 A Soldier’s OrdealDonald E. Shephardsonpage 9 Personal PossessionMary Beilpage 11 Thine The GloryDonald C. Blairpage 12 The ThornJan Holstlawpage 13 A Lord’s Day MorningLinda Campbellpage 14 Observations of a 6-Year-OldTom McPeakpage 15 Jewels of TimeJudith Jerintspage 16 LavenderE. J. B. page 16https://thekeep.eiu.edu/vehicle/1008/thumbnail.jp

Microscopic origins of charge transport in triphenylene systems

We study the effects of molecular ordering on charge transport at the mesoscale level in a layer of approximate to 9000 hexa-octyl-thio-triphenylene discotic mesogens with dimensions of approximate to 20 x 20 x 60 nm(3). Ordered (columnar) and disordered isotropic morphologies are obtained from a combination of atomistic and coarse-grained molecular-dynamics simulations. Electronic structure codes are used to find charge hopping rates at the microscopic level. Energetic disorder is included through the Thole model. Kinetic Monte Carlo simulations then predict charge mobilities. We reproduce the large increase in mobility in going from an isotropic to a columnar morphology. To understand how these mobilities depend on the morphology and hopping rates, we employ graph theory to analyze charge trajectories by representing the film as a charge-transport network. This approach allows us to identify spatial correlations of molecule pairs with high transfer rates. These pairs must be linked to ensure good transport characteristics or may otherwise act as traps. Our analysis is straightforward to implement and will be a useful tool in linking materials to device performance, for example, to investigate the influence of local inhomogeneities in the current density. Our mobility-field curves show an increasing mobility with field, as would be expected for an organic semiconductor