Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State

The crystallization behavior of an archetypical soft/hard hybrid nanocomposite, that is, an <i>n-</i>octadecane C₁₈/SiO₂-nanoparticle composite, was investigated by a combination of differential scanning calorimetry (DSC) and variable-temperature solid-state ¹³C nuclear magnetic resonance (VT solid-state ¹³C NMR) as a function of silica nanoparticles loading. Two latent heat peaks prior to bulk freezing, observed for composites with high silica loading, indicate that a sizable fraction of C₁₈ molecules involve two phase transitions unknown from the bulk C₁₈. Combined with the NMR measurements as well as experiments on alkanes and alkanols at planar amorphous silica surfaces reported in the literature, this phase behavior can be attributed to a transition toward a 2D liquid-like monolayer and subsequently a disorder-to-order transition upon cooling. The second transition results in the formation of a interface-frozen monolayer of alkane molecules with their molecular long axis parallel to the nanoparticles’ surface normal. Upon heating, the inverse phase sequence was observed, however, with a sizable thermal hysteresis in accord with the characteristics of the first-order phase transition. A thermodynamic model considering a balance of interfacial bonding, chain stretching elasticity, and entropic effects quantitatively accounts for the observed behavior. Complementary synchrotron-based wide-angle X-ray diffraction (WAXD) experiments allow us to document the strong influence of this peculiar interfacial freezing behavior on the surrounding alkane melts and in particular the nucleation of a rotator phase absent in the bulk C₁₈

Self-Assembly of Gold Nanoparticles at the Oil–Vapor Interface: From Mono- to Multilayers

Alkylthiol-coated gold nanoparticles spontaneously segregate from dispersion in toluene to the toluene–vapor interface. We show that surface tension drops during segregation with a rate that depends on particle concentration. Mono- and multilayers of particles form depending on particle concentration, time, and temperature. X-ray reflectometry indicates fast monolayer formation and slow multilayer formation. A model that combines diffusion-limited segregation driven by surface energy and heterogeneous agglomeration driven by dispersive van der Waals particle interactions is proposed to describe film formation

What Makes a Good Palliative Care Physician? A Qualitative Study about the Patient’s Expectations and Needs when Being Admitted to a Palliative Care Unit

<div><p>Objective</p><p>The aims of the study were to examine a) patients’ knowledge of palliative care, b) patients’ expectations and needs when being admitted to a palliative care unit, and c) patient’s concept of a good palliative care physician.</p><p>Methods</p><p>The study was based on a qualitative methodology, comprising 32 semistructured interviews with advanced cancer patients admitted to the palliative care unit of the Medical University of Vienna. Interviews were conducted with 20 patients during the first three days after admission to the unit and after one week, recorded digitally, and transcribed verbatim. Data were analyzed using NVivo 10 software, based on thematic analysis enhanced with grounded theory techniques.</p><p>Results</p><p>The results revealed four themes: (1) information about palliative care, (2) supportive care needs, (3) being treated in a palliative care unit, and (4) qualities required of palliative care physicians. The data showed that patients lack information about palliative care, that help in social concerns plays a central role in palliative care, and attentiveness as well as symptom management are important to patients. Patients desire a personal patient-physician relationship. The qualities of a good palliative care physician were honesty, the ability to listen, taking time, being experienced in their field, speaking the patient’s language, being human, and being gentle. Patients experienced relief when being treated in a palliative care unit, perceived their care as an interdisciplinary activity, and felt that their burdensome symptoms were being attended to with emotional care. Negative perceptions included the overtly intense treatment.</p><p>Conclusions</p><p>The results of the present study offer an insight into what patients expect from palliative care teams. Being aware of patient’s needs will enable medical teams to improve professional and individualized care.</p></div

Baseline Characteristics of Patients.

<p>Baseline Characteristics of Patients.</p

Profile of the Study Participants.

<p>Profile of the Study Participants.</p

Interview Guide for the first and second Interview.

<p>Interview Guide for the first and second Interview.</p

Surface Morphology of Vapor-Deposited Chitosan: Evidence of Solid-State Dewetting during the Formation of Biopolymer Films

Chitosan is a useful and versatile biopolymer with several industrial and biological applications. Whereas its physical and physicochemical bulk properties have been explored quite intensively in the past, there is a lack of studies regarding the morphology and growth mechanisms of thin films of this biopolymer. Of particular interest for applications in bionanotechnology are ultrathin films with thicknesses under 500 Å. Here, we present a study of thin chitosan films prepared in a dry process using physical vapor deposition and <i>in situ</i> ellipsometric monitoring. The prepared films were analyzed with atomic force microscopy in order to correlate surface morphology with evaporation parameters. We find that the surface morphology of our final thin films depends on both the optical thickness, i.e., measured with ellipsometry, and the deposition rate. Our work shows that ultrathin biopolymer films can undergo dewetting during film formation, even in the absence of solvents and thermal annealing