Independent gradient model based on Hirshfeld partition (IGMH): A new method for visual study of interactions in chemical systems

The independent gradient model (IGM) originally proposed in Phys. Chem. Chem. Phys., 19, 17928 (2017) has been increasingly popular in visual analysis of intramolecular and intermolecular interactions in recent years, and it has many clear advantages over the widely employed noncovalent interaction (NCI) method, such as intrafragment and interfragment interactions can be elegantly isolated and thus separately studied, the isosurfaces are smoother and less jaggy. However, we frequently observed that there is an evident shortcoming of IGM map in graphically studying weak interactions, that is its isosurfaces are usually too bulgy; in these cases, not only the graphical effect is poor, but also the color on some areas on the isosurfaces is inappropriate and may lead to erroneous analysis conclusions. In addition, the IGM method was originally proposed based on promolecular density, which is quite crude and does not take actual electronic structure into account. In this article, we first present a detailed overview of the IGM analysis, and then propose our new variant of IGM, namely IGM based on Hirshfeld partition of molecular density (IGMH), which replaces the free-state atomic densities involved in the IGM method with the atomic densities derived by Hirshfeld partition of actual molecular electron density. This change makes IGM have more rigorous physical background. In addition, we describe some indices defined on the top of IGM or IGMH framework to quantify contributions from various atoms or atom pairs to interaction between specific fragments. A large number of application examples in this article, including molecular and periodic systems, weak and chemical bond interactions, fully demonstrate the important value of IGMH in intuitively understanding interactions in chemical systems. Comparisons also showed that the IGMH usually has markedly better graphical effect than IGM and overcomes known problems in IGM. Currently IGMH analysis has been efficiently supported in our freely available and user-friendly wavefunction analysis code Multiwfn (http://sobereva.com/multiwfn), and a detailed tutorial is presented. We hope that IGMH will become a new popular method among chemists for exploring interactions in wide variety of chemical systems.

Independent gradient model based on Hirshfeld partition (IGMH): A new method for visual study of interactions in chemical systems

The independent gradient model (IGM) originally proposed in Phys. Chem. Chem. Phys., 19, 17928 (2017) has been increasingly popular in visual analysis of intramolecular and intermolecular interactions in recent years, and it has many clear advantages over the widely employed noncovalent interaction (NCI) method, such as intrafragment and interfragment interactions can be elegantly isolated and thus separately studied, the isosurfaces are smoother and less jaggy. However, we frequently observed that there is an evident shortcoming of IGM map in graphically studying weak interactions, that is its isosurfaces are usually too bulgy; in these cases, not only the graphical effect is poor, but also the color on some areas on the isosurfaces is inappropriate and may lead to erroneous analysis conclusions. In addition, the IGM method was originally proposed based on promolecular density, which is quite crude and does not take actual electronic structure into account. In this article, we first present a detailed overview of the IGM analysis, and then propose our new variant of IGM, namely IGM based on Hirshfeld partition of molecular density (IGMH), which replaces the free-state atomic densities involved in the IGM method with the atomic densities derived by Hirshfeld partition of actual molecular electron density. This change makes IGM have more rigorous physical background. In addition, we describe some indices defined on the top of IGM or IGMH framework to quantify contributions from various atoms or atom pairs to interaction between specific fragments. A large number of application examples in this article, including molecular and periodic systems, weak and chemical bond interactions, fully demonstrate the important value of IGMH in intuitively understanding interactions in chemical systems. Comparisons also showed that the IGMH usually has markedly better graphical effect than IGM and overcomes known problems in IGM. Currently IGMH analysis has been efficiently supported in our freely available and user-friendly wavefunction analysis code Multiwfn (http://sobereva.com/multiwfn), and a detailed tutorial is presented. We hope that IGMH will become a new popular method among chemists for exploring interactions in wide variety of chemical systems.

Prehistoric communities of the River Dee

This volume presents the results of archaeological fieldwork undertaken along the River Dee, Aberdeenshire, north-east Scotland, by the Mesolithic Deeside voluntary community archaeology group between 2017 and 2019. A total of 42 fields were investigated, from which over 11,000 lithics were recovered, representing at least 15 archaeological sites and a span of human activity covering some 10,000 years from around 12,000 BC to c 2000 BC. Finds from the Late Upper Palaeolithic, Mesolithic, Neolithic and Bronze Age were present. Work comprised fieldwalking, test pitting, specialist analysis, and small-scale excavation. The investigation described here is significant not just for the light it throws on the early prehistoric populations along the River Dee but also for the methodology by which investigation was undertaken, as this provides a potential model for work in other areas. Both aspects are covered in the report. The River Dee flows between postglacial gravel and sand terraces, the structure of which has played an important role for the early settlers of the area, and this is covered in some detail in order to provide the physical background framework for the sites. There are also sections on more specialised geophysical and geoscience techniques where these were undertaken, together with a summary of research on the palaeoenvironmental conditions throughout the millennia of prehistory. The artefactual evidence comprises lithic assemblages which were all catalogued as fieldwork progressed; the contents of each site are presented, together with more detailed analysis of the finds from test pitted sites. Finally, given the rich archaeological record from the area, the results of the present project are set into the wider context of the evidence for prehistoric settlement along the river, and there is consideration of future directions for further fieldwork. While all authors have contributed to the whole volume, individual sections that present specialist work by specific teams have been attributed. The distribution maps and GIS are the work of Irvine Ross. Dates given are calibrated BC dates. The Nethermills Farm NM4 dates are calibrated using the Oxford Radiocarbon Accelerator Unit calibration program OxCal 4 (Bronk Ramsey 2009) and their date ranges are calibrated using the IntCal13 atmospheric calibration curve (Reimer et al 2013). Optically stimulated luminescence (OSL) was used to profile sediment accumulations on some of the sites and obtain information relating to site formation, but it was not used for dating in any of the projects.

Proposal on Hybrid Design Method of Outer Port Facilities Using Failure Probability

Lately, many efforts have been made to address the problem concerned with deterministic design using reliability-based design, and the research results are significant. However, there is considerable confusion in the design practice regarding how to use failure probability, the main output of reliability-based design. In this rationale, this study aims to develop a robust hybrid deterministic design method for outer port facilities using the failure probability. To this end, we first reviewed the design process of Eulleungdo East Breakwater, some of which were recently damaged. It was revealed that the exceeding probability of design wave height of 5.2 m was merely 0.65, which corresponds to a return period of 1.53 years, showing that the outer port facilities of Ulleungdo were considerably underdesigned. In an effort to find an alternative that can overcome the limitations of the deterministic design method, which is highly likely to involve subjective judgment, a Level III reliability design was carried out. In doing so, tri-modal Gaussian wave slope distribution was used as a probabilistic model for wave slope. Numerical results show that failure probability was excessively estimated in the Gaussian distribution, and even if the TTP size was slightly reduced, the failure probability increased rapidly. Although failure probability is sensitive to the change in nominal diameter, there is a gradually increasing zone where the failure probability change rapidly decreases when the nominal diameter is larger than the critical value. The presence of a Gradually Increasing Zone mentioned above implies that it is uneconomical and has no physical background to adjust the nominal diameter to be larger than the critical value. Therefore, it can be easily conceived that outer port facility design should be performed using a failure probability provided by Level III reliability-based design.

Physics Doesn't Bite - A Simple Experiment for Introducing Biomechanical Operational Principles of the Temporomandibular Joint

Biophysics is rarely mentioned as one of the most useful parts of dental and medical students' curricula. However, with growing complexity of tools and methods used in diagnostics and therapy, the knowledge of their physical foundations becomes important and helps with choosing the optimal solutions for both, a patient and a doctor. The aim of the proposed activity is to develop students' intuition about simple physical models that help with understanding fundamental properties of temporomandibular joint (TMJ). A simple device, which allows for bite force measurement, is proposed. It is based on beam bending and a strain gauge Wheatstone bridge circuit, mounted on two connected arms: the stiff one and the more elastic one. Linear regression is the only mathematical concept needed for understanding the physical background of the proposed activity. During the proposed activity - measuring of bite force for incisors, premolars and molars - students are confronted with basic concepts, such as lever, torque, electrical circuit, calibration curve. By utilizing a simple idea, instead of a commercially available device, students can understand where the data come from. Proposed system delivers physiologically reasonable results.

Three-Method Hybrid Numerical Simulation for Surface-Plasmon-Enhanced GaInN-Based Light-Emitting Diodes with Metal-Embedded Nanostructures

In this paper, a hybrid numerical simulation tool is introduced and performed for GaInN-based light-emitting diodes (LEDs) with metal-embedded nanostructure to theoretically predict external quantum efficiency (EQE), which composed of finite-difference time-domain, rigorous coupled wave analysis, and ray tracing. The advantage is that the proposed method provides results supported by sufficient physical background within a reasonable calculation time. From the simulation results, the EQE of LED with Ag-nanoparticles embedded nanostructure is expected to be enhanced by as high as ∼1.6 times the conventional LED device in theory.

Liquid crystal lasers: the last decade and the future

The demonstration of the first ruby laser in 1960 led to a revolution in science and technology. The lasers have significantly influenced the development of new approaches to spectroscopy, giving previously undreamed insights into physics, chemistry, and other scientific areas. The search for new materials for light amplification is one of the fundamental subjects of modern photonics and nanotechnology. In this review, we summarize the most appealing progress in developing liquid crystalline (LC) micro and nano-lasers during the last decade, together with their applications and description of perspectives for the future. We will describe the physical background necessary to understand the operation principles of LC lasers, including a description of radiative transition phenomena and LC matter. The article will be divided into separate sections concerning different approaches of LC lasers realization, including; band edge, DFB, DBR, VECSEL, and random cavities utilization. We will also discuss how the LC phases can influence the design of laser devices. Finally, the potential applications, perspectives, and conclusions will be discussed at the end of the article.

On the Physical Background of Nerve Pulse Propagation: Heat and Energy

Recent studies have revealed the complex structure of nerve signals in axons. Besides the electrical signal, mechanical and thermal effects are also detected in many experimental studies. In this paper, the mathematical models of heat generation are analysed within the framework of a general model derived earlier by the authors. The main mechanisms of heat generation are seemingly Joule heating and endo- and exothermic reactions. The concept of internal variables permits to model the heat relaxation typical to these reactions. The general energy balance of the whole signal is analysed based on physical mechanisms responsible for emerging the components of a signal which constitutes a wave ensemble. The novelty of this study is in describing the energy for all the components of the wave ensemble. Some open questions are listed for further studies.