Hasil untuk "physics.ed-ph"

B. Bjellqvist, G. Hughes, C. Pasquali et al.

M. Karnovsky

The lead hydroxide stain of Watson (1958) used for increasing contrast in thin sections for electron microscopy has found acceptance in many laboratories. However, this stain has an unfortunate tendency to form precipitates (probably of lead carbonate (5)) on exposure to the air, thus contaminating the sections and irritating the observer. This drawback has led to the development of several modifications (2, 3) of the original method of staining and the use of ingenious devices (4, 5) for preventing exposure to air and consequent precipitate formation. We offer the following alternative methods which, we believe, are simpler to perform than those hitherto described. They have the additional advantages mentioned below. The methods are based on the observation that highly alkaline solutions of lead salts (pH > 11.5) yield relatively stable solutions which stain rapidly and intensely, thus obviating the hazard of precipitation to a marked degree. The methods have these additional advantages: the staining solutions are easily and rapidly prepared, are simply stored, and are stable for long periods of time. Furthermore, they can be efficiently used, many grids being treated simultaneously, without excessive precautions being taken against lead carbonate precipitation. Finally, "difficult" material, embedded in media which characteristically yield rather low contrast, such as epoxide resins, can be rapidly and easily stained. "C lean" preparations, of high contrast, are routinely obtained. As will be discussed later, it is thought that in these highly alkaline staining solutions lead is present as an hydroxide complex anion (plumbite ion) and that this anion is responsible for the staining. The methods of preparation are based on this hypothesis. Two methods for preparing the staining solutions have been found useful:

F. Gallagher, M. Kettunen, S. Day et al.

C. Liang, Zih-Sin Wang, C. Bruell

E. Padan, E. Bibi, M. Ito et al.

The capacity of bacteria to survive and grow at alkaline pH values is of widespread importance in the epidemiology of pathogenic bacteria, in remediation and industrial settings, as well as in marine, plant-associated and extremely alkaline ecological niches. Alkali-tolerance and alkaliphily, in turn, strongly depend upon mechanisms for alkaline pH homeostasis, as shown in pH shift experiments and growth experiments in chemostats at different external pH values. Transcriptome and proteome analyses have recently complemented physiological and genetic studies, revealing numerous adaptations that contribute to alkaline pH homeostasis. These include elevated levels of transporters and enzymes that promote proton capture and retention (e.g., the ATP synthase and monovalent cation/proton antiporters), metabolic changes that lead to increased acid production, and changes in the cell surface layers that contribute to cytoplasmic proton retention. Targeted studies over the past decade have followed up the long-recognized importance of monovalent cations in active pH homeostasis. These studies show the centrality of monovalent cation/proton antiporters in this process while microbial genomics provides information about the constellation of such antiporters in individual strains. A comprehensive phylogenetic analysis of both eukaryotic and prokaryotic genome databases has identified orthologs from bacteria to humans that allow better understanding of the specific functions and physiological roles of the antiporters. Detailed information about the properties of multiple antiporters in individual strains is starting to explain how specific monovalent cation/proton antiporters play dominant roles in alkaline pH homeostasis in cells that have several additional antiporters catalyzing ostensibly similar reactions. New insights into the pH-dependent Na(+)/H(+) antiporter NhaA that plays an important role in Escherichia coli have recently emerged from the determination of the structure of NhaA. This review highlights the approaches, major findings and unresolved problems in alkaline pH homeostasis, focusing on the small number of well-characterized alkali-tolerant and extremely alkaliphilic bacteria.

S. Hug, O. Leupin

A. Richter, G. Paschew, Stephan Klatt et al.

Stimuli-responsive hydrogels are materials with great potential for development of active functionalities in fluidics and micro-fluidics. Based on the current state of research on pH sensors, hydrogel sensors are described qualitatively and quantitatively for the first time. The review introduces the physical background of the special properties of stimuli-responsive hydrogels. Following, transducers are described which are able to convert the non-electrical changes of the physical properties of stimuli-responsive hydrogels into an electrical signal. Finally, the specific sensor properties, design rules and general conditions for sensor applications are discussed.

R. Rozendal, H. Hamelers, C. Buisman

M. Högberg, P. Högberg, D. Myrold

S. Kemmitt, D. Wright, K. Goulding et al.

Dengyu Pan, Jingchun Zhang, Zhen Li et al.

Huan Meng, Min Xue, T. Xia et al.

I. Yu, Wei Zhang, H. Holdaway et al.

N. N. Salva, H. R. Salva

We study the precession of a Foucault pendulum using a new approach. We characterize the support anisotropy by the difference between the maximum and minimum periods of the pendulum along the principal axes of the support. Then we compute the total precession rate, taking into account both the Airy precession of a spherical pendulum and the Coriolis precession due to the Earth's rotation. To study the resulting motion we developed a calculation loop, period after period, which describes the movement of the oscillatory trajectory of the bob. To test our model, we mounted a test pendulum of 480.3 cm length and measured its periods and precession. The rate of precession is sensitive to the dimensions of the pendulum, the anisotropy of the support, and the initial conditions. We find that for certain amplitudes the precession can stop entirely, while the pendulum continues to oscillate. It is also possible to obtain continuous precession at lower oscillation amplitudes. We give an upper bound for this critical oscillation amplitude. We close with a discussion of the implications of our findings for the design of Foucault pendulums used in demonstrations and lab experiments.

Ruzin Aganoglu, Andrea Bossmann, Ulrike Böhm et al.

Gender imbalance among German physicists persists, with fewer women in advanced degrees and research leadership roles. Although female enrollment in Physics programs increased slightly until 2022, potentially influenced by COVID-19 the long-term trend remains uncertain. Despite the rise in female Ph.D. students and foreign representation, female professors in Physics and Astronomy stagnated below 14 %, indicating significant underrepresentation. Anticipated revisions to the WissZeitVG law may impact female mainstreaming efforts, potentially leading to greater precarization of research staff. Women make up only around 20 % of employed physicists, with low visibility in the community, as seen in the representation of female physicists in prestigious awards. Addressing this imbalance requires structural interventions beyond mere encouragement and empowerment.

Arun Kumar Pati, Vlatko Vedral, Erik Sjoqvist

The fundamental division of the total quantum evolution phase into geometric and dynamical components is a central problem in quantum physics. Here, we prove a remarkably simple and universal law demonstrating that this partitioning is governed, at every instant, solely by a single geometric quantity: the Bargmann angle (Bures angle). This result provides a universally applicable and rigorous way to define the exact fraction of the total phase that is geometric versus dynamical in origin, thereby establishing a new quantitative link between the dynamics of quantum evolution and the geometry of the state space. This finding has immediate practical consequences, furnishing a real-time measure of the geometricity of an evolution for designing high-fidelity geometric quantum gates with optimized robustness, and opening new avenues for quantum speed limit and coherent control.

Wen Shi, Xiaohua Li, Huimin Ma

Robert Harlander, Sven Yannick Klein, Magnus Schaaf

FeynGame is an open-source software tool to draw Feynman diagrams, but also to get acquainted with their structure. This article reports on a number of new features which have been added to FeynGame since its first release. These include full support of LaTeX for the line and vertex labels, the possibility to automatically include momentum arrows, new graphical elements, and new pedagogical features. FeynGame is freely available as jar or MacOS app file from https://web.physik.rwth-aachen.de/user/harlander/software/feyngame, and as source code from https://gitlab.com/feyngame/FeynGame.

D. Vandamme, I. Foubert, I. Fraeye et al.

Carmen Fies, Chris Packham

The San Antonio Teacher Training Astronomy Academy (SATTAA) completed its fourth annual iteration in June 2021 . While the program began as a face-to-face professional development opportunity for future and current school teachers, it transitioned to a fully online opportunity in 2020. In our efforts to offer an astronomy education program that is inclusive and particularly attentive to highly diverse populations, the transition to online programming became a core aspect of scaling up the program. The 2021 iteration featured an international facilitation team, and, for the first time, supported teachers from across the State of Texas. In this paper, we share data on how the facilitation team transitioned from a local to an international group, and on how the participant pool expanded from local to state-wide.