Hasil untuk "physics.ed-ph"

J. W. Clayton, D. Tretiak

R. B. Moon, J. Richards

Observation of the ^(31)P signal from various intracellular phosphates can provide a convenient, nondestructive technique for determining intracellular conditions such as pH. This procedure has been explored with particular reference to the erythrocyte. Both the chemical shift of intracellular inorganic phosphate relative to that of serum phosphate and the positions of, and more especially the difference between, the chemical shifts of 2,3-diphosphoglycerate have been used to monitor intracellular pH of erythrocytes whose hemoglobin has been liganded with carbon monoxide.

T. Rink, R. Tsien, T. Pozzan

Measurements have been made of cytoplasmic pH, (pHi) and free Mg2+ concentration, ( [Mg2+]i), in pig and mouse lymphocytes. pHi was measured in four ways: by a digitonin null-point technique; by direct measurement of the pH of freeze-thawed cell pellets; from the 31P nuclear magnetic resonance (NMR) spectrum of intracellular inorganic phosphate; and by the use of a newly synthesized, intracellularly- trappable fluorescent pH indicator. In HEPES buffered physiological saline with pH 7.4 at 37 degrees C, pHi was close to 7.0. Addition of physiological levels of HCO3- and CO2 transiently acidified the cells by approximately 0.1 U. Mitogenic concentrations of concanavalin A (Con A) had no measurable effect on pH in the first hour. [Mg2+]i was assessed in three ways: (a) from the external Mg2+ null-point at which the ionophore A23187 produced no net movement of Mg2+ or H+; (b) by Mg- sensitive electrode measurements in freeze-thawed pellets; and (c) from the 31P nuclear magnetic resonance spectrum of the gamma-phosphate of intracellular ATP. Total cell Mg2+ was approximately 12 mmol per liter cell water. The NMR data indicated [Mg2+]i greater than 0.5 mM. The null-point method gave [Mg2+]i approximately 0.9 nM. The electrode measurements gave 1.35 mM, which was thought to be an overestimate. Exposure to mitogenic doses of Con A for 1 h gave no detectable change in total or free Mg2+.

R. Zepp

M. Šimek, J. Cooper

S. Ikawa, K. Kitano, S. Hamaguchi

R. A. French, A. Jacobson, Bojeong Kim et al.

Ricardo D. Matheus, Elmer M. Gennaro, Marcelo T. Yamashita

We examine more than a decade of quota policy at Unesp, analyzing Physics, Biology, and Pedagogy as representative programs of distinct assessment styles. Quotas show little impact in Physics, where the admission barrier is low, and in Pedagogy, where high pass rates make it difficult to differentiate students, but they reveal systematic differences in Biology. Focusing the analysis on Calculus I - an introductory course in Physics and other Science, Technology, Engineering, and Mathematics (STEM) programs - for which much larger statistics are available, a clear hierarchy emerges: students admitted through open competition perform best, those from public schools achieve intermediate results, and students from racial quotas perform worst. When students are divided directly by the admittance exam grade, the performance difference is even clearer. Statistical analysis also shows that, contrary to expectation, the probability of passing decreases as the number of attempts increases, indicating that initial educational gaps are difficult to overcome within higher education.

Abhinav Roy, Niti Singh

We present the design and testing of a compact, low-cost stellar spectrometer developed for undergraduate and outreach applications. The instrument employs a 600 lines/mm diffraction grating, a CMOS monochrome sensor, and a 3D-printed mount integrated with reflecting telescopes. Calibration was performed using helium emission sources in the laboratory and Vega as a spectrophotometric standard, supported by a custom Python-based image-processing pipeline for wavelength calibration and spectral stacking. The spectrometer successfully recorded usable spectra of bright stars including Vega, Sirius, Procyon, Capella, and Betelgeuse, covering spectral types A through M. The results demonstrate that meaningful stellar spectroscopy can be achieved with accessible, low-cost equipment, providing a practical framework for student-led astronomical instrumentation projects.

Samuel Bernard-Bernardet, Benjamin Apffel

The spinorial ball is an electronic manipulable device that we recently introduced to discuss the origin of spin-1/2 from rotations group representation, without relying on the quantum mechanics framework. Nevertheless, it is also a macroscopic visualization of a quantum two-level system, and can thus be used to gain intuition on some generic features of qubits. The present article therefore aims to complement and extend our previous work by discussing how the spinorial ball can be used to visualize quantum mechanics features. The Bloch sphere, the Hopf fibration and the Berry phase can for instance easily be seen and manipulated using this original device. We also discuss how the spinorial ball can be used to visualize Hamiltonian evolution, and we describe an explicit mapping between the ball's motion and the evolution of 1/2-spin in arbitrary magnetic field. An electronic implementation of projective measurement that matches the predictions of quantum mechanics is also proposed. The present article is written as a practical guide to manipulate the ball and establishes the exact correspondence between the spinorial ball and a generic two-level system.

Luis Medrano Navarro, Luis Martín Moreno, Sergio G Rodrigo

The research in Artificial Intelligence methods with potential applications in science has become an essential task in the scientific community last years. Physics Informed Neural Networks (PINNs) is one of this methods and represent a contemporary technique that is based on the fundamentals of neural networks to solve differential equations. These kind of networks have the potential to improve or complement classical numerical methods in computational physics, making them an exciting area of study. In this paper, we introduce PINNs at an elementary level, mainly oriented to physics education so making them suitable for educational purposes at both undergraduate and graduate levels. PINNs can be used to create virtual simulations and educational tools that aid in understating complex physical concepts and processes where differential equations are involved. By combining the power of neural networks with physics principles, PINNs can provide an interactive and engaging learning experience that can improve students' understanding and retention of physics concepts in higher education.

M. Tantama, Y. Hung, G. Yellen

Fei Wang, K. Shih

Soumya Das, M. Jim Hendry, Joseph Essilfie-Dughan

S. Parks, J. Chiche, J. Pouysségur

Kejin Zhou, Haoming Liu, Shanrong Zhang et al.

S. Vylkova, A. Carman, H. Danhof et al.

ABSTRACT pH homeostasis is critical for all organisms; in the fungal pathogen Candida albicans, pH adaptation is critical for virulence in distinct host niches. We demonstrate that beyond adaptation, C. albicans actively neutralizes the environment from either acidic or alkaline pHs. Under acidic conditions, this species can raise the pH from 4 to >7 in less than 12 h, resulting in autoinduction of the yeast-hyphal transition, a critical virulence trait. Extracellular alkalinization has been reported to occur in several fungal species, but under the specific conditions that we describe, the phenomenon is more rapid than previously observed. Alkalinization is linked to carbon deprivation, as it occurs in glucose-poor media and requires exogenous amino acids. These conditions are similar to those predicted to exist inside phagocytic cells, and we find a strong correlation between the use of amino acids as a cellular carbon source and the degree of alkalinization. Genetic and genomic approaches indicate an emphasis on amino acid uptake and catabolism in alkalinizing cells. Mutations in four genes, STP2, a transcription factor regulating amino acid permeases, ACH1 (acetyl-coenzyme A [acetyl-CoA] hydrolase), DUR1,2 (urea amidolyase), and ATO5, a putative ammonia transporter, abolish or delay neutralization. The pH changes are the result of the extrusion of ammonia, as observed in other fungi. We propose that nutrient-deprived C. albicans cells catabolize amino acids as a carbon source, excreting the amino nitrogen as ammonia to raise environmental pH and stimulate morphogenesis, thus directly contributing to pathogenesis. IMPORTANCE Candida albicans is the most important fungal pathogen of humans, causing disease at multiple body sites. The ability to switch between multiple morphologies, including a rounded yeast cell and an elongated hyphal cell, is a key virulence trait in this species, as this reversible switch is thought to promote dissemination and tissue invasion in the host. We report here that C. albicans can actively alter the pH of its environment and induce its switch to the hyphal form. The change in pH is caused by the release of ammonia from the cells produced during the breakdown of amino acids. This phenomenon is unprecedented in a human pathogen and may substantially impact host physiology by linking morphogenesis, pH adaptation, carbon metabolism, and interactions with host cells, all of which are critical for the ability of C. albicans to cause disease. Candida albicans is the most important fungal pathogen of humans, causing disease at multiple body sites. The ability to switch between multiple morphologies, including a rounded yeast cell and an elongated hyphal cell, is a key virulence trait in this species, as this reversible switch is thought to promote dissemination and tissue invasion in the host. We report here that C. albicans can actively alter the pH of its environment and induce its switch to the hyphal form. The change in pH is caused by the release of ammonia from the cells produced during the breakdown of amino acids. This phenomenon is unprecedented in a human pathogen and may substantially impact host physiology by linking morphogenesis, pH adaptation, carbon metabolism, and interactions with host cells, all of which are critical for the ability of C. albicans to cause disease.

Xiaona Han, Zhenqiang Dong, Minmin Fan et al.

Ling-ling Wang, Longfei Wang, X. Ren et al.

Andrea López-Incera, Andreas Hartmann, Wolfgang Dür

We present a game-based approach to teach Bell inequalities and quantum cryptography at high school. The approach is based on kinesthetic activities and allows students to experience and discover quantum features and their applications first-hand. We represent quantum states by the orientation of students, and mimic quantitative random behaviour and measurements using dice and apps.