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We believe that a natural focus of the physics education research community is on understanding and improving students' learning in our physics courses. Due to the increase in technology, we can bring laboratory experiments closer to our students. It is necessary to update our laboratories technologically to get closer to the world in which our students live. With this in mind, we have considered the magnetic field created by a linear quadrupole and we have studied its dependence on distance, n being the exponent of distance. The main objective of this exercise is for our students to discover that the exponent n is very close to -4. The purpose of this work is to show that a laboratory is a powerful tool that increases significant learning under three conditions: 1) the practice must not be too sophisticated; 2) students must handle objects in the lab; and 3) the practice must be scientifically accurate, including the fitting using the least-squares approximation, and the following and necessary error calculation. We provide this practice so that all interested physics teachers can use it and adapt it to their specific laboratory.

Fanconi anemia (FA) patients display an exacerbated risk of oral squamous cell carcinoma (OSCC) and oral potentially malignant lesions (OPMLs) at early ages. As patients have defects in their DNA repair mechanisms, standard-of-care treatments for OSCC such as radiotherapy and chemotherapy, give rise to severe toxicities. New methods for early diagnosis are urgently needed to allow for treatment in early disease stages and achieve better clinical outcomes. We conducted a prospective, longitudinal study wherein liquid biopsies from sixteen patients with no clinical diagnoses of OPML and/or OSCC were analyzed for the presence of mutations in cancer genes. The DNA from saliva and plasma were sequentially collected and deep-sequenced, and the clinical evaluation followed over a median time of approximately 2 years. In 9/16 FA patients, we detected mutations in cancer genes (mainly TP53) with minor allele frequencies (MAF) of down to 0.07%. Importantly, all patients that had mutations and clinical follow-up data after mutation detection (n = 6) developed oral precursor lesions or OSCC. The lead-time between mutation detection and tumor diagnosis ranged from 23 to 630 days. Strikingly, FA patients without mutations displayed a significantly lower risk of developing precursor lesions or OSCCs. Therefore, our diagnostic approach could help to stratify FA patients into risk groups, which would allow for closer surveillance for OSCCs or precursor lesions.

This article summarizes a study published in the British Journal of Haematology that examines the outcomes of hematopoietic stem cell transplantation (HSCT) for sickle cell disease (SCD) using different conditioning regimens. The study found that both busulfan-fludarabine (bu-flu) and treosulfan-fludarabine (treo-flu) regimens resulted in excellent overall survival rates and low rates of acute and chronic graft-versus-host disease (GVHD) and graft failure. However, treo-flu had a higher incidence of chronic GVHD and extensive chronic GVHD, but a lower frequency of gonadal damage compared to bu-flu. The study emphasizes the potential of HSCT with myeloablative conditioning in treating SCD patients. The report provides a culturally sensitive and comprehensive analysis of the topic, making it a valuable resource for library patrons conducting research on this subject. [Extracted from the article]

The homotopy perturbation method is used to solve the nonlinear differential equation that governs the nonlinear oscillations of a simple pendulum, and an approximate expression for its period is obtained. Only one iteration leads to high accuracy of the solutions and the relative error for the approximate period is less than 2% for amplitudes as high as 130 degrees. Another important point is that this method provides an analytical expression for the angular displacement as a function of time as the sum of an infinite number of harmonics; although for practical purposes it is sufficient to consider only a finite number of harmonics. We believe that the present study may be a suitable and fruitful exercise for teaching and better understanding perturbation techniques in advanced undergraduate courses on classical mechanics. (Contains 1 figure.)

Interference and diffraction of light are elementary topics in optics. The aim of the work presented here is to develop an accurate and cheap optical-system simulation software that provides a virtual laboratory for studying the effects of propagation in both time and space for the near- and far-field regions. In laboratory sessions, this software can let optical engineering undergraduates simulate many optical systems based on thin slits. The numerical method used is the finite-difference time-domain (FDTD) method that has been successfully applied in many engineering fields. Using this numerical method, the irradiance distribution can be successfully evaluated in different planes far from the simulation grid without degrading performance. In addition, an easy-to-use MATLAB GUI handles all the parameters of the FDTD simulation and computes theoretical values of irradiance for both the Fresnel and Fraunhofer regions. Therefore, by using this software, the student is able to analyze the behavior of the Fresnel and Fraunhofer expressions as a function of the distance. This distance is defined as the space between the slits plane and the plane that contains the virtual screen on which the irradiance pattern is represented. (Contains 1 table and 7 figures.)

An approximate scheme for obtaining the period of a simple pendulum for large-amplitude oscillations is analysed and discussed. When students express the exact frequency or the period of a simple pendulum as a function of the oscillation amplitude, and they are told to expand this function in a Taylor series, they always do so using the oscillation amplitude as the variable, without considering that if they change the variable (in this paper to the new variable "m"), a different Taylor series expansion may be performed which is in addition more accurate than previously published ones. Students tend to believe that there is one and only one way of performing a Taylor series expansion of a specific function. The approximate analytical formula for the period is obtained by means of a Taylor expansion of the exact frequency taking into account the Kidd-Fogg formula for the period. This approach based on the Taylor expansion of the frequency about a suitable value converges quickly even for large amplitudes. We believe that this method may be very useful for teaching undergraduate courses on classical mechanics and helping students understand nonlinear oscillations of a simple pendulum. (Contains 3 figures.)

In this paper, we analyse a simple experiment to study the effects of polarized light. A simple optical system composed of a polarizer, a retarder (cellotape) and an analyser is used to study the effect on the polarization state of the light which impinges on the setup. The optical system is characterized by means of a Jones matrix, and a simple procedure based on Jones vectors is used to obtain an expression for the intensity after the light passes through the optical system. The light intensity is measured by a photodetector and the expression obtained theoretically is experimentally validated. By fitting the experimental intensity data, the value of the retardation introduced by the retarder can also be obtained. (Contains 2 tables and 8 figures.)

A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme. (Contains 3 footnotes and 5 figures.)

A linearization method of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force which allows us to obtain a frequency-amplitude relation which is valid not only for small but also for large amplitudes and, sometimes, for the complete range of oscillation amplitudes. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of the technique. (Contains 6 figures.)