Students' developing knowledge in a subject discipline: insights from combining quantitative and qualitative methods

In this paper we describe an example of research that combined quantitative and qualitative methods in order to investigate students' developing mathematical reasoning over time and to identify factors that were influential in this developmen

Structure and morphology of X-ray selected AGN hosts at 1<z<3 in CANDELS-COSMOS field

We analyze morphologies of the host galaxies of 35 X-ray selected active galactic nucleus (AGNs) at $z\sim2$ in the Cosmic Evolution Survey (COSMOS) field using Hubble Space Telescope/WFC3 imaging taken from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). We build a control sample of 350 galaxies in total, by selecting ten non-active galaxies drawn from the same field with the similar stellar mass and redshift for each AGN host. By performing two dimensional fitting with GALFIT on the surface brightness profile, we find that the distribution of S$\`e$rsic index (n) of AGN hosts does not show a statistical difference from that of the control sample. We measure the nonparametric morphological parameters (the asymmetry index A, the Gini coefficient G, the concentration index C and the M20 index) based on point source subtracted images. All the distributions of these morphological parameters of AGN hosts are consistent with those of the control sample. We finally investigate the fraction of distorted morphologies in both samples by visual classification. Only $\sim$15% of the AGN hosts have highly distorted morphologies, possibly due to a major merger or interaction. We find there is no significant difference in the distortion fractions between the AGN host sample and control sample. We conclude that the morphologies of X-ray selected AGN hosts are similar to those of nonactive galaxies and most AGN activity is not triggered by major merger.Comment: 5 pages, 3 figures, accepted for publication in The Astrophysical Journal Letter

Enhancing the efficiency of human pancreatic islet dissociation

Over half a million children worldwide are affected by type 1 diabetes, an autoimmune disease characterized by the destruction of insulin-producing pancreatic beta cells. Islet transplantation is a treatment that is currently limited by the lack of vascular network to support large islets post-transplantation. A promising proposal is to disperse native islets into single-cell suspensions and re-aggregate them into smaller, uniform “pseudo-islets”. Substantial cell loss during islet dispersion, however, remains an important obstacle that limits the yield of pseudo-islet aggregates, especially considering the scarcity of donor islets. To optimize the dissociation protocol, we experimented with different cell dissociation reagents, concentrations, and times in order to establish standards for future pseudo-islet formation procedure.Isolated human islets were dissociated using Trypsin, TrypLE, Accutase, Accumax, and Dispase. These dissociation reagents were identified through literature and the concentrations as well as dissociation times used were in ranges previously outlined. Cell counts of viable cells were recorded using Trypan Blue and PicoGreen DNA assay to quantify cell loss during islet dispersion, filtration and post-culture. Assessment of the viability of the re-aggregated pseudo-islets post-culture was performed using the Alamar Blue assay.Preliminary results showed the potential for 5.8-fold increase in cell recovery which provides evidence of the significant need to optimize the dissociation protocol. TrypLE showed the highest recovery of cells both post-dissociation and filtration. Results from the project are promising and further investigations will allow the results to become applicable to clinical trials. Improving the recovery and quality of dissociated islet cells will directly help increase the number of treatable patients from the limited supply of donor islets

Digestive System of Anourosorex squamipes - Appearance and Morphological Features

Background: Anourosorex squamipes have a wide range of feeding habits, which is a kind of omnivorous animal. As an indispensable part of organisms, the differentiation degree of digestive system indicates the evolution degree of species. The higher the evolution degree of animals, the higher the differentiation of digestive system. At present, the research on Anourosorex squamipes digestive system mainly focuses on its feeding habits and mainly depends on the direct observation of gastric contents with the naked eye, but the research on the morphology of digestive system has not been reported. Materials, Methods &amp; Results: Twenty adult Anourosorex squamipes were selected to investigate the characteristics of the appearance, including the contour parameters (body weight, body length, forefoot length, posterior foot length, nasal length, tail length), digestive system parameters (length of esophagus, intestinal length, intestinal weight, stomach weight and liver weight) and morphological structure of the small intestine by histological methods. The results showed that there were no significant differences in body weight, body length, forefoot length, posterior foot length, nasal length and tail length between males and females in Anourosorex squamipes, and no significant differences were observed in parameters of digestive system in length of esophagus, intestinal length, intestinal weight, stomach weight and liver weight. There were no significant differences in villus height, muscular layer thickness and villus height/recess depth (V/C) between males and females, but only ileal crypt depth decreased significantly in males. Discussion: Animal morphological characteristics are closely related to their life habits, unique organs and lifestyles ensure that they thrive on earth. In our study, we found that unique characters are found by observing the appearance of Anourosorex squamipes, the snout is blunt and short, the eyes are degenerated, and the tail is very short and covered with scales, which may be related to its feeding habits, the living environment-long-term nocturnal life in underground with minimal exposure to sunlight, and the unique tail can reduce the friction between tail and soil during the movement. There are certain differences in the appearance parameters of male and female Anourosorex squamipes, but are not significant. The esophagus, stomach, intestine, liver and other parameters of Anourosorex squamipes have little difference between males and females, indicating that Anourosorex squamipes don’t have obvious distinctions between males and females in food intake. However, the liver weight of male Anourosorex squamipes is larger than female, indicating that the physiological metabolic capacity of male is larger than female. It is speculated that this may be related to the difference in the amount of activity between males and females in daily life. Males are more active and require more energy, but their digestion and absorption abilities are weaker than females. Therefore, the male Anourosorex squamipes needs more food to provide energy to meet the daily physiological metabolism, and the larger stomach capacity provides the essential conditions for the male to store more food. In addition, we found that the crypt depth of male Anourosorex squamipes is generally greater than that of females, especially in the ileal crypt depth, indicating that the female’s cell maturation rate is greater than that of the male. It is speculated that the female has a greater demand for nutrient absorption and better digestion and absorption of food, because females need to give birth to offspring and require greater nutrition.   Keywords: Anourosorex squamipes, contour characteristics, digestive system, small intestine

A Multi-Pass Optically Pumped Rubidium Atomic Magnetometer with Free Induction Decay

A free-induction-decay (FID) type optically-pumped rubidium atomic magnetometer driven by a radio-frequency (RF) magnetic field is presented in this paper. Influences of parameters, such as the temperature of rubidium vapor cell, the power of pump beam, and the strength of RF magnetic field and static magnetic field on the amplitude and the full width at half maximum (FWHM) of the FID signal, have been investigated in the time domain and frequency domain. At the same time, the sensitivities of the magnetometer for the single-pass and the triple-pass probe beam cases have been compared by changing the optical path of the interaction between probe beam and atomic ensemble. Compared with the sensitivity of ~21.2 pT/Hz^(1/2) in the case of the single-pass probe beam, the amplitude of FID signal in the case of the triple-pass probe beam has been significantly enhanced, and the sensitivity has been improved to ~13.4 pT/Hz^(1/2). The research in this paper provids a reference for the subsequent study of influence of different buffer gas pressure on the FWHM and also a foundation for further improving the sensitivity of FID rubidium atomic magnetometer by employing a~polarization-squeezed light as probe beam, to achieve a sensitivity beyond the photo-shot-noise level.Comment: sensors,2022,22(19):759

Position and Attitude Control Based on Single Neuron PID With Gravity Compensation for Quad Rotor UAV

Aimed at the deficiency of existing PID controller for quad rotor UAV, a single neuron PID controller with gravity compensation is presented. After using feed forward control to compensate gravity, the position loop adopts PID control to ensure control accuracy, while the attitude loop adopts single neuron control to increase adaptive ability. Then, by using Matlab/simulink simulation software, the position control of quad rotor UAV is carried out, and the simulation result shows, compared with the traditional double closed loop PID controller, the control algorithm based on the Single Neuron adaptive PID with gravity compensation can effectively improve the robustness and adaptability of the quad rotor UAV system