Baryon Spin and Magnetic Moments in Relativistic Chiral Quark Models

Spin-flavor fractions of quarks in the proton and several hyperons are obtained from their lowest order chiral fluctuations involving Goldstone bosons. SU(3) flavor breaking, relativistic effects and the axial anomaly are included. The validity of the Karl-Sehgal formulas for magnetic moments is studied as well.Comment: 24 pages, 7 tables, no figure

Pre-registration nursing students’ experiences of stress

This research study aimed to explore stress among pre-registration nursing students in the United Kingdom. The specific objectives of the study were: To explore the experience of stress among pre-registration nursing students; to determine the type of stress and sources of stress in pre-registration nursing field; to investigate the perceptions of pre-registration nursing students on stress and anxiety in pre-registration nursing programme; and to identify suitable measures that can be implemented to help the pre-registration nursing students to cope with stress. Qualitative research method and phenomenological approach was used in this study and the data was collected with the help of face-to-face semi-structured interviews. The setting for the current study was a higher education institution (HEI) that delivers pre-registration nurse education in the UK. The study sample was six pre-registration nursing students from the East Midlands who were in the first, second, and in final year of the study program leading to BSc (Hons) Nursing with NMC Registration. A thematic analysis of the data was conducted which led to four emergent themes: Pre-registration nursing students’ experiences of stress; re-registration nursing students’ perceptions of stress and anxiety; sources of stress in the nursing field; and measures for coping with stress. The findings revealed that the pre-registration nursing students in this study perceived stress as a problem associated with human health that basically is caused by academic pressure presented by either theoretical assignments, projects, and examinations and placement demands such as while caring for patients. Moreover, stress among pre-registration nursing students was found to be a problem embedded in their lifestyle that impacts their wellbeing. Further findings showed that the study participants perceived that stress and anxiety are interrelated; anxiety takes place in response to stress resulting from academic and clinical placement pressure; and anxiety has a strong relationship with stress and is a contributor to depression too. The study participants also perceived that the major causes of stress include social distress, financial problems, academic pressure, demands of clinical placement, and family expectations. Academic pressure was found to be the most common cause of stress among the pre-registration nursing students in this study. Lastly, the findings revealed that the coping strategies that can help pre-registration nursing students to manage stress are adopting social support mechanisms, encouraging physical activities, and spiritual support. Keywords: Pre-registration nursing students, Stress, Coping. DOI: 10.7176/JHMN/85-14 Publication date: January 31st 202

Violations of Lorentz Covariance in Light Front Quark Models

Electromagnetic form factors of the nucleon from relativistic quark models are analyzed: results from null-plane projection of the Feynman triangle diagram are compared with a Bakamjian-Thomas model. The magnetic form factors of the models differ by about 15% at spacelike momentum transfer 0.5 GeV^2, while the charge form factors are much closer. Spurious contributions to electromagnetic form factors due to violations of rotational symmetry are eliminated from both models. One method changes magnetic form factors by about 10%, whereas the charge form factors stay nearly the same. Another one changes the charge form factor of the Bakamjian-Thomas model by more than 50%.Comment: 19 pages, 9 figures, Late

Poor old pores-The challenge of making and maintaining nuclear pore complexes in aging

The nuclear pore complex (NPC) is the sole gateway to the nuclear interior, and its function is essential to all eukaryotic life. Controlling the functionality of NPCs is a tremendous challenge for cells. Firstly, NPCs are large structures, and their complex assembly does occasionally go awry. Secondly, once assembled, some components of the NPC persist for an extremely long time and, as a result, are susceptible to accumulate damage. Lastly, a significant proportion of the NPC is composed of intrinsically disordered proteins that are prone to aggregation. In this review, we summarize how the quality of NPCs is guarded in young cells and discuss the current knowledge on the fate of NPCs during normal aging in different tissues and organisms. We discuss the extent to which current data supports a hypothesis that NPCs are poorly maintained during aging of nondividing cells, while in dividing cells the main challenge is related to the assembly of new NPCs. Our survey of current knowledge points toward NPC quality control as an important node in aging of both dividing and nondividing cells. Here, the loss of protein homeostasis during aging is central and the NPC appears to both be impacted by, and to drive, this process

Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly

During mitosis, the nuclear envelope merges with the endoplasmic reticulum (ER), and nuclear pore complexes are disassembled. In a current model for reassembly after mitosis, the nuclear envelope forms by a reshaping of ER tubules. For the assembly of pores, two major models have been proposed. In the insertion model, nuclear pore complexes are embedded in the nuclear envelope after their formation. In the prepore model, nucleoporins assemble on the chromatin as an intermediate nuclear pore complex before nuclear envelope formation. Using live-cell imaging and electron microscope tomography, we find that the mitotic assembly of the nuclear envelope primarily originates from ER cisternae. Moreover, the nuclear pore complexes assemble only on the already formed nuclear envelope. Indeed, all the chromatin-associated Nup 107–160 complexes are in single units instead of assembled prepores. We therefore propose that the postmitotic nuclear envelope assembles directly from ER cisternae followed by membrane-dependent insertion of nuclear pore complexes

Designing an Arabic Handwritten Segmentation System

The greatest difficulty facing the recognition of Arabic handwritten words is segmentation, because Arabic handwriting is cursive with complex multi-form styles. Hence, intensive research efforts are needed to reach an effective Arabic handwriting segmentation system. This paper presents a system which uses morphological features of the Arabic characters for segmentation. The proposed system segments non-overlapped (horizontally connected -e.g. "حسن") as well as overlapped (vertically connected - e.g. "نجد") characters. The result is not very good one. However, it arrives at good directives for more research. As the writing was freely without any restrictions, both over-segmentation and under-segmentation problems affect the system.

Live imaging of single nuclear pores reveals unique assembly kinetics and mechanism in interphase

Recruitment of nuclear pore complex (NPC) components during interphase occurs in a different order and with slower kinetics than during postmitotic NPC assembly, suggesting the two processes are regulated by distinct mechanisms

Q2Q^2 Independence of QF2/F1QF_2/F_1, Poincare Invariance and the Non-Conservation of Helicity

A relativistic constituent quark model is found to reproduce the recent data regarding the ratio of proton form factors, $F_2(Q^2)/F_1(Q^2)$. We show that imposing Poincare invariance leads to substantial violation of the helicity conservation rule, as well as an analytic result that the ratio $F_2(Q^2)/F_1(Q^2)\sim 1/Q$ for intermediate values of $Q^2$.Comment: 13 pages, 7 figures, to be submitted to Phys. Rev. C typos corrected, references added, 1 new figure to show very high Q^2 behavio