Aging cellular networks: chaperones as major participants

We increasingly rely on the network approach to understand the complexity of cellular functions. Chaperones (heat shock proteins) are key "networkers", which have among their functions to sequester and repair damaged protein. In order to link the network approach and chaperones with the aging process, we first summarize the properties of aging networks suggesting a "weak link theory of aging". This theory suggests that age-related random damage primarily affects the overwhelming majority of the low affinity, transient interactions (weak links) in cellular networks leading to increased noise, destabilization and diversity. These processes may be further amplified by age-specific network remodelling and by the sequestration of weakly linked cellular proteins to protein aggregates of aging cells. Chaperones are weakly linked hubs [i.e., network elements with a large number of connections] and inter-modular bridge elements of protein-protein interaction, signalling and mitochondrial networks. As aging proceeds, the increased overload of damaged proteins is an especially important element contributing to cellular disintegration and destabilization. Additionally, chaperone overload may contribute to the increase of "noise" in aging cells, which leads to an increased stochastic resonance resulting in a deficient discrimination between signals and noise. Chaperone- and other multi-target therapies, which restore the missing weak links in aging cellular networks, may emerge as important anti-aging interventions.Comment: 7 pages, 4 figure

DCC dynamics with the SU(3) linear sigma model

The SU(3) extension of the linear sigma model is employed to elucidate the effect of including strangeness on the formation of disoriented chiral condensates. By means of a Hartree factorization, approximate dispersion relations for the 18 scalar and pseudoscalar meson species are derived and their self-consistent solution makes it possible to trace out the thermal path of the two order parameters as well as delineate the region of instability within which spontaneous pair creation becomes possible. The results depend significantly on the employed sigma mass, with the highest values yielding the largest regions of instability. An approximate solution of the equations of motion for the order parameter in scenarios emulating uniform scaling expansions show that even with a rapid quench only the pionic modes grow unstable. Nevertheless, the rapid and oscillatory relaxation of the order parameters leads to enhanced production of both pions and (to a lesser degree) kaons.Comment: 29 pages, RevTeX, 11 postscript figures, discussion about anomaly term adde

Influence of the U(1)_A Anomaly on the QCD Phase Transition

The SU(3)_{r} \times SU(3)_{\ell} linear sigma model is used to study the chiral symmetry restoring phase transition of QCD at nonzero temperature. The line of second order phase transitions separating the first order and smooth crossover regions is located in the plane of the strange and nonstrange quark masses. It is found that if the U(1)_{A} symmetry is explicitly broken by the U(1)_{A} anomaly then there is a smooth crossover to the chirally symmetric phase for physical values of the quark masses. If the U(1)_{A} anomaly is absent, then there is a phase transition provided that the \sigma meson mass is at least 600 MeV. In both cases, the region of first order phase transitions in the quark mass plane is enlarged as the mass of the \sigma meson is increased.Comment: 5 pages, 3 figures, Revtex, discussion extended and references added. To appear in PR

Distribution of COL9A2 and COL9A3 Gene Polymorphism in Male Chinese Singaporean - A Pilot Observational Study

The association between allelic variants and lumbar disc degenerative disease (DDD) has been investigated in Europe and Northern Asia. However, this has not been investigated in Southeast Asia. This observational study aims to compare the distribution of COL9A2 and COL9A3 gene polymorphism among male Chinese Singaporeans with and without lumbar DDD. COL9A2 gene polymorphism was investigated in p326 (tryptophan 2, Trp2 and glutamine 2, Gln2, alleles) and p335 (valine 2 or Val2 allele). COL9A3 gene polymorphism was investigated in p17 (glycine 3 or Gly3 allele) and p103 (tryptophan 3 or Trp3 allele). The Val2 allele was significantly decreased in the group with lumbar DDD (p < 0.05). No significant difference in allelic distributions of Trp2, Gln2 and Gly3 was found. The Trp3 allele was absent from all the subjects. The presence of at least one Val2 allele appears to have a protective effect against DDD. However, these should be interpreted with caution, given the limitations. Further investigations are warranted in order to verify such genetic predisposition prior to the potential development of preventative or therapeutic strategies in the near future

Implementing a suite of skills modules in a first-year engineering project-based subject

Students commencing engineering at university often have no prior experience of engineering, what the profession entails and the distinctions between disciplines. Consequently, tertiary institutions often offer common first-year engineering subjects that aim to give students an experience of the engineering profession and method, while providing exposure to different disciplines through applied project-based learning. The difficulty with this approach is that there is a wide variance in terms of students’ knowledge, skills, past experiences, and expectations. In a team context, these discrepancies could lead to conflict and poor educational outcomes. Furthermore, if the project is of reasonable length, students might be locked into a discipline-focused project that they realise does not suit them as a potential major. To this end, a suite of self-enrolled skills modules was developed to support student skills development in a first-year, project-based engineering subject under two categories – technical, focusing on skills that had direct applicability to the projectwork and general, focusing on skills related to assessment. The modules aimed to (1) improve individuals’ skills in a team context; (2) give students an opportunity to learn skills unrelated to their chosen project in a low-stakes context; and (3) promote interaction and peer-learning outside of their project team and class, building a wider sense of cohort. This paper discusses the creation of the modules and evaluates their outcomes in achieving their goals based on numerous data gathered throughout the semester and student feedback. Initial results have been positive and suggest future directions for development

QCD and the Chiral Critical Point

As an extension of $QCD$, consider a theory with ``$2+1$'' flavors, where the current quark masses are held in a fixed ratio as the overall scale of the quark masses is varied. At nonzero temperature and baryon density it is expected that in the chiral limit the chiral phase transition is of first order. Increasing the quark mass from zero, the chiral transition becomes more weakly first order, and can end in a chiral critical point. We show that the only massless field at the chiral critical point is a sigma meson, with the universality class that of the Ising model. Present day lattice simulations indicate that $QCD$ is (relatively) near to the chiral critical point.Comment: 7 pages + 2 figures, BNL-GGP-

Returning To On-Campus Activities For First-Year Engineering Skills Development - A Comparative Study

Prior work by the authors on student skills development detailed the implementation of a suite of skills modules in a first-year engineering course. These modules were instrumental components in supporting the course’s project-based framework that offered flexibility of choice and timing in a low-risk setting. It was found that, while receiving overall favourable student feedback, most students only completed the minimum requirements and largely chose technical modules according to the relevance to their project topic. Due to the cessation of on-campus teaching activities caused by the COVID-19 pandemic, these modules were delivered wholly online. With the lifting of restrictions the following year, the modules were made available with several distinctions: (a) the option of completing wholly online or a mix of online and on-campus activities; and (b) a change to a graded assessment scheme to encourage students to put more effort into their completion. An evaluation performed on the modules revealed that online-only modules were attended at a rate comparable to on-campus activities. The distribution of module completions over the semester was influenced by module availability, students\u27 time management and module alignment with their project. A higher concentration of module completions occurring closer to deadlines indicated that students were more time pressed and completed the modules just in time. A change to the grading scheme did not appear to affect the take up rates of the modules but did result in better quality of work. Students still elected to complete modules aligned with their project, consistent with previous trends