Modeling Human Motor Systems in Nonlinear Dynamics: Intentionality and Discrete Movement Behaviors

Attempts to understand human movement systems from the perspective of nonlinear dynamics have increased in recent years, although research has almost exclusively focused on modeling rhythmical movements as limit cycle oscillators. Only a limited amount of work has been undertaken on discrete movements, generally only in the form of numerical simulations and mathematical models. In this paper we briefly overview the key findings from previous research on movement systems as nonlinear dynamical systems, and report data from a behavioral experiment on the coordination observed in a prehension movement under both discrete and rhythmical conditions. In a rhythmical condition subjects grasped dowels in time to a metronomic beat, whereas in a discrete condition a target dowel was grasped within a predetermined movement time. A scanning procedure was implemented to monitor changes in the time of relative final hand closure during hand transport to the dowel. For each condition, a pre-test and post-test of 10 trials were also conducted either side of the scanning trial block. No effects between condition or trial block were noted and there was a large amount of within-subject variability in the coordination data. The findings support previous theoretical modeling suggesting that subject intentionality acts as a more powerful constraint on the intrinsic dynamics of the movement system in discrete compared to rhythmical conditions. The high levels of individual variability were interpreted as being due to the competition between specific and non-specific control parameters (e.g., the subject's intentionality and the metronomic beat). It is concluded that discrete prehension movements appear amenable to a nonlinear dynamical analysis. The data also point to the innovative use of within-subject analyses in future work modeling motor systems as nonlinear dynamical systems.     

MWCNTs/metal (Ni, Co, Fe) oxide nanocomposite as potential material for supercapacitors application in acidic and neutral media

Supercapacitive properties of synthesised metal oxides nanoparticles (MO where M = Ni, Co, Fe) integrated with multi-wall carbon nanotubes (MWCNT) on basal plane pyrolytic graphite electrode (BPPGE) were investigated. Successful modification of the electrode with the MWCNT-MO nanocomposite was confirmed with spectroscopic and microscopic techniques. Supercapacitive properties of the modified electrodes in sulphuric acid (H₂SO₄) and sodium sulphate (Na₂SO₄) electrolytes were investigated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic constant current charge–discharge (CD) techniques. The specific capacitance values followed similar trend with that of the cyclic voltammetry and the electrochemical impedance experiments and are slightly lower than values obtained using the galvanostatic charge–discharge cycling. MWCNT-NiO-based electrode gave best specific capacitance of 433.8 mF?cm^?2 (ca 2,119 F?g^?1) in H₂SO₄. The electrode exhibited high electrochemical reproducibility with no significant changes over 1,000 cyclic voltammetry cycles.     

E2 polarization charge in Sn

The nucleus ¹⁰²Sn, which is the lightest Sn isotope with known excited states, was investigated with the ⁵⁰Cr(⁵⁸Ni,α2n) reaction using delayed in-beam γ-ray and conversion-electron spectroscopy. The experimental setup was designed to study the decay of μs-long isomeric states by placing γ-ray and electron detectors behind the focal plane of the Fragment Mass Analyzer at the Argonne National Laboratory. A 44 keV conversion-electron line corresponding to the (6⁺)→(4⁺) transition in ¹⁰²Sn was identified and a half-life of 0.62^+0.43_−0.19 μs was measured for the (6⁺) state. From the available experimental information neutron effective charges from 1.6 to 2.3 e were deduced, based on the comparison with different shell-model calculations.     

Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium

Neutron-rich isotopes of palladium were produced via the fission of²³⁸U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyväskylä. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For¹¹⁴Pd and¹¹⁶Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of¹¹⁸Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT _1/2=1.9±0.1 s andQ _β=4.0±0.2 MeV. The decay schemes of¹¹⁴Pd,¹¹⁶Pd and¹¹⁸Pd include — respectively — two, two and four 0⁺→1⁺ Gamow-Teller beta transitions with logft values between 4.1 and 5.1. The strength of these transitions is discussed in terms of the extreme single particle shell model with pairing and the spherical proton-neutron quasiparticle random phase approximation. The possible role of deformation is considered using a shell correction method. Predictions for the decay properties of the as yet unobserved¹²⁰Pd are given.     

Hypericin phototoxicity induces different modes of cell death in melanoma and human skin cells

Hypericin, the major component of St. John's Wort, absorbs light in the UV and visible ranges whereupon it becomes phototoxic through the production of reactive oxygen species. Although photodynamic mechanisms (i.e. through endogenous photosensitizers) play a role in UVA phototherapy for the treatment of skin disorders such as eczema and psoriasis, photodynamic therapy employing exogenous photosensitizers are currently being used only for the treatment of certain forms of non-melanoma skin cancers and actinic keratoses. There are few reports however on its use in treating melanomas. This in vitro study analyses the phototoxic effect of UVA (400-315 nm) - activated hypericin in human pigmented and unpigmented melanomas and immortalised keratinocytes and melanocytes. We show that neither hypericin exposure nor UV irradiation alone reduces cell viability. We show that an exposure to 1 microM UVA-activated hypericin does not bring about cell death, while 3 microM activated hypericin induces a necrotic mode of cell death in pigmented melanoma cells and melanocytes and an apoptotic mode of cell death in non-pigmented melanoma cells and keratinocytes. We hypothesis that the necrotic mode of cell death in the pigmented cells is possibly related to the presence of melanin-containing melanosomes in these cells and that the hypericin-induced increase in reactive oxygen species leads to an increase in permeability of melanosomes. This would result in toxic melanin precursors (of an indolic and phenolic nature) leaking into the cytoplasm which in turn leads to cell death. Hypericin localisation in the endoplasmic reticulum in these cells shown by fluorescent microscopy, further support a disruption in cellular processing and induction of cell death. In contrast, this study shows that cells that do not contain melanosomes (non-pigmented melanoma cells and keratinocytes) die by apoptosis. Further, using a mitochondrial-specific fluorescent dye, we show that intracellular accumulation of hypericin induces a mitochondrial-associated caspase-dependent apoptotic mode of cell death. This work suggests that UVA is effective in activating hypericin and that this phototoxicity may be considered as treatment option in some cases of lentigo maligna or lentigo maligna melanoma that are too large for surgical resection.     

Effect of a triaxial nuclear shape on proton tunneling: the decay and structure of 145Tm

Gamma rays deexciting states in the proton emitter 145Tm were observed using the recoil-decay tagging method. The 145Tm ground-state rotational band was found to exhibit the properties expected for an h{11/2} proton decoupled band. In addition, coincidences between protons feeding the 2{+} state in 144Er and the 2{+}-->0{+} gamma-ray transition were detected, the first measurement of this kind, leading to a more precise value for the 2{+} excitation energy of 329(1) keV. Calculations with the particle-rotor model and the core quasiparticle coupling model indicate that the properties of the pi{11/2} band and the proton-decay rates in 145Tm are consistent with the presence of triaxiality with an asymmetry parameter gamma approximately 20 degrees .     

Bound‐states of diatomic molecules in the Dirac equation with the q‐deformed Morse potential

We present the solutions of the ro‐vibrational motion of a diatomic molecule with a spatially dependent mass by solving the Dirac equation with position‐dependent mass for repulsive vector $V(r)$ and attractive scalar $S(r)$ q‐deformed Morse potential for any $\kappa$ value, within the framework of Pekeris approximation of the spin‐orbitcoupling term. The relativistic energy spectra are obtained using theNikiforov‐Uvarov method and the two‐component spinor wavefunctions are obtained in terms of the Laguerre polynomials. It is found that there exist only negative energy states for bound states, and the energy values for a fixed value of $n_r$ increase with decrease in $\kappa$ . © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Radiochemical separation of 82Sr and the preparation of a sterile 82Sr/82Rb generator column

Summary Ion-exchange chromatography using the chelating resins Purolite S950 and Chelex 100 was investigated for the radiochemical separation of ⁸²Sr from a RbCl target. 0.25M NH₄Cl solution was employed for the retention of Sr and elution of Rb, and 2M HCl for the elution of Sr. Although both resins showed very similar results, the conditions for adsorption of Sr were different. The ammonium chloride solution was directly used with Purolite S950 while it was necessary to adjust the pH between 9 and 10 with Chelex 100. Purolite S950 was, therefore, selected for routine production of ⁸²Sr. A procedure has been introduced for the preparation of a hydrous tin dioxide as supporting material for the ⁸²Sr/⁸²Rb generator column. All components of the generator column were made up of stainless steel. The column was 4 cm long, 9.5 mm O.D. and 7.1 mm I.D. Using isotonic saline (0.9% NaCl) for elution of ⁸²Rb, elution curves with different flow rates ranging from 5 to 20 ml/min were obtained. Maximum available ⁸²Rb was eluted in the first 20 ml. The column generator provided a sterile ⁸²Rb in isotonic saline. The breakthrough of ⁸²Sr over 4 weeks of elution using 7 liter of saline was on average 4.5 ^. 10^-5% (based on the first 20 ml eluate).     

Simultaneous determination of 226Ra and 238U in soil and environmental materials by gamma-spectrometry in the absence of radium progeny equilibrium

The determination of ²²⁶Ra and ²³⁸U in environmental samples by gamma-spectrometry is most often carried out by hermetic sealing of the sample in a suitable container, waiting until secular equilibrium that has been established in the ²³⁸U decay chain below ²²⁶Ra and counting of the high intensity emissions of ²¹⁴Pb and ²¹⁴Bi. The 186 keV multiplet can then be corrected to provide a measure of ²³⁵U and hence, ²³⁸U. The work presented in this paper involves a critical examination of the analysis of ²³⁸U and ²²⁶Ra in environmental materials without secular equilibrium established between ²¹⁴Pb, ²¹⁴Bi and their progenitor. Results indicate that the correction of the 186 keV doublet via ²³⁴Th determination is possible, even for low-level samples but careful consideration of both experimental conditions and the composition of the sample matrix is required. This revised version was published online in July 2006 with corrections to the Cover Date.     

Engaging Early-Career Scientists in Global Policy-Making

Pressing global challenges, such as climate change, the COVID-19 pandemic, or antibiotic resistance, require coordinated international responses guided by evidence-informed decisions. For this purpose, it is critical that scientists engage in providing insights during the decision-making process. However, the mechanisms for the engagement of scientists in policy-making are complex and vary internationally, which often poses significant challenges to their involvement. Herein, we address some of the mechanisms and barriers for scientists to engage in policy-making with a global perspective by early-career scientists. We highlight the importance of scientific academies, societies, universities, and early-career networks as stakeholders and how they can adapt their structures to actively contribute to shaping global policies, with representative examples from chemistry-related disciplines. We showcase the importance of raising awareness, providing resources and training, and leading discussions about connecting emerging scientists with global decision-makers to address societal challenges through policies.