Developmental Regulation of Small-Conductance Ca²⁺-Activated K⁺ Channel Expression and Function in Rat Purkinje Neurons

Calcium transients play an important role in the early and later phases of differentiation and maturation of single neurons and neuronal networks. Small-conductance calcium-activated potassium channels of the SK type modulate membrane excitability and are important determinants of the firing properties of central neurons. Increases in the intracellular calcium concentration activate SK channels, leading to a hyperpolarization of the membrane potential, which in turn reduces the calcium inflow into the cell. This feedback mechanism is ideally suited to regulate the spatiotemporal occurrence of calcium transients. However, the role of SK channels in neuronal development has not been addressed so far. We have concentrated on the ontogenesis and function of SK channels in the developing rat cerebellum, focusing particularly on Purkinje neurons. Electrophysiological recordings combined with specific pharmacological tools have revealed for the first time the presence of an afterhyperpolarizing current (I_{AHP}) in immature Purkinje cells in rat cerebellar slices. The channel subunits underlying this current were identified as SK2 and localized by in situ hybridization and subunit-specific antibodies. Their expression level was shown to be high at birth and subsequently to decline during the first 3 weeks of postnatal life, both at the mRNA and protein levels. This developmental regulation was tightly correlated with the expression of I_{AHP} and the prominent role of SK2 channels in shaping the spontaneous firing pattern in young, but not in adult, Purkinje neurons. These results provide the first evidence of the developmental regulation and function of SK channels in central neurons

PARP-2 domain requirements for DNA damage-dependent activation and localization to sites of DNA damage.

Poly(ADP-ribose) polymerase-2 (PARP-2) is one of three human PARP enzymes that are potently activated during the cellular DNA damage response (DDR). DDR-PARPs detect DNA strand breaks, leading to a dramatic increase in their catalytic production of the posttranslational modification poly(ADP-ribose) (PAR) to facilitate repair. There are limited biochemical and structural insights into the functional domains of PARP-2, which has restricted our understanding of how PARP-2 is specialized toward specific repair pathways. PARP-2 has a modular architecture composed of a C-terminal catalytic domain (CAT), a central Trp-Gly-Arg (WGR) domain and an N-terminal region (NTR). Although the NTR is generally considered the key DNA-binding domain of PARP-2, we report here that all three domains of PARP-2 collectively contribute to interaction with DNA damage. Biophysical, structural and biochemical analyses indicate that the NTR is natively disordered, and is only required for activation on specific types of DNA damage. Interestingly, the NTR is not essential for PARP-2 localization to sites of DNA damage. Rather, the WGR and CAT domains function together to recruit PARP-2 to sites of DNA breaks. Our study differentiates the functions of PARP-2 domains from those of PARP-1, the other major DDR-PARP, and highlights the specialization of the multi-domain architectures of DDR-PARPs

Multiple solutions to a magnetic nonlinear Choquard equation

We consider the stationary nonlinear magnetic Choquard equation [(-\mathrm{i}\nabla+A(x))^{2}u+V(x)u=(\frac{1}{|x|^{\alpha}}\ast |u|^{p}) |u|^{p-2}u,\quad x\in\mathbb{R}^{N}%] where $A\$is a real valued vector potential, $V$ is a real valued scalar potential$,$ $N\geq3$, $\alpha\in(0,N)$ and $2-(\alpha/N) <p<(2N-\alpha)/(N-2)$. \ We assume that both $A$ and $V$ are compatible with the action of some group $G$ of linear isometries of $\mathbb{R}^{N}$. We establish the existence of multiple complex valued solutions to this equation which satisfy the symmetry condition $$u(gx)=\tau(g)u(x)\text{\ \ \ for all}g\in G,\text{}x\in\mathbb{R}^{N},$$ where $\tau:G\rightarrow\mathbb{S}^{1}$ is a given group homomorphism into the unit complex numbers.Comment: To appear on ZAM

Temperature dependence of the photoluminescence properties of colloidal Cd Se ∕ Zn S core/shell quantum dots embedded in a polystyrene matrix

We report on the temperature dependence of the photoluminescence (PL) spectrum and of the PL relaxation dynamics for colloidal $\mathrm{Cd}\mathrm{Se}∕\mathrm{Zn}\mathrm{S}$ core/shell quantum dots (QDs) embedded in an inert polystyrene matrix. We demonstrate that the confinement energy in the QDs is independent of the temperature. The coupling with both acoustic and optical phonons is also studied. Quantum confinement results in a strong increase of the exciton\char21{}acoustic-phonon coupling constant, up to 71\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{eV}∕\mathrm{K}, and in a reduced exciton\char21{}longitudinal-optical (LO)-phonon coupling constant, down to $21\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$, with respect to bulk CdSe. In addition, we demonstrate that the main nonradiative process that limits the quantum efficiency of the QD at room temperature is the thermal escape from the dot assisted by scattering with four LO phonons. Thermally activated trapping in surface states is also observed at low temperature, with an activation energy of about $15\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$

Investigation of the impact of additive manufacturing techniques on the acoustic performance of a coiled-up resonator

Acoustic metamaterials (AMMs) offer innovative solutions for physics and engineering problems, allowing lighter, multiphysics, and sustainable systems. They are usually studied analytically or numerically and then tested on prototypes. For this reason, additive manufacturing (AM) techniques are a popular way of quickly realising AMMs' innovative geometrical designs. However, AM parameters are often standardised without considering the specific issues of each AMM geometrical shape, leading to a possible mismatch between the analytical (or numerical) and experimental results. In this study, a simple AMM-a coiled-up resonator-has been produced with different AM technologies [fused deposition modeling (FDM), stereolithography (SLA), and selective laser melting and materials (polylactic acid, polyethylene terephthalate glycol, resin, flexible resin, and stainless steel). The sound absorption performance of these samples has been measured in two research labs in Italy and compared with the analytical and numerical calculations. This permitted the identification of the best combinations of AM technologies, their setup, and materials matching the expected results. The SLA/resin combination performed better overall; however, cheaper and more easily manageable samples made with FDM and polyethylene terephthalate glycol can achieve the same acoustic performance through the optimal AM printing setup. It is expected that this methodology could also be replicated for other AMMs

Organic μ cavities based on thermally evaporated TeOx-LiF distributed Bragg reflectors

We report on the realization of high-quality organic microcavities consisting of distributed Bragg reflectors based on lithium fluoride (LiF) and tellurium dioxide (TeOx) deposited by thermal evaporation. The materials are transparent in the range of 350 nm-5 mum and have an evaporation temperature of about 1000 K. The large difference in the refractive index (about 0.9 in the visible and near-infrared range) allows one to obtain reflectivity higher than 99% over a spectral region about 200 nm wide with a small number of periods. The mirror deposition technique is suitable for the fabrication of organic quantum microcavities in a single deposition process. Three fully evaporated organic lambda cavities with Phyrrometene 580 as the active material are described. The cavities show a Q value of up to 300, good uniformity, and reproducibility

Ground state of excitons and charged excitons in a quantum well

A variational calculation of the ground state of a neutral exciton and of positively and negatively charged excitons (trions) in single quantum well is presented. We study the dependance of the correlation energy and of the binding energy on the well width and on the hole mass. Our results are are compared with previous theoretical results and with avalaible experimental data.Comment: 8 pages, 5 figures presented to OECS

In vivo assessment of CdSe-ZnS quantum dots: coating dependent bioaccumulation and genotoxicity.

Semiconductor nanocrystals, or Quantum Dots (QDs), have gained considerable attention due to their unique size-dependent optical and electronic properties that make them attractive for a wide range of applications, including biology and nanomedicine. Their widespread use, however, poses urgent questions about their potential toxicity, especially because of their heavy metal composition that could cause harmful effects to human health and environment. In this work, we evaluated in vivo the long-term toxicity of CdSe-ZnS QDs with different surface coatings, probing oral administration in the model system Drosophila melanogaster. In particular, we found that all the differently coated QDs significantly affect the lifespan of treated Drosophila populations and induce a marked increase in reactive oxygen species (ROS) levels. Furthermore, we observed that these QDs induce severe genotoxic effects and increased rate of apoptosis in Drosophila haemocytes. These toxic effects were found to be mainly related to the in vivo degradation of QDs with consequent release of Cd(2+) ions, while the coating of QDs can modulate their bioaccumulation in the organism, partly decreasing their overall toxicity

Dislocation density in GaN determined by photoelectrochemical and hot-wet etching

Defects in GaN layers grown by hydride vapor-phase epitaxy have been investigated by photoelectrochemical ~PEC! etching, and by wet etching in hot H3PO4 acid and molten potassium hydroxide ~KOH!. Threading vertical wires ~i.e., whiskers! and hexagonal-shaped etch pits are formed on the etched sample surfaces by PEC and wet etching, respectively. Using atomic-force microscopy, we find the density of ‘‘whisker-like’’ features to be 23109 cm22, the same value found for the etch-pit density on samples etched with both H3PO4 and molten KOH. This value is comparable to the dislocation density obtained in similar samples with tunneling electron microscopy, and is also consistent with the results of Youtsey and co-workers