Thermoelectric Properties of Polymeric Mixed Conductors

The thermoelectric (TE) phenomena are intensively explored by the scientific community due to the rather inefficient way energy resources are used with a large fraction of energy wasted in the form of heat. Among various materials, mixed ion‐electron conductors (MIEC) are recently being explored as potential thermoelectrics, primarily due to their low thermal conductivity. The combination of electronic and ionic charge carriers in those inorganic or organic materials leads to complex evolution of the thermovoltage (V_oc) with time, temperature, and/or humidity. One of the most promising organic thermoelectric materials, poly(3,4‐ethyelenedioxythiophene)‐polystyrene sulfonate (PEDOT‐PSS), is an MIEC. A previous study reveals that at high humidity, PEDOT‐PSS undergoes an ionic Seebeck effect due to mobile protons. Yet, this phenomenon is not well understood. In this work, the time dependence of the V_oc is studied and its behavior from the contribution of both charge carriers (holes and protons) is explained. The presence of a complex reorganization of the charge carriers promoting an internal electrochemical reaction within the polymer film is identified. Interestingly, it is demonstrated that the time dependence behavior of V_oc is a way to distinguish between three classes of polymeric materials: electronic conductor, ionic conductor, and mixed ionic–electronic conductor.     

Impact of Polarization Mode Dispersion in Multi-Hop and Multi-Rate WDM Rings

Fiber polarization mode dispersion (PMD) is perhaps the most critical transmission impairment in optical networks at transmission rates of 10 Gb/s and higher. Since the bandwidth-distance product, or transparency,of the optical circuit is limited by PMD, the overall network design and cost may be significantly altered by the actual fiber PMD values. The paper has three objectives. First, an accurate model for evaluating the PMD effects is presented and verified experimentally. Second, the cost increase of WDM rings due to PMD in a number of design scenarios—first generation, single-hop,multi-hop, and multi-rate networks—is assessed. Third, the polynomial-time algorithm proposed in Cerutti et al. [1] is modified to provide sub-optimal solutions for the above WDM rings, taking into account the limited bandwidth-distance product imposed by PMD. Presented results reveal that at high transmission rates, the cost of the multi-hop ring is less affected by PMD than the costs of first generation and single-hop rings.     

Biomechanical Strain Exacerbates Inflammation on a Progeria‐on‐a‐Chip Model

Organ‐on‐a‐chip platforms seek to recapitulate the complex microenvironment of human organs using miniaturized microfluidic devices. Besides modeling healthy organs, these devices have been used to model diseases, yielding new insights into pathophysiology. Hutchinson‐Gilford progeria syndrome (HGPS) is a premature aging disease showing accelerated vascular aging, leading to the death of patients due to cardiovascular diseases. HGPS targets primarily vascular cells, which reside in mechanically active tissues. Here, a progeria‐on‐a‐chip model is developed and the effects of biomechanical strain are examined in the context of vascular aging and disease. Physiological strain induces a contractile phenotype in primary smooth muscle cells (SMCs), while a pathological strain induces a hypertensive phenotype similar to that of angiotensin II treatment. Interestingly, SMCs derived from human induced pluripotent stem cells of HGPS donors (HGPS iPS‐SMCs), but not from healthy donors, show an exacerbated inflammatory response to strain. In particular, increased levels of inflammation markers as well as DNA damage are observed. Pharmacological intervention reverses the strain‐induced damage by shifting gene expression profile away from inflammation. The progeria‐on‐a‐chip is a relevant platform to study biomechanics in vascular biology, particularly in the setting of vascular disease and aging, while simultaneously facilitating the discovery of new drugs and/or therapeutic targets.     

Antibacterial Action of Nanoparticles by Lethal Stretching of Bacterial Cell Membranes

It is commonly accepted that nanoparticles (NPs) can kill bacteria; however, the mechanism of antimicrobial action remains obscure for large NPs that cannot translocate the bacterial cell wall. It is demonstrated that the increase in membrane tension caused by the adsorption of NPs is responsible for mechanical deformation, leading to cell rupture and death. A biophysical model of the NP–membrane interactions is presented which suggests that adsorbed NPs cause membrane stretching and squeezing. This general phenomenon is demonstrated experimentally using both model membranes and Pseudomonas aeruginosa and Staphylococcus aureus, representing Gram-positive and Gram-negative bacteria. Hydrophilic and hydrophobic quasi-spherical and star-shaped gold (Au)NPs are synthesized to explore the antibacterial mechanism of non-translocating AuNPs. Direct observation of nanoparticle-induced membrane tension and squeezing is demonstrated using a custom-designed microfluidic device, which relieves contraction of the model membrane surface area and eventual lipid bilayer collapse. Quasi-spherical nanoparticles exhibit a greater bactericidal action due to a higher interactive affinity, resulting in greater membrane stretching and rupturing, corroborating the theoretical model. Electron microscopy techniques are used to characterize the NP–bacterial-membrane interactions. This combination of experimental and theoretical results confirm the proposed mechanism of membrane-tension-induced (mechanical) killing of bacterial cells by non-translocating NPs.     

Few electron limit of n-type metal oxide semiconductor single electron transistors

We report the electronic transport on n-type silicon single electron transistors (SETs) fabricated in complementary metal oxide semiconductor (CMOS) technology. The n-type metal oxide silicon SETs (n-MOSSETs) are built within a pre-industrial fully depleted silicon on insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 × 20 nm(2) is obtained by employing electron beam lithography for active and gate level patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a current spin density functional theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronic and quantum variable based devices.     

Saving runs in fractional factorial designs

When it is known a priori that some contrasts are negligible in a factorial design, their expressions can be used to deduce the missing results. In this article we propose a method for using this procedure when, as in the case of fractional designs, it is not known which contrasts will be null. The method is based on first establishing an interval of possible values corresponding to each of the missing results, then identifying which contrasts are always null independently of the value of said results.     

Giant and Reversible Inverse Barocaloric Effects near Room Temperature in Ferromagnetic MnCoGeB0.03

Hydrostatic pressure represents an inexpensive and practical method of driving caloric effects in brittle magnetocaloric materials, which display first‐order magnetostructural phase transitions whose large latent heats are traditionally accessed using applied magnetic fields. Here, moderate changes of hydrostatic pressure are used to drive giant and reversible inverse barocaloric effects near room temperature in the notoriously brittle magnetocaloric material MnCoGeB_0.03. The barocaloric effects compare favorably with those observed in barocaloric materials that are magnetic. The inevitable fragmentation provides a large surface for heat exchange with pressure‐transmitting media, permitting good access to barocaloric effects in cooling devices.     

High Cooling Rate,Regular and Plate Like Cells in Sn–Ni Solder Alloys

Broad ranges of cooling rates () 0.8–30.5 and 0.4–5.0 K s^?1 are attained during directional solidification of eutectic Sn–0.2 wt% Ni and hypereutectic Sn–0.5 wt% Ni alloys, respectively. A reverse high cooling rate cell‐to‐dendrite transition occurs for the eutectic composition and a transition from high cooling rate cells to plate like cells for the hypereutectic alloy. High cooling rate β‐Sn cells are associated with cooling rates >5.5 and >2.7 K s^?1 for eutectic and hypereutectic compositions, respectively. A processing diagram, relating the ‘–Ni content’ space with the microstructural morphology, is proposed. A combination of plate like cells and plate NiSn₄ eutectic phase results in higher ductility.