Heating Neutron Stars with Inelastic Dark Matter and Relativistic Targets

The dense environment of neutron stars makes them an excellent target for probing dark matter interactions with the Standard Model. We study neutron star heating from capture of inelastic dark matter, which can evade direct detection constraints. We investigate kinematics of the inelastic scattering process between quasirelativistic dark matter particles and ultrarelativistic targets in neutron stars, and derive analytical expressions for the maximal mass gap allowed for the scattering to occur. We implement them into a fully relativistic formalism for calculating the capture rate and apply it to various scenarios of inelastic dark matter. The projected constraints from neutron stars can systematically surpass those from terrestrial searches, including direct detection and collider experiments. Neutron stars can also be sensitive to the parameter space of inelastic self-interacting dark matter. Our results indicate that extreme astrophysical environments, such as neutron stars, are an important target for searching dark matter.Comment: 25 pages, 6 figure

Neuronal SOCE: myth or reality?

Store-operated Ca2+ entry (SOCE) is the primary Ca2+ influx pathway in non-excitable cells. Long thought to be absent in nerve cells, neuronal SOCE is gaining popularity. We argue here that the evidence for SOCE in neurons remains contentious, mostly because SOCE imaging assays are inadequate in these cells

Impaired spatial memory and enhanced long-term potentiation in mice with forebrain-specific ablation of the Stim genes

Recent findings point to a central role of the endoplasmic reticulum-resident STIM (Stromal Interaction Molecule) proteins in shaping the structure and function of excitatory synapses in the mammalian brain. The impact of the Stim genes on cognitive functions remains, however, poorly understood. To explore the function of the Stim genes in learning and memory, we generated three mouse strains with conditional deletion (cKO) of Stim1 and/or Stim2 in the forebrain. Stim1, Stim2, and double Stim1/Stim2 cKO mice show no obvious brain structural defects or locomotor impairment. Analysis of spatial reference memory in the Morris water maze revealed a mild learning delay in Stim1 cKO mice, while learning and memory in Stim2 cKO mice was indistinguishable from their control littermates. Deletion of both Stim genes in the forebrain resulted, however, in a pronounced impairment in spatial learning and memory reflecting a synergistic effect of the Stim genes on the underlying neural circuits. Notably, long-term potentiation (LTP) at CA3-CA1 hippocampal synapses was markedly enhanced in Stim1/Stim2 cKO mice and was associated with increased phosphorylation of the AMPA receptor subunit GluA1, the transcriptional regulator CREB and the L-type Voltage-dependent Ca(2+) channel Cav1.2 on protein kinase A (PKA) sites. We conclude that STIM1 and STIM2 are key regulators of PKA signaling and synaptic plasticity in neural circuits encoding spatial memory. Our findings also reveal an inverse correlation between LTP and spatial learning/memory and suggest that abnormal enhancement of cAMP/PKA signaling and synaptic efficacy disrupts the formation of new memories

Development of a low temperature co-fired ceramic fuel processor for the micro-scale solid oxide fuel cell system

The miniaturized solid oxide fuel cells (µ-SOFCs) has become an intensively studied device for portable power generation technology due to its wide choice of hydrocarbon fuels, its high energy density and its great operation efficiency. It is being considered as a battery replacement [1]. The µ-SOFC system, which aims to provide electrical energy (≤ 10 W) at an operating temperature of ca. 550°C, consists of a fuel cell unit for the electrochemical conversion [2-3]; a fuel processing unit for the thermal start-up, fuel reforming and total oxidation of exhausts [4-5]; a system packaging that insulates the fuel cell unit from the operating temperature to the ambient as well as provides fluidic and electronic connections [6-8]; and an electronics module for regulating the power output. As a core module of the entire µ-SOFC system, various fuel processing units have been proposed and developed. Most of those modules have been based on microelectromechanical systems (MEMS), which however shows several critical limitations with regard to electrical and fluidic connections and system integration [9-10]. Here we propose a ceramic based meso-scale gas processer combined with thick film and low-temperature co-fired ceramic technology (LTCC). With an overall size of 12 × 30 × 10 mm3, the ceramic processor, made of Heraeus HeroLock 2000 LTCC materials, mainly functions as a meso-scale hotplate that has a cantilever shape to effectively decouple the heat at the hot zone produced by the start-up heater and/or exothermic fuel processing reactions from the cold zone, in which the temperature is near ambient and thus compatible with normal electrical and fluidic connections (Figure 1). Embedded cavities were integrated into the processor during the fabrication process by using a progressive lamination technique. A thick-film crack-free catalyst paste, containing rhodium-doped ceria-zirconia nanoparticles, was dispensed into the reaction chambers as packed catalytic beds for the processing reactions. An integrated thick-film platinum (Heraeus CL11-6109) heater provides the start-up energy for the exothermic reforming reaction of butane or methane as well as total oxidation reactions. Such a meso-scale monolithic ceramic reactor can carry out the gas processing in a thermally self-sustaining manner, rendering itself to be a functional packaging of the entire µ-SOFC system in the future. In this work, the fabrication process of the gas processor will be discussed in detail, and the results of the fuel processing reactions such as reforming, total oxidation and thermal start-up will be presented as well. References: [1] Bieberle-Hütter, A., Beckel, D., et al. Journal of Power Sources, 177(1), 123–130, (2008) [2] Rey-Mermet, S. and Muralt, P. Solid State Ionics, 179(27–32), 1497-1500, (2008) [3] Evans, A., Bieberle-Hütter, A., et al. Monatshefte für Chemie - Chemical Monthly, 140(9), 975–983, (2009) [4] Shao, Z., Haile, S. M., et al. Nature, 435(7043), 795–798, (2005) [5] Santis-Alvarez, A. J., Nabavi, M., et al. Energy & Environmental Science, 4(8), 3041, (2011) [6] Jiang, B., Maeder, T., Muralt, P. Proceedings, Power MEMS 2010, Leuven (BE), 2010 [7] Jiang, B., Muralt, P., et al. Sensors and Actuators B: Chemical, 175, 218–224, (2012) [8] Maeder, T., Jiang, B., et al. Proceedings, 7th International Conference on Ceramic Interconnect and Ceramic Microsystems Technologies (CICMT), San Diego (USA), 2011 [9] Hotz, N., Osterwalder, N., et al. Chemical Engineering Science, 63(21), 5193–5201, (2008) [10] Vaccaro, S., Malangone, L., Ciambelli, P. Industrial & Engineering Chemistry Research, 49(21), 10924–10933, (2010

A low-temperature co-fired ceramic micro-reactor system for high-efficiency on-site hydrogen production

A ceramic-based, meso-scale fuel processor for on-board production of syngas fuel was demonstrated for applications in micro-scale solid-oxide fuel cells (mu-SOFCs). The processor had a total dimension of 12 mm x 40 mm x 2 mm, the gas reforming micro reactor occupying the hot end of a cantilever had outer dimensions of 12 x 18 mm. The device was fabricated through a novel progressive lamination process in low-temperature co-fired ceramic (LTCC) technology. Both, heating function and desired fluidic structures were integrated monolithically into the processor. Using catalytic partial oxidation of a hydrocarbon fuel (propane) as a reaction model, a thermally self-sustaining hydrogen production was achieved. The output flow is sufficiently high to drive an optimized single membrane mu SOFC cell of about the same footprint as the micro reactor. Microsystem design, fabrication, catalyst integration as well as the chemical characterization are discussed in detail. (C) 2014 Elsevier B.V. All rights reserved

Emotional processing deficits in chronic cannabis use: A replication and extension

Heavy cannabis use is associated with interpersonal problems that may arise in part from the inaccurate perception of emotional faces. Only one study reports impairments in emotional facial affect processing in heavy cannabis users; however, it is not clear whether these findings were attributable to differences between cannabis users and controls in schizotypy or gender, rather than from cannabis use itself. A total of 25 frequent cannabis users and 34 non-using controls completed an emotional processing task in an independent groups design. We asked participants to identify the emotions on faces morphed from neutral to 100% intensity, for six basic emotions. We measured percentage hit rate, sensitivity and response bias. Schizotypy was indexed using the Schizotypal Personality Questionnaire. Cannabis users showed lower accuracy and sensitivity on the emotional recognition task. Gender and schizotypy did not differ between the two groups. Men showed lower accuracy on the emotional processing task, but impairments in cannabis users remained when covarying for gender. Schizotypy negatively correlated with sensitivity scores, but this was unreliable when accounting for the groups. Chronic cannabis users showed generalised impairment in emotional processing. These results appeared as independent of the emotional processing deficits amongst men, and were not related to schizotypy

Endovascular Treatment of a Large Partially Thrombosed Basilar Tip Aneurysm

Despite the remarkable developments in neurosurgical and neuro-interventional procedures, the optimal treatment for large or giant partially thrombosed aneurysms with a mass effect remains controversial. The authors report a case of a partially thrombosed aneurysm with a mass effect, which was successfully treated by stent-assisted coil embolization. A 41-year-old man presented with headache. Brain computed tomography depicted an 18×18 mm sized thrombosed aneurysm in the interpeducular cistern. More than 80% of the aneurysm volume was filled with thrombus and the canalized portion beyond its neck measured 6.8×5.6 mm by diagnostic cerebral angiography. Stent-assisted endovascular coiling was performed on the canalized sac and the aneurysm was completely obliterated. Furthermore, most of the thrombosed aneurysm disappeared in the interpeduncular cistern was clearly visualized follow-up brain magnetic resonance imaging conducted at 21 months. The authors report a case of selective coiling of a large, partially thrombosed basilar tip aneurysm

A nanoparticle bed micro-reactor with high syngas yield for moderate temperature micro-scale SOFC power plants

This work introduces and investigates the a novel compact catalytic nanoparticle bed micro-fabricated reactor suitable for utilization in small-scale intermediate-temperature micro-SOFC systems. It is shown that the presented micro-reactor is able to produce syngas (CO + H2) efficiently from n-butane and propane at temperatures between 550 – 620 °C by means of catalytic partial oxidation (CPOX) using Rh-doped nanoparticles embedded in a foam-like porous ceramic bed as a catalyst. The novel micro-fabricated reactor system is experimentally tested using a carrier specially designed for heating the reactor as well as feeding the fuel and receiving the reaction product gases. Optimization of the syngas production is performed by varying fuel dilutions and reactor temperatures. The performance of the micro-reactor was investigated in two modes: (1) Continuous heating mode, in which two built-in heaters underneath the carrier are kept on throughout the reforming reaction. This simulates the operating state of a micro-SOFC system where the post-combustor provides heat to the micro-reformer continuously. (2) Thermally self-sustained mode, in which the heaters are turned off after the CPOX has been ignited. An estimation of the heat losses of both testing modes is also given. The present micro-reactor is able to achieve syngas yield as high as 60 % for n-butane and 50 % for propane in the continuous heating mode, which is a substantial improvement to state-of-the-art micro-reactors