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The demand for energy sources that are compact, lightweight and powerful has significantly increased in recent years. Traditional chemical batteries which are highly developed are unable to meet the demand for high energy intensity. This gap is expected to widen in the future as electronic devices need more power to support enhanced functionalities. Hydrocarbon fuels have energy densities much greater than the best batteries. Therefore, taking advantage of the high energy density of chemical fuels to generate power becomes an attractive technological alternative to batteries. To address the growing demand for smaller scale and higher energy density power sources, various combustion-based micro power generators are being developed around the world. This review paper provides an update on recent progresses and developments in micro-scale combustion and micro power generators. The paper, broadly divided into four main sections, begins with a review of various methods to enhance and stabilize the combustion at micro-scale, subsequently improving the efficiency. This is followed by a description of various micro-thermophotovoltaic power generators. The third section focuses on MEMS based solid propellant micro-propulsion system. Lastly, a brief review is made to other micro power generators.
Cognitive performance rather than symptoms, especially positive symptoms, is regarded as the primary predictor of functional outcome in schizophrenia. However, contradictory evidence exists and many studies fail to sample from the extremes of outcome measures. This study tested whether the differential importance assigned to symptoms and cognitive impairment is supportable in patients with high and low levels of community independence. Schizophrenia patients with highly unfavorable (n =24) and highly favorable (n =28) functional outcomes as defined by community support requirements were studied. Standard cognitive and psychopathology measures were analyzed using independent groups comparisons and outcome prediction with logistic regression methods. Symptom severity and cognitive data separately accounted for significant amounts of variance in community independence. Positive as well as negative symptoms, non-psychotic psychopathology and cognition generated large effect sizes between highly unfavorable and favorable outcome groups. The conditional validity of both overall psychopathology and positive symptoms was significant over and above the contribution of cognition to outcome prediction. Results suggest researchers may have underestimated the role of psychopathology in general and positive symptoms in particular as potential determinants of functional status in schizophrenia.
Li4Ti4.95V0.05O12 and Li4Ti5O12 powders were successfully prepared by a solid-state method. XRD reveals that both samples have high phase purity. Raman spectroscopy indicates that the Ti–O vibration have a blue shift. SEM shows that Li4Ti4.95V0.05O12 has a slightly smaller particle size and a more regular morphological structure with narrow size distribution than those of Li4Ti5O12. Galvanostatic charge–discharge testing indicates both samples have nearly equal initial capacities at different discharge voltage ranges (0–2 and 0.5–2V), but Li4Ti4.95V0.05O12 has a higher cycling performance than that of Li4Ti5O12. CV suggests that Li4Ti4.95V0.05O12 has lower electrode polarization and high lithium ion diffusivity in solid-state body of sample, implying that the vanadium doping is beneficial to the reversible intercalation and de-intercalation of Li+. The novel Li4Ti4.95V0.05O12 materials may find promising applications in lithium ion batteries and electrochemical cells due to the excellent electrochemical performace and simple synthesis route.
We report a new strategy to design carbon-based electrocatalysts containing nitrogen through the co-pyrolysis of blood protein and carbon black support. The results show that the nitrogen in electrocatalysts is primarily in the form of pyridinic- and pyrrolic-type nitrogen species. High-temperature pyrolysis processes can transfer a significant amount of pyridinic-N to pyrrolic-N. The electrocatalyst containing a higher amount of the pyrrolic-N configuration exhibits better electrocatalytic activity towards oxygen reduction reaction in terms of onset potential, half-wave potential, and limited current density. It is suggested that the pyrrolic-N configuration may be the electrocatalytically active site and may be responsible for the enhanced ORR performance in alkaline media. The carbon black support also plays an important role in the pyrolysis process, improving the ORR catalytic activity.
Precursor synthesis technology is a key factor to improve the electrochemical properties of Li-rich layered oxide (LLO) cathode materials. However, the effect of precursor preparation strategies on the morphology and electrochemical properties of cathode materials has not been clearly elucidated. In this work, an LLO cathode material (denoted as LMNC-300) with highly exposed {010} planes and a lower amount of surface residual lithium is reported via pre-oxidation of a precursor at 300 °C. This LMNC-300 cathode material exhibits an initial Coulombic efficiency of 91.7% with a discharge capacity of 277.2 mA h g−1 at 0.1 C, an excellent high-rate capability with a discharge capacity of 175.1 mA h g−1 even at 5.0 C and a good cycling performance with a capacity retention of 92.6% after 200 cycles at 0.5 C. In addition, a pouch cell consisted of the LMNC-300 cathode and a commercial graphite anode presented good cycling stability with a capacity retention of 81.6% after 500 cycles at 2.0 C. The outstanding electrochemical performance can be ascribed to an accelerated Li+ diffusion dynamics. Therefore, the method reported in this work will be significant to understanding the effects of preparation strategies of transition metal precursors on the electrochemical performance of Li-rich layered cathode materials for high-energy density Li-ion batteries.
A facile sol–gel polymerization and impregnation route is developed to large-scale fabricate the novel mesoporous 3D interconnected NiCo-NiCoO2/carbon xerogel (CX) hybrids with a homogeneous carbon coating layer on the surface of NiCo and NiCoO2 nanoparticles, the metallic NiCo nanoparticles are introduced in the NiCo-NiCoO2/CX hybrids via a partially reducing chemical reaction at a high annealing temperature. The mesoporous 3D interconnected NiCo-NiCoO2/CX hybrids show significantly improved electrochemical performance of high reversible capacity, high-rate capability, and excellent cycling performance as anode electrode materials for Lithium ion batteries (LIBs). After 100 cycles, the NiCo-NiCoO2/CX hybrids anode can still get a reversible capacity of 861mAhg−1 at current density of 100mAg−1, which is 2.8 and 1.9 times higher than that of the CX (305mAhg−1) and NiCoO2/CX hybrid (456mAhg−1), respectively. The greatly enhanced electrochemical lithium ion storage performance of the NiCo-NiCoO2/CX hybrids can be attributed to their unique microstructure characteristics. The elastic nature of CX matrices and carbon layer coating on the surfaces of NiCo and NiCoO2 nanoparticles, renders the NiCo-NiCoO2/CX hybrids very effective in accommodating the volume strain. The highly dispersed NiCo particles display catalytic effect, greatly improve the kinetics of charge-discharge process of the composite anode as the following reaction of NiCo+2Li2O↔NiO+CoO+4Li+ +4e−. The introduction of metallic NiCo can effectively facilitate the decomposition of Li2O and the SEI during the charge-discharge process, thus greatly enhance the electrochemical performance. Secondly, the presence of NiCo in the NiCo-NiCoO2/CX composite anode can greatly improve the electron conductivity, thus charge transfer kinetics of the composite anode for LIBs. EIS result can well confirm this result. While the homogeneous distribution of NiCoO2 with high theoretical capacity in the porous CX matrices, effectively reduces the active sites of the CX matrices, resulting in higher reversible capacity of the NiCo-NiCoO2/CX hybrids.
The objective of the study was to determine if cognitive function is associated with step time variability in people with multiple sclerosis (PwMS). The study included 355 PwMS (218 women), average age 41.1 (SD = 13.5), disease duration 5.9 (SD = 7.3) years, and a median expanded disability status scale score of 2.5. We separately analyzed the sample group of fallers and non-fallers based on their fall history. Gait variability was measured by an electronic walkway and all participants completed a computerized cognitive test battery designed to evaluate multiple cognitive domains. Fallers (43.7%) demonstrated elevated step time variability (%CV), 5.0 (SD = 3.4) vs. 3.5 (SD = 1.6), P < 0.001 compared to the non-faller subjects. According to the regression analysis in the non-fallers’ group, step time variability was found significantly associated with the global cognitive score (P = 0.001), executive function subcategory (P = 0.038), and motor skills subcategory (P < 0.001). No relationship between step time variability and any cognitive domain was demonstrated in the faller group. This study illustrated that the association between gait variability and cognition occurs only in PwMS without a fall history. From a clinical standpoint, these findings might help medical professionals to create improved assessment tests and rehabilitation strategies in the MS population.
In his classic essay “The phenomenological approach to psychopathology”, Karl Jaspers defended the irreducible reality of the “subjective” mental symptoms and stressed the pivotal role of empathy in their diagnostic assessment. However, Jaspers’ account of the epistemological role of empathy in psychopathological diagnosis was far from clear: whereas at several places Jaspers claimed that empathy provides a direct access to patients’ abnormal mental experiences, at other places he stressed that it did so only indirectly, through a whole battery of their observable clinical indicators. The aim of this paper is to reassess Jaspers’ account of the epistemological role of empathy in psychopathological diagnosis.
The influences of Sm and Y on the electron properties of the anodic films on lead at 1.28 V(vs.SCE), 1.5 V(vs.SCE) and 1.8 V(vs.SCE) in 4.5 mol L−1 sulfuric acid are investigated by using electrochemical impedance spectroscopy (EIS), Mott–Schottky plot, galvanic polarization and photo-electrochemical technique. The results show that Sm and Y can significantly decrease the resistances of the anodic films on lead electrode at 1.28 V, 1.5 V and 1.8 V, the oxygen and hydrogen evolutions of lead electrode covered by the anodic film decrease with the addition of Sm or Y. The anodic films on lead electrode at three potentials appear an n-type semi-conductive character, the addition of Sm or Y can decrease the slope of M–S plot of the anodic film, it implying the increment of the defect density within the anodic film, which is beneficial for improving the charge–discharge behavior of the lead acid battery.
Solid electrolyte composed of hybrid organic–inorganic silicate matrix functionalised with tetraalkylammonium group, solvated by viscous organic polar solvent (propylene carbonate (PC) or sulpholane (TMS)), was prepared by the sol–gel method under controlled drying conditions. Tetramethoxysilane (TMOS), N-trimethoxysilylpropyl-N,N,N-tributylammonium chloride (TMOSPTBACl) and organic solvent were principal sol components. Gel formed within 2h and 2 days depending on substrate ratio and the solvent additive. The obtained material was transparent and it loosed about 15% of its mass during first 30 days of ageing. It was characterised by thermogravimetry (TGA), differential scanning calorimetry (DSC), NMR, FT-IR spectroscopy, small angle X-ray scattering (SAXS), and impedance spectroscopy. The transport of redox active molecules was studied by electrochemical methods. The porosity of samples dried in supercritical CO2 was also estimated. The shape of TGA and DSC curve appeared to be similar to that of pure solvent. The IR spectra indicated the silicate network formation with some silanol groups left. The NMR spectrum of the solution used to wash crushed sample indicated that all organic substrate is embedded in silicate matrix. The magnitude of electrical conductivity was close to 10−4 to 10−5 Scm−1, i.e. least more than one order of magnitude larger than that of TMOS based silicate matrix modified with a pure solvent. This conductivity is high enough for electrochemical experiments. Both conductivity and diffusion coefficient of redox probe-ferrocene (Fc) depended on time elapsed after gelation. Their most substantial decrease was observed during first 10 days after gelation and it correlated with mass loss.
As new applications for lithium-ion batteries emerge into the marketplace, a new emphasis is being placed on developing higher capacity electrodes. Two of the higher capacity technologies under development are lithium–sulfur and lithium–air batteries, both of which, in most configurations, use a lithium metal anode. Building on our previous work extending the cycle life of lithium metal anodes via surface functionalization with silane groups, we have identified two separate regimes for the cycle life enhancements based on size of the silane R-groups. Very small R-groups (TMS) and R-groups bulkier than triphenyl show enhanced cycle life compared to control samples while R-groups between these in size show reduced cycle life. Additionally, we present a comparison between different cleaning methods to optimize the hydroxyl functionalized layer on the lithium metal and the influence of these methods on the stability of lithium metal in EC:EMC electrolyte. A solvent based cleaning approach is shown to substantially improve stability when combined with chlorotrimethyl silane treatment.
Introduction Previous research has mainly studied the impact of activity explanation on performances (e.g., Chi, 2009), but little research has been done to examine its impact on the development of a competence. Objective A model of dynamic analysis of competence (Coulet, 2011) has been used to measure the impact of activity explanation on the development of a technical competence. Method Explanation of tasks of varying complexity has been manipulated in two experimental studies; effects of activity explanation have been measured on objective performance, perceptions related to the task and final explanations. Results Participants who explained their activity not only performed better on the tasks, but also showed more positive perceptions of their relations to the task and a better ability to produce didactic explanations. Conclusion Psychological processes involved in explaining activity and their implications are examined and discussed.
Aqueous Li-ion batteries are attracting increasing attention because they are potentially low in cost, safe and environmentally friendly. However, their low energy density (<100 Wh kg−1 based on total electrode weight), which results from the narrow operating potential window of water and the limited selection of suitable negative electrodes, is problematic for their future widespread application. Here, we explore optimized eutectic systems of several organic Li salts and show that a room-temperature hydrate melt of Li salts can be used as a stable aqueous electrolyte in which all water molecules participate in Li+ hydration shells while retaining fluidity. This hydrate-melt electrolyte enables a reversible reaction at a commercial Li4Ti5O12 negative electrode with a low reaction potential (1.55 V versus Li+/Li) and a high capacity (175 mAh g−1). The resultant aqueous Li-ion batteries with high energy density (>130 Wh kg−1) and high voltage (∼2.3–3.1 V) represent significant progress towards performance comparable to that of commercial non-aqueous batteries (with energy densities of ∼150–400 Wh kg−1 and voltages of ∼2.4–3.8 V).
Peptide nucleic acids (PNAs) are synthetic homolog of nucleic acids in which the phosphate-sugar polynucleotide backbone is replaced by a flexible polyamide. They bind complementary polynucleotide sequences with higher affinity and specificity than their natural counterparts. PNAs linked to the appropriate nuclear localization signal (NLS) peptide have been used to selectively down-regulate the expression of several genes in viable cells. For example in Burkitt's lymphoma (BL) cells the c-myc oncogene is translocated in proximity to the Eμ enhancer of the Ig gene locus and upregulated. PNAs complementary to the second exon of c-myc or to the Eμ enhancer sequence (PNAEμ-NLS), selectively and specifically block the expression of the c-myc oncogene and inhibit cell growth in vitro and in vivo. PNAEμ-NLS administration to mice did not exhibit toxic effects even at the highest concentration allowed by the experimental conditions. Because of the accumulating data confirming PNAEμ-NLS potential therapeutic value, PNAEμ-NLS was evaluated for the inability to induce mutations in tester strains of Salmonella typhimurium, Escherichia coli, and at the hprt locus in Chinese hamster ovary cells (CHO). Moreover, the induction of chromosomal aberrations in CHO cells and of micronuclei in human lymphocytes were investigated. We may conclude that PNAEμ-NLS neither induces mutations nor has clastogenic effects as detectable by treatment under the standard test conditions.
Several electrical brass (CuZn37) connector bolts of aircraft batteries failed as a result of stress-corrosion cracking. The batteries are used for emergency supply of the avionics in case of power failure or for complete control in the case of engine failure. For activation, the thermal battery is heated by a pyrotechnic element and then supplies electrical power with 5 A for 20 min up to 240 A for 3 min. For assembly of the batteries, an acetic acid curing silicone resin is used for housing seal on the lid and on the connector bolts. Because of the almost hermetic sealing of the enclosure, the silicone resin cures very slowly and metallic parts are exposed to the acetic acid vapor. So the electrical brass connector showed corrosive attack with the formation of copper acetate (verdigris). Subsequent failure due to stress-corrosion cracking occurred. The failure type and damage mechanisms could be simulated in laboratory experiments.
Electrically conductive dodecyl-benzene-sulfonic-acid (DBSA) doped polyaniline (Pani) nanocomposites were prepared with multi-walled carbon nanotubes (MWCNTs) by in situ oxidative polymerization of aniline in the presence of different amounts of MWCNTs. The stability of the nanocomposites in terms of DC electrical conductivity retention was studied in ambient atmosphere by isothermal accelerated aging and cyclic accelerated aging techniques. The MWCNT/Pani nanocomposites were observed to be thermally more stable under ambient environmental conditions than Pani. Such nanocomposites with high thermal stability may find a place as future materials for the replacement for Pani.
Valve-regulated -lead–acid (VRLA) batteries have been revealed as showing an impressive cycle life performance, which compared with the equivalent flooded type, yields increments as large as three–five times. These impressive results have been achieved even though components, such as lead–calcium alloys, which are not especially adequate for obtaining high cycle lives are used. The report is concerned with the electrochemical factors, that determine such performance. The development of the new ORBITAL™ battery, especially the cycling version, has been possible, through an optimisation process of the parameters determining life performance. In this way lives approaching 1000 cycles at 60% depth-of-discharge (DoD) have been achieved, which open the possibility to use such batteries in cycling applications, up to now restricted to other technologies like gel batteries. A review of the electrochemical factors, determining such performance is presented in an attempt to highlight the electrochemical basis of VRLA performance.
In this work, bare and Ta-substituted Nb2O5 nanofibers are prepared by electrospinning followed by sintering at temperatures in the 800–1100°C range for 1h in air. Obtained bare and Ta-substituted Nb2O5 polymorphs are characterized by X-ray diffraction, scanning electron microscopy, density measurement, and Brunauer, Emmett and Teller surface area. Electrochemical properties are evaluated by cyclic voltammetry and galvanostatic techniques. Cycling performance of Nb2O5 structures prepared at temperature 800°C, 900°C, and 1100°C shows following discharge capacity at the end of 10th cycle: 123, 140, and 164 (±3) mAhg−1, respectively, in the voltage range 1.2–3.0V and at current rate of 150mAg−1 (1.5C rate). Heat treated composite electrode based on M-Nb2O5 (1100°C) in argon atmosphere at 220°C, shows an improved discharge capacity of 192 (±3) mAhg−1 at the end of 10th cycle. The discharge capacity of Ta-substituted Nb2O5 prepared at 900°C and 1100°C showed a reversible capacity of 150, 202 (±3) mAhg−1, respectively, in the voltage range 1.2–3.0V and at current rate of 150mAg−1. Anodic electrochemical properties of M-Nb2O5 deliver a reversible capacity of 382 (±5) mAhg−1 at the end of 25th cycle and Ta-substituted Nb2O5 prepared at 900°C, 1000°C and 1100°C shows a reversible capacity of 205, 130 and 200 (±3) mAhg−1 (at 25th cycle) in the range, 0.005–2.6V, at current rate of 100mAg−1.
We report a novel non-solution synthesis of ultrafine SnO2 nanoparticles within multiwall carbon nanotube (MWCNT) networks by pre-mixing tin(II) 2-ethylhexanoate (C16H30O4Sn) and MWCNTs and subsequently annealing in air at 350°C, at which decomposition and oxidation of tin(II) 2-ethylhexanoate readily went on without destroying the MWCNTs. The resultant SnO2 nanoparticles with average size of ∼5nm were well-distributed either on the surface of MWCNTs or within themselves-constructed networks. When used as anode materials in lithium ion batteries (LIBs), the SnO2-MWCNT nanocomposites showed superior electrochemical properties, delivering discharge capacities of 1144mAhg−1 at 100mAg−1 and 1022mAhg−1 at 200mAg−1 after 50 cycles, 685mAhg−1 at 500mAg−1 and 640mAhg−1 at 1000mAg−1 after 100 cycles. Moreover, the mixture of tin(II) 2-ethylhexanoate and MWCNTs can be directly used as paste for fabrication of binder-free SnO2-MWCNT composite electrodes by simply spreading the mixture on current collectors (ex. Ni foam) and annealing in air. The as-prepared SnO2-MWCNT-Ni composite electrode delivered a discharge capacity of 434mAhg−1 at 500mAg−1 after 200 cycles. Besides, the present non-solution synthetic strategy is promising for low-cost and large-scale fabrication of SnO2/CNTs nanocomposites as high-performance anodes for electrochemical energy-storage.
Driven by the academic interest, we have studied the aqueous electrochemistry of neptunium (Np) in 1M nitric acid solution on the electrochemically reduced graphene oxide (ERGNO) modified glassy carbon (GC) electrode. Similar to our previous experiences on the electrocatalytic action of ERGNO on the electrochemistry of uranium(VI)/uranium(IV) and plutonium(IV)/plutonium(III) redox couples, the present study confirms the robust electrocatalytic ability of ERGNO for the redox reaction of Np(VI)O2 2+/Np(V)O2 + in acidic solution even at high anodic working potentials. The extent of the electrochemical reversibility of Np(VI)O2 2+/Np(V)O2 + redox couple increases on ERGNO compared to the bare GC electrode. For the first time, the electron transfer reaction of Np(VI)O2 2+/Np(V)O2 + redox couple is investigated by electrochemical impedance spectroscopy. The improved sensitivity as well as the lower limit of detection of Np by anodic square wave voltammetry on ERGNO compared to bare GC opens up the application of ERGNO in the nuclear science and technology.