Search

Geopolymers are formed from alumina and silica rich materials by alkali dissolution and subsequent polycondensation into a polymeric network. Geopolymerization technology presents a great potential for positive environmental impact since many alumina- and silica- rich industrial waste materials, such as coal ashes, blast furnace slags, mine tailings, etc., can be used as its precursor materials in a process that requires less energy and gives up less emissions vis-à-vis the current conventional OPC (ordinary Portland cement) technology. In this study, geopolymer samples were prepared using an 85% coal fly ash (CFA) - 10% coal bottom ash (CBA) - 5% rice hull ash (RHA) wt/wt mix proportion and activated using an alkali solution of NaOH-Na2SiO3 at an 80%-20% wt/wt solid-to-liquid ratio. With this mix proportion, two types of specimens were used, a slab type with 50 mm thickness, and a cube type, 50 mm x 50 mm x 50 mm. The slab type specimens were used for evaluating fire resistance using ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials, and the cube type specimens were used to study the effect of foaming agents on the strength and thermal conductivity of the geopolymers formed. Two types of foaming agents, hydrogen peroxide and sodium perborate, at an amount of 0.1% to 0.4% of dry mass mixture, were used. Results from the foamed geopolymers gave compressive strength values ranging from 0.37 to 0.71 MPa and densities of 1430-1560 kg/m3 at 0.3% to 0.4% peroxide added. Values of thermal conductivity of the foamed geopolymers were within 0.033-0.037 W/m-K for all foamed geopolymer samples tested which is a significant reduction compared to the thermal conductivity of the unfoamed geopolymer sample at 0.48 W/m-K. The fire resistance tests show that the unfoamed geopolymer samples perform better than OPC concrete. However, the foamed geopolymers have very low strength compared to the unfoamed sample compressive strength of 18.1 MPa and, thus, are suitable for non-load bearing, insulation applications.

A 56-year-old male with a past medical history significant for a left below-knee amputation and a left total knee replacement presented with knee pain at a non-healing stage 2 prosthesis-related residual limb ulcer. The ulcer at the weight-bearing surface at the anterior patella had not closed despite three years of conservative management; including offloading and wound clinic follow up. To assist with the healing process, the ulcer was treated with autologous micro-fragmented adipose tissue therapy. He was injected with 8 mLs of minimally manipulated adipose tissue (Lipogems) underneath the ulcer. Upon the four-week follow-up, his pain had resolved, and the wound was significantly reduced in size with new skin appearing. The goal of this case report is to examine if autologous micro-fragmented adipose tissue can represent a feasible and safe treatment option for chronic prosthesis-related residual limb ulcers. To our knowledge, this is the first reported case using micro-fragmented adipose therapy to treat a chronic prosthesis-related residual limb ulcer.

Objective:. This case series describes the effect of angiotensin II administration on hemodynamics in patients with parenchymal lung injury due to submersion injury. Case Summary:. A 33-year-old female and a 72-year-old female were both brought to the emergency department after incidents of near drowning. Upon arrival to the emergency department, both patients were hemodynamically unstable and were eventually intubated for airway protection. Imaging done by conventional chest radiograph for both patients revealed bilateral pulmonary edema. Due to their hemodynamic status, vasopressors were initiated for both patients and were quickly titrated, leading to the initiation of angiotensin II. In one patient, angiotensin II was initiated early in shock and resulted in rapid improvement of hemodynamics. In the other patient, angiotensin II was initiated later and a more muted response was observed. Conclusions:. In patients with near drowning, angiotensin II appeared to improve hemodynamic status rapidly. This is the first case series to report the use of this new vasoactive agent in this population and poses noteworthy mechanistic considerations.

A combinatorial film of the LaCo1-xCrxO3 system was fabricated using the LaCoO3 and LaCrO3 targets at the NIST Pulsed Laser Deposition (PLD) facility. As the ionic size of Cr3+ is greater than that of Co3+, the unit cell volume of the series increases with increasing x. Using a custom screening tool, the Seebeck coefficient of LaCo1-xCrxO3 approaches a measured maximum of 286 μV/K, near to the cobalt-rich end of the film library (with x ≈ 0.49). The resistivity value increases continuously with increasing x. The measured power factor, PF, of this series, which is related to the efficiency of energy conversion, also exhibits a maximum at the composition of x ≈ 0.49, which corresponds to the maximum value of the Seebeck coefficient. Our results illustrate the efficiency of applying the high-throughput combinatorial technique to study thermoelectric materials.

Autism spectrum disorder (ASD), characterized by impairments in social communication and repetitive behaviors, often includes altered responses to sensory inputs as part of its phenotype. The neurobiological basis for altered sensory processing is not well understood. The UC Davis Medical Investigation of Neurodevelopmental Disorders Institute Autism Phenome Project is a longitudinal, multidisciplinary study of young children with ASD and age-matched typically developing (TD) controls. Previous analyses of the magnetic resonance imaging data from this cohort have shown that ∼15% of boys with ASD have disproportionate megalencephaly (DM) or brain size to height ratio, that is 1.5 standard deviations above the TD mean. Here, we investigated electrophysiological responses to auditory stimuli of increasing intensity (50-80 dB) in young toddlers (27-48 months old). Analyses included data from 36 age-matched boys, of which 24 were diagnosed with ASD (12 with and 12 without DM; ASD-DM and ASD-N) and 12 TD controls. We found that the two ASD subgroups differed in their electrophysiological response patterns to sounds of increasing intensity. At early latencies (55-115 ms), ASD-N does not show a loudness-dependent response like TD and ASD-DM, but tends to group intensities by soft vs. loud sounds, suggesting differences in sensory sensitivity in this group. At later latencies (145-195 ms), only the ASD-DM group shows significantly higher amplitudes for loud sounds. Because no similar effects were found in ASD-N and TD groups, this may be related to their altered neuroanatomy. These results contribute to the effort to delineate ASD subgroups and further characterize physiological responses associated with observable phenotypes. Autism Res 2019, 12: 1236-1250. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Approximately 15% of boys with ASD have much bigger brains when compared to individuals with typical development. By recording brain waves (electroencephalography) we compared how autistic children, with or without big brains, react to sounds compared to typically developing controls. We found that brain responses in the big-brained group are different from the two other groups, suggesting that they represent a specific autism subgroup.

Privative adjectives such as fake have long posed problems to theories of adjectives in a compositional semantics. In this paper, I argue that a theory like Del Pinal’s recent Dual Content semantics, which encodes lexical entries with both an extension-determining component and a conceptual component, is best equipped to account for privativity while maintaining compositionality, but requires some revisions to do so. I provide some novel evidence for this system regarding recursive privativity to justify a new denotation for fake, use this to derive the patterns in some recent experimental data, and introduce an extension to the system to account for privative behaviors of intersective adjectives.

The synthesis, structure, and temperature dependent thermal and electrical properties of off-stoichiometric polycrystalline modified zinc blende quaternary chalcogenides Cu1.33+xZn1.33-xIn1.33Se4, where x ​= ​0, 0.1, 0.2 and 0.3, are investigated. Temperature-dependent electrical properties reveal these compositions to be semiconductors with alteration of the carrier concentration and electrical transport via stoichiometric variation. The thermal conductivity is low for all specimens and intrinsic to these materials. First principles calculations are also reported in establishing a fundamental investigation that illustrates the large variation in stoichiometry that is possible in these materials. This stoichiometric variation results in the observed variation of the transport properties. The results presented reveal fundamental structure-property relationships in these quaternary chalcogenides, and provides a basis for further research into the viability for large stoichiometric variation in other materials that are of interest for technological applications.

I argue for a reanalysis of "wh-the-hell" questions as restrictions on the domain of alternatives, rather than polarity items or domain extensions. This analysis returns to their original characterization as "aggressively non-D-linked" by specifying what it means to be D-linked, and in doing so captures a number of otherwise unconnected properties of such questions without positing extraneous features. Consequences of the proposal include a new notion of question-specific contextuality, evidence for an inquisitive semantic condition on sluicing, and a potential general discourse restriction on wh-movement.

Quaternary chalcogenides form a large class of materials that continue to be of interest for energy-related applications. Certain compositions have recently been identified as possessing good thermoelectric properties however these materials typically have the kesterite structure type with limited variation in composition. In this study we report on the structural, optical and electrical properties of the quaternary chalcogenides CuZn2InTe4 and CuCd2InTe4 which crystallize in the modified zinc-blende crystal structure, and compare their properties with that of CuZn2InSe4. These p-type semiconductors have direct band gaps of about 1 eV resulting in relatively high Seebeck coefficient and resistivity values. This work expands on the research into quaternary chalcogenides with new compositions and structure types in order to further the fundamental investigation of multinary chalcogenides for potential thermoelectrics applications.

A hydrothermal approach was employed to efficiently synthesize SnSe nanorods. The nanorods were consolidated into polycrystalline SnSe by spark plasma sintering for low temperature electrical and thermal properties characterization. The low temperature transport properties indicate semiconducting behavior with a typical dielectric temperature dependence of the thermal conductivity. The transport properties are discussed in light of the recent interest in this material for thermoelectric applications. The nanorod growth mechanism is also discussed in detail.

A suite of complementary high-throughput screening systems for combinatorial films was developed at National Institute of Standards and Technology to facilitate the search for efficient thermoelectric materials. These custom-designed capabilities include a facility for combinatorial thin film synthesis and a suite of tools for screening the Seebeck coefficient, electrical resistance (electrical resistivity), and thermal effusivity (thermal conductivity) of these films. The Seebeck coefficient and resistance are measured via custom-built automated apparatus at both ambient and high temperatures. Thermal effusivity is measured using a frequency domain thermoreflectance technique. This paper will discuss applications using these tools on representative thermoelectric materials, including combinatorial composition-spread films, conventional films, single crystals, and ribbons.

Adaptive radar systems will be required to operate in different frequency bands with spectrum requirements that will likely change both in time and with geographic region. A new algorithm is presented that allows direct optimisation of an amplifier's load reflection coefficient to find a Pareto optimum between the power-added efficiency (PAE) and adjacent-channel power ratio. Comparisons of simulation and measurement results are presented. The new algorithm's results compare well with traditionally acquired data and show consistency between the optimum values for PAE that are obtained from different starting points. Measurement comparison is performed with the previous optimisation algorithm reported by the authors, and results show that up to a 50% reduction in the number of measured experimental queries can be obtained. This translates into a significant time savings in reconfiguring a radar transmitter power amplifier.

Power amplifiers in modern wireless systems must meet increasingly stringent spectral constraints while still operating with high power efficiency. A new peak-search algorithm is demonstrated to find the Pareto optimum of power-added efficiency (PAE) while producing an adjacent channel power ratio (ACPR) value under a specified maximum. A peak-search is first performed for the maximum PAE, and then a small-step steepest descent walk in the ACPR is taken from the PAE maximum toward the ACPR minimum until ACPR requirements are met. This approach reasonably approximates the Pareto optimum for the device. Simulation and measurement data are presented for searches from multiple starting points, and good correspondence is obtained for the Pareto optimum reflection coefficient, as well as the optimum PAE and ACPR values. This measurement-based algorithm is expected to find useful application in real-time adaptive radio and radar transmitters, as well as in bench-top measurements for amplifier design.

Large-volume, phase-pure synthesis of BC8 silicon ($Ia\overline{3}$, $cI16$) has enabled bulk measurements of optical, electronic, and thermal properties. Unlike previous reports that conclude BC8-Si is semimetallic, we demonstrate that this phase is a direct band gap semiconductor with a very small energy gap and moderate carrier concentration and mobility at room temperature, based on far- and midinfrared optical spectroscopy, temperature-dependent electrical conductivity, Seebeck and heat capacity measurements. Samples exhibit a plasma wavelength near $11\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$, indicating potential for infrared plasmonic applications. Thermal conductivity is reduced by 1--2 orders of magnitude depending on temperature as compared with the diamond cubic (DC-Si) phase. The electronic structure and dielectric properties can be reproduced by first-principles calculations with hybrid functionals after adjusting the level of exact Hartree--Fock (HF) exchange mixing. These results clarify existing limited and controversial experimental data sets and ab initio calculations.

We have developed a custom apparatus for the consecutive measurement of the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of materials between 300 K and 12 K. These three transport properties provide for a basic understanding of the thermal and electrical properties of materials. They are of fundamental importance in identifying and optimizing new materials for thermoelectric applications. Thermoelectric applications include waste heat recovery for automobile engines and industrial power generators, solid-state refrigeration, and remote power generation for sensors and space probes. The electrical resistivity is measured using a four-probe bipolar technique, the Seebeck coefficient is measured using the quasi-steady-state condition of the differential method in a 2-probe arrangement, and the thermal conductivity is measured using a longitudinal, multiple gradient steady-state technique. We describe the instrumentation and the measurement uncertainty associated with each transport property, each of which is presented with representative measurement comparisons using round robin samples and/or certified reference materials. Transport properties data from this apparatus have supported the identification, development, and phenomenological understanding of novel thermoelectric materials.

Imaging from strongly scattering objects requires nonlinear inverse algorithms and multiple scattering can yield improved resolution. However, near resonance, weak scattering inverse methods can still prove useful. We investigate this phenomenon using strongly resonant meta-atoms.

There are a variety of material systems employing different strategies in an effort to establish a new paradigm for thermoelectric materials performance. One approach is the PGEC, or “phonon-glass electron crystal”, approach were research towards optimization of the electrical properties of very low thermal conductivity materials is key. Other efforts focus on materials that exhibit high power factors via quantum-confinement or nano-scale affects. Still others focus on “engineering” metastable phases that possess properties that are distinct, if not unique, to solid state chemistry. All these approaches are valid and provide a fundamental knowledge base whereby present and future scientific materials discoveries will lead to new technological improvements. This paper focuses on bulk materials, in particular those material systems currently under investigation in the novel materials laboratory at the University of South Florida and the requirements and strategies for their optimization towards improved thermoelectric properties.

There are a variety of material systems employing different strategies in an effort to establish a new paradigm for thermoelectric materials performance. One approach is the PGEC, or “phonon-glass electron crystal”, approach were research towards optimization of the electrical properties of very low thermal conductivity materials is key. Other efforts focus on materials that exhibit high power factors via quantum-confinement or nano-scale affects. Still others focus on “engineering” metastable phases that possess properties that are distinct, if not unique, to solid state chemistry. All these approaches are valid and provide a fundamental knowledge base whereby present and future scientific materials discoveries will lead to new technological improvements. This paper focuses on bulk materials, in particular those material systems currently under investigation in the novel materials laboratory at the University of South Florida and the requirements and strategies for their optimization towards improved thermoelectric properties.

Combinatorial metrology has evolved as a useful approach to rapidly determine the composition-structure-property relationships for solid solution systems in a far more efficient way than the traditional one composition at a time approach. The success of this method applied in thermoelectric (TE) research relies on screening tools to evaluate the TE properties for a combinatorial library. We report here on a thermoelectric screening tool capable of performing temperature dependent measurement of the Seebeck coefficient and electrical resistivity from 300 K to 800 K. The validity of the apparatus is demonstrated by screening the power factor of a filled skutterudite combinatorial film at room temperature and at elevated temperatures as well. The accuracy of the measurement is verified using the low temperature Seebeck coefficient Standard Reference Material (NIST SRM 3451) and a heavily doped SiGe specimen for high temperature comparison. Several important parameters, such as measurement atmosphere, film substrate, and probe configuration, are identified that directly affect the Seebeck coefficient measurement in this and other similar apparatus.

Spectral constraints placed on radar systems by regulatory agencies require the design of highly linear amplifiers. Spectral spreading in power amplifiers is a result of transistors operated in the non-linear regime to optimise efficiency. Various methods are employed by power amplifier designers to maximise both linearity and efficiency. The methods of predistortion, feedforward, envelope tracking, Doherty and `linear amplification using non-linear components` are discussed in this article. Trade-offs and challenges inherent in these design approaches are surveyed.