Hybrid rockets have distinct advantages over their pure solid or liquid propellant counterparts, and their performance can be improved by inclusion of metal additives. Several metallic additives ...(micro-Al, micro-Ti, micro-Mg, micro-Zr, nano-Al, nano-B, and Mg-coated nano-B) were selected as potential candidates for hybrid rocket applications and characterized by applicable microscopy techniques. The regression rates and combustion efficiencies of plain HTPB and HTPB loaded with each additive at various concentrations (10%, 20%, and 30% by mass) burning in GOX were evaluated at moderate oxidizer mass fluxes (10-150 kg/m
2
-s) and pressures (
0.86 MPa, 125 psia). In general, the inclusion of any of the metallic additives led to a reduction in the regression rate and did not significantly change the combustion efficiency. The only exceptions were fuel formulations containing micro-Zr, which yielded a moderate (10-20%) increase in the regression rate at a concentration of 10%. The observed trends were more prevalent at higher oxidizer mass fluxes and higher additive loadings. The reductions in regression rate were attributed to heat transfer blocking effects derived from accumulation of additive particles on the fuel surface layer. These phenomena were especially prevalent in highly loaded fuel formulations containing the nano-additives that exhibited unstable combustion and periodic surface-layer shedding. Zirconium appears to be the best metallic additive available since it can yield the highest theoretical density-specific impulse under the lowest O/F operation ratio without resulting in decrements to overall performance. Notably, combustion efficiency data for all fuel formulations were well correlated to the combustion residence time, and high combustion efficiencies (>95%) were achievable when a satisfactory residence time (~75 ms) was realized.
The dielectric properties and loss tangents of low-density polyimide aerogels have been characterized at various frequencies. Relative dielectric constants as low as 1.16 were measured for polyimide ...aerogels made from 2,2'-dimethylbenzidine (DMBZ) and biphenyl 3,3',4,4'-tetracarbozylic dianhydride (BPDA) cross-linked with 1,3,5-triaminophenoxybenzene (TAB). This formulation was used as the substrate to fabricate and test prototype microstrip patch antennas and benchmark against state of practice commercial antenna substrates. The polyimide aerogel antennas exhibited broader bandwidth, higher gain, and lower mass than the antennas made using commercial substrates. These are very encouraging results, which support the potential advantages of the polyimide aerogel-based antennas for aerospace applications.
Hybrid rockets have many advantages over pure solid or liquid propellant rockets, but low solid fuel regression rates and correspondingly low thrust have hindered their application to operational ...systems. Paraffin-based fuels regress significantly faster than traditional polymeric formulations, such as HTPB, and paraffin inclusion in HTPB represents a potential tool for performance augmentation in hybrid rockets. A survey of the available literature indicated disparities regarding the utility of this approach which are resolved herein. Fuel specimen consisting of plain HTPB; plain paraffin; and HTPB loaded with molten macrocrystalline paraffin wax (10–75%) or solid microcrystalline paraffin particles (10–60%) were manufactured and evaluated for their thermal decomposition and ballistic properties. Fuel samples were heated (10 K/min) in an argon atmosphere in simultaneous TGA/DTA experiments. The inclusion of macrocrystalline paraffin enhanced the low-temperature decomposition of HTPB, while the inclusion of microcrystalline paraffin had the opposite effect. The prepared fuel grains were burned in gaseous oxygen on one of two lab-scale hybrid rockets over a range of oxidizer mass fluxes (5–430 kg/m2-s) and pressures (0.5–1.0 MPa). The plain macrocrystalline paraffin fuel exhibited a 300% increase in regression rate over plain HTPB. However, none of the mixed-fuel formulations exhibited notable, if any, regression rate enhancement at the evaluated operating conditions. First principles modeling was completed for the combustion of plain HTPB, plain paraffin, and mixed-fuel systems comprised of HTPB containing molten liquid paraffin or solid paraffin particles. The combustion of mixed-fuel systems is dominated by the pyrolysis of HTPB which does not allow for the formation of a melt layer at the fuel surface, such that any enhancement is due to an increase in the vaporization rate of the fuel and not entrainment effects. This study was the first to concurrently evaluate the inclusion of both molten liquid paraffin and solid paraffin particles in HTPB and demonstrated a lack of performance augmentation with either strategy in two separate laboratories. The results presented herein resolve the disparities in the literature and indicate that paraffin inclusion in HTPB is not a viable means for tailoring the combustion behavior of hybrid rocket systems.
As letters form the vocabulary of a language, biochemical ‘symbols’ (the building blocks of oligo- and polymers) make writing molecular messages possible. Compared to nucleotides and amino acids, ...sugars have chemical properties that facilitate to reach an unsurpassed level of oligomer diversity. These glycans are a part of the ubiquitous cellular glycoconjugates. Cyto- and histochemically, the glycans’ structural complexity is mapped by glycophenotyping of cells and tissues using receptors (‘readers’, thus called lectins), hereby revealing its dynamic spatiotemporal regulation: these data support the concept of a sugar code. When proceeding from work with plant (haem)agglutinins as such tools to the discovery of endogenous (tissue) lectins, it became clear that a broad panel of biological meanings can indeed be derived from the sugar-based vocabulary (the natural glycome incl. post-synthetic modifications) by glycan-lectin recognition in situ. As consequence, the immunocyto- and histochemical analysis of lectin expression is building a solid basis for the steps toward tracking down functional correlations, for example in processes leading to cell adhesion, apoptosis, autophagy or growth regulation as well as targeted delivery of glycoproteins. Introduction of labeled tissue lectins to glycan profiling assists this endeavor by detecting counterreceptor(s) in situ. Combining these tools and their applications strategically will help to take the trip toward the following long-range aim: to compile a dictionary for the glycan vocabulary that translates each message (oligosaccharide) into its bioresponse(s), that is to crack the sugar code.
The problems of resistance and side effects associated with cisplatin and other chemotherapeutic drugs have boosted research aimed at finding new compounds with improved properties. The use of ...platinum(IV) prodrugs is one alternative, although there is some controversy regarding the predictive ability of the peak reduction potentials. In the work described here a series of fourteen chloride Pt(II) and Pt(IV) compounds was synthesised and fully characterised. The compounds contain different bidentate arylazole heterocyclic ligands. Their cytotoxic properties against human lung carcinoma (A549), human breast carcinoma (MCF7) and human colon carcinoma (HCT116 and HT29) cell lines were studied. A clear relationship between the type of ligand and the anti-proliferative properties was found, with the best results obtained for the Pt(II) compound that contains an aniline fragment, (13), thus evidencing a positive effect of the NH2 group. Stability and aquation studies in DMSO, DMF and DMSO/water mixtures were carried out on the active complexes and an in-depth analysis of the two aquation processes, including DFT analysis, of 13 was undertaken. It was verified that DNA was the target and that cell death occurred by apoptosis in the case of 13. Furthermore, the cytotoxic derivatives did not exhibit haemolytic activity. The reduction of the Pt(IV) compounds whose Pt(II) congeners were active was studied by several techniques. It was concluded that the peak reduction potential was not useful to predict the ability for reduction. However, a correlation between the cytotoxic activity and the standard reduction potential was found.
Synopsis for Graphical Abstract
The cytotoxicity against different cancer cell lines of Pt(II) and Pt(IV) compounds containing heterocyclic ligands was studied with the best results obtained when a aniline fragment was present. DNA was the target. For the Pt(IV) compounds, the standard reduction potential was a more reliable parameter than the peak reduction potential. Display omitted
•Standard reduction potential as predicting tool for Pt(IV) prodrugs.•A chloride Pt(II) complex with an aniline fragment very cytotoxic.•Study of two aquation processes by DFT analysis.
Intensive size-selective harvesting can drive evolution of sexual maturity at smaller body size. Conversely, prehistoric, low-intensity subsistence harvesting is not considered an effective agent of ...size-selective evolution. Uniting archaeological, palaeontological and contemporary material, we show that size at sexual maturity in the edible conch Strombus pugilis declined significantly from pre-human (approx. 7 ka) to prehistoric times (approx. 1 ka) and again to the present day. Size at maturity also fell from early- to late-prehistoric periods, synchronous with an increase in harvesting intensity as other resources became depleted. A consequence of declining size at maturity is that early prehistoric harvesters would have received two-thirds more meat per conch than contemporary harvesters. After exploring the potential effects of selection biases, demographic shifts, environmental change and habitat alteration, these observations collectively implicate prehistoric subsistence harvesting as an agent of size-selective evolution with long-term detrimental consequences. We observe that contemporary populations that are protected from harvesting are slightly larger at maturity, suggesting that halting or even reversing thousands of years of size-selective evolution may be possible.
In hematology there has recently been increasing interest in inorganic polyphosphate. This polymer accumulates in platelet granules and its functions include modulating various stages of blood ...coagulation, inducing angiogenesis, and provoking apoptosis of plasma cells. In this study we evaluated the characteristics of intracellular polyphosphate in myeloma cell lines, in primary myeloma cells from patients, and in other human B-cell populations from healthy donors.
We have developed a novel flow cytometric method for detecting levels of polyphosphate in cell populations. We also used confocal microscopy and enzymatic analysis to study polyphosphate localization and characteristics.
We found that myeloma plasma cells contain higher levels of intracellular polyphosphate than normal plasma cells and other B-cell populations. Localization experiments indicated that high levels of polyphosphate accumulate in the nucleolus of myeloma cells. As the principal function of the nucleolus involves transcription of ribosomal DNA genes, we found changes in the cellular distribution of polyphosphate after the inhibition of nucleolar transcription. In addition, we found that RNA polymerase I activity, responsible for transcription in the nucleolus, is also modulated by polyphosphate, in a dose-dependent manner.
Our results show an unusually high accumulation of polyphosphate in the nucleoli of myeloma cells and a functional relationship of this polymer with nucleolar transcription.
During the last two decades, Global Positioning System (GPS) geodetic-grade receivers and accelerometers have been implemented in Structural Health Monitoring (SHM). Most recently, the use of sensors ...integrated in smartphones has been evolving. Although some of their capabilities are validated for small and local structures, there is a gap in knowledge about the use of sensors embedded in smartphones and other electronic devices for SHM of complex structures as bridges. To contribute in this area, this paper demonstrates the application of GPS receivers, accelerometers, and smartphones, integrating a smart sensor for the SHM of bridges. In order to validate its capabilities, the alternative smart sensor is used to study a particular bridge with vibration problems. Semistatic and dynamic displacements are obtained by means of GPS measurements. Accelerations in three directions of the bridge are determined using the accelerometer and the smartphone. Based on the results of the alternative smart sensor, inappropriate structural behavior is detected in the vertical direction of the bridge. In addition, dynamic characteristics are extracted using the smart sensor applying the Fast Fourier Transformation (FFT) and periodogram to the structural responses. As a result, it is verified the applicability of the fused smart sensor for SHM on real-scale bridges.
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