The Direct Broadcast Satellite: The Need For Effective International Regulation

This article examines the need for international laws and cooperation in the use of communications satellites

Effects of the Amount of Fillers and of the Crosslink Density on the Mechanical Behavior of Carbon-Black Filled Styrene Butadiene Rubbers

Several carbon-black filled styrene-butadiene rubbers are subjected to monotonic uniaxial tension tests in order to investi-gate the effects of the amount of fillers and of the crosslink density on their mechanical properties. The Young modulus, the volume changes associated with material damage and the stretch to failure are extracted and discussed. Results compare well to the literature results when exist and quantitative analysis are proposed when possible. Results show that filled rubbers are not incompressible when submitted to uniaxial tension tests and their volume changes are strongly dependent of the amount of fillers but are unaffected by the crosslink density. The latter shows strong impact on the filled rubbers stretch to failure but more interestingly this impact is com-parable to what is encountered in unfilled rubbers. The stretch to failure is improved by the addition of fillers with an optimum for material filled around 30 phr

An Analysis of the Competitive Dynamics Behind the Disruptor’s Dilemma

The introduction of a potentially disruptive technology into a mature multisided ecosystem often faces a seemingly dilemmatic challenge: persuading a critical mass of incumbents to support the technology that might eventually disrupt them. We analyse this apparently perplexing phenomenon under the lens of a global coordination game of incomplete public and private information; and more precisely an adaptation of a game of regime change. Incumbents can decide to support or not the potential disruptor, who becomes successful only if a sufficient mass of supporters is attained. The proposed model assumes a multi-round game where each round gives the opportunity for yet-not-supporting incumbents to irrevocably side with the potential disruptor. Only a two-round game is detailed, while elements for generalization to an arbitrary number of rounds are suggested. The first round constitutes a rather typical—i.e., extensively scrutinized in the literature—global game, for which it has already formally been established that a monotone equilibrium exists and is unique provided an adequate precision of the information structure. Subsequently, when making their decision during the second round, incumbents gain additional information derived from the first round. Although we do not formally prove the results, we conducted an extensive set of simulations revealing that the new information leads to either no equilibrium or a multiplicity of equilibria. Bearing in mind that our model is overly stylized, those observations suggest that the second round is prone to coordination failure; whereas the precision of information plays an essential role during the first round for incumbents to make an informed decision. It follows that a wise strategy consists for the potential disruptor in investing, at the very outset, in communicating precise information so as to ensure the existence of a unique equilibrium and, should the underlying fundamentals allow, succeed in the first round

Strukturelle Analyse des Enzyms N-Formylmethanofuran:Tetrahydromethanopterin-Formyltransferase

Archaea represent a third domain of life and some archaea exhibit a high degree of tolerance to extreme environmental conditions. Several members are methanogens and present in many anaerobic environments. Most methanogens are able to maintain growth simply on H2 and CO2 via the enzymatically catalyzed reaction 4H2 + CO2 > CH4 + 2 H2O. The archaeon Methanopyrus kandleri grows optimally at temperatures of 84°C to 110°C, pH values of 5.5 to 7.0 and NaCl concentrations 0.2% to 4%. The enzyme N-formylmethanofuran tetrahydromethanopterin formyltransferase (MkFTR) catalyzes the transfer of a formyl group from the cofactor N-formylmethanofuran (FMF) to the cofactor tetrahydromethanopterin (H4MPT), the second step of the above reaction. X-ray crystallographic analysis yielded insights into the structure and function of MkFTR, (1) the MkFTR monomer exhibits a pseudo-two fold structure suggestive of an evolutionary gene duplication. (2) The structure is a D2 homo-tetramer with prominent cleft-like surface features. Analysis of the interface contacts showed that the tetramer is best described as a dimer of dimers. The clefts were associated with the monomer:monomer interface and were weakly occupied by extra electron density which might be attributed to the H4MPT analog folate. (3) This suggested that the clefts are active sites and their association with oligomer interfaces suggested a basis for the dependence of activity on oligomerization. (4) The thermal stability of MkFTR most likely arises from the greater number of H- and ionic-bonds within the monomer and between monomers with respect to mesophilic protein structures. (5) The structure showed a large number of surface exposed negatively charged, glutamate and aspartate residues. These residues explain the salt dependent oligomerization, as only at high enough salt concentration is the electrostatic charge compensated by cation binding and neutralized allowing oligomerization. (6) These residues also improve the solubility of MkFTR at high salt concentration by increased charge repulsion. (7) Comparison of MkFTR structures from low and hight salt conditions showed that surface glutamate residues bind slightly more water molecules at high salt conditions further contributing to MkFTR solubility at high salt concentration.Eine kleine Gruppe von Organismen, die Methanogene, sind fähig, Methan zu erzeugen. Diese Gruppe von Organismen gehört ausschließlich der Domäne der Archaea an. Methanogene sind unter mesophilen, thermophilen, hyperthermophilen und halophilen Archaea vertreten. Das methanogene Archaeon Methanopyrus kandleri wurde in der Umgebung einer hydrothermalen Tiefseequelle entdeckt und wächst optimal bei Temperaturen zwischen 84°C und 110°C und bei pH-Werten von 5,5 bis 7,0 und NaCl-Konzentrationen zwischen 0,2% und 4%. Bis auf wenige Ausnahmen sind Methanogene in der Lage, auf Wasserstoff und Kohlendioxyd als einzigen Energiesubstraten zu wachsen und die Reaktion 4H2 + CO2 > CH4 + 2H2O zu katalysieren. Andere mögliche Substrate sind zum Beispiel Acetat und Methanol. Schritt 2: der Transfer einer Formylgruppe von FMF auf den Folate-ähnlichen Cofaktor Tetrahydromethanopterin (H4MPT) wird von der N-Formylmethanofuran:Tetrahydromethanopterin-Formyltransferase (FTR) durchgeführt. Ziel dieser Arbeit war die kristallografische Aufklärung der Proteinstruktur der FTR aus dem extrem thermophilen und salztoleranten Archaeon Methanopyrus kandleri (MkFTR). Die Bestimmung und die Analyse der Struktur könnte die strukturelle Basis der enzymatischen Aktivität und die Basis der extremen Thermostabilität und Salztoleranz der Enzyme erklären. Erstes Ergebnis dieser Arbeit war der Ausbau der MkFTR- Struktur aus Kristallform P, also PEG8000, als Fällungsmittel. Die Struktur besteht aus vier identischen Ketten pro asymmetrischer Einheit. Die Ketten bilden ein Tetramer mit D2-Symmetrie. Die unterschiedliche Größe der Kontaktfläche zwischen verschiedenen Monomeren lässt das MkFTR-Tetramer eher als ein Dimer von zwei Dimeren bezeichnen. Eine genauere Betrachtung des Monomers führt zu dem Schluss, dass das MkFTR- Monomer trotz fehlender Sequenzhomologie aus zwei Domänen besteht, und dass die beiden Domänen eine ähnliche Faltung haben. Die Domänen konnten mit dem DALI-Server überlagert werden. Dieses Ergebnis deutet eine evolutionäre Genverdoppelung an. Die Oberfläche des MkFTR-Tetramers zeigt vier große, symmetrisch verteilte Spalten. Diese Spalten haben jeweils drei Abzweigungen und liegen zum Teil direkt auf der Grenzfläche zwischen MkFTR-Monomeren. Der Zusammenhang dieser Stellen mit der Grenzfläche zwischen Monomeren verweist auf eine mögliche strukurelle Erklärung des Zusammenhangs zwischen der Aktivität und dem Oligomerzustand des MkFTR-Enzyms. Ein weiteres Indiz dafür, dass die Stellen Substrate-bindend sind, liegt daran, dass eine zusätzliche Elektronendichte in diesen Stellen zu finden war. Die Elektronendichte lässt sich nicht als Wassermoleküle modellieren. Eine mögliche Alternative wäre Folat, vielleicht in Form von Tetrahydro- oder Dihydrofolat. MkFTR könnte dies als Substratanalog zu H4MPT nach der heterologen Proteinproduktion in E. coli binden. Die höhere thermische Stabilität von MkFTR liegt wahrscheinlich an einer höheren Zahl von Wasserstoff- und Ionenbrücken, sowohl innerhalb eines Monomers als auch zwischen den Monomeren. Die Zahl der Ionenbrücken pro Aminosäurerest liegt deutlich höher gegenüber dem Durchschnittswert für mesophile Proteine. Die MkFTR-Struktur zeigt eine große Anzahl an negativ geladenen Resten auf der Moleküloberfläche, die für die höhere Löslichkeit und salzabhängige Thermostabilität der MkFTR verantwortlich sind. Diese Eigenschaft ist auch für die salzabhängige Oligomerisierung der MkFTR verantwortlich, weil die elektrostatische Abstoßung der Monomere erst bei erhöhter Salzkonzentration kompensiert wird, indem sich also an der Oberfläche Kationen anbinden. Die molekulare Basis der Salztoleranz von MkFTR könnte durch den Vergleich von Strukturen erklärt werden, die unter verschiedenen Salzkonzentrationen gelöst werden. Daraufhin wurde die MkFTR bei hoher Salzkonzentration (1% PEG 8000, 1.2M (NH4)2SO4 kristallisiert, Kristallform S und die gelöste Struktur mit der Struktur aus niedriger Salzkonzentration, Kristallform P (22% PEG 8000, 0.3M (NH4)2SO4, verglichen. Die Struktur der MkFTR Kristallform S wurde mittels Molekular-Ersatz (MR) gelöst und verfeinert. Die asymmetrische Einheit enthielt zwei MkFTR Monomere. Weiterhin zeigt der Vergleich der MkFTR Kristallform P- und S-Strukturen, dass Glutamatreste in Kristallform S eine geringfügig höhere Anzahl von Wassermolekülen gegenüber Kristallform P binden, circa 1,5 mal so viele Wassermoleküle pro Glutamat. Die größere Anzahl von gebundenen Wassermolekülen könnte zu der höheren Löslichkeit der MkFTR bei erhöhter Salzkonzentration beitragen. Die zusätzlichen gebundenen Wassermoleküle könnten die Hydrationsschicht des Proteins erweitern und dadurch die hydrophobe Oberfläche effektiv minimieren. Dies würde dazu führen, dass die hydrophobischen Wechselwirkungen, also der “salting-out“-Effekt, reduziert, und die MkFTR-Löslichkeit bei hoher Salzkonzentration erhöht würde

Bielschowsky head-tilt test-I. Ocular counterrolling and Bielschowsky head-tilt test in 23 cases of superior oblique palsy

We have measured the amplitude of ocular counterrolling (OCR) and the change in vertical deviation in the Bielschowsky head-tilt test (BHT) in 23 cases of unilateral superior oblique palsy. OCR was measured with a photographical method, using limbal, conjunctival vessels as landmarks. Average OCR of the healthy eye was 5.4 ± 2.4 (SD) deg either side, at 45 deg of body-tilt. BHT and OCR (of the healthy eye) were not related in the group as a whole. An important perturbing factor was the duration of the palsy. To clarify the relation between BHT, OCR and duration of palsy, the BHT/OCR ratio was calculated in each patient. Six cases with a palsy of presumed recent onset had BHT/OCR ratio of 0.57 ± 0.09, while twelve cases of long-standing palsy had a BHT/OCR ratio of 1.04 ± 0.71. This means that in cases of recent onset, the relation was relatively fixed. All high BHT/OCR ratio's occurred in long-standing palsies, whether acquired or congenital. In our opinion, disproportionately large amplitudes in the Bielschowsky head-tilt test are caused by secondary innervational changes or contractures

Mass-fraction of oxygen as a predictor of HHV of gaseous, liquid and solid fuels

The higher heating value (HHV) of gaseous, liquid and solid fuels is demonstrated to be a strong function of the mass fraction of oxygen required for combustion, and suitable correlations are proposed to describe this relationship accurately. A 4th order correlation was found to be the best for estimating HHV as an all-purpose correlation with a root-mean-square error (RMSE) of 1.2 MJ/kg, coefficient of determination (R2) value of 0.9900 and mean bias error (MBE) of 0.40 %. A 3rd order correlation was as accurate with an RMSE of 1.2 MJ/kg, R2 value of 0.9898 and an MBE of – 0.16 %. In addition, the linear relationship between the HHV and oxygen required for combustion on a mole basis is demonstrated and an alternative mole-based correlation is proposed. A total of 311 HHV data from various sources are used to validate these correlations and 13 other correlations available in the literature are used for further comparison.The Paper Manufacturers Association of South Africa (PAMSA), as well as the guidance and resources provided by the Future Energy Cluster at the Mäladalens Högskola, Sweden.http://www.elsevier.com/locate/procediaam2018Chemical Engineerin

Pyrolysis oil composition and catalytic activity estimated by cumulative mass analysis using Py-GC/MS EGA-MS

Please read abstract in the article.The Paper Manufacturers Association of South Africa (PAMSA)http://www.elsevier.com/locate/energy2021-11-28hj2021Chemical Engineerin

Oxygen consumption as the definitive factor in predicting heat of combustion

Please read abstract in the article.The Paper Manufacturers Association of South Africa (PAMSA), as well as the guidance and resources provided by the Future Energy Cluster at the Mäladalens Högskola, Sweden.http://www.elsevier.com/locate/apenergy2020-02-01hj2018Chemical Engineerin

Post-pyrolysis treatments of biochars from sewage sludge and A. mearnsii for ammonia (NH4-n) recovery

NH4-N-loaded biochars are suitable candidates for soil amendment and fertilization. Sewage sludge-based biochar and biochar from the invasive species black wattle were used as sorbents for the adsorption of ammonia from a concentrated solution to mimic the wastewater treatment plant reject water stream. To increase ammonium recovery efficiency, two post-pyrolysis activation techniques were compared: steam activation and hydrogen peroxide treatment. It was found that the success of the treatment options was material dependent; therefore, post-pyrolysis treatments will require optimization for different applications based on feedstock. A simplified version of an adsorption process simulated in Aspen Tech predicts that NH4-N may be recovered at an energy cost lower than that of the Haber-Bosch process for black wattle biochar yields of below 19.5%. The biooil and syngas produced during pyrolysis can be used to lessen the energy requirements of the process, so that the solid portion may be utilized as an adsorbent and soil fertilizer. The energy-based sustainability of this technology warrants a more in-depth investigation for evaluation of the techno-economic feasibility for this class of loaded sorbents, and whether this method of nitrogen capture from wastewater is a suitable replacement of the costly Haber-Bosch process.http://www.elsevier.com/locate/apenergyhj2020Chemical Engineerin