Infrared studies of the surface acidity of oxides and zeolites using adsorbed probe molecules

The use of infrared spectroscopy to probe the surface acidity of oxides and molecular sieves is reviewed. The experimental requirements and the type and nature of probe molecules available are also discussed. Special emphasis is given to the criteria that have to be met to arrive at a characterization of the solid that is useful for its catalytic application.     

Neuere Ergebnisse des Betriebes der Pilotanlage zum Hochtemperatur-Winkler-Verfahren

Recent results obtained on operation of a pilot plant for the high-temperature Winkler process . Rheinische Braunkohlenwerke AG is developing the high-temperature Winkler (HTW) process for gasification of coal and biomass in a fluidized bed. Preliminary studies in a lab-scale plant at the Technical University of Aachen served as a basis for construction of a pilot plant with a throughput of 25 tonnes of dry lignite per day which went into operation in mid 1978. The gasification pressure was raised to 10 bar and the temperature to over 1000 °C, and the exiting dust was recycled to the fluidized bed, with the aim of significantly improving the specific performance relative to operation at atmospheric pressure. In view of experience gained in operation with both low-ash and high-ash lignite, the availability of the pilot plant could be increased to almost 75% and the performance greatly improved. Thus significantly higher values were achieved than by the atmospheric-pressure Winkler process: 96% C-gasification and almost 1 600 m³ of synthesis gas per tonne of dry lignite; at over 7700 m³ of synthesis gas per tonne of dry lignite per m² reactor cross-section and per hour, the performance exceeds three times the former figure.     

Wavelength demultiplexer integrated on AlGaInAs/InP for 1.5 mu m operation

Wavelength demultiplexers, based on the two-mode interference principle, are demonstrated for the first time in the AlGaInAs/InP material system. Wavelength separation between 35 and 100 nm has been achieved in the 1.3-1.6 mu m spectral range, with channel isolation as high as 17 dB for unpolarised light.<>     

Determinants of functional status in healthy Italian nonagenarians and centenarians: a comprehensive functional assessment by the instruments of geriatric practice

OBJECTIVE: To evaluate the physical ability and psychocognitive status of a population more than 90 years of age with regard to sociodemographic, behavioral, and biomedical variables known to affect functional status in old age. DESIGN: A survey design was used. SETTING: Emilia Romagna, Northern Italy. PARTICIPANTS: Eighty-four healthy community-dwelling subjects aged 90 to 106 years. MEASUREMENTS: Sociodemographic variables, health behavior, anthropometric indices, and serum DHEAS levels were recorded. Functional assessment was performed by instruments currently used in geriatric practice: the Mini-Mental State Examination (MMSE), Geriatric Depression Scale (GDS), and Activities of Daily Living (ADL) scale. A stepwise multiple regression analysis was performed. RESULTS: GDS scores correlated directly with MMSE scores and inversely with ADL severity scores. Poor education, institutionalization, sensory impairment, muscular mass loss, and lower DHEAS levels were the variables with the highest correlation to functional impairment. Smoking, alcohol consumption, and marital status were relatively unimportant. An inverse association was found between DHEAS levels and dependency scores of single ADLs (continence, mobility). CONCLUSION: Impaired cognitive and physical ability with no increase in depression prevalence was found in a sample of subjects more than 90 years of age free of major age-related disease. Muscular mass and DHEAS levels seem to play a role in maintaining physical independence. In turn, physical independence, as well as social and cultural factors, strongly affect the compliance of long-lived subjects with psychocognitive tests currently used in the clinical evaluation of younger old people, suggesting that these instruments are not reliable for screening for cognitive impairment and depression in the oldest old subjects.     

The mitochondrial permeability transition

This review summarizes recent work on the regulation of the permeability transition pore, a cyclosporin A-sensitive mitochondrial channel that may play a role in intracellular calcium homeostasis and in a variety of forms of cell death. The basic bioenergetics aspects of pore modulation are discussed, with some emphasis on the links between oxidative stress and pore dysregulation as a potential cause of mitochondrial dysfunction that may be relevant to cell injury.     

Modelluntersuchungen zur Strömung und Durchmischung in metallurgischen Pfannen

Im Rahmen der vorgelegten Arbeit wurden praktische und theoretische Untersuchungen an Wassermodellen von bodengeblasenen metallurgischen Pfannen durchgeführt. Um die Strömungsverhältnisse herauszuarbeiten, wurden zunächst Lichtschnittuntersuchungen durchgeführt. Dabei wurden das H/D-Verhältnis und der Gasdurchsatz in weiten Bereichen variiert. Die Lichtschnittuntersuchungen vermittelten Erkenntnisse über die Abhängigkeit der Vermischungsvorgänge von den Versuchsparametern. In gleicher Weise wurden Farbspur- und vor allem Laser-Doppler-Anemometer-Versuche zur Ermittlung der lokalen Strömungsgeschwindigkeiten durchgeführt. Besondere Beachtung wurde dem Bodenbereich geschenkt, der durch die Partikeleinstreumethode nochmals gesondert untersucht wurde. Der Vergleich von berechneten Strömungsverläufen mit den tatsächlich beobachteten zeigt, daß tendenziell vergleichbare Zusammenhänge bestehen. Im einzelnen ist aber für die Beurteilung von Reaktorteilräumen die Erfassung der Strömungsverhältnisse, Teilraumgrößen und Konzentrationsverläufe aus unmittelbaren Messungen notwendig. Die theoretischen Berechnungen der Konzentrationsverläufe aus einer mathematischen Beschreibung des Pfannenmodells mit Hilfe von drei ideal gemischten Teilräumen ergab qualitativ vergleichbare Zeitabhängigkeiten, wie die unmittelbaren gemittelten Messungen an verschiedenen Stellen im Pfannenmodell. Die Durchmischung wird hiernach durch den Umlaufstrom bzw. die Massenaustauschströme zwischen den Teilräumen, die Teilraumgrößen und ihre Anordnungen bestimmt. Die physikalischen Bedingungen wie Rühren bzw. Antrieb durch das Gas bestimmen sowohl die Massenströme als auch die Ausbildungsformen und Größen der Teilräume.     

Barriers to international trade

Five cross sections of international trade data are analyzed by means of a gravity model in order to measure the impact of geographical distance, preferential agreements, language similarities, historical ties, and exchange rate volatilities on the pattern of world trade. The model is derived as a reduced form of a partial price equilibrium. A heteroscedastic log-linear specification is chosen in the econometric application, which is estimated by the maximum quasi-likelihood approach. Results show significant coefficients with expected signs in almost all cases.     

Hand preference during behavioral tests and spontaneous activity in two species of common marmoset (Callithrix jacchus and Callithrix penicillata)

Hand preference in two adult C. jacchus (one male and one female) and five C. penicillata (three adult females and two 70-day-old male and female infants) was examined in this study. Animals were housed in large wire mesh cages and daily tested twice during 40 consecutive days in 15-minute experimental sessions. Tests were carried out with dog food pellets and were as follows: 1) food taking from a glass cylinder (12 cm long x 5 cm diameter), 2) food taking from an opaque plastic flask (11 cm long x 9.5 cm diameter) behind wire mesh, 3) food taking under the cage floor and 4) spontaneous activity (food manipulation, self-grooming and scratching behavior, and grasping wire mesh). It was observed that 1) subjects exhibit a high manual ability in all testing conditions, 2) hand biases occurred, but the subjects either reversed hand preference or the preference was ambiguous as the performances are examined in a longitudinal perspective, 3) hand biases were clearly more visible in test 1, which may be due to the complexity of this task itself, 4) hand biases were not similar in all testing conditions--i.e., subjects were left--in one test and right-handed in another-, and 5) the main results were very similar in both C. jacchus and C. penicillata and seem to be not dependent on either sex or age.     

Application of thermomechanical treatment on medium-carbon microalloyed steels continuously cooled from forging temperature

In the high-production-drop-forging of parts for automobile and truck engines the classical quench and tempering (QT) of low-alloyed steels is nowadays - in a lot of plants in Europe - substituted by direct continuous cooling (CC) of microalloyed steels without the necessity of additional heat treatment and expensive straightening as well as stress relieving cycles. Nevertheless, there are some limitations on strength and toughness achievable by this technique. On two commercial medium-carbon (0.3%C) steels microalloyed with vanadium or vanadium and titanium, modified deformation parameters were applied. The mechanical properties, determined by the tensile test, can be improved by decreasing the deformation temperature. Nevertheless, the values of yield strength (resp. 0.2%-proof stress) as well as reduction of area remain inferior to those after QT of the same steels.     

Heat generation and transport in the heart

During contraction of the heart, a large part of the energy in energy metabolism is converted to heat. The article presents the results of measurements of mechanical stresses in the myocardium and blood vessels, temperatures and rate of heat generation. Experimental data correlate well with the numerical solutions of the biothermal problem. Laboratory for Physiology, Institute for Cardiovascular Research, Free University, Amsterdam, the Netherlands. Published in Inzhenerno-Fizicheskii Zhurnal Vol. 69, No. 3, pp. 364–376, May–June, 1996.