Future heavy duty trucking engine requirements

Developers of advanced heavy duty diesel engines are engaged in probing the opportunities presented by new materials and techniques. This process is technology driven, but there is neither assurance that the eventual users of the engines so developed will be comfortable with them nor, indeed, that those consumers will continue to exist in either the same form, or numbers as they do today. To ensure maximum payoff of research dollars, the equipment development process must consider user needs. This study defines motor carrier concerns, cost tolerances, and the engine parameters which match the future projected industry needs. The approach taken to do that is to be explained and the results presented. The material to be given comes basically from a survey of motor carrier fleets. It provides indications of the role of heavy duty vehicles in the 1998 period and their desired maintenance and engine performance parameters

Evidence for “dark charge” from photoluminescence measurements in wide InGaN quantum wells

Wide (15-25 nm) InGaN/GaN quantum wells in LED structures were studied by time-resolved photoluminescence (PL) spectroscopy and compared with narrow (2.6 nm) wells in similar LED structures. Using below-barrier pulsed excitation in the microsecond range, we measured increase and decay of PL pulses. These pulses in wide wells at low-intensity excitation show very slow increase and fast decay. Moreover, the shape of the pulses changes when we vary the separation between them. None of these effects occurs for samples with narrow wells. The unusual properties of wide wells are attributed to the presence of “dark charge” i.e., electrons and holes in the ground states. Their wave functions are spatially separated and due to negligible overlap they do not contribute to emission. However, they screen the built-in field in the well very effectively so that excited states appear with significant overlap and give rise to PL. A simple model of recombination kinetics including “dark charge” explains the observations qualitatively

Magnetic anisotropy of UFe10-xNixSi2 intermetallic alloys

The magnetic anisotropy in UF10x- Nix Si2 series has been studied by torsion magnetometry and initial ac magnetic susceptibility measurements in the temperature range of 77-293 K. The effective anisotropy constant changes with Ni content showing some increase for intermediate concentration. An increase in magnetic anisotropy energy at low temperatures is due to the uranium sublattice ordering. Magnetic anisotropy behaviour in UFe2Ni8 Si2 is influenced by an additional enhancement of the 3d sublattice connected with the ordering Fe magnetic moments

On the Crystal and Magnetic Behavior of ScFe4Al8 Single Crystal

Nuclear and magnetic properties of the ScFe4Al8 single crystal were found to exhibit unparalleled complexity of nuclear and magnetic structures. Our previous neutron measurements revealed presence of two modulation vectors, both along [", ", 0], however with dfferent critical temperatures. Recent experiments forced us to revise our knowledge of the structural ordering in the sample. So far, the crystal structure of this alloy, being of ThMn12-type, has never been questioned

Exercise intensity while hooked is associated with physiological status of longline-captured sharks

Some shark populations face declines owing to targeted capture and by-catch in longline fisheries. Exercise intensity during longline capture and physiological status may be associated, which could inform management strategies aimed at reducing the impacts of longline capture on sharks. The purpose of this study was to characterize relationships between exercise inten- sity and physiological status of longline-captured nurse sharks (Ginglymostoma cirratum) and Caribbean reef sharks (Carcharhinus perezi). Exercise intensity of longline-captured sharks was quantified with digital cameras and accelerometers, which was paired with blood-based physiological metrics from samples obtained immediately post-capture. Exercise intensity was associated with physiological status following longline capture. For nurse sharks, blood pH increased with capture dur- ation and the proportion of time exhibiting low-intensity exercise. Nurse sharks also had higher blood glucose and plasma potassium concentrations at higher sea surface temperatures. Associations between exercise intensity and physiological sta- tus for Caribbean reef sharks were equivocal; capture duration had a positive relation with blood lactate concentrations and a negative relationship with plasma chloride concentrations. Because Caribbean reef sharks did not appear able to influence blood pH through exercise intensity, this species was considered more vulnerable to physiological impairment. While both species appear quite resilient to longline capture, it remains to be determined if exercise intensity during capture is a useful tool for predicting mortality or tertiary sub-lethal consequences. Fisheries management should consider exercise during cap- ture for sharks when developing techniques to avoid by-catch or reduce physiological stress associated with capture

Mixed infections with distinct cytomegalovirus glycoprotein B genotypes in Polish pregnant women, fetuses, and newborns

The purpose of this investigation was to describe a distribution of cytomegalovirus (CMV) single and multiple genotypes among infected pregnant women, their fetuses, and newborns coming from Central Poland, as well as congenital cytomegaly outcome. The study involved 278 CMV-seropositive pregnant women, of whom 192 were tested for viral DNAemia. Human cytomegalovirus (HCMV) genotyping was performed for 18 of 34 pregnant women carrying the viral DNA and for 12 of their 15 offspring with confirmed HCMV infections. Anti-HCMV antibodies levels were assessed by chemiluminescence immunoassay (CLIA) and enzyme-linked fluorescence assay (ELFA) tests. Viral DNA loads and genotypes were determined by real-time polymerase chain reaction (PCR) assays for the UL55 gene. In the pregnant women, we identified HCMV gB1, gB2, gB3, and gB4 genotypes. Single gB2, gB3, or gB4 genotypes were observed in 14 (77.8 %) women, while multiple gB1–gB2 or gB2–gB3 genotypes were observed in four (22.2 %). Maternal HCMV genotypes determined the genotypes identified in their fetuses and newborns (p ≤ 0.050). Half of them were infected with single HCMV gB1, gB2, or gB3 genotypes and the other half with multiple gB1–gB2 or gB2–gB3 genotypes. Single and multiple genotypes were observed in both asymptomatic and symptomatic congenital cytomegaly, although no gB3 genotype was identified among asymptomatic cases. In Central Poland, infections with single and multiple HCMV strains occur in pregnant women, as well as in their fetuses and neonates, with both asymptomatic and symptomatic infections. HCMV infections identified in mothers seem to be associated with the viral genotypes in their children

Magnetic and hyperfine interaction in RFe4Al8 (R = Ce,Sc) compounds

Magnetic properties of ScFe4Al8 and CeFe4Al8 compounds have been studied by magnetization and Mössbauer effect measurements. Magnetic transition temperatures estimated from Mössbauer spectra (B = 0) 170 K for CeFe4Al8 and 225 K for ScFe4Al8 are not confirmed by magnetization measurements. Contrary, the pronounced maxima at Tmax = 130 and 125 K in DC magnetization curves (B = 1 kOe) were found for ScFe4Al8 and CeFe4Al8, respectively. Thermomagnetic, the so-called zero field (ZFC) and field cooling (FC) experiments show temperature-dependent irreversibilities below the "freezing" temperature, Tf, which diminishes with application of external magnetic field. The Mössbauer studies show the coexistence of magnetically (sextet) and non-magnetically (quadrupole doublet) split patterns in the wide temperature range far away from Tmax. All these observations indicate that the systems studied are either a spin-glass or are the mixture of AF and spin-glass state. © 2001 Elsevier Science B.V

Si in GaN -- On the Nature of the Background Donor

A characterization of the Si impurity in GaN is performed by Raman spectroscopy. Applying hydrostatic pressure up to 25 GPa the authors study the behavior of the LO phonon-plasmon mode in a series of high mobility Si doped GaN films. In contrast to earlier results on unintentionally doped bulk GaN crystals no freeze out of the free carriers could be observed in Si doped samples. The authors find that Si is a shallow hydrogenic donor throughout the pressure range studied. This result positively excludes Si incorporation as a dominant source of free electrons in previously studied bulk GaN samples

Magnetic properties and Moessbauer effect studies of Ce1-xScxFe4Al8 system

The investigations of the magnetic and electrical properties as well as the 57Fe Moessbauer effect are presented for Ce1-xScxFe4Al8 solid solution with 0<x<1 in the temperature range 4-300 K. Magnetic susceptibility follows a Curie-Weiss law above 200 K. The effective magnetic moment decreases with the Sc content. At temperatures lower than 130 K all compounds studied are antiferromagnets. The Neel temperature, TN is not affected by substitution of Sc for Ce. TN has no reflection in any anomaly in ρ(T). The Moessbauer spectra at temperatures lower than TN exhibit one Zeeman sextet related to the Fe nucleus at the 8(f) position. The hyperfine parameters Hhf, IS, QS have been estimated as a function of Sc concentration. The increasing of Sc content diminishes Hhf on the Fe nucleus. The calculations of electron-density distribution along the 〈1 1 1〉 direction in elemental crystallographic cell indicate a remarkable increase of electron charge at the Fe sites with the Sc content increasing. The 40-49° cone angles of the Fe sublattices at 12 K have been estimated from Moessbauer spectra analysis

Evidence for superconductivity and a pseudogap in the new magnetic compound PrAg₆In₆

Direct evidence for superconductivity in the new magnetic compound PrAg₆In₆ is revealed for the first time. The distinct Andreev-reflection current is observed in metallic point contacts (PC) based on this compound. The data obtained provide reason enough to suggest that the rise of superconductivity strongly depends on the local magnetic order varying over the sample volume. The triangular-shaped PC spectra (dV/dI V ( )) in the vicinity of the zero-bias voltage suggest an unconventional type of superconducting pairing. As follows from the temperature and magnetic field dependences of the PC spectra, the superconducting energy gap structure transforms into the pseudogap one as the temperature or the magnetic field increases