Earnings of Black and White Youth and Their Relation to Poverty

This paper examines the relation between youth employment and poverty for black and white families. An increase in the employment proportions of black men ages 16–19, which have lagged far behind their white counterparts, would reduce poverty among blacks to a moderate but meaningful degree. We provide evidence of a small positive feedback relation between black youth employment and family incomes that would magnify gains in both variables if either variable were increased. We also provide evidence that improvements in labor market conditions that affect youth employment, in the educational attainments of black youth, and in other policy-related variables would raise both youth employment and their family incomes.

Zirconia toughened ceramics

The objectives for the thesis were to generate tough ceramics utiising the toughening mechanisms inherent to zirconia materials. The aims have been realised with the successful fabrication of hot pressed silicon nitride / zirconia composite ceramics. The zirconia was prestabilised with two different types of dopant additives, yttria and ceria, with the intention of understanding the chemical compatibility with the silicon nitride matrix and the overall effect on the subsequent mechanical properties. The volume fraction of added zirconia was also varied. The increased toughness over silicon nitride materials alone was attributed to the toughening agents inherent to zirconia which existed either in the form of the tetragonal polymorph or the monoclinic variant. The toughening modes were dependent on initial chemistry of the composite system. When the zirconia was prestabilised with yttria the tetragonal polymorph was retained within the composite. The enhanced toughness was attributed to a transformation toughening mechanism. However, when the zirconia was prestabiised with ceria the depletion of Ce from solid solution with the zirconia during processing resulted in the formation of the unstabiised monoclinic variant. The enhanced toughness was attributed, in this case, to a microcrack type energy absorption mechanism, similar to several ZTA composite ceramics. Additionally, an experiment using ultrasound non-destructive testing, indicated that Tetragonal Zirconia Polycrystals (TZP) is ferroelastic and, as such, can provide a significant contribution to enhanced levels of fracture toughness in these materials or composites containing the same. Further work has been conducted to actually observe, as a function of applied unia.xial stress, the crystallographic changes occurring within the bulk of a 3Y-TZP ceramic via neutron elastic scattering at the ILL, Grenoble, France. This experiment has provided clear direct proof of the ferroelastic nature of zirconia. A similar experiment will be carried out at the Rutherford Laboratory, though with significantly improved statistics. An approach to improve the high temperature properties of TZP via the chemical alteration of the grain boundary phase was also considered. As a preliminary step the grain boundary volume was increased through controlled additions of the grain boundary composition in the form of both a premilled and a premelted glass. Poor fired densities were attained, however, due to the solute additive partitioning from the generation of an enhanced grain boundary phase to overstabilisation of the zirconia resulting in the formation of cubic stabilised zirconia. Furthermore, the incorporation of nitrogen within the grain boundary phase, via sintering TZP with sole additions of A1N, resulted in the attainment of poor fired densities and hence was not considered a suitable method for grain boundary modification

AIRNET: A real-time comunications network for aircraft

A real-time local area network was developed for use on aircraft and space vehicles. It uses token ring technology to provide high throughput, low latency, and high reliability. The system was implemented on PCs and PC/ATs operating on PCbus, and on Intel 8086/186/286/386s operating on Multibus. A standard IEEE 802.2 logical link control interface was provided to (optional) upper layer software; this permits the controls designer to utilize standard communications protocols (e.g., ISO, TCP/IP) if time permits, or to utilize a very fast link level protocol directly if speed is critical. Both unacknowledged datagram and reliable virtual circuit services are supported. A station operating an 8 MHz Intel 286 as a host can generate a sustained load of 1.8 megabits per second per station, and a 100-byte message can be delivered from the transmitter's user memory to the receiver's user memory, including all operating system and network overhead, in under 4 milliseconds

Rate-dependent propagation of cardiac action potentials in a one-dimensional fiber

Action potential duration (APD) restitution, which relates APD to the preceding diastolic interval (DI), is a useful tool for predicting the onset of abnormal cardiac rhythms. However, it is known that different pacing protocols lead to different APD restitution curves (RCs). This phenomenon, known as APD rate-dependence, is a consequence of memory in the tissue. In addition to APD restitution, conduction velocity restitution also plays an important role in the spatiotemporal dynamics of cardiac tissue. We present new results concerning rate-dependent restitution in the velocity of propagating action potentials in a one-dimensional fiber. Our numerical simulations show that, independent of the amount of memory in the tissue, waveback velocity exhibits pronounced rate-dependence and the wavefront velocity does not. Moreover, the discrepancy between waveback velocity RCs is most significant for small DI. We provide an analytical explanation of these results, using a system of coupled maps to relate the wavefront and waveback velocities. Our calculations show that waveback velocity rate-dependence is due to APD restitution, not memory.Comment: 17 pages, 7 figure

Quantitative Nanofriction Characterization of Corrugated Surfaces by Atomic Force Microscopy

Atomic Force Microscopy (AFM) is a suitable tool to perform tribological characterization of materials down to the nanometer scale. An important aspect in nanofriction measurements of corrugated samples is the local tilt of the surface, which affects the lateral force maps acquired with the AFM. This is one of the most important problems of state-of-the-art nanotribology, making difficult a reliable and quantitative characterization of real corrugated surfaces. A correction of topographic spurious contributions to lateral force maps is thus needed for corrugated samples. In this paper we present a general approach to the topographic correction of AFM lateral force maps and we apply it in the case of multi-asperity adhesive contact. We describe a complete protocol for the quantitative characterization of the frictional properties of corrugated systems in the presence of surface adhesion using the AFM.Comment: 33 pages, 9 figures, RevTex 4, submitted to Journal of Applied Physic

Room-temperature multiferroic behavior in layer-structured Aurivillius phase ceramics

Multiferroics that simultaneously exhibit ferroelectricity and ferromagnetism have recently attracted great attention due to their potential application in next generation electronic devices. However, only a few single-phase multiferroic materials exhibit ferroelectric and ferromagnetic orders at room temperature. Recently, some bismuth layer-structured Aurivillius compounds were reported as multiferroics at room temperature, but the origin of their magnetic property is still under debate because the net magnetization may originate from the presence of secondary phases that are not easily detected by laboratory XRD diffractometers. Here, textured Aurivillius phase Bi5.25La0.75FeCoTi3O18 ceramics were prepared by Spark Plasma Sintering. The ferromagnetic character of the ceramics was indicated by the magnetic field-induced reversible intensity changes of a certain set of crystalline planes belonging to the Aurivillius phase, as measured by in situ neutron diffraction under the applied magnetic field. The first principles calculations indicate that the ferromagnetism originates from double exchange interactions Fe3þ–O–Fe3þ, Co3þ–O–Co3þ, and Fe3þ–O–Co3þ in the ferro-toroidal main phase. The magnetic-controlled ferroelectric domain switching was observed by piezoelectric force microscopy at room temperature. The prepared Aurivillius phase ceramics, with Co/Fe contributing to magnetization and polarization at the same time, can be considered an intrinsic room-temperature multiferroic

In the Interests of clients or commerce? Legal aid, supply, demand, and 'ethical indeterminacy' in criminal defence work

As a professional, a lawyer's first duty is to serve the client's best interests, before simple monetary gain. In criminal defence work, this duty has been questioned in the debate about the causes of growth in legal aid spending: is it driven by lawyers (suppliers) inducing unnecessary demand for their services or are they merely responding to increased demand? Research reported here found clear evidence of a change in the handling of cases in response to new payment structures, though in ways unexpected by the policy's proponents. The paper develops the concept of 'ethical indeterminacy' as a way of understanding how defence lawyers seek to reconcile the interests of commerce and clients. Ethical indeterminacy suggests that where different courses of action could each be said to benefit the client, the lawyer will tend to advise the client to decide in the lawyer's own interests. Ethical indeterminacy is mediated by a range of competing conceptions of 'quality' and 'need'. The paper goes on to question the very distinction between 'supply' and 'demand' in the provision of legal services

Methane Mitigation:Methods to Reduce Emissions, on the Path to the Paris Agreement

The atmospheric methane burden is increasing rapidly, contrary to pathways compatible with the goals of the 2015 United Nations Framework Convention on Climate Change Paris Agreement. Urgent action is required to bring methane back to a pathway more in line with the Paris goals. Emission reduction from “tractable” (easier to mitigate) anthropogenic sources such as the fossil fuel industries and landfills is being much facilitated by technical advances in the past decade, which have radically improved our ability to locate, identify, quantify, and reduce emissions. Measures to reduce emissions from “intractable” (harder to mitigate) anthropogenic sources such as agriculture and biomass burning have received less attention and are also becoming more feasible, including removal from elevated-methane ambient air near to sources. The wider effort to use microbiological and dietary intervention to reduce emissions from cattle (and humans) is not addressed in detail in this essentially geophysical review. Though they cannot replace the need to reach “net-zero” emissions of CO2, significant reductions in the methane burden will ease the timescales needed to reach required CO2 reduction targets for any particular future temperature limit. There is no single magic bullet, but implementation of a wide array of mitigation and emission reduction strategies could substantially cut the global methane burden, at a cost that is relatively low compared to the parallel and necessary measures to reduce CO2, and thereby reduce the atmospheric methane burden back toward pathways consistent with the goals of the Paris Agreement

Dielectric constants of bulk ferroelectric PZTmeasured by terahertz time-domain spectroscopy

The complex permittivity of bulk ceramic ferroelectric of nominal composition PbZr0.4Ti0.6O3 was measured in the range 0.2–2 THz using transmission time-domain spectroscopy. The results indicate strong absorption and dispersion in this frequency range as often seen in highly disordered and polar materials. The results are compared to equivalent thin film data in the literature, and significant differences in the real and imaginary permittivity suggest that substrate clamping and degree of polarisation of the ferroelectric thin film materials affect dielectric properties even at these high frequencies