The Calcumeter

The Calcumeter adder appeared shortly after 1900, prospered for a while, and then apparently stopped production by 1920. Before its demise, as many as 100000 adders may have been made. The Calcumeter is an interesting, well made, small adding machine that is sought by collectors. The two names that are associated with it are James J. Walsh and Herbert North Morse: Walsh was the inventor and Morse apparently managed the business     

Strategies to obtain pattern fidelity in nanowire growth from large-area surfaces patterned using nanoimprint lithography

Position controlled nanowire growth is important for nanowire-based optoelectronic components which rely on light emission or light absorption. For solar energy harvesting applications, dense arrays of nanowires are needed; however, a major obstacle to obtaining dense nanowire arrays is seed particle displacement and coalescing during the annealing stage prior to nanowire growth. Here, we explore three different strategies to improve pattern preservation of large-area catalyst particle arrays defined by nanoimprint lithography for nanowire growth. First, we see that heat treating the growth substrate prior to nanoimprint lithography improves pattern preservation. Second, we explore the possibility of improving pattern preservation by fixing the seed particles in place prior to annealing by modifying the growth procedure. And third, we show that a SiN _x growth mask can fully prevent seed particle displacement. We show how these strategies allow us to greatly improve the pattern fidelity of grown InP nanowire arrays with dimensions suitable for solar cell applications, ultimately achieving 100% pattern preservation over the sampled area. The generic nature of these strategies is supported through the synthesis of GaAs and GaP nanowires.

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Iterative channel estimation for turbo equalization of time-varying frequency-selective channels

We investigate turbo equalization, or iterative equalization and decoding, as a receiver technology for systems where data is protected by an error-correcting code, shuffled by an interleaver, and mapped onto a signal constellation for transmission over a frequency-selective channel with unknown time-varying channel impulse response. The focus is the concept of soft iterative channel estimation, which is to improve the channel estimate over the iterations by using soft information fed back from the decoder from the previous iteration to generate "extended training sequences" between the actual transmitted training sequences.     

Prostate-specific antigen in the follow-up of conservatively treated prostatic cancer

The determination of serum prostate specific antigen (PSA) has made the diagnosis of prostate cancer easier. PSA is also used extensively in the follow-up of patients, both treated and untreated. On the basis of material from 308 patients who were mainly managed conservatively, we discuss the usefulness of this practice. It is important to monitor PSA after radical treatment because an increase may indicate local recurrence. In some patients this may lead to further treatment with cure as the aim. For patients under observation only, or those being treated by endocrine intervention, the value of regular PSA measurements is less certain. Where such patients were followed up for at least three years, we found considerable overlaping of PSA values among patients with different outlooks. Within the present therapeutic possibilities it may be better to base their management on clinical signs rather than on PSA. Regular measurements of PSA lead to focusing on this variable, causing unnecessary distress to patients months, or even years, before clinical progression of the disease.     

Potential effects of broadband wireline telecommunications on the HF spectrum

Power line telecommunications and various forms of digital subscriber line transmissions are recent and rapidly evolving technologies using the existing electricity power or telephone lines for data transmission at rates higher than 1 Mb/s. As these lines were not designed for transmission of high data rates, they produce noiselike interferences in the HF range. The intensity depends on the electrical characteristics of the lines (balance, match, screening) as well as on the density and area coverage of these new systems. Exact calculations are impossible at this time because of missing models for the new wirebound communication systems with respect to emission of radio noise in the HF band. Early measurements and estimations showed that radio noise from PLT and xDSL has the potential to cause problems for military HF radio communications and communication intelligence. A Research Task Group under NATO was assigned to study the issue and determine possible solutions. Briefly, the findings of the RTG do indicate that PLT emissions have the potential to cause appreciable degradation in the exploitation of the HF spectrum by military users.