Self-tuning bandpass filter

An electronic filter is described which simultaneously maintains a constant bandwidth and a constant center frequency gain as the input signal frequency varies, and remains self-tuning to that center frequency over a decade range. The filter utilizes a field effect transistor (FET) as a voltage variable resistance in the bandpass frequency determining circuit. The FET is responsive to a phase detector to achieve self-tuning

A self-tuning filter

Self-tuning filter automatically adjusts its center frequency to track signal frequency. This permits the use of a filter with a bandwidth smaller than the range of input signal frequencies

Precision full-wave rectifier

Simplified circuit uses one operational amplifier and two precision resistors. The amplifier is operated open loop for switching and closed loop for linear gain, both simultaneously

AIROscope stellar acquisition

The acquisition system which operates in conjunction with a balloon-borne TV system, boresighted to a telescope is described. It has two main functions, a star field monitor and an offset star tracker. The design of the system was strongly influenced by the TV camera, which uses the same interlaced scanning system as is employed in commercial television broadcasting. To reduce power and bandwidth requirements, the star field information transmitted in our system consists only of the horizontal and vertical coordinates of each star and its brightness. As a star field monitor the system provides video thresholding, camera blemish suppression, coordinate digitization in 3 axes, circuity to recognize as single star the dispersed video signals resulting from one star overlapping adjacent scanning lines and storage of all signals for readout by the telemetry at appropriate times

The expanding distribution of Ixodes scapularis and associated pathogens in the Chicago, IL, metropolitan area

The geographic distribution of Lyme disease in the United States has increased considerably since the first description of the illness in the 1970s. The primary vector of Lyme disease, the tick Ixodes scapularis (Acari: Ixodidae), has expanded its range concurrently with the disease including into urban landscapes. To investigate landscape factors that may influence the colonization of I. scapularis and its associated pathogens in an urban ecosystem, 45 sites were sampled along three transects spanning the urban-to-rural human land use gradient in the Chicago, Illinois, metropolitan area. I collected four species of ticks (88% were I. scapularis) which exhibited variable infection rates for six pathogens, including Borrelia burgdorferi, the causative agent of Lyme disease, and B. lonestari and B. miyamotoi, both reported for the first time in Illinois. Logistic regression modeling indicated the presence of I. scapularis was positively correlated with forest land cover and negatively correlated with developed land cover, while the presence of B. burgdorferi was positively correlated with forest land cover. Neither the presence of the tick or the pathogen were correlated with distance to the nearest major river way. This study suggests that the range of I. scapularis and its pathogens have expanded in the Chicago metropolitan area since previous studies were conducted, including into forested urban areas near to the urban core. As tick and pathogen continue to colonize new areas, active monitoring and increased public education will be needed to protect vulnerable human populations

Collection Management and the Budget Crunch: Are We Adequately Preparing Library Students for Current Practices?

Purpose – The purpose of this paper is to determine whether collection management practices that evolved as a result of recent budgetary constraints are included in the LIS curriculum or not. Design/methodology/approach – Ten collection management trends related to budgetary constraints were identified through a review of the literature. Then, collection management educators at ALISE member institutions were identified and surveyed regarding the inclusion of the aforementioned trends in their curricula. Survey results were analyzed using descriptive statistics and content analysis. Findings – Four trends (collaborative collection development, just-in-time acquisitions, patron-driven-acquisitions, and participation in consortia) were mentioned in nearly all curricula; six others were covered with varying frequency. Professional standards are also found to include limited information on collection management. Additionally, a review of two popular collection development texts revealed that very few of the trends were covered in a budgetary context. Originality/value – This study examines collection management education in a novel way and highlights the disconnect between professional practice, professional standards, and education. The paper also adds the domain of collection development to the discussion of how or why LIS courses are influenced by practice

Program schemes with deep pushdown storage.

Inspired by recent work of Meduna on deep pushdown automata, we consider the computational power of a class of basic program schemes, TeX, based around assignments, while-loops and non- deterministic guessing but with access to a deep pushdown stack which, apart from having the usual push and pop instructions, also has deep-push instructions which allow elements to be pushed to stack locations deep within the stack. We syntactically define sub-classes of TeX by restricting the occurrences of pops, pushes and deep-pushes and capture the complexity classes NP and PSPACE. Furthermore, we show that all problems accepted by program schemes of TeX are in EXPTIME

Are Incomplete Denitrification Pathways a Common Trait in Thermus Species from Geothermal Springs in China?

Temperature has strong impacts on ecosystem function and biogeochemical cycles, particularly within extreme environments such as geothermal springs above 60 °C. The primary focus of this study was to investigate the denitrification pathways of Thermus (Bacteria) isolates from geothermal springs from Tengchong, China. This study tested the hypothesis that incomplete denitrification is a common characteristic of the genus Thermus, regardless of geographic origin or species affiliation, which would implicate them in the efflux of nitrous oxide (a strong greenhouse gas) to the atmosphere. In this study, we cultivated 25 isolates, including six known Thermus species, and measured the stoichiometry of nitrogenous products of nitrate respiration using gas chromatography and colorimetric assays. We also designed custom primers for polymerase chain reaction (PCR) amplification of denitrification genes including narG, nirS, nirK, and norB to screen for the genetic capacity for each step in denitrification. Experimental results show that all Thermus strains tested display incomplete denitrification pathways terminating at nitrite (NO2 -) or nitrous oxide (N2O), and possibly nitric oxide (NO)

Applying causality principles to the axiomatization of probabilistic cellular automata

Cellular automata (CA) consist of an array of identical cells, each of which may take one of a finite number of possible states. The entire array evolves in discrete time steps by iterating a global evolution G. Further, this global evolution G is required to be shift-invariant (it acts the same everywhere) and causal (information cannot be transmitted faster than some fixed number of cells per time step). At least in the classical, reversible and quantum cases, these two top-down axiomatic conditions are sufficient to entail more bottom-up, operational descriptions of G. We investigate whether the same is true in the probabilistic case. Keywords: Characterization, noise, Markov process, stochastic Einstein locality, screening-off, common cause principle, non-signalling, Multi-party non-local box.Comment: 13 pages, 6 figures, LaTeX, v2: refs adde