2,877 research outputs found
Brief Note Preliminary Studies of the Vocal Responses of Territorial Cardinals (Cardinalis Cardinalis) to Songs of a Strange Male
Author Institution: Department of Zoology, Miami Universit
Theory and design of cyclotron-wave traveling-wave amplifiers
A theory and design procedure for traveling-wave tubes using cyclotron-wave interactions is developed. An analysis is presented of the energy exchange mechanism and the axial beam velocity spread induced by the r.f. interactions. The analysis of the energy spread in a realistic model of the beam with nonzero size and nonzero space-charge density shows that higher maximum efficiencies at higher power is attainable (with collector depression) in cyclotron-wave amplifiers than in synchronous-wave amplifiers.
A one-watt, and a ten-watt cyclotron-wave amplifier at 3 GHz, utilizing bifilar helix circuits, scaled from a 2 kW, 5 GHz design, were constructed. A computer was used to design a pitch taper for the circuit of the ten-watt tube to maintain synchronism between beam and circuit waves so as to enable the extraction of more energy from the beam.
In general, test results verify the theory, and indicate the possibility of attaining efficiencies of the order of 70% in a 2 kW, 5 GHz cyclotron-wave amplifier. Because of the relatively low interaction impedance available for transverse-wave interactions, it is estimated that gains of the order of 1 dB/inch are possible
The Ministry of the Word According to Titus Chapter I
All three of Paul\u27s \u27\u27Pastoral Epistles I and II Timothy and Titus furnish a wealth of material for the diligent study and restudy of the scriptural teaching regarding the Ministry of the Word. In this paper an attempt is made to treat exegetically on the basis of the original Greek the first chapter of Titus, all of which has direct bearing upon the doctrine of the ministry. Moreover the fifth verse of this chapter presents proof for the divine institution of a local ministry
Diffusing proteins on a fluctuating membrane: Analytical theory and simulations
Using analytical calculations and computer simulations we consider both the
lateral diffusion of a membrane protein and the fluctuation spectrum of the
membrane in which the protein is embedded. The membrane protein interacts with
the membrane shape through its spontaneous curvature and bending rigidity. The
lateral motion of the protein may be viewed as diffusion in an effective
potential, hence, the effective mobility is always reduced compared to the case
of free diffusion. Using a rigorous path-integral approach we derive an
analytical expression for the effective diffusion coefficient for small ratios
of temperature and bending rigidity, which is the biologically relevant limit.
Simulations show very good quantitative agreement with our analytical result.
The analysis of the correlation functions contributing to the diffusion
coefficient shows that the correlations between the stochastic force of the
protein and the response in the membrane shape are responsible for the
reduction.
Our quantitative analysis of the membrane height correlation spectrum shows
an influence of the protein-membrane interaction causing a distinctly altered
wave-vector dependence compared to a free membrane. Furthermore, the time
correlations exhibit the two relevant timescales of the system: that of
membrane fluctuations and that of lateral protein diffusion with the latter
typically much longer than the former. We argue that the analysis of the
long-time decay of membrane height correlations can thus provide a new means to
determine the effective diffusion coefficient of proteins in the membrane.Comment: 12 pages, 8 figure
Bulk and contact-sensitized photocarrier generation in single layer TPD devices
In this paper, we report on the photoelectronic properties of TPD studied in
sandwich geometry. In particular, we have obtained from both forward and
reverse bias measurements the "mew-tau" product for holes in TPD. "mew" is the
hole mobility and "tau" the carrier trapping time. The "mew-tau" product is a
measure of the electronic quality of the material and allows a quantitative
comparison of different samples. We have carried out numerical simulations to
understand the photocurrent in these structures. We show that in reverse bias,
the photocurrent (PC) is due to bulk. The carrier generation is governed by
field assisted exciton dissociation at electric fields greater than 10^6 V/cm.
At lower fields the generation of carriers occurs spontaneously in the bulk of
the sample. In forward bias, the photocurrent is due to exciton dissociation at
the ITO contact. We also obtain a "mew-tau" product for holes from forward bias
PC measurements which is in agreement with the value obtained from reverse bias
measurements. Based on our experiments, we demonstrate that TPD in a sandwich
structure is a good candidate for cheap large area solar blind UV detector
arrays.Comment: Submitted to J. Appl. Phy
AI Solutions for MDS: Artificial Intelligence Techniques for Misuse Detection and Localisation in Telecommunication Environments
This report considers the application of Articial Intelligence (AI) techniques to
the problem of misuse detection and misuse localisation within telecommunications
environments. A broad survey of techniques is provided, that covers inter alia
rule based systems, model-based systems, case based reasoning, pattern matching,
clustering and feature extraction, articial neural networks, genetic algorithms, arti
cial immune systems, agent based systems, data mining and a variety of hybrid
approaches. The report then considers the central issue of event correlation, that
is at the heart of many misuse detection and localisation systems. The notion of
being able to infer misuse by the correlation of individual temporally distributed
events within a multiple data stream environment is explored, and a range of techniques,
covering model based approaches, `programmed' AI and machine learning
paradigms. It is found that, in general, correlation is best achieved via rule based approaches,
but that these suffer from a number of drawbacks, such as the difculty of
developing and maintaining an appropriate knowledge base, and the lack of ability
to generalise from known misuses to new unseen misuses. Two distinct approaches
are evident. One attempts to encode knowledge of known misuses, typically within
rules, and use this to screen events. This approach cannot generally detect misuses
for which it has not been programmed, i.e. it is prone to issuing false negatives.
The other attempts to `learn' the features of event patterns that constitute normal
behaviour, and, by observing patterns that do not match expected behaviour, detect
when a misuse has occurred. This approach is prone to issuing false positives,
i.e. inferring misuse from innocent patterns of behaviour that the system was not
trained to recognise. Contemporary approaches are seen to favour hybridisation,
often combining detection or localisation mechanisms for both abnormal and normal
behaviour, the former to capture known cases of misuse, the latter to capture
unknown cases. In some systems, these mechanisms even work together to update
each other to increase detection rates and lower false positive rates. It is concluded
that hybridisation offers the most promising future direction, but that a rule or state
based component is likely to remain, being the most natural approach to the correlation
of complex events. The challenge, then, is to mitigate the weaknesses of
canonical programmed systems such that learning, generalisation and adaptation
are more readily facilitated
Developmental and tissue-specific expression of the Q5k gene
Expression of the Q5k gene was examined by
northern blot analysis and polymerase chain reaction
(PCR) in the AKR mouse and various cell lines, each of
the H-2k haplotype. Our results show that Q5k mRNA is
present during the whole postimplantational development
of the AKR embryo/fetus (gestation day 6 to 15). In the
juvenile mouse (week 2 to 4) transcription of the Q5k
gene persisted in all organs examined. In contrast, in the
adult animal expression of the Q5k gene was limited to
the thymus and uterus of the pregnant mouse. Upon malignant
transformation, the amount of Q5k-specific mRNA
increased dramatically in thymus and could also be
observed in the spleen of thymoma bearing animals. Expression
of the Q5k gene was also detectable in several
transformed mouse cell lines. Mitogen stimulation or
treatment with cytokines induced Q5k expression in
primary spleen cell cultures. A possible explanation for
the tissue-restricted expression in the adult AKR mouse
is discussed
Embolization of sacral tumors
Journal ArticleThe management of sacral tumors is challenging because of difficulties in accessing the lesion, the high rate of local recurrence, extensive vascularity causing significant intraoperative blood loss, resistance to radiation therapy, and risk of malignant transformation. Although surgery is the main treatment for many sacral tumors, embolization is a valuable primary and adjunctive therapy. Patients with benign lesions, including aneurysmal bone cysts and giant cell tumors, have responded to embolization with resolution of their symptoms and with ossification of their lesions. Embolization is used as a primary therapy for metastatic lesions and results in neurological improvement, reduced tumor size, and decreased spinal canal compromise. It is also used as an adjuvant therapy to reduce intraoperative blood loss and to aid in the resection of benign, malignant, and metastatic sacral lesions. It is important to note that embolization techniques are a valuable resource in the treatment of sacral tumors, and, overall, embolization should always be considered in patients with sacral tumors
What Is Left of Listener Standing? The D.C. Circuit\u27s Continuing Flirtation with a Dying Doctrine
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