2,444 research outputs found
Germanium Detector with Internal Amplification for Investigation of Rare Processes
Device of new type is suggested - germanium detector with internal
amplification. Such detector having effective threshold about 10 eV opens up
fresh opportunity for investigation of dark matter, measurement of neutrino
magnetic moment, of neutrino coherent scattering at nuclei and for study of
solar neutrino problem. Construction of germanium detector with internal
amplification and perspectives of its use are described.Comment: 13 pages, latex, 3 figures, report at NANP-99, International
Conference on Non-Accelerator Physics, Dubna, Russia, June 29- July 3, 1999.
To be published in the Proceeding
Entropic phase separation of linked beads
We study theoretically a model system of a transient network of microemulsion
droplets connected by telechelic polymers and explain recent experimental
findings. Despite the absence of any specific interactions between either the
droplets or polymer chains, we predict that as the number of polymers per drop
is increased, the system undergoes a first order phase separation into a dense,
highly connected phase, in equilibrium with dilute droplets, decorated by
polymer loops. The phase transition is purely entropic and is driven by the
interplay between the translational entropy of the drops and the
configurational entropy of the polymer connections between them. Because it is
dominated by entropic effects, the phase separation mechanism of the system is
extremely robust and does not depend on the particlular physical realization of
the network. The discussed model applies as well to other polymer linked
particle aggregates, such as nano-particles connected with short DNA linkers
Paper Session II-A - Results of a Wheel Electrometer for Measuring the Triboelectric Properties of Martian Regolith
The preliminary results of a prototype Wheel Electrometer System (WES) are presented that show that it is indeed possible to use the static electricity generated between polymers and soils after contact (triboelectricity) as a means of detecting property changes. Changes in the triboelectric signals offer information as to the mechanical properties of the soil such as grain size differences, texture, hardness and even moisture content. Initially, four polymers are chosen that span the triboelectric series such as Teflon, Lucite, Fiberglass and Lexan. It is shown that the average charge on Teflon is much higher when rolled over beach sand as compared to Martian simulant and limestone. Lucite was the most susceptible to particle size differences, while Lexan was able to detect underlying materials in the case of a soil lightly covered with a different soil type. All polymers responded differently when rolled over dry soil compared with moist soil. This information can be used as a type of triboelectric spectroscopy when a library of data is used to categorize the unique charging characteristics of individual polymers. This system is of great interest to planetary scientists and such measurements may be included in future Mars rover missions
Effect of Non-Magnetic Impurities (Zn,Li) in a Hole Doped Spin-Fermion Model for Cuprates
The effect of adding non-magnetic impurities (NMI), such as Zn or Li, to
high-Tc cuprates is studied applying Monte Carlo techniques to a spin-fermion
model. It is observed that adding Li is qualitatively similar to doping with
equal percentages of Sr and Zn. The mobile holes (MH) are trapped by the NMI
and the system remains insulating and commensurate with antiferromagnetic (AF)
correlations. This behavior persists in the region %NMI > %MH. On the other
hand, when %NMI < %MH magnetic and charge incommensurabilities are observed.
The vertical or horizontal hole-rich stripes, present when % NMI=0 upon hole
doping, are pinned by the NMI and tend to become diagonal, surrounding finite
AF domains. The %MH-%NMI plane is investigated. Good agreement with
experimental results is found in the small portion of this diagram where
experimental data are available. Predictions about the expected behavior in the
remaining regions are made.Comment: Four pages with four figures embedded in tex
Characterization of defatted products obtained from the Parmigiano–Reggiano manufacturing chain: Determination of peptides and amino acids content and study of the digestibility and bioactive properties
Parmigiano–Reggiano (PR) is a worldwide known Italian, long ripened, hard cheese. Its inclusion in the list of cheeses bearing the protected designation of origin (PDO, EU regulation 510/2006) poses restrictions to its geographic area of production and its technological characteristics. To innovate the Parmigiano–Reggiano (PR) cheese manufacturing chain from the health and nutritional point of view, the output of defatted PR is addressed. Two defatting procedures (Soxhlet, and supercritical CO2 extraction) were tested, and the obtained products were compared in the composition of their nitrogen fraction, responsible for their nutritional, organoleptic, and bioactive functions. Free amino acids were quantified, and other nitrogen compounds (peptides, proteins, and non-proteolytic aminoacyl derivatives) were identified in the extracts and the mixtures obtained after simulated gastrointestinal digestion. Moreover, antioxidant and angiotensin converting enzyme (ACE) inhibition capacities of the digests were tested. Results obtained from the molecular and biofunctional characterization of the nitrogen fraction, show that both the defatted products keep the same nutritional properties of the whole cheese
Paper Session I-A - Electrostatic Charging of Polymers by Particle Impact at Martian Atmospheric Pressurs
Studies of the electrostatic interaction between micrometer-sized particles and polymer surfaces are of great interest to NASA’s planetary exploration program. The unmanned landing missions to Mars planned for this decade as well as the possible manned missions that might take place during the second decade of this century require a better understanding of the electrostatic response of the materials used in landing crafts and equipment when exposed to wind-blown dust or to surface dust and sand particles. We report on preliminary experiments designed to measure the electrostatic charge developed on three polymer surfaces as they are impacted by Mars simulant particles less than 5 micrometers in diameter moving at 20 m/s. Experiments were performed in a CO2 atmosphere at 10 mbars of pressure using a particle delivery method that propels the particles without contact. The polymer surfaces, commonly used in space applications, were chosen so that they span the triboelectric series
Monolayer dual gate transistors with a single charge transport layer
A dual gate transistor was fabricated using a self-assembled monolayer as the semiconductor. We show the possibility of processing a dielectric on top of the self-assembled monolayer without deteriorating the device performance. The two gates of the transistor accumulate charges in the monomolecular transport layer and artifacts caused by the semiconductor thickness are negated. We investigate the electrical transport in a dual gate self-assembled monolayer field-effect transistor and present a detailed analysis of the importance of the contact geometry in monolayer field-effect transistors.
Charge-based silicon quantum computer architectures using controlled single-ion implantation
We report a nanofabrication, control and measurement scheme for charge-based
silicon quantum computing which utilises a new technique of controlled single
ion implantation. Each qubit consists of two phosphorus dopant atoms ~50 nm
apart, one of which is singly ionized. The lowest two energy states of the
remaining electron form the logical states. Surface electrodes control the
qubit using voltage pulses and dual single electron transistors operating near
the quantum limit provide fast readout with spurious signal rejection. A low
energy (keV) ion beam is used to implant the phosphorus atoms in high-purity
Si. Single atom control during the implantation is achieved by monitoring
on-chip detector electrodes, integrated within the device structure, while
positional accuracy is provided by a nanomachined resist mask. We describe a
construction process for implanted single atom and atom cluster devices with
all components registered to better than 20 nm, together with electrical
characterisation of the readout circuitry. We also discuss universal one- and
two-qubit gate operations for this architecture, providing a possible path
towards quantum computing in silicon.Comment: 9 pages, 5 figure
Economic evaluation of Medically Assisted Reproduction: An educational overview of methods and applications for healthcare professionals
Economic evaluations of the value-for-money of Medically Assisted Reproduction (MAR) interventions are increasingly important due to growing pressure on healthcare budgets. Although such evaluations are commonplace in the published literature, the number/methodological complexity of different evaluations available, and the challenges specific to MAR interventions, can complicate the interpretation of such analyses for fertility treatments. This article aims to serve as an educational resource and provide context on the design/interpretation of economic analyses for MAR interventions. Several areas are relevant for first-line providers and decision makers: scope of analysis, comparator used, perspective/time horizon considered, outcomes used to measure success, and how results from cost-effectiveness studies can be summarised and used in clinical practice. We aim to help clinicians better understand the strengths/weaknesses of economic analyses, to enable the best use of the evidence in practice, so resources available for MAR interventions can provide maximum value to patients and society
Repressive Transcription
2011 July 9 Author ManuscriptHow are active and repressed portions of the genome established and maintained during development? In vertebrates, about 2 m of DNA is packaged into chromatin in a manner that allows for active transcription of some loci and repression of others. Most chromatin regulators do not recognize specific DNA sequences, so how are they recruited to specific sites throughout the genome? For actively transcribed genes, transcription factors or the transcription initiation apparatus recruit regulators associated with active chromatin (1). For genes that are repressed, recent studies suggest a counterintuitive model: Transcription initiates the formation of repressive chromatin (2–9)
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