Unknown Fraction Research Articles

Temporal measurement of plasma density variations above a semiconductor bridge (SCB)

The plasma density variations above a semiconductor bridge (SCB) device employing a capacitor discharge firing set have been measured in vacuum (/spl les/10/sup -5/ torr). A novel diagnostic technique using a microwave resonator probe was used to measure the resultant plasma density variations as a function of time. This method is superior to Langmuir probes in this application because Langmuir probe measurements are affected by sheath effects, small bridge area, and unknown fraction of multiple ions. Our experimental results indicate that the plasma density is observed to increase to a peak value of 5.5/spl times/ 10/sup 11/ cm/sup -3/ and decay exponentially with time, which is consistent with diffusion dominating the plasma transport. The time needed for reaching the peak plasma density is about 1.6 /spl mu/s, which is the duration of the late time discharge of an SCB device.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The contribution of Alaskan, Siberian, and Canadian coastal polynyas to the cold halocline layer of the Arctic Ocean

Numerous Arctic Ocean circulation and geochemical studies suggest that ice growth in polynyas over the Alaskan, Siberian, and Canadian continental shelves is a source of cold, saline water which contributes to the maintenance of the Arctic Ocean halocline. The purpose of this study is to estimate for the 1978–1987 winters the contributions of Arctic coastal polynyas to the cold halocline layer of the Arctic Ocean. The study uses a combination of satellite, oceanographic, and weather data to calculate the brine fluxes from the polynyas; then an oceanic box model is used to calculate their contributions to the cold halocline layer of the Arctic Ocean. This study complements and corrects a previous study of dense water production by coastal polynyas in the Barents, Kara, and Laptev Seas. Recurrent polynyas form on the Canadian and Alaskan coasts from Banks Island to the Bering Strait and on the Siberian coast from the Bering Strait to the New Siberian Islands. In the Bering Sea, polynyas form in Norton Sound, south and west of St. Lawrence Island, and in the Gulf of Anadyr. Two regions that account for almost 50% of the total dense water production are the Siberian coastal polynyas in the adjacent regions of the Gulf of Anadyr and Anadyr Strait and the Alaskan coastal polynyas which occur along the coast from Cape Lisburne to Point Barrow. For all of the western Arctic coastal regions examined, the mean annual total brine flux is 0.5±0.2 Sv. Combination of this flux with the contribution from the Barents, Kara, and Laptev Seas, which is recalculated from data in the earlier study, shows that over the entire Arctic, coastal polynyas generate about 0.7–1.2 Sv of dense water. This compares well with the theoretical estimates of 1–1.5 Sv. Because an unknown fraction of the Barents, Kara, and Laptev brine flux must go to the Eurasian Basin deep water, the coastal polynyas alone cannot renew the halocline layer. Other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms. For example, during February 1982 an intense storm generated a large region of low ice concentration in the eastern Chukchi Sea over Barrow Canyon. The refreezing of the region was followed by the flow of a dense plume down Barrow Canyon. Although the ocean dynamical response to this refreezing needs to be established, the possible response of a Barrow Canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the Arctic Ocean halocline.

Biochemical composition in relation to the energetics of growth and sexual maturation in the ommastrephid squid Illex argentinus

The proximate (protein, lipid, carbohydrate and ash) and elemental (C, H, N and P) composition of the major tissues were measured for 18 male and 51 female Illex argentinus sampled from the feeding grounds over the Patagonian Shelf. In most tissues the chemical composition did not vary with sexual maturity, although the mass of the tissue increased significantly because sexual maturation and growth were proceeding simultaneously. The composition of the ovary and associated tissues (nidamental gland, oviducal gland) did change significantly during sexual maturation. Several tissues contained significant amounts of one or more unknown components. The nitrogen content of an unknown component in the testis was similar to that of DNA. In the spermatophoric complex the nitrogen content suggested the unknown fraction may be an amino acid or short peptide, whereas in the nidamental gland the nitrogen content suggested an amino-sugar or polysaccharide derivative. The digestive gland was rich in lipid and continued to accumulate substantial reserves of energy throughout the period of sexual maturation on the feeding grounds. During this period there was no evidence for the utilization of either digestive gland or mantle tissues to supply energy for gonads. Accumulation of carbon and energy (estimated stoichiometrically from carbon) during the final 50 days on the feeding grounds indicated that energy demands for tissue synthesis in females were almost twice those of the smaller males, and that a relatively small fraction of the demands were for reproductive tissues (5% in males, 15% in females). Most energy intake in this period was directed to the digestive gland (40% in males, 47% in females) and other somatic growth (54% in males, 38% in females). A preliminary power budget suggested that during the final days of feeding before migrating to the spawning grounds, energy intake of Illex argentinus is 4-5% body energy content per day, growth efficiencies are low (17-22%) and that energy reserves in the digestive gland would fuel migration in the absence of feeding for 14 days in males and 21 days in females

Measurement of plasma electron density generatedby asemiconductor bridge (SCB)

To gain better understanding of semiconductor bridge (SCB) discharge behaviour, we have measured the plasma electron density generated by SCBs using a microwave resonator probe technique in a vacuum (<or=10/sup -5/ torr). This method is superior to Langmuir probes in this application because of sheath effects, small bridge areas, and unknown fraction of multiple ions.

Neural network applications for jamming state information generator

A known jamming state information (JSI) scheme for a coded frequency-hopped M-ary frequency-shift-keying (FH/MFSK) system under partial-band noise jamming, plus additive white Gaussian noise, utilizes the maximum a posteriori (MAP) rule based on the total energy received in the M-tone signaling bands. It is assumed that the knowledge of partial-band noise jamming fraction is available to the JSI generator. Because this scheme reduces the M-dimensional information into one dimension, i.e., the total energy, the generated JSI may not be the best. In this paper, a neural network approach to the JSI generation is presented. The efficiency of the new JSI generator with known partial-band noise jamming fraction is compared with the MAP generator. The neural network scheme is then generalized to increase its robustness by allowing for an unknown partial-band noise jamming fraction. The neural network JSI generator with or even without knowledge of jamming fraction offers significantly better performance for a coded FH/MFSK communication system than the MAP JSI generator for high code rate.

Capture-Recapture Models

nimal ecologists sample the populations they study in a variety of ways. Those who study bird populations in Hawaiian forests may count the number of birds seen and/or heard while walking a transect line or standing at a fixed point in the forest. Those who study red and grey kangaroos in the arid rangelands of central Australia may count animals from a fixed-wing airplane flying along transect lines. The fisheries biologist in the northern Pacific may count the number of halibut caught in a commercial fisheries operation, and the mammalogist in oldfield habitat in eastern North America may count the number of meadow voles caught overnight in a grid of small mammal traps. All these ecologists share a common problem. They have obtained a count statistic (animals seen, heard, or caught), but in most cases it is likely that this statistic is smaller than the actual number of animals present in the sampled area. That is, they have sampled some unknown fraction of the population of interest. The count statistic by itself is thus of little use to the ecologist, except to provide a minimum bound on population size. We need to know some-

Experimental Determination of the 14C Initial Activity of Calcareous Deposits

We have reconstructed the initial activity of calcareous sediments by 1) measuring the 14C activity of recent pre-bomb-test calcareous deposits, 2) calculating the ratio of the 14C activity of the calcareous sediment to that of the adjacent coeval wood, and 3) extrapolating 14C activity of the deep lacustrine sediment layers to the surface, assuming a constant sedimentation rate. We show here that the uppermost sediment is affected by the global increase of atmospheric 14C activity due to thermonuclear bomb tests in the early 1960s. 14C activity of submerged aquatic plants showed values similar to 14C activity of DIC. Thus, organic residue of the sediment cannot be used for reliable 14C dating because of the unknown fraction of aquatic plant detritus. The initial activity, A0, obtained in a case study of the geochronology of carbonates in the Plitvice Lakes area, ranged from 70.5 to 72.2 pMC for Lake Prošće sediment, and from 75.9 to 76.7 pMC for Lake Kozjak sediment. These values also agree with calculated values based on the downstream increase of 14C activity of DIC in freshwater open to the atmosphere.

Hereditary Ovarian Cancer

An unknown fraction of the ovarian cancer burden occurs in women with a family history indicative of a putative autosomal dominantly inherited cancer susceptibility syndrome. The results from a five-generation, extended, hereditary breast-ovarian cancer kindred are described 10 years after it was initially ascertained. Significantly more cancers were observed in high-risk family members during this decade than were expected (P less than 0.001). The age of ovarian cancer diagnosis was studied in additional ovarian cancer-prone families of three types: site-specific ovarian cancer syndrome, the breast-ovarian cancer syndrome, and Lynch syndrome II. The age of onset in each of the three sets was significantly (P less than 0.001) earlier than the general population mean of 59, and there were significant differences in the age of onset (P = 0.050) among these three cohorts. Ovarian cancer histology was similar to that of patients with negative family histories. There may be clinically significant heterogeneity in the age at diagnosis of ovarian cancer among these ovarian cancer-prone syndromes. This has important implications for understanding its natural history and targeting surveillance-management strategies.

Hereditary ovarian cancer. Heterogeneity in age at diagnosis

An unknown fraction of the ovarian cancer burden occurs in women with a family history indicative of a putative autosomal dominantly inherited cancer susceptibility syndrome. The results from a five-generation, extended, hereditary breast-ovarian cancer kindred are described 10 years after it was initially ascertained. Significantly more cancers were observed in high-risk family members during this decade than were expected (P less than 0.001). The age of ovarian cancer diagnosis was studied in additional ovarian cancer-prone families of three types: site-specific ovarian cancer syndrome, the breast-ovarian cancer syndrome, and Lynch syndrome II. The age of onset in each of the three sets was significantly (P less than 0.001) earlier than the general population mean of 59, and there were significant differences in the age of onset (P = 0.050) among these three cohorts. Ovarian cancer histology was similar to that of patients with negative family histories. There may be clinically significant heterogeneity in the age at diagnosis of ovarian cancer among these ovarian cancer-prone syndromes. This has important implications for understanding its natural history and targeting surveillance-management strategies.

Comments on Solar Convection

AbstractThis contribution discusses observational aspects of the evolution of individual structures of solar convection.It has been shown, that mesogranulation is a convective phenomenon that fits well into the gap between granulation and supergranulation. Apparently this observation justifies the view that the three members of the granulation family represent sections of a broad continuum of convective motions spanning the range of sizes from a yet unknown fraction of 1 Mm to about 50 Mm. Nevertheless, power spectra of velocity and brightness fluctuations exhibit three maxima, separated by intervals with significantly less power near 3 Mm and 7.5 Mm. Do these gaps give reasons for reconsidering the old idea, that each of the three characteristic scales has its own source layer at a certain depth in the convection zone?Power spectra of the granular energy distribution near the observational limit of spatial resolution suggest a continuous transfer of kinetic energy to smaller eddies by turbulent decay of the larger scale elements. Morphological studies of granular evolution and a comparison of the observed spectral line bisectors with theoretical predictions seem to disprove this idea. These observations imply either that the turbulent cascade, if it exists, is buried in the spatially unresolved part of the power distribution, or that radiative losses ultimately limit the life time of individual granules on all scales.

2-Pyrrolidinone in human cerebrospinal fluid: a major constituent of total gamma-aminobutyric acid.

2-Pyrrolidinone, the lactam of gamma-aminobutyric acid (GABA), is identified as the major constituent of total GABA in human CSF. Structural elucidation was done by mass spectrometry. In lumbar CSF of four patients, 2-pyrrolidinone represented about 54% of GABA found after acid hydrolysis, thus accounting for essentially all of the hitherto unknown GABA fraction in CSF.

Dual lanczos transformation theory; exact continued fraction expression for resonant γ-ray absorption spectrum of a harmonically bound atom executing classical motion described by smoluchowski dynamics

Implementing the mathematical apparatus of dual Lanczos transformation theory with the aid of symbolic manipulation techniques, we construct a previously unknown exact continued fraction expression for the resonant γ-ray absorption spectrum of a harmonically bound atom with an excited nucleus possessing a single radiative lifetime and executing classical motion described by Smoluchowski dynamics.

Dual lanczos transformation theory: closed set of algebraic equations connecting lanczos parameters with moments in moment expansions of time-dependent quantities

We report the derivation of a closed set of algebraic equations connecting the Lanczos parameters (of dual Lanczos transformation theory) with the moments appearing in the moment expansion (Maclaurin series) of time-dependent quantities. The utility of this set of equations is illustrated by using them with the aid of symbolic manipulation on a computer to construct a previously unknown exact continued fraction for the spectral density of the incoherent scattering function associated with a Fokker-Planck paricle in a spatially homogeneous, isotropic environment.

Recognition of sexual abuse in children.

Although of children has likely been present for ages, its recognition in the United States and other countries has dramatically increased in the past 5 years. Reported cases, which represent an unknown fraction of actual cases, now account for approximately 25% of all and neglect reports. Local, county, and state agencies are staggering under the load, and many are relying heavily on pediatricians to assist them in their work. DEFINITION Sexual can be defined as the engaging of a child in activites that the child does not understand, to which the child cannot give informed consent, or which violate the social taboos of society. This definition is broad and includes intrafamilial and extrafamilial forms and all types of activities (eg, exhibitionism, fondling, child pornography, oral, anal, and genital contact). The interface between normal exploratory behavior and sexual abuse is not clearly defined. Pediatricians should, however, use common sense. If two 4-year-old children are found to be playing without clothes, touching each others9 genitals and giggling, there is probably little to worry about. The same is true if two 15-year-old adolescents are discovered together. A probably exists if the 15-year-old child (some states set statutory 2- to 4-year limits within which activities are not to be considered abuse) or if one 4-year-old child is engaging in fellatio or attempting intercourse with another preschool-aged child.

Recognition of Sexual Abuse in Children

Although sexual abuse of children has likely been present for ages, its recognition in the United States and other countries has dramatically increased in the past 5 years. Reported cases, which represent an unknown fraction of actual cases, now account for approximately 25% of all abuse and neglect reports. Local, county, and state agencies are staggering under the load, and many are relying heavily on pediatricians to assist them in their work. DEFINITION Sexual abuse can be defined as the engaging of a child in sexual activites that the child does not understand, to which the child cannot give informed consent, or which violate the social taboos of society. This definition is broad and includes intrafamilial and extrafamilial forms and all types of sexual activities (eg, exhibitionism, fondling, child pornography, oral, anal, and genital sexual contact). The interface between "normal sexual exploratory behavior" and "sexual abuse" is not clearly defined. Pediatricians should, however, use common sense. If two 4-year-old children are found to be playing without clothes, touching each others' genitals and giggling, there is probably little to worry about. The same is true if two 15-year-old adolescents are discovered together. A probably exists if the 15-year-old child (some states set statutory 2- to 4-year limits within which sexual activities are not to be considered abuse) or if one 4-year-old child is engaging in fellatio or attempting intercourse with another preschool-aged child.

Influence of intravascular activity on the determination of blood flow and oxygen extraction in normal and ulcerated legs using the 15O steady-state technique and positron emission tomography.

An analysis using the 15O steady-state inhalation technique has been carried out into the effects of correction for intravascular activity on the determination of blood flow and oxygen extraction ratio (OER) in the legs of patients affected by ulceration. Transaxial images of the distribution of activity in a plane passing through the ulcer were obtained during steady-state inhalation of C15O2 and 15O2, respectively, using a single slice positron emission tomographic scanner. From these, the basic tracer model equations were solved to obtain blood flow and oxygen extraction with and without additional correction for the presence of intravascular activity. The latter was obtained from a scan following the inhalation of a tracer quantity of 11CO, which labels the red blood cell pool. Mean blood flow and OER in ulcerated regions were 0.087 ml/ml/min and 0.33, respectively. With correction for blood volume, assumed to be all venous, the mean OER decreased to 0.12. In the "mirror" region of normal legs mean blood flow was 0.011 ml/ml/min with uncorrected and corrected OER values of 0.87 and 0.75, respectively. The effect of assuming a nonzero arterial volume increases as flow and OER decrease but is uncertain due to the unknown arterial fraction. Correction for intravascular 15O is essential and generally the assumption that all blood volume is venous is adequate.

Familial mesothelioma: Review and family study

To date, with few exceptions, primary attention to the etiology of malignant mesothelioma has been focused on environmental factors. However, several reports of familial aggregations of mesothelioma strongly support the supposition that host factors, in concert with environmental exposure, particularly asbestos, may contribute etiologically to an as yet unknown fraction of occurrences of this disease. However, in evaluation of familial mesothelioma, it is important to consider the possibility of household exposure to asbestos. We report a family in which two brothers with prolonged occupational asbestos exposure manifested malignant pleural mesotheliomas of similar histology.

Resonance ionization mass spectrometry of technetium

Three-photon, two-color resonance ionization mass spectrometry (RIMS) is described for technetium. The wavelengths used to effect ionization of Tc are between 420 and 620 nm. Twenty-two unique ionization paths originating in the atomic ground state are observed and identified. An unknown fraction of the sample Tc is vaporized in molecular form and cannot be addressed by normal atomic photoionization methods.

Chromatographic Techniques for Characterization of Coal Tar Pitch Volatiles

Although the benzene-soluble fraction (BSF) method has traditionally been used to evaluate exposure to coal tar pitch volatiles (CTPV), it fails to identify any components in the sample. Traditional gas or liquid chromatography techniques used in conjunction with the BSF will measure specific compounds, which constitute only a portion of the total contents of the sample. In this work, three distinct chromatographic techniques for CTPV will be presented: 1) an LC method for calculating total poly cyclic aromatic hydrocarbons (3- to 6-ring); 2) a capillary GC method for identifying and quantifying interference by mineral oil; and 3) a column chromatographic technique for separating PAH from oil on a class basis. A discussion of an unknown fraction commonly found in CTPV samples, but which cannot be measured by traditional chromatographic techniques, will also be presented. Conclusions will be drawn from specific aluminum plant field data as to the composition of CTPV samples, and specific recommendations wi...

Chromatographic Techniques for Characterization of Coal Tar Pitch Volatiles

Although the benzene-soluble fraction (BSF) method has traditionally been used to evaluate exposure to coal tar pitch volatiles (CTPV), it fails to identify any components in the sample. Traditional gas or liquid chromatography techniques used in conjunction with the BSF will measure specific compounds, which constitute only a portion of the total contents of the sample. In this work, three distinct chromatographic techniques for CTPV will be presented: 1) an LC method for calculating total poly cyclic aromatic hydrocarbons (3- to 6-ring); 2) a capillary GC method for identifying and quantifying interference by mineral oil; and 3) a column chromatographic technique for separating PAH from oil on a class basis. A discussion of an unknown fraction commonly found in CTPV samples, but which cannot be measured by traditional chromatographic techniques, will also be presented. Conclusions will be drawn from specific aluminum plant field data as to the composition of CTPV samples, and specific recommendations will be given for correcting the BSF measurement for interfering substances.