Balance of dark and luminous mass in rotating galaxies

A fine balance between dark and baryonic mass is observed in spiral galaxies. As the contribution of the baryons to the total rotation velocity increases, the contribution of the dark matter decreases by a compensating amount. This poses a fine-tuning problem for galaxy formation models, and may point to new physics for dark matter particles or even a modification of gravity.     

Method for reducing the ambiguity of comprehensive two-dimensional chromatography retention times

Comprehensive two-dimensional chromatography generates a two-dimensional chromatogram from a one-dimensional signal array. This process can only be done unambiguously when the range of secondary retention times is less than the modulation period. However, complex samples often produce wider ranges of secondary retention times. Peaks with retention times that exceed the modulation period are said to be "wrapped-around". A simple algorithm has been developed that determines absolute retention times when wrap-around occurs. A sample is first analyzed under standard modulation conditions and then re-analyzed with a modulation period that is increased by an integer fraction of the original modulation period. Retention shifts along the secondary axis are used to determine absolute retention times. A theoretical analysis has been performed to optimize the implementation conditions and characterize the technique limitations. The efficacy of this algorithm has been tested through a series of isothermal GC x GC separations. This method has been found to be particularly useful during the initial stages of method development.     

The performance of matched-field track-before-detect methods using shallow-water Pacific data

Matched-field track-before-detect processing, which extends the concept of matched-field processing to include modeling of the source dynamics, has recently emerged as a promising approach for maintaining the track of a moving source. In this paper, optimal Bayesian and minimum variance beamforming track-before-detect algorithms which incorporate a priori knowledge of the source dynamics in addition to the underlying uncertainties in the ocean environment are presented. A Markov model is utilized for the source motion as a means of capturing the stochastic nature of the source dynamics without assuming uniform motion. In addition, the relationship between optimal Bayesian track-before-detect processing and minimum variance track-before-detect beamforming is examined, revealing how an optimal tracking philosophy may be used to guide the modification of existing beamforming techniques to incorporate track-before-detect capabilities. Further, the benefits of implementing an optimal approach over conventional methods are illustrated through application of these methods to shallow-water Pacific data collected as part of the SWellEX-1 experiment. The results show that incorporating Markovian dynamics for the source motion provides marked improvement in the ability to maintain target track without the use of a uniform velocity hypothesis.     

The effects of nonstoichiometry and electron concentration on the properties of LixHfTe2−y

In order to assess the relative contributions of excess electrons from lithium interstitials and tellurium vacancies to the electronic structure of HfTe₂, samples of Li_xHfTe_2?y were prepared by high-temperature synthesis. Powder X-ray diffraction analysis shows the hexagonal a parameter to be a weak function of surplus electron count (x + 2y), but the c parameter to be a strong function of Li content. Magnetic measurements indicate that the lithium interstitials donate more electrons to the conduction band than donated by the tellurium vacancies. Several of the samples with high surplus electron count show unusual magnetic behavior at low temperatures and low fields.     

Qualitative and quantitative analysis of mixtures of sulfonamides. IX

In our final paper in this series we first discuss a determination of the sodium content.A rapid quantitative estimation of a mixture of sulfonamides is possible after separation of the components by means of paper chromatography without their removal from the paper. The linear relationship between the area of a spot on the chromatogram and the logarithm of the amount of compound present forms the basis of this method.     

Isomerizationi of small ring lithium dialkylamides

Lithiu N-butylcycloprpylamide ($\text{1}$) and lithium N-propylcyclobutylamide ($\text{2}$) rearrrange in ethereal solvents by nucleophilic eliminative rings fission processes; amide $\text{1}$ is highly reactive whereas amide $\text{2}$ is somewhat stable.     

Attitudes of Children With Dysphonia

SUMMARY: Because voice disorders in childhood may have a negative impact on communicative effectiveness, social development, and self-esteem, the objective was to determine the impact of voice disorders on lives of children from the perspective of chronically dysphonic children and their parents. This study consisted of focused interviews with chronically dysphonic children and their caregivers. Focused interviews were conducted with 10 children in each of the following age groups: Toddler (2-4 years old), Young Child (5-7 years old), School-Aged Child (8-12 years old), and Adolescent (13-18 years old). Interview questions were formulated to elicit attitudes in the following conceptual domains: emotional, social/functional, and physical. Interviews were transcribed and subjected to systematic qualitative analyses that identified common themes within each age group for each conceptual domain. For Toddlers, interviews relied heavily on parents and the biggest concerns were found in the physical and functional domains. Young Children expressed that their biggest issues related to voice were physical ("run out of air," "sometimes voice does not work"). Ninety percent of Young Children were repeatedly asked to use a quieter voice. Emotional factors and physical factors were prominent in the interviews of School-Aged Children and Adolescents. Children and Adolescents often felt that their dysphonic voice received undue attention and also limited their participation in important events. Anger, sadness, and frustration were also expressed. Chronic dysphonia negatively affects the lives of children. This work will serve as the basis for development of a valid, reliable, and age-appropriate measure of voice-related quality of life in children.     

Untargeted Metabolomics Strategies—Challenges and Emerging Directions

Metabolites are building blocks of cellular function. These species are involved in enzyme-catalyzed chemical reactions and are essential for cellular function. Upstream biological disruptions result in a series of metabolomic changes and, as such, the metabolome holds a wealth of information that is thought to be most predictive of phenotype. Uncovering this knowledge is a work in progress. The field of metabolomics is still maturing; the community has leveraged proteomics experience when applicable and developed a range of sample preparation and instrument methodology along with myriad data processing and analysis approaches. Research focuses have now shifted toward a fundamental understanding of the biology responsible for metabolomic changes. There are several types of metabolomics experiments including both targeted and untargeted analyses. While untargeted, hypothesis generating workflows exhibit many valuable attributes, challenges inherent to the approach remain. This Critical Insight comments on these challenges, focusing on the identification process of LC-MS-based untargeted metabolomics studies—specifically in mammalian systems. Biological interpretation of metabolomics data hinges on the ability to accurately identify metabolites. The range of confidence associated with identifications that is often overlooked is reviewed, and opportunities for advancing the metabolomics field are described.

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