780 research outputs found
Near-infrared spectroscopy of 1999 JU3, the target of the Hayabusa 2 mission
Context. Primitive asteroids contain complex organic material and ices
relevant to the origin of life on Earth. These types of asteroids are the
target of several-sample return missions to be launched in the next years. 1999
JU3 is the target of the Japanese Aerospace Exploration Agency's Hayabusa 2
mission. Aims. 1999 JU3 has been previously identified as a C-class asteroid.
Spectroscopic observations at longer wavelengths will help to constrain its
composition. Methods. We obtained spectroscopy of 1999 JU3 from 0.85 to 2.2
microns, with the 3.6 m Telescopio Nazionale Galileo using the low resolution
mode of the Near Infrared Camera Spectrograph. Results. We present a
near-infrared spectrum of 1999 JU3 from 0.85 to 2.2microns that is consistent
with previously published spectra and with its C-type classification.
Conclusions. Our spectrum confirms the primitive nature of 1999 JU3 and its
interest as target of the sample-return mission Hayabusa 2.Comment: Research Note: 3 pages 1 Figure Received December 2012; accepted 4
March 201
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Investigation of Novel Electrochemical Synthesis of Bioapatites and Use in Elemental Bone Analysis
In this research, electrochemical methods are used to synthesize the inorganic fraction of bone, hydroxyapatite, for application in biological implants and as a calibration material for elemental analysis in human bone. Optimal conditions of electrochemically deposited uniform apatite coatings on stainless steel were investigated. Apatite is a ceramic with many different phases and compositions that have beneficial characteristics for biomedical applications. Of those phases hydroxyapatite (HA) is the most biocompatible and is the primary constituent of the inorganic material in bones. HA coatings on metals and metal alloys have the ability to bridge the growth between human tissues and implant interface, where the metal provides the strength and HA provides the needed bioactivity. The calcium apatites were electrochemically deposited using a modified simulated body fluid adjusted to pH 4-10, for 1-3 hours at varying temperature of 25-65°C while maintaining cathodic potentials of -1.0 to -1.5V. It was observed that the composition and morphology of HA coatings change during deposition by the concentration of counter ions in solution, pH, temperature, applied potential, and post-sintering. The coatings were characterized by powder x-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The precipitated powders from the experiment were also characterized, with results showing similarities to biological apatite. There is a need for quantitative elemental analysis of calcified biological matrices such as bone and teeth; however there are no suitable calibration materials commercially available for quantitative analysis. Matrix-matched standards are electrochemically synthesized for LA-ICP-MS analysis of human bone. The synthetic bioapatite is produced via a hydrothermal electrochemical process using a simulated body fluid solution to form hydroxyapatite. Additional bioapatite standards are synthesized containing trace amounts of metals. The x-ray diffraction of the synthesized standards shows an increase in cell volume for the crystal structure from 0.534 to 0.542 nm3 with the substitution of metals into the crystal structure. The analyte concentration and recoveries for the synthesized standards and reference materials were determined by ICP-MS with % RSD below 6.3% and limits of detection below 1.2 ng/mL for trace metals. The electrochemically synthesized bioapatite was also compared to standard reference materials with X-ray diffraction, FTIR, and Raman spectroscopy. Optimum laser ablation parameters were determined for the standards and human bone. The synthesized standards were homogeneous and the reproducibility for the isotope concentrations determined by LA-ICP-MS was between 3-10 % compared to 10-35% for SRM 1486 Bone Meal and SRM 1486 Bone Ash. A quantitative method has been developed for 2D mapping using LA-ICP-MS and the matrix-matched standards of metal-doped biopaptite to characterize metal concentrations in human bone. Laser ablation parameters for the method are refined resulting in concentration (ug/g) contour map measurements for each isotope measured in the human bone. Essential and non-essential metals, Al, Ca, Cu, Fe, Pb, and Zn are quantitatively mapped using these parameters. Limit of detection for the metals in the bone range from 0.001 to 0.08 ug/g. The LA-ICP-MS analysis method developed proves to be a straightforward and simple method for quantitative analysis of human bone
Interactions between subunits a and b in the rotary ATP synthase as determined by cross-linking
The interaction of the membrane traversing stator subunits a and b of the rotary ATP synthase was probed by substitution of a single Cys into each subunit with subsequent Cu2+ catalyzed cross-linking. Extensive interaction between the transmembrane (TM) region of one b subunit and TM2 of subunit a was indicated by cross-linking with 6 Cys pairs introduced into these regions. Additional disulfide cross-linking was observed between the N-terminus of subunit b and the periplasmic loop connecting TM4 and TM5 of subunit a. Finally, benzophenone-4-maleimide derivatized Cys in the 2–3 periplasmic loop of subunit a were shown to cross-link with the periplasmic N-terminal region of subunit b. These experiments help to define the juxtaposition of subunits b and a in the ATP synthase
Does prohibitin expression regulate sperm mitochondrial membrane potential, sperm motility, and male fertility?
Prohibitin (PHB) is a highly conserved major sperm mitochondrial membrane protein whose absence in somatic cells is associated with mitochondrial membrane depolarization and increased generation of reactive oxygen species (ROS). Our recent findings suggest that high levels of oxidants in human semen may contribute to male infertility and that sperm motility could be the earliest and most sensitive indicator of oxidative damage. Based on PHB's roles in mitochondrial sub-compartmentalization and respiratory chain assembly, we examine sperm PHB expression and mitochondrial membrane potential (MITO) in infertile men with poor sperm motility (asthenospermia, A) and/or low sperm concentrations (oligoasthenospermia, OA). Here, we demonstrate that MITO is significantly lower in sperm from A and OA subjects than in normospermic (N) subjects; the decrease is more severe for OA than for A subjects. PHB expression is also significantly lower in sperm from A and OA subjects. Significantly positive correlations are found among PHB expression, MITO, and sperm motility in normospermic, asthenospermic, and oligoasthenospermic subjects. Collectively, our observations lead to the hypothesis that PHB expression is an indicator of sperm quality in infertile men, and that it regulates sperm motility via an alteration in MITO and increased ROS levels. © Copyright 2012, Mary Ann Liebert, Inc.published_or_final_versio
MED12 regulates a transcriptional network of calcium-handling genes in the heart
The Mediator complex regulates gene transcription by linking basal transcriptional machinery with DNA-bound transcription factors. The activity of the Mediator complex is mainly controlled by a kinase submodule that is composed of 4 proteins, including MED12. Although ubiquitously expressed, Mediator subunits can differentially regulate gene expression in a tissue-specific manner. Here, we report that MED12 is required for normal cardiac function, such that mice with conditional cardiac-specific deletion of MED12 display progressive dilated cardiomyopathy. Loss of MED12 perturbs expression of calcium-handling genes in the heart, consequently altering calcium cycling in cardiomyocytes and disrupting cardiac electrical activity. We identified transcription factors that regulate expression of calcium-handling genes that are downregulated in the heart in the absence of MED12, and we found that MED12 localizes to transcription factor consensus sequences within calcium-handling genes. We showed that MED12 interacts with one such transcription factor, MEF2, in cardiomyocytes and that MED12 and MEF2 co-occupy promoters of calcium-handling genes. Furthermore, we demonstrated that MED12 enhances MEF2 transcriptional activity and that overexpression of both increases expression of calcium-handling genes in cardiomyocytes. Our data support a role for MED12 as a coordinator of transcription through MEF2 and other transcription factors. We conclude that MED12 is a regulator of a network of calcium-handling genes, consequently mediating contractility in the mammalian heart
On perhaps becoming what you had previously despised: Psychologists as prescribers of medication
The authors contend that organized psychology's efforts to gain limited prescriptive privileges may be misguided. The modification of psychology's traditional scope of practice may produce harm in the form of lessened patient regard, devaluation of nonpharmacologic elements of practice, and markedly increased exposure to claims of malpractice. The authors also decry the disingenuous use of psychopharmacologically “underserved” populations as rationales for the pursuit of prescriptive privileges. Psychology may mount a major effort to make this change without sufficient justification, in the view of the authors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44851/1/10880_2005_Article_BF01989620.pd
Towards a framework for critical citizenship education
Increasingly countries around the world are promoting forms of "critical" citizenship in the planned curricula of schools. However, the intended meaning behind this term varies markedly and can range from a set of creative and technical skills under the label "critical thinking" to a desire to encourage engagement, action and political emancipation, often labelled "critical pedagogy". This paper distinguishes these manifestations of the "critical" and, based on an analysis of the prevailing models of critical pedagogy and citizenship education, develops a conceptual framework for analysing and comparing the nature of critical citizenship
Who are We? Highlighting Nuances in Asian American Experiences in Ecology and Evolutionary Biology
As ecologists and evolutionary biologists, it is important to recognize that issues surrounding AAPI do not exist in a vacuum and that these issues affect some of our students and colleagues in and outside of the classroom and lab. Recently, anti-Asian racism has been brought to the forefront of US society. Though media attention has primarily focused on how COVID-19 fears motivated both violent and nonviolent racist incidents against East Asians in 2020 (e.g., Chinese and Taiwanese Americans) (Tessler et al. 2020), attacks on other AAPI groups, such as South and Southeast Asians (e.g., Filipino, Pakistani, and Vietnamese Americans) (Truong 2020, Kuo and Bui 2021), have continued to occur. Thus, there is a need to both discuss and address how issues of racism toward the AAPI community manifest in our own academic communities
An atomic and molecular database for analysis of submillimetre line observations
Atomic and molecular data for the transitions of a number of astrophysically
interesting species are summarized, including energy levels, statistical
weights, Einstein A-coefficients and collisional rate coefficients. Available
collisional data from quantum chemical calculations and experiments are
extrapolated to higher energies. These data, which are made publically
available through the WWW at http://www.strw.leidenuniv.nl/~moldata, are
essential input for non-LTE line radiative transfer programs. An online version
of a computer program for performing statistical equilibrium calculations is
also made available as part of the database. Comparisons of calculated emission
lines using different sets of collisional rate coefficients are presented. This
database should form an important tool in analyzing observations from current
and future (sub)millimetre and infrared telescopes.Comment: Accepted for publication in A&A, 14 pages, 5 figure
Smaller and better: The university of Michigan experience
This paper discusses several hierarchical and sequential reduction options, including Balderston's budgetary strategies and this author's curricular change options. The latter are based on data gathered in a 1979-80 survey of 46 states on patterns of program reduction. Having introduced various reduction categories, the paper then focuses on the institutional shrinkage process currently being implemented at the University of Michigan. Four specific strategies are being discussed: (1) across-the-board cuts, (2) reduction of nonacademic programs; (3) long-range faculty reduction procedures, and (4) program discontinuance. A host of potential problems regarding the elimination of academic programs is described. The paper concludes by providing several general recommendations for institutional shrinkage procedures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43589/1/11162_2004_Article_BF00992049.pd
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