Gendered Citation Practices in the Field of Communication.

In disciplines outside of communication, papers with women as first and last (i.e., senior) authors attract fewer citations than papers with men in those positions. Using data from 14 communication journals from 1995 to 2018, we find that reference lists include more papers with men as first and last author, and fewer papers with women as first and last author, than would be expected if gender were unrelated to referencing. This imbalance is driven largely by the citation practices of men and is slowly decreasing over time. The structure of men's co-authorship networks partly accounts for the observed over-citation of men by other men. We discuss ways researchers might approach gendered citations in their work.

Bright carbonate veins on asteroid (101955) Bennu: Implications for aqueous alteration history.

The composition of asteroids and their connection to meteorites provide insight into geologic processes that occurred in the early Solar System. We present spectra of the Nightingale crater region on near-Earth asteroid Bennu with a distinct infrared absorption around 3.4 micrometers. Corresponding images of boulders show centimeters-thick, roughly meter-long bright veins. We interpret the veins as being composed of carbonates, similar to those found in aqueously altered carbonaceous chondrite meteorites. If the veins on Bennu are carbonates, fluid flow and hydrothermal deposition on Bennu's parent body would have occurred on kilometer scales for thousands to millions of years. This suggests large-scale, open-system hydrothermal alteration of carbonaceous asteroids in the early Solar System.

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu.

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

Application of TMAH thermochemolysis to the detection of nucleobases: Application to the MOMA and SAM space experiment.

Thermochemolysis of seven nucleobases-adenine, thymine, uracil, cytosine, guanine, xanthine, and hypoxanthine-in tetramethylammonium hydroxide (TMAH) was studied individually by pyrolysis gas chromatography mass spectrometry in the frame of the Mars surface exploration. The analyses were performed under conditions relevant to the Sample Analysis at Mars (SAM) instrument of the Mars Curiosity Rover and the Mars Organic Molecule Analyzer (MOMA) instrument of the ExoMars Rover. The thermochemolysis products of each nucleobase were identified and the reaction mechanisms studied. The thermochemolysis temperature was optimized and the limit of detection and quantification of each nucleobase were also investigated. Results indicate that 600°C is the optimal thermochemolysis temperature for all seven nucleobases. The methylated products trimethyl-adenine, 1, 3-dimethyl-thymine, 1, 3-dimethyl-uracil, trimethyl-cytosine, 1, 3, 7-trimethyl-xanthine (caffeine), and dimethyl-hypoxanthine, respectively, are the most stable forms of adenine, thymine, uracil, cytosine, guanine, and xanthine, and hypoxanthine in TMAH solutions. The limits of detection for adenine, thymine, and uracil were 0.075 nmol; the limits of detection for guanine, cytosine, and hypoxanthine were higher, at 0.40, 0.55, and 0.75 nmol, respectively. These experiments allowed to well constrain the analytical capabilities of the thermochemolysis experiments that will be performed on Mars to detect nucleobases.

The unexpected surface of asteroid (101955) Bennu.

NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.

Automated Integration of Multimodal MRI for the Probabilistic Detection of the Central Vein Sign in White Matter Lesions.

BACKGROUND AND PURPOSE: The central vein sign is a promising MR imaging diagnostic biomarker for multiple sclerosis. Recent studies have demonstrated that patients with MS have higher proportions of white matter lesions with the central vein sign compared with those with diseases that mimic MS on MR imaging. However, the clinical application of the central vein sign as a biomarker is limited by interrater differences in the adjudication of the central vein sign as well as the time burden required for the determination of the central vein sign for each lesion in a patient's full MR imaging scan. In this study, we present an automated technique for the detection of the central vein sign in white matter lesions. MATERIALS AND METHODS: Using multimodal MR imaging, the proposed method derives a central vein sign probability, πij, for each lesion, as well as a patient-level central vein sign biomarker, ψi. The method is probabilistic in nature, allows site-specific lesion segmentation methods, and is potentially robust to intersite variability. The proposed algorithm was tested on imaging acquired at the University of Vermont in 16 participants who have MS and 15 participants who do not. RESULTS: By means of the proposed automated technique, participants with MS were found to have significantly higher values of ψ than those without MS (ψMS = 0.55 ± 0.18; ψnon-MS = 0.31 ± 0.12; P < .001). The algorithm was also found to show strong discriminative ability between patients with and without MS, with an area under the curve of 0.88. CONCLUSIONS: The current study presents the first fully automated method for detecting the central vein sign in white matter lesions and demonstrates promising performance in a sample of patients with and without MS.

An Automated Statistical Technique for Counting Distinct Multiple Sclerosis Lesions.

BACKGROUND AND PURPOSE: Lesion load is a common biomarker in multiple sclerosis, yet it has historically shown modest association with clinical outcome. Lesion count, which encapsulates the natural history of lesion formation and is thought to provide complementary information, is difficult to assess in patients with confluent (ie, spatially overlapping) lesions. We introduce a statistical technique for cross-sectionally counting pathologically distinct lesions. MATERIALS AND METHODS: MR imaging was used to assess the probability of a lesion at each location. The texture of this map was quantified using a novel technique, and clusters resembling the center of a lesion were counted. Validity compared with a criterion standard count was demonstrated in 60 subjects observed longitudinally, and reliability was determined using 14 scans of a clinically stable subject acquired at 7 sites. RESULTS: The proposed count and the criterion standard count were highly correlated (r = 0.97, P < .001) and not significantly different (t59 = -.83, P = .41), and the variability of the proposed count across repeat scans was equivalent to that of lesion load. After accounting for lesion load and age, lesion count was negatively associated (t58 = -2.73, P < .01) with the Expanded Disability Status Scale. Average lesion size had a higher association with the Expanded Disability Status Scale (r = 0.35, P < .01) than lesion load (r = 0.10, P = .44) or lesion count (r = -.12, P = .36) alone. CONCLUSIONS: This study introduces a novel technique for counting pathologically distinct lesions using cross-sectional data and demonstrates its ability to recover obscured longitudinal information. The proposed count allows more accurate estimation of lesion size, which correlated more closely with disability scores than either lesion load or lesion count alone.

OSIRIS-REx Contamination Control Strategy and Implementation.

OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and <180 ng/cm2 of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.

Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars.

The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150-300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles. KEY POINTS: First in situ evidence of nonterrestrial organics in Martian surface sediments Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM Organics preserved in sample exposed to ionizing radiation and oxidative condition.

Does aspartic acid racemization constrain the depth limit of the subsurface biosphere?

Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of ~89 years for 1 km depth and 27 °C and 1-2 years for 3 km depth and 54 °C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 °C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

Differential gene expression governed by chromosomal spatial asymmetry.

The activity of the transcription factor sigmaF is confined to one (the forespore) of two cells created by asymmetric division during sporulation in B. subtilis. We show that sigmaF activation is partly governed by the position of the gene for the unstable anti-sigmaF factor SpoIIAB. Because cytokinesis precedes chromosome segregation, most of the chromosome is translocated into the forespore after division. We hypothesize that because spoIIAB enters the forespore late, SpoIIAB lost to proteolysis is temporarily not replenished. Thus, chromosome asymmetry would be translated into the asymmetric distribution of SpoIIAB. Supporting this idea, transposition of spoIIAB to sites present in the forespore at the time of division impaired sporulation when a second pathway that participates in sigmaF activation was disabled.

Functional outcomes after supracricoid laryngectomy.

OBJECTIVES: Local control and 5-year survival rates are similar for patients undergoing total laryngectomy and supracricoid laryngectomy for the treatment of advanced-stage laryngeal carcinoma. However, comprehensive studies of functional outcomes after supracricoid laryngectomy are lacking. STUDY DESIGN: Cohort study. METHODS: This investigation provides objective voice laboratory data, skilled listener impressions of voice samples, swallowing evaluations, and patient self-perceptions of speech ability obtained from 10 supracricoid laryngectomees. RESULTS: Results demonstrated variable acoustic and speech aerodynamic disturbances, hoarse-breathy vocal quality, and speech dysfluency. Patients' self-perceptions of voice revealed severe dysphonia that induced certain emotional, physical, and functional setbacks. However, blinded judges rated these individuals as possessing intelligible speech and communication skills. All patients demonstrated premature spillage of the bolus and varying degrees of laryngeal penetration, aspiration, and retention during swallowing studies. However, each patient used a compensatory strategy to protect the airway. Voice and swallowing abilities appeared to depend on the mobility of the arytenoid cartilages, base of tongue action, and residual supraglottic tissue for the creation of a competent neoglottal sphincter complex that vibrated during phonation efforts and protected the airway during deglutition. CONCLUSIONS: Supracricoid laryngectomy avoids the potential complications, limitations, and emotional problems associated with a permanent tracheostoma. All patients demonstrated intelligible voice and effective swallowing function postoperatively, supporting supracricoid laryngectomy as a suitable alternative surgical approach to the total laryngectomy in select patients.

How urban African American young adolescents spend their time: time budgets for locations, activities, and companionship.

The time budgets of a population of youth provide important information about their daily experience and socialization. This study reports data on the time budgets of a sample of 253 urban African American poor to working- and middle-class 5th-8th graders in Chicago. These youth were found to spend less time in school than other postindustrial adolescent populations, but spent no less time doing homework than White suburban U.S. young adolescents. They spent large quantities of time at home and with their families--at rates comparable to rates for young adolescents in a society with collectivist values like India. Unlike with other populations, early adolescence was not associated with major age changes in time allocations. Amount of time in schoolwork did not differ by grade, and amount of time with family did not show the decline with age that has been found for European American suburban adolescents.

Age trends in the experience of family discord in single-mother families across adolescence.

This study utilized the Family Environment Scale and the Experience Sampling Method to evaluate how overall family discord and discord in immediate family interactions were related to adolescents' age, in 101 single-mother families. Mothers' reports of overall family discord decreased across adolescence. In immediate interactions, adolescent boys reported feeling more anger towards their mothers with age, while girls reported feeling less anger with age.

Men's work and family lives in India: the daily organization of time and emotion.

This article examines daily patterns of work and family life for a sample of middle-class men in northern India. One hundred fathers of 8th graders provided information on their hour-to-hour time use and subjective states, by means of the experience sampling method. They reported little time spent on family work but substantial amounts of time with their children and thinking about their families. At their jobs, they reported high levels of attention but more negative emotion. By contrast, the home sphere elicited lower attention, more favorable affect, and more feeling of choice. Unlike for American samples, little relationship was found between experience at work and home, including little influence of men's work emotions on the family in the evening. These findings reflect how strong traditional family roles in India shape men's daily lives.

Self-assembling amphiphilic molecules: Synthesis in simulated interstellar/precometary ices.

Interstellar gas and dust constitute the primary material from which the solar system formed. Near the end of the hot early phase of star and planet formation, volatile, less refractory materials were transported into the inner solar system as comets and interplanetary dust particles. Once the inner planets had sufficiently cooled, late accretionary infall seeded them with complex organic compounds [Oró, J. (1961) Nature (London) 190, 389-390; Delsemme, A. H. (1984) Origins Life 14, 51-60; Anders, E. (1989) Nature (London) 342, 255-257; Chyba, C. F. & Sagan, C. (1992) Nature (London) 355, 125-131]. Delivery of such extraterrestrial compounds may have contributed to the organic inventory necessary for the origin of life. Interstellar ices, the building blocks of comets, tie up a large fraction of the biogenic elements available in molecular clouds. In our efforts to understand their synthesis, chemical composition, and physical properties, we report here that a complex mixture of molecules is produced by UV photolysis of realistic, interstellar ice analogs, and that some of the components have properties relevant to the origin of life, including the ability to self-assemble into vesicular structures.

A kinetic estimate of the free aldehyde content of aldoses.

The relative free aldehyde content of eight hexoses and four pentoses has been estimated within about 10% from the rate constants for their reaction with urazole (1,2,4-triazole-3,5-dione). These values of the percent free aldehyde are in agreement with those estimated from CD measurements, but are more accurate. The relative free aldehyde contents for the aldoses were then correlated to various literature NMR measurements to obtain the absolute values. This procedure was also done for three deoxyaldoses, which react much more rapidly than can be accounted for by the free aldehyde content. This difference in reactivity between aldoses and deoxyaldoses is due to the inductive effect of the H versus the OH on C-2'. This may help explain why deoxyribonucleosides hydrolyze much more rapidly than ribonucleosides.