Phobos: Low Velocity Impacts

Marss inner moon, Phobos, is located deep in the planets gravity well and orbits far below the planets synchronous orbit. Images of the surface of Phobos, in particular from Viking Orbiter 1, MGS, MRO, and MEX, reveal a rich collisional history, including freshlooking impact craters and subdued older ones, very large impact structures (compared to the size of Phobos), such as Stickney, and much smaller ones. Sources of impactors colliding with Phobos include a priori: A) Impactors from outside the martian system (asteroids, comets, and fragments thereof); B) Impactors from Mars itself (ejecta from large impacts on Mars); and C) Impactors from Mars orbit, including impact ejecta launched from Deimos and ejecta launched from, and reintercepted by, Phobos. In addition to individual craters on Phobos, the networks of grooves on this moon have also been attributed in part or in whole to impactors from some of these sources, particularly B. We report the preliminary results of a systematic survey of the distribution, morphology, albedo, and color characteristics of fresh impact craters and associated ejecta deposits on Phobos. Considering that the different potential impactor sources listed above are expected to display distinct dominant compositions and different characteristic impact velocity regimes, we identify specific craters on Phobos that are more likely the result of low velocity impacts by impactors derived from Mars orbit than from any alternative sources. Our finding supports the hypothesis that the spectrally Redder Unit on Phobos may be a superficial veneer of accreted ejecta from Deimos, and that Phoboss bulk might be distinct in composition from Deimos

Sleep Profiles of Elite Swimmers During Different Training Phases

This study aims to describe the sleeping patterns during different training phases in competitive swimmers. Twelve national- and international-level swimmers (3 females and 9 males) were monitored during 4 different phases, consisting of a preparation training phase, a taper phase, a competition phase, and a rest phase. Sleep parameters were assessed using wrist activity monitors and self-reported sleep diaries. There was a moderately higher (d = 0.70–1.00) sleep onset latency during the competition phase compared with taper, train, and rest phases. Trivial to small differences were observed for total sleep time between phases (d = 0.05–0.40). Sleep efficiency was moderately higher (d = 0.60–0.75) in the training and taper phases compared with competition and rest. Restfulness and fragmentation index (FI) were lowest in the rest with differences between phases being small (d = 0.43–0.51) for restfulness and small to moderate (d = 0.43–0.62) for FI. Time in and out of bed was very largely later (d = 1.96–2.34) in rest compared with the other phases. Total nap time was moderately lower in rest (d = 1.13–1.18) compared with the training and competition phases, whereas there was a small difference (d = 0.46) compared with taper. To conclude, while there were trivial to small differences in sleep quantity between phases, there are small to moderate differences in other sleep parameters. Specifically, sleep onset latency was higher during the competition phase. In addition, this study highlights the substantial between-individual variations in sleep responses during different training phases

Prolonged activation of S6K1 does not suppress IRS or PI-3 kinase signaling during muscle cell differentiation

Background: Myogenesis in C2C12 cells requires the activation of the PI3K/mTOR signaling pathways. Since mTOR signaling can feedback through S6K1 to inhibit the activation of PI3K, the aim of this work was to assess whether feedback from S6K1 played a role in myogenesis and determine whether siRNA mediated knockdown of S6K1 would lead to an increased rate of myotube formation. Results: S6K1 activity increased in a linear fashion following plating and was more than 3-fold higher after Day 3 of differentiation (subconfluent = 11.09 ± 3.05, Day 3 = 29.34 ± 3.58). IRS-1 levels tended to increase upon serum withdrawal but decreased approximately 2-fold (subconfluent = 0.88 ± 0.10, Day 3 = 0.42 ± 0.06) 3 days following differentiation whereas IRS-2 protein remained stable. IRS-1 associated p85 was significantly reduced upon serum withdrawal (subconfluent = 0.86 ± 0.07, Day 0 = 0.31 ± 0.05), remaining low through day 1. IRS-2 associated p85 decreased following serum withdrawal (subconfluent = 0.96 ± 0.05, Day 1 = 0.56 ± 0.08) and remained suppressed up to Day 3 following differentiation (0.56 ± 0.05). Phospho-tyrosine associated p85 increased significantly from subconfluent to Day 0 and remained elevated throughout differentiation. siRNA directed against S6K1 and S6K2 did not result in changes in IRS-1 levels after either 48 or 96 hrs. Furthermore, neither 48 nor 96 hrs of S6K1 knockdown caused a change in myotube formation. Conclusions: Even though S6K1 activity increases throughout muscle cell differentiation and IRS-1 levels decrease over this period, siRNA suggests that S6K1 is not mediating the decrease in IRS-1. The decrease in IRS-1/2 associated p85 together with the increase in phospho-tyrosine associated p85 suggests that PI3K associates primarily with scaffolds other than IRS-1/2 during muscle cell differentiation

Cooler Intensity Limitations

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Molecular brakes regulating mTORC1 activation in skeletal muscle following synergist ablation

The goal of the current work was to profile positive (mTORC1 activation, autocrine/paracrine growth factors) and negative [AMPK, unfolded protein response (UPR)] pathways that might regulate overload-induced mTORC1 (mTOR complex 1) activation with the hypothesis that a number of negative regulators of mTORC1 will be engaged during a supraphysiological model of hypertrophy. To achieve this, mTORC1- IRS-1/2 signaling, BiP/CHOP/IRE1, and AMPK activation were determined in rat plantaris muscle following synergist ablation (SA). SA resulted in significant increases in muscle mass of 4% per day throughout the 21 days of the experiment. The expression of the insulin-like growth factors (IGF) were high throughout the 21st day of overload. However, IGF signaling was limited, since IRS-1 and -2 were undetectable in the overloaded muscle from day 3 to day 9. The decreases in IRS-1/2 protein were paralleled by increases in GRB10 Ser501/503 and S6K1 Thr389 phosphorylation, two mTORC1 targets that can destabilize IRS proteins. PKB Ser473 phosphorylation was higher from 3– 6 days, and this was associated with increased TSC2 Thr939 phosphorylation. The phosphorylation of TSC2 Thr1345 (an AMPK site) was also elevated, whereas phosphorylation at the other PKB site, Thr1462, was unchanged at 6 days. In agreement with the phosphorylation of Thr1345, SA led to activation of AMPK1 during the initial growth phase, lasting the first 9 days before returning to baseline by day 12. The UPR markers CHOP and BiP were elevated over the first 12 days following ablation, whereas IRE1 levels decreased. These data suggest that during supraphysiological muscle loading at least three potential molecular brakes engage to downregulate mTORC1. m

Toward a descriptive model of solar particles in the heliosphere

During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made

A Call for Change in the Public Education System in Nova Scotia

The United Nation’s International Decade for People of African Descent and Nova Scotia’s Ministry of African Nova Scotian Affairs recognize that students of African descent continue to experience inequities. As previous studies indicate, parents of Black learners identified that many educators lack knowledge and experience in understanding students of African descent.This study explored student achievement from the perspective of parents of children of African descent attending public schools in Nova Scotia. Participants included individual interviews and focus groups with parents from rural and urban areas. Based on Bronfenbrenner’s ecological theory framework, a thematic analysis of the data was conducted, a dominant storyline related to the families’ experiences in school and subsequent themes emerged: we are treated differently; we don’t feel connected; we know there are challenges: the resistance of parents; and we deal with injustices but persevere. These findings provide recommendations to improve the educational success for Black learners. Keywords: African Canadian, academic achievement and success, Black students, education, schooling challenges, students of African descentLa déclaration des Nations Unies de la Décennie internationale des personnes d’ascendance africaine et le Ministre des affaires Afro-néo-écossaises reconnaissent que les élèves d’ascendance africaine continuent à vivre des inégalités. Des études antérieures démontrent que les parents d’apprenants Noirs ont identifié que plusieurs éducateurs manquent de connaissances et d’expérience quant à la compréhension d’élèves d’ascendance africaine. Cette étude explore la réussite scolaire de la perspective des parents d’enfants d’ascendance africaine fréquentant des écoles publiques en Nouvelle-Écosse. Les participants incluent des entretiens individuels et des groupes de discussion avec des parents provenant de régions rurales et urbaines en Nouvelle-Écosse. Basée sur le cadre théorique écologique de Bronfenbrenner, une analyse thématique des données a été entreprise, un fil conducteur dominant lié aux expériences scolaires des familles, et des thèmes résolutoires ont émergé : nous sommes traités différemment ; et nous ne nous sentons pas connectés ; nous sommes conscients qu’il y a des défis ; la résistance des parents ; et nous font face à des injustices mais nous persistons. Ces constats fournissent des recommandations pour améliorer le succès académique des apprenants Noirs. Mots-clés : Afro-canadiens, performance et succès académique, élèves noirs, éducation, défis scolaires, élèves d’ascendance Africain

Intensity modulated radiation therapy dose painting for localized prostate cancer using(11)C-choline positron emission tomography scans

PURPOSE: To demonstrate the technical feasibility of intensity modulated radiation therapy (IMRT) dose painting using¹¹C-choline positron emission tomography PET scans in patients with localized prostate cancer. METHODS AND MATERIALS: This was an RT planning study of 8 patients with prostate cancer who had ¹¹C-choline PET scans prior to radical prostatectomy. Two contours were semiautomatically generated on the basis of the PET scans for each patient: 60% and 70% of the maximum standardized uptake values (SUV(60%) and SUV(70%)). Three IMRT plans were generated for each patient: PLAN(78), which consisted of whole-prostate radiation therapy to 78 Gy; PLAN(78-90), which consisted of whole-prostate RT to 78 Gy, a boost to the SUV(60%) to 84 Gy, and a further boost to the SUV(70%) to 90 Gy; and PLAN(72-90), which consisted of whole-prostate RT to 72 Gy, a boost to the SUV(60%) to 84 Gy, and a further boost to the SUV(70%) to 90 Gy. The feasibility of these plans was judged by their ability to reach prescription doses while adhering to published dose constraints. Tumor control probabilities based on PET scan-defined volumes (TCP(PET)) and on prostatectomy-defined volumes (TCP(path)), and rectal normal tissue complication probabilities (NTCP) were compared between the plans. RESULTS: All plans for all patients reached prescription doses while adhering to dose constraints. TCP(PET) values for PLAN(78), PLAN(78-90), and PLAN(72-90) were 65%, 97%, and 96%, respectively. TCP(path) values were 71%, 97%, and 89%, respectively. Both PLAN(78-90) and PLAN(72-90) had significantly higher TCP(PET) (P=.002 and .001) and TCP(path) (P<.001 and .014) values than PLAN(78). PLAN(78-90) and PLAN(72-90) were not significantly different in terms of TCP(PET) or TCP(path). There were no significant differences in rectal NTCPs between the 3 plans. CONCLUSIONS: IMRT dose painting for localized prostate cancer using (11)C-choline PET scans is technically feasible. Dose painting results in higher TCPs without higher NTCPs.Joe H. Chang, Daryl Lim Joon, Sze Ting Lee, Sylvia J. Gong, Nigel J. Anderson, Andrew M. Scott, Ian D. Davis, David Clouston, Damien Bolton, Christopher S. Hamilton, Vincent Kho

Protein Requirements of Pre-Menopausal Female Athletes: Systematic Literature Review

This systematic literature review aimed to determine the protein requirements of pre-menopausal (e.g., 18&ndash;45 years) female athletes and identify if the menstrual cycle phase and/or hormonal contraceptive use influence protein requirements. Four databases were searched for original research containing pre-menopausal female athletes that ingested protein alongside exercise. The Academy of Nutrition and Dietetics Quality Criteria Checklist was used to determine study quality. Fourteen studies, which included 204 recreationally active or competitive females, met the eligibility criteria for inclusion in this review, and all were assessed as positive quality. The estimated average requirement (EAR) for protein intake of pre-menopausal recreational and/or competitive female athletes is similar for those undertaking aerobic endurance (1.28&ndash;1.63 g/kg/day), resistance (1.49 g/kg/day) and intermittent exercise (1.41 g/kg/day) of ~60&ndash;90 min duration. The optimal acute protein intake and influence of menstrual cycle phase or hormonal contraceptive use on protein requirements could not be determined. However, pre- and post-exercise protein intakes of 0.32&ndash;0.38 g/kg have demonstrated beneficial physiological responses in recreational and competitive female athletes completing resistance and intermittent exercise. The protein requirements outlined in this review can be used for planning and assessing protein intakes of recreational and competitive pre-menopausal female athletes