scholarly journals How cores grow by pebble accretion

2018 ◽  
Vol 611 ◽  
pp. A65 ◽  
Author(s):  
M. G. Brouwers ◽  
A. Vazan ◽  
C. W. Ormel
Keyword(s):  
Second Phase ◽  
Temperature Dependent ◽  
Core Mass ◽  
The Core ◽  
Third Phase ◽  
The Mean ◽  
Inner Region ◽  
Core Accretion ◽  
Mean Molecular Weight ◽  
Ablated Mass

Context. Planet formation by pebble accretion is an alternative to planetesimal-driven core accretion. In this scenario, planets grow by the accretion of cm- to m-sized pebbles instead of km-sized planetesimals. One of the main differences with planetesimal-driven core accretion is the increased thermal ablation experienced by pebbles. This can provide early enrichment to the planet’s envelope, which influences its subsequent evolution and changes the process of core growth. Aims. We aim to predict core masses and envelope compositions of planets that form by pebble accretion and compare mass deposition of pebbles to planetesimals. Specifically, we calculate the core mass where pebbles completely evaporate and are absorbed before reaching the core, which signifies the end of direct core growth. Methods. We model the early growth of a protoplanet by calculating the structure of its envelope, taking into account the fate of impacting pebbles or planetesimals. The region where high-Z material can exist in vapor form is determined by the temperature-dependent vapor pressure. We include enrichment effects by locally modifying the mean molecular weight of the envelope. Results. In the pebble case, three phases of core growth can be identified. In the first phase (Mcore < 0.23–0.39 M⊕), pebbles impact the core without significant ablation. During the second phase (Mcore < 0.5M⊕), ablation becomes increasingly severe. A layer of high-Z vapor starts to form around the core that absorbs a small fraction of the ablated mass. The rest of the material either rains out to the core or instead mixes outwards, slowing core growth. In the third phase (Mcore > 0.5M⊕), the high-Z inner region expands outwards, absorbing an increasing fraction of the ablated material as vapor. Rainout ends before the core mass reaches 0.6 M⊕, terminating direct core growth. In the case of icy H2O pebbles, this happens before 0.1 M⊕. Conclusions. Our results indicate that pebble accretion can directly form rocky cores up to only 0.6 M⊕, and is unable to form similarly sized icy cores. Subsequent core growth can proceed indirectly when the planet cools, provided it is able to retain its high-Z material.

Comparisons of atomic thermal motions for graphite at 300 K based on X-ray, neutron, and phonon-spectrum data

1978 ◽  
Vol 34 (6) ◽  
pp. 979-982 ◽  
Author(s):  
R. Chen ◽  
P. Trucano
Keyword(s):  
Phonon Spectrum ◽  
Mean Square ◽  
Temperature Dependent ◽  
X Ray ◽  
The Core ◽  
Out Of Plane ◽  
Density Analysis ◽  
Atomic Scattering ◽  
The Mean ◽  
Spectrum Model

The mean-square amplitudes of vibration in graphite based on an X-ray charge-density analysis are 0.0032 (2) and 0.0140 (3) Å2 parallel to and perpendicular to the basal plane, respectively. Values for the parallel vibrations of 0.0031 (6) and 0.0032 Å2 were derived from temperature-dependent neutron measurements and a calculated phonon spectrum. The neutron measurements and the phonon spectrum both predict lower values [0.0090 (20) and 0.0098 Å2] for the out-of-plane vibrations. This small discrepancy may be caused by small changes in the core atomic scattering factors from the free-atom values or by a deficiency in the phonon-spectrum model.

A Method for Automatic Recording of the Osmotic Fragility of Blood Platelets

1970 ◽  
Vol 23 (01) ◽  
pp. 182-188
Author(s):  
J Zahavi ◽  
D Danon ◽  
F Dreyfuss ◽  
D Nelken
Keyword(s):  
Light Transmission ◽  
Blood Platelets ◽  
Osmotic Fragility ◽  
Slow Phase ◽  
Rapid Rate ◽  
Temperature Dependent ◽  
Sodium Chloride Solutions ◽  
Third Phase ◽  
The Mean ◽  
Phosphate Buffered Saline

SummaryA method for automatically recording the osmotic fragility of blood platelets, using a Fragiligraph, was developed. Platelet specimens taken from 20 healthy males and 9 females were examined. The mean rate of platelet change and the extent of increase in light transmission (LT) of washed platelets suspended in veronal, Tris, or phosphate buffered saline and dialyzed against water and 0.1% sodium chloride solutions, were analyzed. The recorded curves showed a slow phase lasting 2–74 sec, followed by a phase representing a rapid rate of platelet change in which gradually swelling of the platelets occurred concomitantly with an increase in the LT. This was followed by a third phase of plateau formation. The mean rate of platelet swelling was temperature-dependent, having twice the value at 37° C as at 15° C; the extent (% increase in LT) did not vary with temperature.

scholarly journals Unveiling the planet population at birth

2021 ◽  
Vol 503 (1) ◽  
pp. 1526-1542 ◽  
Author(s):  
James G Rogers ◽  
James E Owen
Keyword(s):  
Mass Distribution ◽  
Mass Fraction ◽  
Additional Mass ◽  
Core Mass ◽  
Water Ice ◽  
The Core ◽  
Core Composition ◽  
Peak Mass ◽  
Core Accretion ◽  
Atmospheric Mass

ABSTRACT The radius distribution of small, close-in exoplanets has recently been shown to be bimodal. The photoevaporation model predicted this bimodality. In the photoevaporation scenario, some planets are completely stripped of their primordial H/He atmospheres, whereas others retain them. Comparisons between the photoevaporation model and observed planetary populations have the power to unveil details of the planet population inaccessible by standard observations, such as the core mass distribution and core composition. In this work, we present a hierarchical inference analysis on the distribution of close-in exoplanets using forward models of photoevaporation evolution. We use this model to constrain the planetary distributions for core composition, core mass, and initial atmospheric mass fraction. We find that the core-mass distribution is peaked, with a peak-mass of ∼4M⊕. The bulk core-composition is consistent with a rock/iron mixture that is ice-poor and ‘Earth-like’; the spread in core-composition is found to be narrow ($\lesssim 16{{\ \rm per\ cent}}$ variation in iron-mass fraction at the 2σ level) and consistent with zero. This result favours core formation in a water/ice poor environment. We find the majority of planets accreted a H/He envelope with a typical mass fraction of $\sim 4{{\ \rm per\ cent}}$; only a small fraction did not accrete large amounts of H/He and were ‘born-rocky’. We find four times as many super-Earths were formed through photoevaporation, as formed without a large H/He atmosphere. Finally, we find core-accretion theory overpredicts the amount of H/He cores would have accreted by a factor of ∼5, pointing to additional mass-loss mechanisms (e.g. ‘boil-off’) or modifications to core-accretion theory.

Evaluation of depression scores in 150 women in reproductive age menstrual cycle

2011 ◽  
Vol 26 (S2) ◽  
pp. 1662-1662
Author(s):  
A. Fakhari ◽  
S. Pour Abolghasem ◽  
E. Afsar
Keyword(s):  
Menstrual Cycle ◽  
Reproductive Age ◽  
Second Phase ◽  
Mild Depression ◽  
Basic Study ◽  
Hormone Levels ◽  
Third Phase ◽  
The Mean ◽  
Spss Software ◽  
Fertile Women

IntroductionDepression is one of the prevalent mood disorders and it's the second debilitating disorder in the world. Female menstrual cycle is one of natural and psychological stage in fertility period and this cycle has different behavioral symptoms. In this study, changes in depression scores were studied during different phases of menstrual cycle.Material and methodsDuring a basic study, 150 fertile women were chosen and were evaluated by Beck and Hamilton Questionnaires during a menstrual cycle. Data were gathered and analyzed by SPSS software.ResultThirty four people were removed because of confounding factors. About 53.4% of them were single by the mean age of 22.10 years ( ± 4.67 SD), and 46.6% were married by the mean age of 34.65 years ( ± 7.51 SD). The mean score of Back questionnaire in the first phase was 11.49, in the second phase was 9.65, and in the third phase was 11.87. The score of Hamilton questionnaire in the first phase was 11.03, in the second phase was 9.45, and in third phase was 11.04, which there was significant differences in both of the tests.ConclusionDepression scores increase by reduction of hormone levels in days 2–3 and they classified as mild depression on average and during days 11–14. On the other hand, depression scores decreased by increment of hormone levels to maximum during ovulation days, as well as in days 23–26, depression scores increase by reduction of hormone levels and on average they classified as mild depression.

Some Comments on the Problem of Rotation and Mixing in Stars

2002 ◽  
Vol 12 ◽  
pp. 304-306
Author(s):  
Leon Mestel
Keyword(s):  
Time Scale ◽  
Main Sequence ◽  
Prima Facie ◽  
Gravitational Acceleration ◽  
The Core ◽  
Convective Core ◽  
Thermally Driven ◽  
The Mean ◽  
Rapid Rotator ◽  
Mean Molecular Weight

In the 1950’s, Sweet (1950) and Öpik (1951) rediscussed the resolution of the von Zeipel paradox in a uniformly rotating stellar radiative zone, showing that the time-scale of the Eddington (1929)-Vogt (1925) thermally-driven circulation would be of the order of the Kelvin-Helmholtz timeτK H,divided by an appropriate value for the ratioqof centrifugal to gravitational acceleration. In a Cowling-type star, the streamlines emerge near the poles of the convective core, traverse the radiative envelope, and return to the core at the equator. In a rapid rotator, the time τcof circulation is still short compared with the time-scale τnfor transmutation in the core of H into He, and it seemed that the mean molecular weightμwould remain nearly uniform, with the star evolving up and slightly to the left of the Main Sequence in the H-R Diagram; while in a moderate rotator, there could still be enough mixing to affect noticeably the expected evolution towards the Giant Domain.Prima facie, significant mixing would occur provided the valueq(rc) ofqat the convective core surface exceededτK H/τn≈ 10−3.

PENERAPAN MODEL QUANTUM LEARNING UNTUK MENINGKATKAN HASIL BELAJAR AUTOCAD SISWA KELAS X TEKNIK PEMESINAN SMK NEGERI 1 STABAT

2013 ◽  
Vol 5 (1) ◽  
Author(s):  
Abdul Hasan Saragih
Keyword(s):  
Positive Response ◽  
Phase 1 ◽  
First Grade ◽  
Learning Model ◽  
Second Phase ◽  
Phase 2 ◽  
Phase 3 ◽  
The Third ◽  
Third Phase ◽  
Quantum Learning

This classroom research was conducted on the autocad instructions to the first grade of mechinary class of SMK Negeri 1 Stabat aiming at : (1) improving the student’ archievementon autocad instructional to the student of mechinary architecture class of SMK Negeri 1 Stabat, (2) applying Quantum Learning Model to the students of mechinary class of SMK Negeri 1 Stabat, arising the positive response to autocad subject by applying Quantum Learning Model of the students of mechinary class of SMK Negeri 1 Stabat. The result shows that (1) by applying quantum learning model, the students’ achievement improves significantly. The improvement ofthe achievement of the 34 students is very satisfactory; on the first phase, 27 students passed (70.59%), 10 students failed (29.41%). On the second phase 27 students (79.41%) passed and 7 students (20.59%) failed. On the third phase 30 students (88.24%) passed and 4 students (11.76%) failed. The application of quantum learning model in SMK Negeri 1 Stabat proved satisfying. This was visible from the activeness of the students from phase 1 to 3. The activeness average of the students was 74.31% on phase 1,81.35% on phase 2, and 83.63% on phase 3. (3) The application of the quantum learning model on teaching autocad was very positively welcome by the students of mechinary class of SMK Negeri 1 Stabat. On phase 1 the improvement was 81.53% . It improved to 86.15% on phase 3. Therefore, The improvement ofstudent’ response can be categorized good.

Evaluation of Road Utilisation as Space For Holding Social Ceremonies in Indigenous Residential Area of Ogbomoso, Nigeria

2018 ◽  
Vol 1 (March 2018) ◽  
Author(s):  
S.A Okanlawon ◽  
O.O Odunjo ◽  
S.A Olaniyan
Keyword(s):  
Transport Infrastructure ◽  
Noisy Environment ◽  
Policy Makers ◽  
The Core ◽  
Local Roads ◽  
Strict Enforcement ◽  
The Mean ◽  
The One ◽  
The City ◽  
The Town

This study examined Residents’ evaluation of turning transport infrastructure (road) to spaces for holding social ceremonies in the indigenous residential zone of Ogbomoso, Oyo State, Nigeria. Upon stratifying the city into the three identifiable zones, the core, otherwise known as the indigenous residential zone was isolated for study. Of the twenty (20) political wards in the two local government areas of the town, fifteen (15) wards that were located in the indigenous zone constituted the study area. Respondents were selected along one out of every three (33.3%) of the Trunk — C (local) roads being the one mostly used for the purpose in the study area. The respondents were the residents, commercial motorists, commercial motorcyclists, and celebrants. Six hundred and forty-two (642) copies of questionnaire were administered and harvested on the spot. The Mean Analysis generated from the respondents’ rating of twelve perceived hazards listed in the questionnaire were then used to determine respondents’ most highly rated perceived consequences of the practice. These were noisy environment, Blockage of drainage by waste, and Endangering the life of the sick on the way to hospital; the most highly rated reasons why the practice came into being; and level of acceptability of the practice which was found to be very unacceptable in the study area. Policy makers should therefore focus their attention on strict enforcement of the law prohibiting the practice in order to ensure more cordial relationship among the citizenry, seeing citizens’ unacceptability of the practice in the study area.

Mixed-Methods Evaluation as Scaffold to the Development of a Mobile Health Application to Support the Prescription of Wheelchairs and Postural Support Devices (Preprint)

2020 ◽  
Author(s):  
Adriana Klein ◽  
Roseli de Deus Lopes ◽  
Rodrigo Suigh
Keyword(s):  
Mixed Methods ◽  
Mobile Health ◽  
Second Phase ◽  
The Third ◽  
Evaluation Approach ◽  
Mixed Methods Evaluation ◽  
Usability Tests ◽  
Third Phase ◽  
Postural Support ◽  
Support Devices

BACKGROUND EasySeating is a mobile health (mHealth) app that supports the prescription of wheelchair and postural support devices (WPSD). It can be used by occupational therapists (OT) and physiotherapists (PT) who prescribe WPSD. The app offers a standardization of the prescription procedure, showing images, metrics and details that guide the prescriber to decide on the best equipment. It was developed with an iterative mixed-methods evaluation approach. Objective: The aim of this study was to investigate the processes involved in the prescription of WPSD and to propose, develop and evaluate a mHealth to support OT and PT prescribers. OBJECTIVE The aim of this study was to investigate the processes involved in the prescription of WPSD and to propose, develop and evaluate a mHealth to support OT and PT prescribers. METHODS This study was divided into three phases and was carried out as an iterative process composed of user consulting/testing (using a mixed-methods evaluation approach), system (re)design and software development. The first phase consisted of the collection of qualitative and quantitative data to map and understand the users requirements and of the development of the first prototype (v1) of the app. This data collection was performed through semi-structured interviews with 14 OT and PT prescribers, 5 specialized technicians and 5 WPSD users. The second phase aimed at improving the overall functionality of the app and consisted in the development, test and evaluation of the prototypes v1, v2, v3 and v4. A total of 59 prescribers tested and evaluated these prototypes by means of open interviews, semi-structured questionnaires and focus groups. The third phase focused in the usability aspects of the app. It consisted in the development and test of the prototype v5. Eight technology specialists assessed its usability through heuristics evaluation. RESULTS Data collected in phase one indicated there is a lack of standardization on the prescription of postural support devices (PSD). A divergent nomenclature for the PSDs was also found and classified in eight categories. These information guided the development of the first prototype of the EasySeating app. Phase two results pointed that the prescribers value the insertion of the app into their clinical practice, as it accelerates and increases the quality of the evaluation process and improves the organization of the prescription information. Significant suggestions for the improvement of the app were given during the users tests, including the use of images to represent the PSDs. The usability tests from the third phase revealed two strong issues that must be solved: the need of greater feedback and failures in the persistence of the input data. CONCLUSIONS This study demonstrated that there is a lack of systematization of the WPSD prescription process. The evaluation of the developed EasySeating app demonstrated that there is a potential to standardize, integrate and organize the WPSD prescription information, supporting and facilitating the decision making process of the prescribers. CLINICALTRIAL This study was approved by the Research Ethics Board of the Universidade de São Paulo (registered protocol n°53929516.6.0000.0065) URL - http://plataformabrasil.saude.gov.br/login.jsf

Foucault as Superauthor

2019 ◽  
Vol 29 (2) ◽  
pp. 104-125
Keyword(s):  
Free Speech ◽  
Second Phase ◽  
Contemporary Society ◽  
Sovereign Power ◽  
Ancient Greek ◽  
Main Motivation ◽  
Critical Attitude ◽  
The Third ◽  
Third Phase ◽  
Lecture Courses

Three phases in Foucault’s examination of authorship and free speech were essential to him throughout his life. They can be linked to such texts as the three lectures “What is an Author?” (first phase), “What is Critique?,” and “What is Revolution?” (second phase), and the two lecture courses, “Fearless Speech,” and “The Courage of Truth” (third phase). Initially, Foucault merely describes the founders of discursivity (hence, “superauthors”), among whom he reckoned only Marx and Freud, as the sole alternative to his own conceptualization of the author function, which is exhibited en masse in contemporary society. He then modifies his views on superauthorship by making Kant the paradigm and by linking his own concept of free speech to a Kan-tian critical attitude. However, Foucault claims only the half of Kant’s philosophical legacy that is related to the study of the ontology of the self.The article advances the hypothesis that the sovereign power of speech, which can be found in Marx and Heidegger and in generally in the concept of “superauthorship,” becomes unacceptable for Foucault. During the third phase, the danger of a tyrannical use of free speech compels Foucault to make a number of fruitful but questionable choices in his work. He focuses on a single aspect of free speech in which a speaker is in a weaker position and therefore has to overcome his fear in order to tell the truth. Foucault associates this kind of free speech with the ancient Greek notion of parrhesia, which according to his interpretation means “fearless speech”; however, this reading is not always supported by the ancient Greek sources. Foucault’s deliberations bring him to the radical conclusion that free speech transforms into performative “aesthetics of existence.” Foucault’s main motivation for pursuing this line of thought all through his life was to investigate his own abilities and powers as an author

scholarly journals Large Bent Jets in the Inner Region of CSS

1996 ◽  
Vol 175 ◽  
pp. 71-72
Author(s):  
F. Mantovani ◽  
W. Junor ◽  
M. Bondi ◽  
L. Padrielli ◽  
W. Cotton ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Radio Sources ◽  
Ambient Media ◽  
The Core ◽  
Gaseous Environment ◽  
Radio Jets ◽  
Large Size ◽  
Superluminal Motion ◽  
Inner Region ◽  
Quasars And Radio Galaxies

Recently we focussed our attention on a sample of Compact Steep-spectrum Sources (CSSs) selected because of the large bent radio jets seen in the inner region of emission. The largest distortions are often seen in sources dominated by jets, and there are suggestions that this might to some extent be due to projection effects. However, superluminal motion is rare in CSSs. The only case we know of so far is 3C147 (Alef at al. 1990) with a mildly superluminal speed of ≃ 1.3v/c. Moreover, the core fractional luminosity in CSSs is ≃ 3% and ≤ 0.4% for quasars and radio galaxies respectively. Similar values are found for large size radio sources i.e. both boosting and orientations in the sky are similar for the two classes of objects. An alternative possibility is that these bent-jet sources might also be brightened by interactions with the ambient media. There are clear indications that intrinsic distortions due to interactions with a dense inhomogeneous gaseous environment play an important role. Observational support comes from the large RMs found in CSSs (Taylor et al. 1992; Mantovani et al. 1994; Junor et al. these proc.) and often associated with strong depolarization (Garrington & Akujor, t.p.). The CSSs also have very luminous Narrow Line Regions emission, with exceptional velocity structure (Gelderman, t.p.).

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