4,057 research outputs found
Are there compact heavy four-quark bound states?
We present an exact method to study four-quark systems based on the
hyperspherical harmonics formalism. We apply it to several physical systems of
interest containing two heavy and two light quarks using different quark-quark
potentials. Our conclusions mark the boundaries for the possible existence of
compact, non-molecular, four-quark bound states. While states
may be stable in nature, the stability of states would imply
the existence of quark correlations not taken into account by simple quark
dynamical modelsComment: 10 pages, 1 figure. Accepted for publication in Phys. Rev.
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Moving Beyond Youth Prisons: Lessons from New York City’s Implementation of Close to Home
In the mid-1990s, New York’s youth prison system reflected the dominant paradigm across the country – a heavy reliance on incarceration for young people caught up in the juvenile justice system. During this time, roughly 3,800 youth convicted of crimes annually were sent to large facilities, operated either by the New York State Office of Children and Family Services (OCFS) or by private providers contracted by OCFS. These facilities were largely located in upstate New York, far from youths’ homes and communities, particularly for youth from New York City (Sickmund et al. 2017; New York State (NYS) Office of the State Comptroller 2001). Upon returning home from these placements, youth often felt disconnected, resulting in poor outcomes. A 2009 study indicated that by age 28, 71 percent of boys released from New York State’s juvenile placement system spent some time in an adult jail or prison (Coleman, Do Han Kim & Therese 2009).
Fast forward twenty years, and things in New York looked dramatically different. By 2016, New York City no longer sent any youth from its Family Court to state-operated youth prisons. Today, only around 100 New York City youth are placed from Family Court into any kind of residential facility, about a dozen of whom are in a locked facility. Not only are there dramatically fewer youth in residential placements, but those who do get placed now go to smaller, more home-like settings that attend to public safety without mirroring the punitive, correctional approaches embodied by previous youth prisons.
This case study outlines what happened in the intervening years to achieve these remarkable results. By sharing New York City’s story, we offer a roadmap for other jurisdictions looking to realign their juvenile justice systems, adapting the lessons learned about what worked and what did not to meet their specific circumstances
Asteroids in the Inner Solar System II - Observable Properties
This paper presents synthetic observations of long-lived, coorbiting
asteroids of Mercury, Venus, the Earth and Mars. Our sample is constructed by
taking the limiting semimajor axes, differential longitudes and inclinations
for long-lived stability provided by simulations. The intervals are randomly
populated with values to create initial conditions. These orbits are
re-simulated to check that they are stable and then re-sampled every 2.5 years
for 1 million years. The Mercurian sample contains only horseshoe orbits, the
Martian sample only tadpoles. For both Venus and the Earth, the greatest
concentration of objects on the sky occurs close to the classical Lagrange
points at heliocentric ecliptic longitudes of 60 and 300 degrees. The
distributions are broad especially if horseshoes are present in the sample. The
full-width half maximum (FWHM) in heliocentric longitude for Venus is 325
degrees and for the Earth is 328 degrees. The mean and most common velocity of
these coorbiting satellites coincides with the mean motion of the parent
planet, but again the spread is wide with a FWHM for Venus of 27.8 arcsec/hr
and for the Earth of 21.0 arcsec/hr. For Mars, the greatest concentration on
the sky occurs at heliocentric ecliptic latitudes of 12 degrees. The peak of
the velocity distribution occurs at 65 arcsec/hr, significantly less than the
Martian mean motion, while its FWHM is 32.3 arcsec/hr. The case of Mercury is
the hardest of all, as the greatest concentration occurs at heliocentric
longitudes close to the Sun.Comment: 16 pages, 11 figures, Monthly Notices (in press). Higher quality
figures available at
http://www-thphys.physics.ox.ac.uk/users/WynEvans/home.htm
On the existence of exotic and non-exotic multiquark meson states
To obtain an exact solution of a four-body system containing two quarks and
two antiquarks interacting through two-body terms is a cumbersome task that has
been tackled with more or less success during the last decades. We present an
exact method for the study of four-quark systems based on the hyperspherical
harmonics formalism that allows us to solve it without resorting to further
approximations, like for instance the existence of diquark components. We apply
it to systems containing two heavy and two light quarks using different
quark-quark potentials. While states may be stable in nature,
the stability of states would imply the existence of quark
correlations not taken into account by simple quark dynamical models.Comment: 3 pages. Contribution to the 20th European Conference on Few-Body
Problems in Physics, Pisa, Italy. To be published in Few-Body system
Hybrid Threats and Asymmetric Warfare: What to do? Conference proceeding February 2018
The international security environment has seemingly departed from a post-cold war period of everlasting peace and has instead evolved into a volatile and increasingly grey area of war and peace. Security challenges arising from both hybrid wars and hybrid threats are high on security agendas in Sweden and Europe as well as internationally. However, despite the attention there is a lack of research that addresses how such “new” wars and threats should be handled. While studies do exist on specific issues, a comprehensive approach to how hybrid wars and threats are to be handled is still lacking. This is particularly the case when it comes to the sharing of experiences between states. This workshop constituted a first step towards developing such a comprehensive approach. The workshop’s aim was to be a bridge across disciplinary boundaries as well as between researchers and practitioners within and outside Sweden; integrating each group’s extensive experiences and knowledge into a coherent whole. Besides producing and disseminating new knowledge, the intention of the workshop was to establish a foundation for long-term collaboration; the first step in the creation of a European Network on Hybrid Warfare Capabilities that can work across borders and link state of the art of research and practice. Although mainly a scientific workshop, a number of practitioners were invited, with a mix of presentations by academics and practitioners. This was intended to foster innovative and reflective discussions across the academic-practitioner divide. The workshop also aimed to develop new ideas associated with hybrid threats/warfare in order to facilitate future cooperation These proceedings include a summary of the key points made by the presenters, along with conclusions and policy recommendations derived from the ensuing discussions. Conference programme and a list of abstracts for the papers and presentations can be found in the appendix
An interstellar precursor mission
A mission out of the planetary system, with launch about the year 2000, could provide valuable scientific data as well as test some of the technology for a later mission to another star. Primary scientific objectives for the precursor mission concern characteristics of the heliopause, the interstellar medium, stellar distances (by parallax measurements), low energy cosmic rays, interplanetary gas distribution, and mass of the solar system. Secondary objectives include investigation of Pluto. Candidate science instruments are suggested. Individual spacecraft systems for the mission were considered, technology requirements and problem areas noted, and a number of recommendations made for technology study and advanced development. The most critical technology needs include attainment of 50-yr spacecraft lifetime and development of a long-life NEP system
RING-type E3 ligases: Master manipulators of E2 ubiquitin-conjugating enzymes and ubiquitination
AbstractRING finger domain and RING finger-like ubiquitin ligases (E3s), such as U-box proteins, constitute the vast majority of known E3s. RING-type E3s function together with ubiquitin-conjugating enzymes (E2s) to mediate ubiquitination and are implicated in numerous cellular processes. In part because of their importance in human physiology and disease, these proteins and their cellular functions represent an intense area of study. Here we review recent advances in RING-type E3 recognition of substrates, their cellular regulation, and their varied architecture. Additionally, recent structural insights into RING-type E3 function, with a focus on important interactions with E2s and ubiquitin, are reviewed. This article is part of a Special Issue entitled: Ubiquitin–Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf
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The helicase Ded1p controls use of near-cognate translation initiation codons in 5' UTRs.
The conserved and essential DEAD-box RNA helicase Ded1p from yeast and its mammalian orthologue DDX3 are critical for the initiation of translation1. Mutations in DDX3 are linked to tumorigenesis2-4 and intellectual disability5, and the enzyme is targeted by a range of viruses6. How Ded1p and its orthologues engage RNAs during the initiation of translation is unknown. Here we show, by integrating transcriptome-wide analyses of translation, RNA structure and Ded1p-RNA binding, that the effects of Ded1p on the initiation of translation are connected to near-cognate initiation codons in 5' untranslated regions. Ded1p associates with the translation pre-initiation complex at the mRNA entry channel and repressing the activity of Ded1p leads to the accumulation of RNA structure in 5' untranslated regions, the initiation of translation from near-cognate start codons immediately upstream of these structures and decreased protein synthesis from the corresponding main open reading frames. The data reveal a program for the regulation of translation that links Ded1p, the activation of near-cognate start codons and mRNA structure. This program has a role in meiosis, in which a marked decrease in the levels of Ded1p is accompanied by the activation of the alternative translation initiation sites that are seen when the activity of Ded1p is repressed. Our observations indicate that Ded1p affects translation initiation by controlling the use of near-cognate initiation codons that are proximal to mRNA structure in 5' untranslated regions
A Bima Array Survey of Molecules in Comets Linear (C/2002 T7) and Neat (C/2001 Q4)
We present an interferometric search for large molecules, including methanol,
methyl cyanide, ethyl cyanide, ethanol, and methyl formate in comets LINEAR
(C/2002 T7) and NEAT (C/2001 Q4) with the Berkeley-Illinois-Maryland
Association (BIMA) array. In addition, we also searched for transitions of the
simpler molecules CS, SiO, HNC, HN13C and 13CO . We detected transitions of
methanol and CS around Comet LINEAR and one transition of methanol around Comet
NEAT within a synthesized beam of ~20''. We calculated the total column density
and production rate of each molecular species using the variable temperature
and outflow velocity (VTOV) model described by Friedel et al.(2005).Considering
the molecular production rate ratios with respect to water, Comet T7 LINEAR is
more similar to Comet Hale-Bopp while Comet Q4 NEAT is more similar to Comet
Hyakutake. It is unclear, however, due to such a small sample size, whether
there is a clear distinction between a Hale-Bopp and Hyakutake class of comet
or whether comets have a continuous range of molecular production rate ratios.Comment: Accepted for Publication in the Astrophysical Journa
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