7,482 research outputs found
The polar temperature of Venus
Interferometric and polarization measurements of polar regions of Venu
J/psi dissociation by light mesons in an extended Nambu Jona-Lasinio model
An alternative model for the dissociation of the J/psi is proposed. Chiral
symmetry is properly implemented. Abnormal parity interactions and mesonic form
factors naturally arise from the underlying quark sub-structure. Analytic
confinement for the light quarks is generated by appropriately chosen the quark
interaction kernels. Dissociation cross sections of the J/psi by either a pion
or a rho meson are then evaluated and discussed.Comment: 24 pages, 13 figures, final versio
Anion receptor chemistry: highlights from 2011 and 2012
This review covers advances in anion complexation in the years 2011 and 2012. The review covers both organic and inorganic systems and also highlights the applications to which anion receptors can be applied such as self-assembly and molecular architecture, sensing, catalysis and anion transport
Protecting mammalian hair cells from aminoglycoside-toxicity: assessing phenoxybenzamine’s potential
Aminoglycosides (AGs) are widely used antibiotics because of their low cost and high efficacy against gram-negative bacterial infection. However, AGs are ototoxic,causing the death of sensory hair cells in the inner ear. Strategies aimed at developing or discovering agents that protect against aminoglycoside ototoxicity have focused on inhibiting apoptosis or more recently, on preventing antibiotic uptake by the hair cells. Recent screens for ototoprotective compounds using the larval zebrafish lateral line identified phenoxybenzamine as a potential protectant for aminoglycoside induced hair cell death. Here we used live imaging of FM1-43 uptake as a proxy for aminoglycoside entry, combined with hair-cell death assays to evaluate whether phenoxybenzamine can protect mammalian cochlear hair cells from the deleterious effects of the aminoglycoside antibiotic neomycin. We show that phenoxybenzamine can block FM1-43 entry into mammalian hair cells in a reversible and dose-dependent manner, but pre-incubation is required for maximal inhibition of entry. We observed differential effects of phenoxybenzamine on FM1-43 uptake in the two different types of cochlear hair cell in mammals, the outer hair cells (OHCs) and inner hair cells (IHCs).The requirement for pre-incubation and reversibility suggests an intracellular rather than an extracellular site of action for phenoxybenzamine. We also tested the efficacy of phenoxybenzamine as an otoprotective agent. In mouse cochlear explants the hair cell death resulting from 24 h exposure to neomycin was steeply dose-dependent, with 50% cell death occurring at ~230 uM for both IHC and OHC. We used 250 uM neomycin in subsequent hair-cell death assays. At 100 uM with 1 h pre-incubation, phenoxybenzamine conferred significant protection to both IHCs and OHCs, however at higher concentrations phenoxybenzamine itself showed clear signs of ototoxicity and an additive toxic effect when combined with neomycin. These data do not support the use of phenoxybenzamine as a therapeutic agent in mammalian inner ear. Our findings do share parallels with the observations from the zebrafish lateral line model but they also highlight the necessity for validation in the mammalian system and the potential for differential effects on sensory hair cells from different species, in different systems and even between cells in the same organ
Socially stable matchings in the hospitals / residents problem
In the Hospitals/Residents (HR) problem, agents are partitioned into hospitals and residents. Each agent wishes to be matched to an agent in the other set and has a strict preference over these potential matches. A matching is stable if there are no blocking pairs, i.e., no pair of agents that prefer each other to their assigned matches. Such a situation is undesirable as it could lead to a deviation in which the blocking pair form a private arrangement outside the matching. This however assumes that the blocking pair have social ties or communication channels to facilitate the deviation. Relaxing the stability definition to take account of the potential lack of social ties between agents can yield larger stable matchings.
In this paper, we define the Hospitals/Residents problem under Social Stability (HRSS) which takes into account social ties between agents by introducing a social network graph to the HR problem. Edges in the social network graph correspond to resident-hospital pairs in the HR instance that know one another. Pairs that do not have corresponding edges in the social network graph can belong to a matching M but they can never block M. Relative to a relaxed stability definition for HRSS, called social stability, we show that socially stable matchings can have different sizes and the problem of finding a maximum socially stable matching is NP-hard, though approximable within 3/2. Furthermore we give polynomial time algorithms for three special cases of the problem
Modeling Stable Matching Problems with Answer Set Programming
The Stable Marriage Problem (SMP) is a well-known matching problem first
introduced and solved by Gale and Shapley (1962). Several variants and
extensions to this problem have since been investigated to cover a wider set of
applications. Each time a new variant is considered, however, a new algorithm
needs to be developed and implemented. As an alternative, in this paper we
propose an encoding of the SMP using Answer Set Programming (ASP). Our encoding
can easily be extended and adapted to the needs of specific applications. As an
illustration we show how stable matchings can be found when individuals may
designate unacceptable partners and ties between preferences are allowed.
Subsequently, we show how our ASP based encoding naturally allows us to select
specific stable matchings which are optimal according to a given criterion.
Each time, we can rely on generic and efficient off-the-shelf answer set
solvers to find (optimal) stable matchings.Comment: 26 page
Highly effective yet simple transmembrane anion transporters based upon ortho-phenylenediamine bis-ureas
Simple, highly fluorinated receptors are shown to function as highly effective transmembrane anion antiporters with the most active transporters rivalling the transport efficacy of natural anion transporter prodigiosin for bicarbonate
Typical properties of optimal growth in the Von Neumann expanding model for large random economies
We calculate the optimal solutions of the fully heterogeneous Von Neumann
expansion problem with processes and goods in the limit .
This model provides an elementary description of the growth of a production
economy in the long run. The system turns from a contracting to an expanding
phase as increases beyond . The solution is characterized by a universal
behavior, independent of the parameters of the disorder statistics. Associating
technological innovation to an increase of , we find that while such an
increase has a large positive impact on long term growth when , its
effect on technologically advanced economies () is very weak.Comment: 8 pages, 1 figur
Profound vision loss impairs psychological well-being in young and middle-aged individuals.
PurposeThe aim of this study was to evaluate the effects of profound vision loss on psychological well-being in adolescents, young adults, and middle-aged adults with regard to mood, interpersonal interactions, and career-related goals. In addition, we assessed the significance of the resources that may be used to enhance psychological well-being in cases of profound vision loss, and in particular, examined the utility of low vision aids and the role of the ophthalmologist as a provider of emotional support.MethodsA questionnaire was issued to individuals aged 13-65 years with profound vision loss resulting from Leber's hereditary optic neuropathy (LHON). Depression prevalence was evaluated with questions regarding major depressive disorder symptomatology. Participants appraised the effects of vision loss on their interpersonal interactions and career goals by providing an impact rating (IR) on a 21-point psychometric scale from -10 to +10. Social well-being index was defined as the average of interpersonal IR and career IR. Subjects were additionally asked about the use of low vision aids and sources of emotional support.ResultsA total of 103 participants (mean age =26.4±11.2 years at LHON diagnosis; mean ± standard deviation) completed the questionnaire. Nearly half (49.5%) met the depression criteria after vision loss. Negative impacts on interpersonal interactions (median IR = -5) and career goals (median IR = -6) were observed; both ratings were worse (P<0.001) for depressed versus nondepressed subjects. Older age at diagnosis corresponded to higher depression prevalence and increased incidence of negative interpersonal IR and career IR. Sixty-eight percent of subjects used electronic vision aids; controlling for age, social well-being index was higher among these individuals than for those who did not use electronic aids (P=0.03). Over half of the participants (52.4%) asserted that they derived emotional support from their ophthalmologist.ConclusionProfound vision loss in adolescents, young adults, and middle-aged adults is associated with significant negative psychological and psychosocial effects, which are influenced by age and use of electronic vision aids. Ophthalmologists, in addition to managing vision loss, may serve an important role in the emotional adaptation of these patients
Drug-induced stress granule formation protects sensory hair cells in mouse cochlear explants during ototoxicity
Stress granules regulate RNA translation during cellular stress, a mechanism that is generally presumed to be protective, since stress granule dysregulation caused by mutation or ageing is associated with neurodegenerative disease. Here, we investigate whether pharmacological manipulation of the stress granule pathway in the auditory organ, the cochlea, affects the survival of sensory hair cells during aminoglycoside ototoxicity, a common cause of acquired hearing loss. We show that hydroxamate (-)-9, a silvestrol analogue that inhibits eIF4A, induces stress granule formation in both an auditory cell line and ex-vivo cochlear cultures and that it prevents ototoxin-induced hair-cell death. In contrast, preventing stress granule formation using the small molecule inhibitor ISRIB increases hair-cell death. Furthermore, we provide the first evidence of stress granule formation in mammalian hair cells in-vivo triggered by aminoglycoside treatment. Our results demonstrate that pharmacological induction of stress granules enhances cell survival in native-tissue, in a clinically-relevant context. This establishes stress granules as a viable therapeutic target not only for hearing loss but also other neurodegenerative diseases.EI:595 - Action on Hearing Loss; 091092/Z/09/Z - Wellcome Trust (Wellcome); MR/N004329/1 - RCUK | Medical Research Council (MRC)Published versio
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