Dark Energy and Gravity

I review the problem of dark energy focusing on the cosmological constant as the candidate and discuss its implications for the nature of gravity. Part 1 briefly overviews the currently popular `concordance cosmology' and summarises the evidence for dark energy. It also provides the observational and theoretical arguments in favour of the cosmological constant as the candidate and emphasises why no other approach really solves the conceptual problems usually attributed to the cosmological constant. Part 2 describes some of the approaches to understand the nature of the cosmological constant and attempts to extract the key ingredients which must be present in any viable solution. I argue that (i)the cosmological constant problem cannot be satisfactorily solved until gravitational action is made invariant under the shift of the matter lagrangian by a constant and (ii) this cannot happen if the metric is the dynamical variable. Hence the cosmological constant problem essentially has to do with our (mis)understanding of the nature of gravity. Part 3 discusses an alternative perspective on gravity in which the action is explicitly invariant under the above transformation. Extremizing this action leads to an equation determining the background geometry which gives Einstein's theory at the lowest order with Lanczos-Lovelock type corrections. (Condensed abstract).Comment: Invited Review for a special Gen.Rel.Grav. issue on Dark Energy, edited by G.F.R.Ellis, R.Maartens and H.Nicolai; revtex; 22 pages; 2 figure

De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome

Around 60% of individuals with neurodevelopmental disorders (NDD) remain undiagnosed after comprehensive genetic testing, primarily of protein-coding genes1. Large genome-sequenced cohorts are improving our ability to discover new diagnoses in the non-coding genome. Here, we identify the non-coding RNA RNU4-2 as a syndromic NDD gene. RNU4-2 encodes the U4 small nuclear RNA (snRNA), which is a critical component of the U4/U6.U5 tri-snRNP complex of the major spliceosome2. We identify an 18 bp region of RNU4-2 mapping to two structural elements in the U4/U6 snRNA duplex (the T-loop and Stem III) that is severely depleted of variation in the general population, but in which we identify heterozygous variants in 115 individuals with NDD. Most individuals (77.4%) have the same highly recurrent single base insertion (n.64_65insT). In 54 individuals where it could be determined, the de novo variants were all on the maternal allele. We demonstrate that RNU4-2 is highly expressed in the developing human brain, in contrast to RNU4-1 and other U4 homologs. Using RNA-sequencing, we show how 5’ splice site usage is systematically disrupted in individuals with RNU4-2 variants, consistent with the known role of this region during spliceosome activation. Finally, we estimate that variants in this 18 bp region explain 0.4% of individuals with NDD. This work underscores the importance of non-coding genes in rare disorders and will provide a diagnosis to thousands of individuals with NDD worldwide

Evalita 2011: Automatic Speech Recognition Large Vocabulary Transcription

In this paper we describe design, setup and results of the speech recognition task in the framework of the Evalita campaign for the Italian language, giving details on the released corpora and tools used for the challenge. A general discussion about approaches to large vocabulary speech recognition introduces the recognition tasks. Systems are compared for recognition accuracy on audio sequences of Italian par- liament. Although only a few systems have participated to the tasks, the contest provides an overview of the state-of-the-art of speech-to-text transcription technologies; the document reports systems performance, computed as Word Error Rate (WER), showing that the current approaches provide effective results. The best system achieves a WER as low as 5.4% on the released testset

A double blind, placebo controlled study of the effects of low dose testosterone undecanoate on the growth of small for age, prepubertal boys.

OBJECTIVE--To assess whether very low doses of testosterone can accelerate growth without an undue advance in bone age in prepubertal boys with constitutional delay of growth. SUBJECTS--23 prepubertal boys aged 11-14 years with height at or below the third centile for chronological age. DESIGN--Randomised, double blind trial comparing oral testosterone undecanoate 20 mg once daily versus placebo for six months. The 18 months' observation period of each subject comprised a six month pretreatment period, followed by a six month treatment (testosterone undecanoate or placebo) period, and a six month period after termination of treatment. OUTCOME MEASURES--At intervals of six months standing and sitting height were measured. Bone age, pubertal stage, weight, and lean body mass were also determined. Growth hormone, luteinising hormone, and follicle stimulating hormone secretion and testosterone concentration were measured before, after, and six months after treatment. RESULTS--Boys taking testosterone undecanoate (n = 11) showed a significantly greater height velocity (mean (SEM) 5.84 (0.53) cm/year) and sitting height velocity (3.54 (0.57) cm/year) during treatment than the placebo treated boys (n = 12, height velocity = 3.38 (0.22) cm/year, sitting height velocity = 1.58 (0.19) cm/year. There were no significant differences between the groups regarding changes in growth hormone, gonadotrophins, testosterone, or dihydrotestosterone concentrations. Bone age was not advanced significantly more rapidly in either group. CONCLUSIONS--There is accelerated gain in height during six months of treatment with low dose testosterone undecanoate, without a significantly greater rise in bone age compared with controls. Testosterone undecanoate is a safe, well tolerated, and effective treatment in the management of constitutional delay of growth

Verteporfin therapy of subfoveal choroidal neovascularization in age-related macular degeneration: two-year results of a randomized clinical trial including lesions with occult with no classic choroidal neovascularization--verteporfin in photodynamic therapy report 2

PURPOSETo determine if photodynamic therapy with verteporfin (Visudyne; Novartis AG, Bülach, Switzerland), termed verteporfin therapy, can safely reduce the risk of vision loss compared with a placebo (with sham treatment) in patients with subfoveal choroidal neovascularization caused by age-related macular degeneration who were identified with a lesion composed of occult with no classic choroidal neovascularization, or with presumed early onset classic choroidal neovascularization with good visual acuity letter score.METHODSThis was a double-masked, placebo-controlled (sham treatment), randomized, multicenter clinical trial involving 28 ophthalmology practices in Europe and North America. The study population was patients with age-related macular degeneration, with subfoveal choroidal neovascularization lesions measuring no greater than 5400 microm in greatest linear dimension with either 1) occult with no classic choroidal neovascularization, best-corrected visual acuity score of at least 50 (Snellen equivalent approximately 20/100), and evidence of hemorrhage or recent disease progression; or 2) evidence of classic choroidal neovascularization with a best-corrected visual acuity score of at least 70 (better than a Snellen equivalent of approximately 20/40); assigned randomly (2:1) to verteporfin therapy or placebo therapy. Verteporfin (6 mg per square meter of body surface area) or placebo (5% dextrose in water) was administered by means of intravenous infusion of 30 ml over 10 minutes. Fifteen minutes after the start of the infusion, a laser light at 689 nm delivered 50 J/cm(2) by application of an intensity of 600 mW/cm(2) over 83 seconds using a spot size with a diameter 1000 microm larger than the greatest linear dimension of the choroidal neovascularization lesion on the retina. At follow-up examinations every 3 months, retreatment with the same regimen was applied if angiography showed fluorescein leakage. The main outcome measure was at least moderate vision loss, that is, a loss of at least 15 letters (approximately 3 lines), adhering to an intent-to-treat analysis with the last observation carried forward to impute for missing data.RESULTSTwo hundred ten (93%) and 193 (86%) of the 225 patients in the verteporfin group compared with 104 (91%) and 99 (87%) of the 114 patients in the placebo group completed the month 12 and 24 examinations, respectively. On average, verteporfin-treated patients received five treatments over the 24 months of follow-up. The primary outcome was similar for the verteporfin-treated and the placebo-treated eyes through the month 12 examination, although a number of secondary visual and angiographic outcomes significantly favored the verteporfin-treated group. Between the month 12 and 24 examinations, the treatment benefit grew so that by the month 24 examination, the verteporfin-treated eyes were less likely to have moderate or severe vision loss. Of the 225 verteporfin-treated patients, 121 (54%) compared with 76 (67%) of 114 placebo-treated patients lost at least 15 letters (P =.023). Likewise, 67 of the verteporfin-treated patients (30%) compared with 54 of the placebo-treated patients (47%) lost at least 30 letters (P =.001). Statistically significant results favoring verteporfin therapy at the month 24 examination were consistent between the total population and the subgroup of patients with a baseline lesion composition identified as occult choroidal neovascularization with no classic choroidal neovascularization. This subgroup included 166 of the 225 verteporfin-treated patients (74%) and 92 of the 114 placebo-treated patients (81%). In these patients, 91 of the verteporfin-treated group (55%) compared with 63 of the placebo-treated group (68%) lost at least 15 letters (P =.032), whereas 48 of the verteporfin-treated group (29%) and 43 of the placebo-treated group (47%) lost at least 30 letters (P =.004). Other secondary outcomes, including visual acuity letter score worse than 34 (approximate Snellen equivalent of 20/200 or worse), mean change in visual acuity letter score, development of classic choroidal neovascularization, progression of classic choroidal neovascularization and size of lesion, favored the verteporfin-treated group at both the month 12 and month 24 examination for both the entire study group and the subgroup of cases with occult with no classic choroidal neovascularization at baseline. Subgroup analyses of lesions composed of occult with no classic choroidal neovascularization at baseline suggested that the treatment benefit was greater for patients with either smaller lesions (4 disc areas or less) or lower levels of visual acuity (letter score less than 65, an approximate Snellen equivalent of 20/50(-1) or worse) at baseline. Prospectively planned multivariable analyses confirmed that these two baseline variables affected the magnitude of treatment benefit. (ABSTRACT TRUNCATED