784 research outputs found
The dyad gene is required for progression through female meiosis in Arabidopsis
In higher plants the gametophyte consists of a gamete in association with a small number of haploid cells, specialized for sexual reproduction. The female gametophyte or embryo sac, is contained within the ovule and develops from a single cell, the megaspore which is formed by meiosis of the megaspore mother cell. The dyad mutant of Arabidopsis, described herein, represents a novel class among female sterile mutants in plants, dyad ovules contain two large cells in place of an embryo sac. The two cells represent the products of a single division of the megaspore mother cell followed by an arrest in further development of the megaspore. We addressed the question of whether the division of the megaspore mother cell in the mutant was meiotic or mitotic by examining the expression of two markers that are normally expressed in the megaspore mother cell during meiosis. Our observations indicate that in dyad the megaspore mother cell enters but fails to complete meiosis, arresting at the end of meiosis 1 in the majority of ovules, This was corroborated by a direct observation of chromosome segregation during division of the megaspore mother cell, showing that the division is a reductional and not an equational one. In a minority of dqad ovules, the megaspore mother cell does not divide. Pollen development and male fertility in the mutant is normal, as is the rest of the ovule that surrounds the female gametophyte. The embryo sac is also shown to have an influence on the nucellus in wild type. The dyad mutation therefore specifically affects a function that is required in the female germ cell precursor for meiosis. The identification and analysis of mutants specifically affecting female meiosis is an initial step in understanding the molecular mechanisms underlying early events in the pathway of female reproductive development
Software engineering approach to bug prediction models using machine learning as a service (MLaaS)
The presence of bugs in a software release has become inevitable. The loss incurred by a company due to the presence of bugs in a software release is phenomenal. Modern methods of testing and debugging have shifted focus from âdetectingâ to âpredictingâ bugs in the code. The existing models of bug prediction have not been optimized for commercial use. Moreover, the scalability of these models has not been discussed in depth yet. Taking into account the varying costs of fixing bugs, depending on which stage of the software development cycle the bug is detected in, this paper uses two approaches - one model which can be employed when the 'cost of changing code' curve is exponential and the other model can be used otherwise. The cases where each model is best suited are discussed. This paper proposes a model that can be deployed on a cloud platform for software development companies to use. The model in this paper aims to predict the presence or absence of a bug in the code, using machine learning classification models. Using Microsoft Azure's machine learning platform this model can be distributed as a web service worldwide, thus providing Bug Prediction as a Service (BPaaS)
Characterization 410 Stainless Steel by Vacuum Tempering Process
It has been reported that low-temperature vacuum tempering of 410 stainless steel hard layer improving wear resistance and hardness. Grade 410 stainless steel being a hardened material were modified by low temperature tempering process. By the process of tempering, brittleness on the stainless steel material will be reduced and ductility will be promoted. The microstructure, surface hardness and erosion-corrosion resistance were systematically evaluated. Vacuum tempering is done at low temperature of 430â can form a hardened layer, and with the treated time prolong, the thickness of the layer increased. The stainless specimens were vacuum tempered for 30 minutes, 60 minutes and 120 minutes. Wear tests were conducted with the help of pin on disc apparatus. The output results were determined with various metallographic tests like scanning electron microscope and optical microscope results
Elevated maternal lipoprotein (a) and neonatal renal vein thrombosis: a case report
<p>Abstract</p> <p>Introduction</p> <p>Renal vein thrombosis, although rare in adults, is well recognized in neonates and is one of the most common manifestations of neonatal thromboembolic events. The etiology of renal vein thrombosis remains unidentified in the majority of cases. We report a case of renal vein thrombosis in a neonate associated with elevated maternal lipoprotein (a).</p> <p>Case presentation</p> <p>A full-term female infant, appropriate for gestational age, was born via spontaneous vaginal delivery to an 18-year-old primigravida. The infant's birth weight was 3680 g and the Apgar scores were eight and nine at 1 and 5 minutes respectively. Evaluation of the infant in the newborn nursery revealed a palpable mass in the right lumbar area. Tests revealed hematuria and a high serum creatinine level of 1.5 mg/dl. An abdominal ultrasound Doppler flow study demonstrated an enlarged right kidney, right renal vein thrombosis, and progression of the thrombosis to the inferior vena cava. There was no evidence of saggital sinus thrombosis. An extensive work-up of parents for hypercoagulable conditions was remarkable for a higher plasma lipoprotein (a) level of 73 mg/dl and an elevated fibrinogen level of 512 mg/dl in the mother. All paternal levels were normal. The plasma lipoprotein (a) level in the neonate was also normal. The neonate was treated with low molecular weight heparin (enoxaparin) at 1.5 mg/kg/day every 12 hours for 2 months, at which time a follow-up ultrasound Doppler flow study showed resolution of the thrombosis in both the renal vein and the inferior vena cava.</p> <p>Conclusion</p> <p>There have been no studies to date that have explored the effect of abnormal maternal risk factors on fetal hemostasis. A case-control study is required to investigate whether elevated levels of maternal lipoprotein (a) may be a risk factor for neonatal thrombotic processes. Although infants with this presentation are typically treated with anticoagulation, there is a lack of evidence-based guidelines. Treatment modalities vary between study and treatment centers which warrants the establishment of a national registry.</p
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Reduced Recombination and Capacitor-like Charge Buildup in an Organic Heterojunction
Organic photovoltaic (OPV) efficiencies continue to rise, raising their prospects for solar energy conversion. However, researchers have long considered how to suppress the loss of free carriers by recombinationâpoor diffusion and significant Coulombic attraction can cause electrons and holes to encounter each other at interfaces close to where they were photogenerated. Using femtosecond transient spectroscopies, we report the nanosecond grow-in of a large transient 20 Stark effect, caused by nanoscale electric fields of ~487 kV/cm between photogenerated free carriers in the device active layer. We find that particular morphologies of the active layer lead to an energetic cascade for charge carriers, suppressing pathways to recombination, which is ~2000 times less than predicted by Langevin theory. This in turn leads to the build-up of electric charge in donor and acceptor domainsâaway from the interfaceâresistant to bimolecular recombination. 25 Interestingly, this signal is only experimentally obvious in thick films, due to the different scaling of electro-absorption and photo-induced absorption signals in transient absorption spectroscopy. Rather than inhibiting device performance, we show that devices up to 600 nm thick maintain efficiencies of > 8 % because domains can afford much higher carrier densities. These observations suggest that with particular nanoscale morphologies, the bulk heterojunction can go beyond its established role in charge photogeneration, and can act as a capacitor, where adjacent free charges are held away from the interface and can be protected from bimolecular recombination
Search for CP violation in D+âÏÏ+ and D+sâK0SÏ+ decays
A search for CP violation in D + â ÏÏ + decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fbâ1 at a centre of mass energy of 7 TeV. The CP -violating asymmetry is measured to be (â0.04 ± 0.14 ± 0.14)% for candidates with K â K + mass within 20 MeV/c 2 of the Ï meson mass. A search for a CP -violating asymmetry that varies across the Ï mass region of the D + â K â K + Ï + Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D+sâK0SÏ+ decay is measured to be (0.61 ± 0.83 ± 0.14)%
Differential branching fraction and angular analysis of the decay B0âKâ0ÎŒ+ÎŒâ
The angular distribution and differential branching fraction of the decay B 0â K â0 ÎŒ + ÎŒ â are studied using a data sample, collected by the LHCb experiment in pp collisions at sâ=7 TeV, corresponding to an integrated luminosity of 1.0 fbâ1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
Measurement of the branching fraction
The branching fraction is measured in a data sample
corresponding to 0.41 of integrated luminosity collected with the LHCb
detector at the LHC. This channel is sensitive to the penguin contributions
affecting the sin2 measurement from The
time-integrated branching fraction is measured to be . This is the most precise measurement to
date
Measurements of the branching fractions of B+âppK+ decays
The branching fractions of the decay B+ â ppÌK+ for different intermediate states are measured using data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment. The total branching fraction, its charmless component MppÌ < 2.85 GeV/c2 and the branching fractions via the resonant ccÌ states η c(1S) and Ï(2S) relative to the decay via a J/Ï intermediate state are [Equation not available: see fulltext.] Upper limits on the B + branching fractions into the η c(2S) meson and into the charmonium-like states X(3872) and X(3915) are also obtained
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