The multiple personalities of Watson and Crick strands

<p>Abstract</p> <p>Background</p> <p>In genetics it is customary to refer to double-stranded DNA as containing a "Watson strand" and a "Crick strand." However, there seems to be no consensus in the literature on the exact meaning of these two terms, and the many usages contradict one another as well as the original definition. Here, we review the history of the terminology and suggest retaining a single sense that is currently the most useful and consistent.</p> <p>Proposal</p> <p>The <it>Saccharomyces </it>Genome Database defines the Watson strand as the strand which has its 5'-end at the short-arm telomere and the Crick strand as its complement. The Watson strand is always used as the reference strand in their database. Using this as the basis of our standard, we recommend that Watson and Crick strand terminology only be used in the context of genomics. When possible, the centromere or other genomic feature should be used as a reference point, dividing the chromosome into two arms of unequal lengths. Under our proposal, the Watson strand is standardized as the strand whose 5'-end is on the short arm of the chromosome, and the Crick strand as the one whose 5'-end is on the long arm. Furthermore, the Watson strand should be retained as the reference (plus) strand in a genomic database. This usage not only makes the determination of Watson and Crick unambiguous, but also allows unambiguous selection of reference stands for genomics.</p> <p>Reviewers</p> <p>This article was reviewed by John M. Logsdon, Igor B. Rogozin (nominated by Andrey Rzhetsky), and William Martin.</p

LATE-TIME PHOTOMETRY OF TYPE IA SUPERNOVA SN 2012cg REVEALS THE RADIOACTIVE DECAY OF Co-57

Seitenzahl et al. have predicted that roughly three years after its explosion, the light we receive from a Type Ia supernova (SN Ia) will come mostly from reprocessing of electrons and X-rays emitted by the radioactive decay chain 57Co → 57Fe, instead of positrons from the decay chain 56Co → 56Fe that dominates the SN light at earlier times. Using the Hubble Space Telescope, we followed the light curve of the SN Ia SN 2012cg out to 1055 days after maximum light. Our measurements are consistent with the light curves predicted by the contribution of energy from the reprocessing of electrons and X-rays emitted by the decay of 57Co, offering evidence that 57Co is produced in SN Ia explosions. However, the data are also consistent with a light echo ∼14 mag fainter than SN 2012cg at peak. Assuming no light-echo contamination, the mass ratio of 57Ni and 56Ni produced by the explosion, a strong constraint on any SN Ia explosion models, is 0.043 0.011 0.012 - + , roughly twice Solar. In the context of current explosion models, this value favors a progenitor white dwarf with a mass near the Chandrasekhar limit

tf.data service: A Case for Disaggregating ML Input Data Processing

Machine learning (ML) computations commonly execute on expensive specialized hardware, such as GPUs and TPUs, which provide high FLOPs and performance-per-watt. For cost efficiency, it is essential to keep these accelerators highly utilized. This requires preprocessing input data at the rate at which the accelerators can ingest and perform ML computations on the data. To avoid data stalls, the host CPU and RAM required for input data processing per accelerator core used for ML computations varies across jobs. Hence, the traditional approach of processing input data on ML accelerator hosts with a fixed hardware ratio leads to either under-utilizing the accelerators or the host CPU and RAM. In this paper, we address these concerns by building a disaggregated ML data processing system. We present tf.data service, an open-source disaggregated input data processing service built on top of tf.data in TensorFlow. We show that disaggregating data preprocessing has three key advantages for large-scale ML training jobs. First, the service can horizontally scale-out to right-size CPU/RAM host resources for data processing in each job, saving 32x training time and 26x cost, on average. Second, the service can share ephemeral preprocessed data results across jobs, to optimize CPU usage and reduce redundant computations. Finally, the service supports coordinated reads, a technique that avoids stragglers due to different input sizes in distributed training, reducing training time by 2.2x, on average. Our design is inspired by lessons learned from deploying tf.data service in production, including relaxing data visitation guarantees without impacting model accuracy

Sublimation and deposition in gaseous mixtures

The sublimation and deposition behaviors of the Helium-Argon mixture is analyzed numerically in the temperature range where Helium is only in gaseous state while Argon can sublimate and deposit on its own solid phase. The McCormack model is implemented to model the Boltzmann collision term. Three kinds of potential are used for simulation of the intermolecular collisions: Hard Sphere, Lennard-Jones potential, and ab initio. The matrices of the kinetic coefficients have been obtained for different values of the rarefaction parameters and molar fraction of non-sublimating gas. The influence of the intermolecular potential on the kinetic coefficients as well as on the gas macroscopic profiles has been analyzed. © 2020 Elsevier LtdThe work of A. Polikarpov was financially supported by the Ministry of Science and Higher Education of the Russian Federation, the research project no. FEUZ-2020-0057. I. Graur would like to acknowledge the financial support provided by the European Union network program H2020, MIGRATE project under Grant Agreement No. 643095. F. Sharipov acknowledges the Brazilian Agency CNPq for the support of his research, grant 304831/2018-2

Modern surgical tactic in Mirizzi syndrome

Catedra 2 Chirurgie, USMF „Nicolae Testemiţanu”, Chişinău, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Scopul studiului a fost optimizarea tratamentului chirurgical al fistulelor colecisto-coledociene (sindromului Mirizzi). Material şi metode: Pe parcursul ultimilor 20 de ani în Clinica 2 Chirurgie au fost trataţi 64 (0,24%) pacienţi cu sindromul Mirizzi dintr-un lot total de 26.530 cazuri de colecistită calculoasă. Rezultate: Sonografic am apreciat prezenţa stazei biliare, a unui colecist deformat cu lipsa unui coraport obişnuit cu CBP, prezenţa colecistului „călăreţ” pe CBP. Diagnosticul topic a fost stabilit prin ERCP în 46 (71,8%) cazuri. Din ele în 10 (15,6%) observaţii am recurs adăugător la CRMN, care a soluţionat în 100% situaţia diagnostică dată. În celelalte 8 (12,5%) cazuri diagnosticul s-a stabilit intraoperator. Tratamentul chirurgical a inclus obligatoriu: înlăturarea fistulei colecistocoledociene şi coledocolitotomie. Aşa în 27 (42,1%) cazuri, unde defectul parietal coledocian a fost sub 1/3 din diametrul lui, am finisat intervenţia cu un drenaj tip Kehr al CBP. Pentru 8 (12,5%) observaţii, la care defectul coledocian a fost de 2/3 din diametru, am rezolvat situaţia prin plastia CBP cu lambou vascularizat din vezica biliară şi un eventual drenaj al CBP după Vişnevskii. La 19 (29,6%) pacienţi vezica biliară şi CBP formau o cavitate comună cu calculi biliari în lumen. La toţi aceşti pacienţi am efectuat colecistectomie cu coledocolitotomie şi coledocojejunoanastomoză pe ansa jejunală izolată a la Roux. Cazuri letale portoperatorii nu au fost. Concluzii: Sindromul Mirizzi este una din cele mai nefavorabile evoluţii a colecistitei calculoase, ce necesită un program de diagnostic complex şi o atitudine chirurgicală strict individuală.Aim of the study was to optimize surgical treatment of Mirizzi syndrome. Material and methods: In the last 20 years in surgical departament no.2 were treated 64 (0.24%) patients with Mirizzi syndrome from total of 26.530 cases of cholelithiasis. Results: We appreciated sonographic bile stasis, presence of a deformed gallbladder, lack of co-report CBP accustomed to the presence of gallbladder „rider” on CBP. The topical diagnosis was established by CPGRE in 46 (71.8%) cases, in 10 (15.6%) cases we used additionally to CNMR, which settled 100% once the diagnostic situation, in the other eight (12.5%) cases the diagnosis has been established intraoperatively. Surgical treatment included mandatory removal of colecistocoledocian fistula and coledocolitotomie. In 27 (42.1%) cases where the parietal duct defect was under 1/3 of circumference, the intervention was finished with a Kehr drainage of CBP. In eight (12.5%) cases the defect was 2/3 of the duct diameter, we have solved the situation by CBP plasty with vascularized flap of gallbladder and CBP drainage by Vishnevski. In 19 (29.6%) patients gallbladder and CBP were a gallstone in the common cavity lumen. In all patients we performed cholecystectomy with coledocolitotomy and coledocojejunostomy on isolated Roux jejunal loop. Postoperative lethality has not been determined. Conclusions: Mirizzi syndrome is one of the worst developments of cholelithiasis, which requires a complex diagnostic program and a strictly individual surgical tactics