Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from ttˉt\bar t production at the Tevatron

We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in $t\bar t$ production in dilepton final states using 9.7 fb$^{-1}$ of proton-antiproton collisions at $\sqrt{s}=1.96$ TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible $t\bar t$ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of $A^{t\bar t} = (15.0 \pm 6.4 \text{ (stat)} \pm 4.9 \text{ (syst)})\%$ and a top-quark polarization times spin analyzing power in the beam basis of $\kappa P = (7.2 \pm 10.5 \text{ (stat)} \pm 4.2 \text{ (syst)})\%$, with a correlation of $-56\%$ between the measurements. If we constrain the forward-backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of $\kappa P = (11.3 \pm 9.1 \text{ (stat)} \pm 1.9 \text{ (syst)})\%.$ If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of $A^{t\bar t} = (17.5 \pm 5.6 \text{ (stat)} \pm 3.1 \text{ (syst)})\%.$ A combination with the D0 $A^{t\bar t}$ measurement in the lepton+jets final state yields an asymmetry of $A^{t\bar t} = (11.8 \pm 2.5 \text{ (stat)} \pm 1.3 \text{ (syst)})\% .$ Within their respective uncertainties, all these results are consistent with the standard model expectations.Comment: 16 pages, 16 figures, published versio

Inclusive production of the X(4140)X(4140) state in pp‾p \overline p collisions at D0

We present a study of the inclusive production of the $X(4140)$ with the decay to the $J/\psi \phi$ final state in hadronic collisions. Based on $10.4~\rm{fb^{-1}}$ of $p \overline p$ collision data collected by the D0 experiment at the Fermilab Tevatron collider, we report the first evidence for the prompt production of $X(4140)$ and find the fraction of $X(4140)$ events originating from $b$ hadrons to be $f_b=0.39\pm 0.07 {\rm \thinspace (stat)} \pm 0.10 {\rm \thinspace (syst)}$. The ratio of the non-prompt $X(4140)$ production rate to the $B_s^0$ yield in the same channel is $R=0.19 \pm 0.05 {\rm \thinspace (stat)} \pm 0.07 {\rm \thinspace (syst)}$. The values of the mass $M=4152.5 \pm 1.7 (\rm {stat}) ^{+6.2}_{-5.4} {\rm \thinspace (syst)}$~MeV and width $\Gamma=16.3 \pm 5.6 {\rm \thinspace (stat)} \pm 11.4 {\rm \thinspace (syst)}$~MeV are consistent with previous measurements. 8 pages, 2 figuesComment: Submitted to PRL. * pages, 2 figure

Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting

We measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in top-antitop to lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/- 0.85(syst) GeV.Comment: 10 pages, 2 figures, 2 tables, subm. to Phys. Lett.

Efficient C(sp³)−H Carbonylation of Light and Heavy Hydrocarbons with Carbon Monoxide via Hydrogen Atom Transfer Photocatalysis in Flow

Despite their abundance in organic molecules, considerable limitations still exist in synthetic methods that target the direct C−H functionalization at sp3-hybridized carbon atoms. This is even more the case for light alkanes, which bear some of the strongest C−H bonds known in Nature, requiring extreme activation conditions that are not tolerant to most organic molecules. To bypass these issues, synthetic chemists rely on prefunctionalized alkyl halides or organometallic coupling partners. However, new synthetic methods that target regioselectively C−H bonds in a variety of different organic scaffolds would be of great added value, not only for the late-stage functionalization of biologically active molecules but also for the catalytic upgrading of cheap and abundant hydrocarbon feedstocks. Here, we describe a general, mild and scalable protocol which enables the direct C(sp3)−H carbonylation of saturated hydrocarbons, including natural products and light alkanes, using photocatalytic hydrogen atom transfer (HAT) and gaseous carbon monoxide (CO). Flow technology was deemed crucial to enable high gas-liquid mass transfer rates and fast reaction kinetics, needed to outpace deleterious reaction pathways, but also to leverage a scalable and safe process.</p

Myelopexy: A novel technique in posttraumatic syringomyelia

Posttraumatic syringomyelia (PTS) is a well-reported phenomenon that usually takes place in the long-term course of patients following spinal cord injury. Different surgical procedures have been described: spinal cordectomy is usually a last option technique, but might be an excellent choice in patients with severe spinal cord injuries. We present a young patient with complete spinal cord injury after spine trauma, who developed posttraumatic syringomyelia with progressive motor deterioration twelve years after fixation. We performed a novel surgical technique (myelopexy) with excellent resolution of syringomyelia, sparing the negative implications of complete cord transection. Some artistic illustrations made by one of the corresponding authors are included, to better understanding of operative details. La siringomielia postraumática (SPT) es un fenómeno bien documentado, que suele ocurrir en la recuperación a largo plazo de los pacientes después de una lesión de la médula espinal. Se han descrito diferentes procedimientos quirúrgicos: la cordectomía de la médula espinal es generalmente una técnica que se considera como última opción, pero podría ser una excelente elección para pacientes con lesiones graves en dicha zona. Presentamos el caso de un paciente joven con una lesión completa de la médula espinal después de un traumatismo de la columna vertebral, que desarrolló una siringomielia postraumática con un deterioro motor progresivo 12 años después de la fijación. Aplicamos una novedosa técnica quirúrgica (mielopexia) con una excelente resolución de la siringomielia, evitando las implicaciones negativas de la transección completa de la médula. Se incluyen algunas ilustraciones realizadas por uno de los autores para una mejor comprensión de los detalles de la intervención quirúrgica

Lighting-Induced Changes in Central and Peripheral Retinal Thickness and Shape after Short-Term Reading Tasks in Electronic Devices

Background: To assess retinal and optical changes associated with near vision reading for different lighting conditions in electronic screens. Methods: Twenty-four young healthy subjects participated in the study; an iPad and an Ebook were chosen as stimuli for 5 min of reading task with different lighting conditions. Central and peripheral retinal thicknesses in the macular ETDRS areas by optical coherence tomography were analyzed. Results: Significant differences were found between basal retinal thickness and retinal thickness after reading with iPad and high illumination, in the N6 (p = 0.021) and I6 (p = 0.049) areas, and low illumination (S3: p = 0.008, N3: p = 0.018, I3: p = 0.021, N6: p = 0.018 and I6: p = 0.020), being thinner after reading. The same trend was observed after reading with an Ebook and high lighting in the N3 (p = 0.037) and N6 (p = 0.028). For low lighting conditions, only retinal thinning was observed. After reading, retinal shape analysis revealed significant changes from computed basal eccentricity for high lighting conditions only. At the periphery, those differences in eccentricity values were statistically significant for both lighting conditions. Conclusions: Young people can recover visual quality after 5 min of reading tasks at different lighting levels on electronic devices, while peripheral retinal expansion remains altered, especially at low lighting levels

Cyclopentadienyl iron dicarbonyl styrene chalcogenosulfonates: synthesis and structure of CpFe(CO)(2)SeSO2CH=CHPh

In this contribution, we report the preparation of iron thiosulfonato complex CpFe(CO)(2)SSO2CH=CHPh (1) and its selenosulfonato analogue CpFe(CO)(2)SeSO2CH=CHPh (2) featuring styrene moiety. 1 and 2 are obtained by electrophilic attack of (mu-E-x)CpFe(CO)(2)](2) (E = S; x = 2-4, E = Se; x = 1) on the sulfur atom of styrene sulfonyl chloride ClSO2CH=CHPh. The new compounds, 1 and 2 have been characterized by elemental analyses, IR, H-1-, C-13{H-1}-NMR, UV-Vis spectroscopy and the structure of 2 is determined by X-ray crystallography

Dual role of benzophenone enables a fast and scalable C-4 selective alkylation of pyridines in flow

The efficient C-4 selective modification of pyridines is a major challenge for the synthetic community. Current strategies are plagued with at least one drawback regarding functional group-tolerant electronic activation of the heteroarene, mild generation of the required alkyl radicals, regioselectivity, safety and/or scalability. Herein, we describe a fast, safe and scalable flow process which allows preparation of said C-4 alkylated pyridines. The process involves a photochemical hydrogen atom transfer (HAT) event to generate the carbon-centered radicals needed to alkylate the C-2 blocked pyridine. In a two-step streamlined flow process, this light-mediated alkylation step is combined with a nearly instantaneous inline removal of the blocking group. Notably, cheap benzophenone plays a dual role in the pyridine alkylation mechanism by activating the hydrocarbon feedstock reagents via a HAT mechanism, and by acting as a benign, terminal oxidant. The key role of benzophenone in the operative reaction mechanism has also been revealed through a combination of experimental and computational studies

Twisted One-Dimensional Charge Transfer and Related Y-Shaped Chromophores with a 4 H-Pyranylidene Donor: Synthesis and Optical Properties

Three series of push-pull derivatives bearing 4H-pyranylidene as electron donor group and a variety of acceptors were designed. On one hand, one-dimensional chromophores with a thiophene ring (series 1H) or 5-dimethylaminothiophene moiety (series 1N) as an auxiliary donor, non-coplanar with the p-conjugated system, were synthesized. On the other hand, related two-dimensional (2D) Y-shaped chromophores (series 2) were also prepared to compare how the diverse architectures affect the electrochemical, linear, and second-order nonlinear optical (NLO) properties. The presence of the 5-dimethylaminothiophene moiety in the exocyclic C= C bond of the pyranylidene unit gives rise to oxidation potentials rarely low, and the protonation (with an excess of trifluoroacetic acid) of its derivatives results in the apparition of a new blue-shifted band in the UV-visible spectra. The analysis of the properties of derivatives with and without the additional thiophene ring shows that this auxiliary donor leads to a higher NLO response, accompanied by an enhanced transparency. Y-shaped chromophores of series 2 present a blue-shifted absorption, higher molar extinction coefficients, and higher Eox values compared to their linear twisted counterparts. As concerns NLO properties, 2D Y-shaped architecture gives rise to somewhat lower µß values (except for thiobarbiturate derivatives)

Pyranylidene/trifluoromethylbenzoic acid-based chromophores for dye-sensitized solar cells

The synthesis and photovoltaic study of five dyes based on 4H-pyranylidene moiety as donor moiety is reported. A thiophene unit conjugated with/without an ethynyl bond acts as the p-relay and benzoic acid as the anchor group with/without a trifluoromethyl group. Their electrochemical and optical properties are analyzed by using a joint experimental and theoretical approach. The presence of the trifluoromethyl group leads to an enhancement of the molar extinction coefficient, being slightly when a hexyl chain is introduced in the thiophene ring, but does not modify the oxidation potential. For the preparation of derived solar cells an antiaggregant is essential in all cases. The photovoltaic performance is sensitive to the structural modification of the dye: the CF3 group and the hexyl chain of the thiophene spacer were shown to improve the efficiency. The lack of a triple bond in the p-spacer involves a lower photovoltaic efficiency, and the trifluoromethyl group leads to a lower dye-load, but a decrease of the recombination processes. These results are in accordance with the electrochemistry impedance spectroscopy studies carried out. Moreover, the organic dyes have been also tested with a fluorescent lamp (indoor conditions), leading to an increase of the efficiency, reaching a 36% for the best dye. © 2022 The Author