Search for a bound di-neutron by comparing 3^3He(e,e'p)d and 3^3H(e,e'p)X measurements

We report on a search for a bound di-neutron by comparing electron-induced proton-knockout $(e,e'p)$ measurements from Helium-3 ($^3$He) and Tritium ($^3$H). The measurements were performed at Jefferson Lab Hall A with a 4.326 GeV electron beam, and kinematics of large momentum transfer $Q^2 \approx 1.9$ (GeV/$c$)$^2$ and $x_B>1$, to minimize contributions from non quasi-elastic (QE) reaction mechanisms. Analyzing the measured $^3$He missing mass ($M_{miss}$) and missing energy ($E_{miss}$) distributions, we can distinguish the two-body break-up reaction, in which the residual proton-neutron system remains bound as a deuteron. In the $^3$H mirror case, under the exact same kinematic conditions, we do not identify a signature for a bound di-neutron with similar binding energy to that of the deuteron. We calculate exclusion limits as a function of the di-neutron binding energy and find that, for binding equivalent to the deuteron, the two-body break-up cross section on $^3$H is less than 0.9% of that on $^3$He in the measured kinematics at the 95% confidence level.Comment: 6 pages, 3 figure

Heteroleptic copper(I) sensitizers with one versus two hole-transporting units in functionalized 2,9-dimethyl-1,10-phenanthroline ancillary ligands

A series of homoleptic [Cu(L)2][PF6] complexes in which L is a 2,9-dimethyl-1,10-phenanthroline fused at the 5,6-positions with a 2′-functionalized imidazole (ligands 1–4), or substituted at the 4,7-positions with electron-donating 4-(diphenylamino)phenyl groups (ligand 5) is described; the imidazole 2′-functionality in 1 is 4-bromophenyl, in 2 is 4-(diphenylamino)phenyl, in 3 is 4-(bis(4-n-butoxy)phenylamino)phenyl, and in 4 is 4-(carbazol-9-yl)phenyl. The copper complexes were characterized by mass spectrometry, NMR and absorption spectroscopies and cyclic voltammetry; the single crystal structure of ligand 4 has been determined. Compared to the solution absorption spectra of [Cu(1)2][PF6], [Cu(2)2][PF6], [Cu(3)2][PF6] and [Cu(4)2][PF6], that of [Cu(5)2][PF6] shows increased absorbance at wavelengths >375 nm. An on-surface strategy was used to assemble heteroleptic [Cu(6)(L)]+ dyes on TiO2 electrodes where 6 is ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid); solid-state absorption spectra confirmed enhanced light-harvesting between 375 and 600 nm for [Cu(6)(5)]+ with respect to [Cu(6)(1)]+, [Cu(6)(2)]+, [Cu(6)(3)]+ and [Cu(6)(4)]+. Comparison of the performances of dye-sensitized solar cells (DSCs) containing [Cu(6)(2)]+, [Cu(6)(3)]+ and [Cu(6)(4)]+ with those with [Cu(6)(1)]+ indicate only a marginal influence of the diphenylamine or carbazole hole-transporting domains in 5,6-substituted phenanthroline dyes. The introduction of the 4-(diphenylamino)phenyl hole-transporting units in the 4- and 7-positions of the phen unit in 5 proves to be beneficial, with DSCs containing [Cu(6)(5)]+ performing better than those with the other four dyes; duplicate DSCs were tested for each dye to validate the results. While the values of the maximum external quantum efficiencies (EQEmax) for [Cu(6)(1)]+ and [Cu(6)(4)]+ are greater than for [Cu(6)(5)]+, the extension of the EQE spectrum for [Cu(6)(5)]+ to longer wavelengths results in higher short-circuit current densities (JSC) compared to DSCs with [Cu(6)(1)]+, [Cu(6)(2)]+, [Cu(6)(3)]+ and [Cu(6)(4)]+

Phyteumosides A and B: New saponins with unique triterpenoid aglycons from Phyteuma orbiculare L.

Phyteumosides A (1) and B (2), two saponins with unprecedented triterpenoid aglycons were isolated from the aerial parts of Phyteuma orbiculare (Campanulaceae). Their structures were elucidated by spectroscopic and chemical methods, and corroborated by X-ray diffraction analyses of the aglycons obtained through enzymatic hydrolysis. The aglycon of 1 can be considered as an incompletely cyclized onoceroid or gammaceroid triterpene with two additional tetrahydropyran rings arising from oxygen bridges. Compound 2 possesses a new 17-polypodene aglycon

A pilot study of prophylactic donor lymphocyte infusions to prevent relapse in adult acute lymphoblastic leukemias after allogeneic hematopoietic stem cell transplantation

The outcome of patients with acute lymphoblastic leukemia (ALL) receiving therapeutic donor lymphocyte infusions (DLIs) in relapse after stem cell transplantation (SCT) is poor. We analyzed the impact of prophylactic DLIs in ALL on chimerism and sustained complete remission (CR). Eighty-five patients with ALL were allografted between January 1998 and September 2004. Twenty-six of them received prophylactic DLIs and were included in this analysis. A total of 12 of 13 patients, who were treated with mixed chimerism (MC) converted to complete donor chimerism (92%) and 10 of 12 patients had persistent donor chimerism and sustained CR during subsequent follow-up. Overall, 18 of 26 patients developed graft-versus-host disease (GVHD) after DLIs (69%), acute GVHD in 46 and chronic GVHD in 62%. After a median follow-up of 42 months (14-72) after SCT, 18 of 26 patients (70%) are alive, 16 in CR. Probability of event-free survival (EFS) for patients treated with DLIs is 62%, and overall survival is 70% at 3 years. Our preliminary data support a graft-versus-leukemia effect of prophylactic DLIs able to induce stable donor chimerism and ongoing CR after SCT. As the accompanying GVHD rate was considerable, careful selection of patients for prophylactic DLIs is mandatory