Using optical measurements, we demonstrate that the rotation of micron-scale graphene nanoplatelets levitated in a quadrupole ion trap in high vacuum can be frequency locked to an applied radio frequency electric field E rf . Over time, frequency locking stabilizes the nanoplatelet so that its axis of rotation is normal to the nanoplatelet and perpendicular to E rf . We observe that residual slow dynamics of the direction of the axis of rotation in the plane normal to E rf are determined by an applied magnetic field. We present a simple model that accurately describes our observations. From our data and model we can infer both a diamagnetic polarizability and a magnetic moment proportional to the frequency of rotation, which we compare to theoretical values. Our results establish that trapping technologies have applications for materials measurements at the nanoscale. * These authors contributed equally to this work. P.N. is currently
Clinical trials of novel salvage therapies have encouraging outcomes for relapsed/refractory transplant‐eligible classic Hodgkin lymphoma (R/R cHL) but comparison with conventional chemotherapy is lacking. Herein, we report the final analysis of a multicenter retrospective cohort of R/R cHL assessing outcomes by type of salvage therapy before autologous stem cell transplant (ASCT). R/R cHL patients who underwent ASCT at 14 institutions across the United States were included. Outcomes were compared among patients receiving conventional chemotherapy, brentuximab vedotin (BV) + chemotherapy, BV alone, and a checkpoint inhibitor (CPI)‐based regimens before ASCT. Study endpoints included event‐free survival (EFS), progression‐free survival (PFS), and overall survival (OS). All endpoints are defined from relapse. Of 936 patients, 728 received conventional chemotherapy, 73 received BV + chemotherapy, 70 received BV alone, and 65 received CPI‐based regimens prior to ASCT. When adjusted for time to relapse, pre‐ASCT response and use of BV maintenance, patients receiving CPI‐based regimens had superior 2‐year EFS compared to conventional chemotherapy, BV + chemotherapy, and BV alone (79.7, 49.6, 62.3, and 36.9%, respectively, p < .0001). Among 649 patients transplanted after 1 line of salvage therapy, CPI‐based regimens were associated with superior 2‐year PFS compared to conventional chemotherapy (98% vs. 68.8%, hazard ratio: 0.1, 95% confidence interval: 0.03–0.5, p < .0001). OS did not differ by pre‐ASCT salvage regimen. In this large multicenter retrospective study, CPI‐based regimens improved EFS and PFS compared to other salvage regimens independent of pre‐ASCT response. These data support earlier sequencing of CPI‐based regimens in R/R cHL in the pre‐ASCT setting.
We discuss the design and implementation of a system for generating charged multilayer graphene nanoplatelets and introducing a nanoplatelet into a quadrupole ion trap in high vacuum. Levitation decouples the platelet from its environment and enables sensitive mechanical and magnetic measurements. The platelets are generated via liquid exfoliation of graphite pellets and charged via electrospray ionization. A single platelet is trapped at a pressure of several hundred millitorr and transferred to a trap in a second chamber, which is pumped to UHV pressures for further study.
Cyclopenta-2,4-dienyl)cyclopentyl trichloroacetate (I) can be converted into the same polymer (A) as is obtained from cyclopentadiene. This is due to the occurrence of two consecutive reactions, the first leading from cyclopentadiene to the ester (I), and the second, slower reaction, giving polymer (A). A kinetic investigation of this polymerisation has been carried out and the degree (n) of polymerisation under different conditions determined. The results are compatible with proton-transfer in the initiation and incorporation of the ester (I) into growing carbonium-ion pairs during propagation and termination. It is suggested that all steps involve hydrogen shifts and that propagation and termination are accompanied by elimination of trichloroacetic acid. This mechanism accounts for the observed kinetics and n values, and for the formation of non-linear species containing a short and a long sequence of conjugated double bonds.THE preceding paper describes trichloroacetic acid-catalysed reactions of substances containing endocyclic double bonds in five-membered rings, which lead to deeply coloured polymers of unusual properties. An attempt is now made to elucidate the mechanism of one of these polymerisations. The formation of one polymer, termed (A),l was selected for study because the starting material, cyclopentadiene, is easily available and because this polymer has been more extensively investigated than the other products.This paper deals with the stoicheiometry of the polymerisation which is formally, but not kinetically, a polycondensation, with the degree and rate of polymerisation, and with oxidative degradation. A detail of general interest is a method of calculus used for solution of a differential rate equation relating to two consecutive reactions. EXPERIMENTALThe preparation of 3-(cyclopenta-2,4-dienyl)cyclopentyltricliloroacetate (I), the purification of trichloroacetic acid, cyclopentadiene, solvents, and added substances, removal of traces of peroxides, optical density measurements in absence of atmospheric oxygen, electrical conductancc measurements and electrometric titrations have been described elsewhere.l-'j Spectrophotometric and conductometric measurements showed that the ester (I) contained less than 2% of polymer (A). The equivalent weight of the ester was always somewhat lower than the theoretical value, owing to the presence of free acid, probably trichloroacetic acid (cf. below). The term N E in equation ( 5 ) (below) is the sum of the number of moles of ester (I) and of free acid. In measuring the rate of polymerisation of ester (I), by titrating liberated trichloroacetic acid, a correction was made for the free acid present in the ester a t the start of the run. Titrations of liberated acid were carried out in benzene-ethanol or carbon tetrachloride-ethanol with in-dicator~,*~*~ or electrometrically 1, if the solution was intensely coloured. In most experiments alcoholic potassium hydroxide was used, an excess of alkali being avoided. Control experiments with isopentylamine in benz...
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