Analysis of quantum conductance of carbon nanotube junctions by the effective mass approximation

The electron transport through the nanotube junctions which connect the different metallic nanotubes by a pair of a pentagonal defect and a heptagonal defect is investigated by Landauer's formula and the effective mass approximation. From our previous calculations based on the tight binding model, it has been known that the conductance is determined almost only by two parameters,i.e., the energy in the unit of the onset energy of more than two channels and the ratio of the radii of the two nanotubes. The conductance is calculated again by the effective mass theory in this paper and a simple analytical form of the conductance is obtained considering a special boundary conditions of the envelop wavefunctions. The two scaling parameters appear naturally in this treatment. The results by this formula coincide fairly well with those of the tight binding model. The physical origin of the scaling law is clarified by this approach.Comment: RevTe

Low-Dose Intravenous Alteplase in Wake-Up Stroke

Background and Purpose—We assessed whether lower-dose alteplase at 0.6 mg/kg is efficacious and safe for acute fluid-attenuated inversion recovery-negative stroke with unknown time of onset. Methods—This was an investigator-initiated, multicenter, randomized, open-label, blinded-end point trial. Patients met the standard indication criteria for intravenous thrombolysis other than a time last-known-well >4.5 hours (eg, wake-up stroke). Patients were randomly assigned (1:1) to receive alteplase at 0.6 mg/kg or standard medical treatment if magnetic resonance imaging showed acute ischemic lesion on diffusion-weighted imaging and no marked corresponding hyperintensity on fluid-attenuated inversion recovery. The primary outcome was a favorable outcome (90-day modified Rankin Scale score of 0–1). Results—Following the early stop and positive results of the WAKE-UP trial (Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke), this trial was prematurely terminated with 131 of the anticipated 300 patients (55 women; mean age, 74.4±12.2 years). Favorable outcome was comparable between the alteplase group (32/68, 47.1%) and the control group (28/58, 48.3%; relative risk [RR], 0.97 [95% CI, 0.68–1.41]; P=0.892). Symptomatic intracranial hemorrhage within 22 to 36 hours occurred in 1/71 and 0/60 (RR, infinity [95% CI, 0.06 to infinity]; P>0.999), respectively. Death at 90 days occurred in 2/71 and 2/60 (RR, 0.85 [95% CI, 0.06–12.58]; P>0.999), respectively. Conclusions—No difference in favorable outcome was seen between alteplase and control groups among patients with ischemic stroke with unknown time of onset. The safety of alteplase at 0.6 mg/kg was comparable to that of standard treatment. Early study termination precludes any definitive conclusions

Roadmap on machine learning in electronic structure

In recent years, we have been witnessing a paradigm shift in computational materials science. In fact, traditional methods, mostly developed in the second half of the XXth century, are being complemented, extended, and sometimes even completely replaced by faster, simpler, and often more accurate approaches. The new approaches, that we collectively label by machine learning, have their origins in the fields of informatics and artificial intelligence, but are making rapid inroads in all other branches of science. With this in mind, this Roadmap article, consisting of multiple contributions from experts across the field, discusses the use of machine learning in materials science, and share perspectives on current and future challenges in problems as diverse as the prediction of materials properties, the construction of force-fields, the development of exchange correlation functionals for density-functional theory, the solution of the many-body problem, and more. In spite of the already numerous and exciting success stories, we are just at the beginning of a long path that will reshape materials science for the many challenges of the XXIth century

Post-translational amino acid conversion in photosystem II as a possible origin of photosynthetic oxygen evolution

How photosynthetic oxygen evolution is originated on ancient Earth is unknown. Here, the authors find that some amino acid residues at the ligand sites of the Mn cluster can be posttranslationally converted to the original carboxylate residues, which could have contributed to the evolutionary process of photosynthetic oxygen evolution

Tumor-Treating Fields Therapy for Pediatric Brain Tumors

Tumor-treating fields (TTFields) are alternating electric fields applied continuously to the brain by attaching two-pair arrays on the scalp. Although TTFields therapy has demonstrated efficacy against supratentorial glioblastoma (GBM) in adults, its safety and efficacy in children have not been confirmed. Despite differences in the genetic etiology of the adult and pediatric forms of GBM, both have certain clinical behaviors in common, allowing us to test TTFields therapy in pediatric GBM. Recently, several, pediatric case-series using TTFields therapy have been published, and a few, prospective, pediatric studies are ongoing. Because GBMs are extremely rare in pediatric patients, where they comprise a wide variety of genetic subtypes, these pediatric studies are feasibility studies targeting various types of malignant brain tumor. Although they are important for confirming the safety and feasibility of TTFields therapy in the pediatric population, confirming its efficacy against each type of pediatric brain tumor, including the GBM, is difficult. Our clinical research team, therefore, planned an investigator-initiated clinical trial targeting pediatric supratentorial GBMs (as in adults) with the aim of expanding regulatory approval of TTFields therapy for pediatric GBM treatment based on safety and exploratory efficacy data in combination with the accumulated evidence on adult GBMs