Testing Hereditary Properties of Sequences

A hereditary property of a sequence is one that is preserved when restricting to subsequences. We show that there exist hereditary properties of sequences that cannot be tested with sublinear queries, resolving an open question posed by Newman et al. This proof relies crucially on an infinite alphabet, however; for finite alphabets, we observe that any hereditary property can be tested with a constant number of queries

Variable Pathways for Oxygen Atom Insertion into Metal-Carbon Bonds: The Case of Cp*W(O)₂(CH₂SiMe₃)

Article discussing variable pathways for oxygen atom insertion into metal-carbon bonds and the case of Cp*W(O)2(CH2SiMe3)

Variable Pathways for Oxygen Atom Insertion into Metal–Carbon Bonds: The Case of Cp*W(O)₂(CH₂SiMe₃)

Cp*W­(O)₂(CH₂SiMe₃) (<b>1</b>) (Cp* = η⁵-pentamethylcyclopentadienyl) reacts with oxygen atom donors (e.g., H₂O₂, PhIO, IO₄^–) in THF/water to produce TMSCH₂OH (TMS = trimethylsilyl). For the reaction of <b>1</b> with IO₄^–, the proposed pathway for alcohol formation involves coordination of IO₄^– to <b>1</b> followed by concerted migration of the −CH₂TMS ligand to the coordinated oxygen of IO₄^– with concomitant dissociation of IO₃^– to produce Cp*W­(O)₂(OCH₂SiMe₃) (<b>3</b>), which undergoes protonolysis to yield free alcohol. In contrast to the reaction with IO₄^–, the reaction of <b>1</b> with H₂O₂ results in the formation of the η²-peroxo complex Cp*W­(O)­(η²-O₂)­(CH₂SiMe₃) (<b>2</b>). In the presence of acid (HCl) or base (NaOH), complex <b>2</b> produces TMSCH₂OH. The conversion of <b>2</b> to TMSCH₂OH catalyzed by Brønsted acid is proposed to occur through protonation of the η²-peroxo ligand, which facilitates the transfer of the −CH₂TMS ligand to a coordinated oxygen of the η²-hydroperoxo ligand. In contrast, the hydroxide promoted conversion of <b>2</b> to TMSCH₂OH is proposed to involve hydroxide coordination, followed by proton transfer from the hydroxide ligand to the peroxide ligand to yield a κ¹-hydroperoxide intermediate. The migration of the −CH₂TMS ligand to the coordinated oxygen of the κ¹-hydroperoxo produces an alkoxide complex, which undergoes protonolysis to yield free alcohol

The formation of low-temperature sedimentary pyrite and its relationship with biologically-induced processes

This contribution is an updated review on sedimentary pyrite and on its role in well-consolidated research topics, such as the biogeochemical cycles and the studies on sediment-hosted ore deposit studies, as well as new frontiers of research, such as astrobiology. Textural and compositional information preserved in sedimentary pyrite from sediment-hosted ore deposits has contributed to elucidate their environment of forzmation. In particular, the content of redox-sensitive elements such as Ni, Co, Mo, and V has implications for defining the syn- and post-sedimentary conditions. In addition, the stable isotope compositions are useful indicators of the pathways of both biogenic and abiogenic pyrite formation. Despite the longstanding research on pyrite and the mechanism of its formation, there are still significant gaps in our knowledge. In this nonexhaustive review, we briefly touch on different current aspects of research on sedimentary pyrite, exemplifying how sedimentary pyrite remains relevant to geoscientists, and becomes more and more relevant in understanding some basic aspects of knowledge, such as the origin of life and the search for extraterrestrial life, as well as aspect of classical applied science, such as the implications for ore deposition

Comparative Effects of Therapy With Captopril and Digoxin in Patients With Mild to Moderate Heart Failure

This multicenter, double-blind, placebo-controlled study compares the effects of captopril treatment with those of digoxin treatment during maintenance diuretic therapy in patients with mild to moderate heart failure. Compared with placebo, captopril therapy resulted in significantly improved exercise time (mean increase, 82 s vs 35 s) and improved New York Heart Association class (41% vs 22%), but digoxin therapy did not. Digoxin treatment increased ejection fraction (4.4% increase) compared with captopril therapy (1.8% increase) and placebo (0.9% increase). The number of ventricular premature beats decreased 45% in the captopril group and increased 4% in the digoxin group in patients with more than ten ventricular premature beats per hour. Treatment failures, increased requirements for diuretic therapy, and hospitalizations were significantly more frequent in patients receiving placebo compared with those receiving either active drug. Transitory hypotension occurred more frequently with administration of captopril. Captopril treatment is significantly more effective than placebo and is an alternative to digoxin therapy in patients with mild to moderate heart failure who are receiving diuretic maintenance therapy.(JAMA 1988;259:539-544