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Spin-triplet superconductors potentially host topological excitations that are of interest for quantum information processing. We report the discovery of spin-triplet superconductivity in UTe₂, featuring a transition temperature of 1.6 kelvin and a very large and anisotropic upper critical field exceeding 40 teslas. This superconducting phase stability suggests that UTe₂ is related to ferromagnetic superconductors such as UGe₂, URhGe, and UCoGe. However, the lack of magnetic order and the observation of quantum critical scaling place UTe₂ at the paramagnetic end of this ferromagnetic superconductor series. A large intrinsic zero-temperature reservoir of ungapped fermions indicates a highly unconventional type of superconducting pairing.

Magnetism is widely considered to be a key ingredient of unconventional superconductivity. In contrast to cuprate high-temperature superconductors, antiferromagnetism in most Fe-based superconductors (FeSCs) is characterized by a pair of magnetic propagation vectors, ( π ,0) and (0, π ). Consequently, three different types of magnetic order are possible. Of these, only stripe-type spin-density wave (SSDW) and spin-charge-density wave (SCDW) orders have been observed. A realization of the proposed spin-vortex crystal (SVC) order is noticeably absent. We report a magnetic phase consistent with the hedgehog variation of SVC order in Ni-doped and Co-doped CaKFe 4 As 4 based on thermodynamic, transport, structural and local magnetic probes combined with symmetry analysis. The exotic SVC phase is stabilized by the reduced symmetry of the CaKFe 4 As 4 structure. Our results suggest that the possible magnetic ground states in FeSCs have very similar energies, providing an enlarged configuration space for magnetic fluctuations to promote high-temperature superconductivity. Iron-based superconductors: making a hedgehog spin-vortex crystal The magnetic texture of a new superconductor adopts a in-out spin, spin-vortex crystal motif, fulfilling theoretical predictions. Many iron-based superconductors have magnetic phases arising from combining two basic magnetic structures, but only two of three possible combinations had previously been observed. A team led by Paul Canfield of Iowa State University and Ames Laboratory have synthesised a material with the third type of magnetic structure called a hedgehog spin-vortex crystal. The authors began with a compound with spatial symmetry that could help stabilise the structure, but without magnetic order. By tuning the chemical composition they induced magnetism and successfully obtained the desired phase. The sensitivity of the magnetic state to the symmetry and composition indicates that different phases are energetically close, suggesting magnetic fluctuations may play a significant role in the physics of iron-based superconductors.

The report of the first room-temperature, ambient-pressure superconductivity in copper-doped lead apatite Pb10−xCux(PO4)6O has attracted lots of attention. However, subsequent studies revealed the presence of numerous impurity phases in the polycrystalline sample, and the sharp superconducting-like transition is not due to a superconducting transition but most likely due to a reduction in resistivity caused by the first-order structural phase transition of Cu2S at around 385 K from the β phase at high temperature to the γ phase at low temperature. Before now, only bulk measurements have been performed on a Pb10−xCux(PO4)6O powder sample, which could be affected by the impurity phases, masking the intrinsic properties of Pb10−xCux(PO4)6O. In this study, 31P and 63/65Cu nuclear magnetic resonance (NMR) measurements have been performed on a Pb10−xCux(PO4)6O powder sample to investigate its physical properties from a microscopic point of view. Our NMR data evidence the non-magnetic insulating nature of Pb10−xCux(PO4)6O without any trace of electron correlation effects. Furthermore, the 63/65Cu NMR results suggest that no copper or very little copper is substituted for Pb in Pb10(PO4)6O prepared by sintering Pb2SO5 and Cu3P.

Chronic ethanol consumption induces liver diseases, such as alcoholic hepatitis and cirrhosis. The enhancement of alcohol oxidation is important in the prevention of these liver diseases. Chronic supplementation with branched chain amino acids (BCAAs) prevents liver cirrhosis. Therefore, BCAAs may be associated with enhanced ethanol oxidation. To evaluate this hypothesis, we investigated the effect of the administration of individual BCAAs on ethanol oxidation and changes in alcohol-metabolizing enzyme activities following acute alcohol intake in rats. Blood ethanol concentrations and the activities of alcohol-metabolizing enzymes, such as alcohol dehydrogenase (ADH) and low and high Km aldehyde dehydrogenase (ALDH), were measured in the liver following acute ethanol administration in rats; the ethanol was administered 30 min after the treatment with amino acids [such as leucine (Leu), isoleucine (Ile), valine (Val) or alanine (Ala)]. Leu significantly decreased the blood ethanol concentration 1 h after ethanol administration compared to the water-treated control (C) [C 0.46 ± 0.09, Leu 0.18 ± 0.04, Ile 0.27 ± 0.09, Val 0.46 ± 0.1, Ala 0.43 ± 0.06, mean ± SEM (g/l), P < 0.05]. In addition, leucine significantly stimulated ADH activity 30 min after ethanol intake [C 0.042 ± 0.014, Leu 0.090 ± 0.016, Ile 0.042 ± 0.008, Val 0.022 ± 0.010, Ala 0.070 ± 0.016, mean ± SEM (unit/mg protein), P < 0.05] and low Km ALDH activity 15 min after ethanol intake [C 0.51 ± 0.63, Leu 3.72 ± 0.66, Ile 1.26 ± 0.89, Val: ND, Ala 1.86 ± 1.57, mean ± SEM (unit/mg protein), P < 0.05]. However, leucine and its metabolite α-keto-isocaproic acid did not enhance ethanol clearance in isolated rat hepatocytes. These results indicate that leucine accelerates ethanol oxidation by indirectly enhancing ADH and low Km ALDH activities in the liver.

Nuclear magnetic resonance reveals the ground state of frustrated magnets [Also see Report by Fu et al. ] Being able to determine the ground state of a frustrated quantum magnet has been a long-sought goal in condensed matter physics. In general, frustration results from the inability to achieve a desired outcome. In solid-state systems, frustration can arise in relation to electron spin, one of an electron's degrees of freedom. The antiferromagnetic (AFM) interaction between electron spins means that the spins minimize their energy by orienting opposite to their neighbors. For example, if spin A was “up,” spin B would be “down,” antiparallel to spin A. However, introducing the third spin, as in an antiferromagnetically coupled equilateral triangle of electron spins, presents frustration (see the figure, panel A). Here, spin C cannot simultaneously satisfy the up-down interactions with spins A and B. Because spin C cannot achieve its “desired outcome” of being oppositely aligned with both its nearest neighbors, it is “frustrated.” On page 655 of this issue, Fu et al. ( 1 ) investigate the ground state of such a system by using nuclear magnetic resonance (NMR) to measure the intrinsic low-energy spin excitation of the ideal frustrated quantum magnet ZnCu 3 (OH) 6 Cl 2 .

An insect dorsal vessel (DV) is well suited for a bioactuator since it is capable of contracting autonomously, and its tissue and cells are more environmentally robust under culturing conditions compared with mammalian tissue. In this study, electrical pulse stimulation was examined so as to regulate a bioactuator using the DV tissue. The DV tissue of a larva of Ctenoplusia agnate was assembled on a micropillar array, which was stimulated after culturing for about 3 wk. The contraction of the DV tissue was evaluated by image analysis to measure lateral displacements at the micropillar top. As a result, suitable stimulation conditions in a 35-mm petri dish were determined as: applied voltage of 10 V with 20-ms duration. Next, the time lag between the onset of electrical stimulus and the onset of mechanical contraction (electromechanical delay (EMD)) was estimated. A light-emitting diode (LED) was connected serially with the petri dish, and the LED flashed when electrical pulses were given. Movie images were analyzed in which electrical pulses made the DV tissue contract and the LED flashed virtually simultaneously; from these, the EMD was estimated as approximately 50 ms. These results suggest that the electrical pulse stimulation is capable of regulating the DV tissue, and the micropillar array is a useful biological tool to investigate physiological properties of muscle tissue.

We previously reported that in rats, long-term Zn deficiency significantly reduced taste sensitivity and total carbonic anhydrase (CA) activity in the submandibular gland. We therefore investigated the effects of Zn deficiency on salivary secretion and the expressions of CA isozymes (II and VI) in the rat submandibular gland, since those isozymes are thought to be related to taste sensation and salivary secretion. Male Sprague–Dawley rats, age 4 weeks, were divided into three groups (Zn-def, low-Zn and pair-fed, that were fed a diet containing 2·2, 4·1 or 33·7 mg Zn/kg, respectively, for 42 d). Northern blot analysis indicated that Zn deficiency reduced CA II mRNA expression in the submandibular gland without reducing CA VI mRNA expression. In Western blot analysis, Zn deficiency significantly reduced CA II (erythrocyte CA) protein expression in the submandibular gland without reducing CA VI protein expression. Salivary secretion was lower in the Zn-def group than in the pair-fed group. These results suggest that decreased CA isozyme II expression underlies the decreased CA activity previously reported in the submandibular gland in Zn-def rats, and this may reduce regular salivary secretion.

Biotin is a member of the vitamin B-complex family. Biotin deficiency has been associated with hyperglycaemia and insulin resistance in animals and humans. In the present study, we investigated the pharmacological effects of biotin on hypertension in the stroke-prone spontaneously hypertensive rat (SHRSP) strain. We observed that long-term administration of biotin decreased systolic blood pressure in the SHRSP strain; also, a single dose of biotin immediately decreased systolic blood pressure in this strain. Pretreatment with the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazole [4,3-α]quinoxalin-1-one abolished the hypotensive action of biotin in the SHRSP strain, while pretreatment with the NO synthase inhibitor NG-nitro-l-arginine methyl ester had no effect on the action of biotin. Biotin reduced coronary arterial thickening and the incidence of stroke in the SHRSP strain. These results suggest that the pharmacological dose of biotin decreased the blood pressure of the SHRSP via an NO-independent direct activation of soluble guanylate cyclase. Our findings reveal the beneficial effects of biotin on hypertension and the incidence of stroke.

SrMn₂P₂ and CaMn₂P₂ are insulators that adopt the trigonal CaAl₂Si₂-type structure containing corrugated Mn honeycomb layers. Magnetic susceptibility χ and heat capacity versus temperature T data reveal a weak first-order antiferromagnetic (AFM) transition at the Néel temperature T N = 53(1) K for SrMn₂P₂ and a strong first-order AFM transition at T N = 69.8(3) K for CaMn₂P₂. Both compounds exhibit isotropic and nearly T-independent χ(T ≤ T N), suggesting magnetic structures in which nearest-neighbor moments are aligned at ≈120◦ to each other. The 31P NMR measurements confirm the strong first-order transition in CaMn₂P₂ but show critical slowing down above T N for SrMn₂P₂, thus also evidencing second-order character. The 31P NMR measurements indicate that the AFM structure of CaMn₂P₂ is commensurate with the lattice whereas that of SrMn₂P₂ is incommensurate. These first-order AFM transitions are unique among the class of (Ca, Sr, Ba)Mn₂ (P, As, Sb, Bi)₂ compounds that otherwise exhibit second-order AFM transitions. This result challenges our understanding of the circumstances under which first-order AFM transitions occur.