First ray mobility in hallux rigidus, hallux valgus, and normal feet based on weightbearing computed tomography and three-dimensional analysis: A case-control study.

BACKGROUND: Hallux valgus and hallux rigidus are disorders affecting the first ray and are associated with hypermobility of this structure. This study aimed to investigate the three-dimensional mobility of each joint of the first ray between feet with hallux valgus or hallux rigidus and healthy feet using weightbearing and nonweightbearing computed tomography (CT). METHODS: This case-control study analyzed 17 feet of 11 healthy volunteers (control group), 16 feet of 16 patients with hallux valgus (HV group), and 16 feet of 11 patients with hallux rigidus (HR group). First, nonweightbearing foot CT imaging was performed in the supine position on a loading device with no load applied, with the legs extended and the ankle in the neutral position. Next, a load equivalent to body weight was applied for weightbearing CT imaging. Distal bone displacement relative to the proximal bone was quantified three-dimensionally under both conditions. RESULTS: In the HV group, the talonavicular joint showed significantly greater eversion (P = 00.011) compared with the control group and significantly greater dorsiflexion (P = 00.027) and eversion (P < 00.01) compared with the HR group. In the medial cuneiform joint, the HV group showed significantly greater eversion (P < 00.01) and abduction (P = 00.011) than the control group. For the first tarsometatarsal joint, the HV group showed significantly greater dorsiflexion (P = 00.014), inversion (P = 00.028), and adduction (P < 00.01) than the control group, and greater inversion (P < 00.01) and adduction (P < 00.01) than the HR group. Dorsiflexion of the first tarsometatarsal joint was significantly greater in the HR group compared with the control group (P = 00.026). CONCLUSION: Hypermobility of the first ray appears to be three-dimensional: in hallux valgus, it is centered at the first tarsometatarsal joint, while in hallux rigidus it is mainly in the sagittal plane at the first tarsometatarsal joint only. This difference may explain the different deformities ultimately observed in each condition.

Electron-Transfer Activity in a Cyanide-Bridged Fe42 Nanomagnet.

The ability to switch a molecule between different magnetic states is of considerable importance for the development of new molecular electronic devices. Desirable properties for such applications include a large-spin ground state with an electronic structure that can be controlled via external stimuli. Fe42 is a cyanide-bridged stellated cuboctahedron of mixed-valence Fe ions that exhibits an extraordinarily large S = 45 spin ground state. We have found that the spin ground state of Fe42 can be altered by controlling the humidity and temperature. Dehydration results in a 15 µB reduction of the saturation magnetization that can be partially recovered upon rehydration. The complementary use of UV-vis, IR, L2,3-edge X-ray absorption spectroscopy and X-ray magnetic circular dichroism is applied to uncover the mechanism for the observed dynamic behavior. It is identified that dehydration is concurrent with metal-to-metal electron transfer between Fe pairs via a cyanide π hybridization. Upon dehydration, electron transfer occurs from low-spin {FeII(Tp)(CN)3} sites to high-spin FeIII centers. The observed reduction in magnetization upon dehydration of Fe42 is inconsistent with a ferrimagnetic ground state and is proposed to originate from a change in zero-field splitting at electron-reduced high-spin sites.

Giant Exchange Coupling Evidenced with a Magnetization Jump at 52 T for a Gadolinium-Nitroxide Chelate.

The Gd-radical complex [GdIII(hfac)3(6bpyNO)] (6bpyNO = 2,2'-bipyridin-6-yl tert-butyl nitroxide; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) showed a magnetization jump at 52 T observed in a pulsed-field facility, corresponding to an exchange coupling constant of -17.4 K. Furthermore, hysteretic behavior due to a relatively slow magnetization reversal was recorded around 2 T. From the high-frequency EPR study, the exchange coupling between Gd and radical spins accompanies an anisotropic character, which is responsible for both the broad jump and the slow magnetization reversal.

Electronic Structure of a Mixed-Metal Fluoride-Centered Triangle Complex: A Potential Qubit Component.

A novel fluoride-centered triangular-bridged carboxylate complex, [Ni2Cr(µ3-F)(O2C(t)Bu)6(HO2C(t)Bu)3] (1), is reported. Simple postsynthetic substitution of the terminal pivalic acids in 1 with pyridine and 4-methylpyridine led to the isolation of [Ni2Cr(µ3-F)(O2C(t)Bu)6(C5H5N)3] (2) and [Ni2Cr(µ3-F)(O2C(t)Bu)6((4-CH3)C5H4N)3] (3). Structural and magnetic characterizations carried out on the series reveal a dominating antiferromagnetic interaction between the nickel and chromium centers leading to an S = (1)/2 ground state with a very unusual value of geff = 2.48.

Spin frustration from cis-edge or -corner sharing metal-centered octahedra.

A new strategy using cis-edge or -corner sharing metal-centered octahedra is described which enables interesting frustrated spin lattices to be targeted. The examination of "CuV2" triangular motifs in the two new compounds [enH2]Cu(H2O)2[V2O2F8] (1) and [Cu(H2O)(2,2'-bpy)]2[V2O2F8] (2) (where enH2 = ethylenediammonium and 2,2'-bpy =2,2'-bipyridyl) reveals that the [VOF4](2-) anions, which exhibit cis structure directing properties, lead to frustrated lattices owing to the competing ferro and antiferromagnetic interactions. There is direct coordination through two cis F(-) ligands (i.e., the F(-) ligand trans to O(2-) and one equatorial F(-) ligand) in both 1 and 2 owing to the significant π-bonding between the vanadium and the oxide ligand. We emphasize that most of triangular motifs reported in the literature are built of cis-edge or -corner sharing metal-centered octahedra, thus they can be used to target new materials exhibiting interesting magnetism such as spin frustration.

Three-Dimensional Analysis of the Windlass Mechanism Using Weightbearing Computed Tomography in Healthy Volunteers.

BACKGROUND: The windlass mechanism (WM) increases the longitudinal arch of the foot via tension of the plantar aponeurosis during dorsiflexion of the metatarsophalangeal (MTP) joint. The purpose of this study was to perform a 3-dimensional evaluation of the displacement of each joint and the height of the navicular during dorsiflexion of the first MTP joint by using weightbearing computed tomography (CT). METHODS: Participants were 6 men and 8 women with 23 healthy feet. CT of the foot with a load equivalent to the participant's body weight was performed. The first MTP joint was in the neutral position and dorsiflexed 30 degrees. Between the conditions, we measured the (1) rotation of each bone, (2) rotation of the distal bone with respect to the proximal bone at each joint, and (3) height of the navicular. RESULTS: With respect to the tibia, the calcaneus was at 0.8 ± 0.7 degrees dorsiflexion and 1.4 ± 0.9 degrees inversion, while the talus was at 2.0 ± 1.2 degrees dorsiflexion and 0.1 ± 0.8 degrees eversion. The navicular was at 1.3 ± 1.2 degrees dorsiflexion and 3.2 ± 2.1 degrees inversion, whereas the medial cuneiform was at 0.3 ± 0.6 degrees plantarflexion and 1.3 ± 1.1 degrees inversion. At the talonavicular joint, the navicular was at 0.7 ± 1.3 degrees plantarflexion, whereas at the cuneonavicular joint, the medial cuneiform bone was at 1.4 ± 1.4 degrees plantarflexion. The height of the navicular increased by 1.1 ± 0.6 mm. CONCLUSION: We 3-dimensionally confirmed the dynamics of WM and found that the calcaneus, navicular, and medial cuneiform moved in all 3 planes. The results suggest that the cuneonavicular joint has the greatest movement among the joints. We believe that these findings will help to elucidate the pathogenesis of WM-related diseases and lead to advances in treatments for pathologies involving the longitudinal arch. LEVEL OF EVIDENCE: Level IV, case series.

Characterization of photoinduced normal state through charge density wave in superconducting YBa2Cu3O6.67.

The normal state of high-Tc cuprates has been considered one of the essential topics in high-temperature superconductivity research. However, compared to the high magnetic field study of it, understanding a photoinduced normal state remains elusive. Here, we explore a photoinduced normal state of YBa2Cu3O6.67 through a charge density wave (CDW) with time-resolved resonant soft x-ray scattering, as well as a high magnetic field x-ray scattering. In the nonequilibrium state where people predict a quenched superconducting state based on the previous optical spectroscopies, we experimentally observed a similar analogy to the competition between superconductivity and CDW shown in the equilibrium state. We further observe that the broken pairing states in the superconducting CuO2 plane via the optical pump lead to nucleation of three-dimensional CDW precursor correlation. Ultimately, these findings provide a critical clue that the characteristics of the photoinduced normal state show a solid resemblance to those under magnetic fields in equilibrium conditions.

Capacitive detection of magnetostriction, dielectric constant, and magneto-caloric effects in pulsed magnetic fields.

We report on the development of a capacitance measuring system that allows measurements of capacitance in pulsed magnetic fields up to 61 T. By using this system, magnetic-field responses of various physical quantities, such as magnetostriction, magnetic-field-induced change in complex dielectric constant, and magneto-caloric effect, can be investigated in pulsed-magnetic-field conditions. Here, we examine the validity of our system for investigations of these magnetic-field-induced phenomena in pulse magnets. For the magnetostriction measurement, magnetostriction of a specimen can be measured through a change in the capacitance between two aligned electrodes glued on the specimen and a dilatometer. We demonstrate a precise detection of valley polarization in semimetallic bismuth through a magnetostriction signal with a resolution better than 10-6 of the relative length change. For the magnetic-field-induced change in complex dielectric constant, we successfully observed clear dielectric anomalies accompanied by magnetic/magnetoelectric phase transitions in multiferroic Pb(TiO)Cu4(PO4)4. For the measurement of magneto-caloric effect, a magnetic-field-induced change in sample temperature was verified for Gd3Ga5O12 with a capacitance thermometer made of a non-magnetic ferroelectric compound KTa1-xNbxO3 (x = 0.02) whose capacitance is nearly field-independent. These results show that our capacitance measuring system is a promising tool to study various magnetic-field-induced phenomena, which have been difficult to detect in pulsed magnetic fields.

Magnetoresistance and Thermal Transformation Arrest in Pd2Mn1.4Sn0.6 Heusler Alloys.

The magnetization, electric resistivity, and magnetoresistance properties of Pd 2 Mn 1 . 4 Sn 0 . 6 Heusler alloys were investigated. The Curie temperature of the parent phase, martensitic transformation temperatures, and magnetic field dependence of the martensitic transformation temperatures were determined. The magnetoresistance was investigated from 10 to 290 K, revealing both intrinsic and extrinsic magnetoresistance properties for this alloy. A maximum of about - 3 . 5 % of intrinsic magnetoresistance under 90 kOe and of about - 30 % of extrinsic magnetoresistance under 180 kOe were obtained. Moreover, the thermal transformation arrest phenomenon was confirmed in the Pd 2 Mn 1 . 4 Sn 0 . 6 alloy, and an abnormal heating-induced martensitic transformation (HIMT) behavior was observed.