A magnetically powered nanomachine with a DNA clutch.

Machines found in nature and human-made machines share common components, such as an engine, and an output element, such as a rotor, linked by a clutch. This clutch, as seen in biological structures such as dynein, myosin or bacterial flagellar motors, allows for temporary disengagement of the moving parts from the running engine. However, such sophistication is still challenging to achieve in artificial nanomachines. Here we present a spherical rotary nanomotor with a reversible clutch system based on precise molecular recognition of built-in DNA strands. The clutch couples and decouples the engine from the machine's rotor in response to encoded inputs such as DNA or RNA. The nanomotor comprises a porous nanocage as a spherical rotor to confine the magnetic engine particle within the nanospace (∼0.004 µm3) of the cage. Thus, the entropically driven irreversible disintegration of the magnetic engine and the spherical rotor during the disengagement process is eliminated, and an exchange of microenvironmental inputs is possible through the nanopores. Our motor is only 200 nm in size and the clutch-mediated force transmission powered by an embedded ferromagnetic nanocrystal is high enough (∼15.5 pN at 50 mT) for the in vitro mechanical activation of Notch and integrin receptors, demonstrating its potential as nano-bio machinery.

Hydrogel Magnetomechanical Actuator Nanoparticles for Wireless Remote Control of Mechanosignaling In Vivo.

As a new enabling nanotechnology tool for wireless, target-specific, and long-distance stimulation of mechanoreceptors in vivo, here we present a hydrogel magnetomechanical actuator (h-MMA) nanoparticle. To allow both deep-tissue penetration of input signals and efficient force generation, h-MMA integrates a two-step transduction mechanism that converts magnetic anisotropic energy to thermal energy within its magnetic core (i.e., Zn0.4Fe2.6O4 nanoparticle cluster) and then to mechanical energy to induce the surrounding polymer (i.e., pNiPMAm) shell contraction, finally delivering forces to activate targeted mechanoreceptors. We show that h-MMAs enable on-demand modulation of Notch signaling in both fluorescence reporter cell lines and a xenograft mouse model, demonstrating its utility as a powerful in vivo perturbation approach for mechanobiology interrogation in a minimally invasive and untethered manner.

Constrained Sintering in Fabrication of Solid Oxide Fuel Cells.

Solid oxide fuel cells (SOFCs) are inevitably affected by the tensile stress field imposed by the rigid substrate during constrained sintering, which strongly affects microstructural evolution and flaw generation in the fabrication process and subsequent operation. In the case of sintering a composite cathode, one component acts as a continuous matrix phase while the other acts as a dispersed phase depending upon the initial composition and packing structure. The clustering of dispersed particles in the matrix has significant effects on the final microstructure, and strong rigidity of the clusters covering the entire cathode volume is desirable to obtain stable pore structure. The local constraints developed around the dispersed particles and their clusters effectively suppress generation of major process flaws, and microstructural features such as triple phase boundary and porosity could be readily controlled by adjusting the content and size of the dispersed particles. However, in the fabrication of the dense electrolyte layer via the chemical solution deposition route using slow-sintering nanoparticles dispersed in a sol matrix, the rigidity of the cluster should be minimized for the fine matrix to continuously densify, and special care should be taken in selecting the size of the dispersed particles to optimize the thermodynamic stability criteria of the grain size and film thickness. The principles of constrained sintering presented in this paper could be used as basic guidelines for realizing the ideal microstructure of SOFCs.

Accelerated sintering in phase-separating nanostructured alloys.

Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W-Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs.

Ectopic insertion of the pectoralis minor tendon: inter-reader agreement and findings in the rotator interval on MRI.

OBJECTIVE: To evaluate magnetic resonance imaging (MRI) observer variability to detect ectopic insertion of the pectoralis minor tendon (EIPMT) and to investigate changes in the rotator interval in patients with EIPMT using MRI. MATERIALS AND METHODS: A total of 507 shoulder MRIs (male:female = 259:248; mean age, 55.4 years) were classified into 1) normal type insertion of the pectoralis minor tendon, 2) complete type EIPMT, and 3) partial type EIPMT independently by two radiologists. Inter-observer agreement was calculated using the kappa coefficient. Thickness of the fibrotic scar tissue in the subcoracoid triangle and humeral side axillary recess was measured. MRIs were reviewed by consensus with regard to the grade of fibrotic scar tissue proliferation in the rotator interval. Comparisons were made between normal and EIPMT and between partial and complete type EIPMT. RESULTS: The incidence of EIPMT was 13.4% (complete type, 7.7%; partial type, 5.7%). Inter-observer agreement was substantial (κ = 0.775). Fibrotic scar tissue in the subcoracoid triangle was thicker, and the grade of fibrotic scar tissue proliferation in the rotator interval was higher in the EIPMT group than those in the control group. No significant difference was observed in the thickness of humeral side axillary recess. The thicknesses of fibrotic scar tissue in the subcoracoid triangle and humeral side axillary recess as well as the grade of fibrotic scar tissue in the rotator interval were not significantly different between complete and partial type EIPMT. CONCLUSION: MRI enabled detection of EIPMT with substantial observer agreement. Patients with EIPMT show a high tendency for fibrotic scar tissue proliferation in the rotator interval.

Morphometric analysis of maxillary alveolar regions for immediate implantation.

PURPOSE: The purpose of this study was to provide an actual guideline in determining the shape, diameter, and position of the implant in immediate implantation by the measurement of the thickness of facial and palatal plate, the thickness of cortical bone on the facial and palatal plate, the diameter of the root, and the distance between the roots in the cadavers. MATERIALS AND METHODS: The horizontal sections of 20 maxillae were measured and analyzed to obtain the average values. Resin blocks were produced and cut serially at 1 mm intervals from the cervical line to the root apex. Images of each section were obtained and the following measurements were performed: The thickness of the facial and palatal residual bone at each root surface, the thickness of the facial and palatal cortical bone at the interdental region, the diameter of all roots of each section on the faciopalatal and mesiodistal diameter, and the interroot distance. Three specimens with measurements close to the average values were chosen and 3-dimensional images were reconstructed. RESULTS: The thickness of the facial and palatal cortical bone at the interdental region in the maxilla, the buccal cortical bone was thicker in the posterior region compared to the anterior region. The interroot distance of the alveolar bone thickness between the roots increased from anterior to posterior region and from coronal to apical in the maxilla. CONCLUSION: In this study, the limited results of the morphometric analysis of the alveolar ridge using the sections of maxilla in the cadavers may offer the useful information when planning and selecting optimal implant for immediate implantation in the maxilla.

Alveolar regions of the mandible for the installation of immediate-implant fixtures and bone screws of alveolar distractors.

The purposes of this study were to elucidate the anatomic relationship between the dental roots and surrounding tissues and to identify the optimal sites at which to install dental surgical devices including immediate-implant fixtures and alveolar distractors. We made 5 types of measurements on horizontal cross sections obtained at 1-mm intervals from 20 Korean mandibles. The following results were obtained: (1) the mandibular facial plate was thinnest at the canine (0.5-0.7 mm) and became thicker toward the molar region; (2) the thicknesses of the facial and lingual cortical bone in the interdental region increased from anterior to posterior and from coronal to apical aspects; (3) in each section, the buccolingual root was narrower than 4 mm at depths greater than 8 and 9 mm in the central and lateral incisors, respectively, and the maximum mesiodistal root widths were 3.0 and 3.3 mm; (4) the interroot distance increased from anterior to posterior and from coronal to apical aspects; and (5) on the sections of the first and second molars, the diameter of the septal bone ranged from 4.2 to 7.9 mm buccolingually and from 1.3 to 3.3 mm mesiodistally. Achieving successful placements of implant fixtures and bone screws requires an accurate understanding of the anatomic structure at the installation site. The reported anatomic data might facilitate successful treatments and provide crucial information for use when planning and performing placements of dental surgical devices.

High-dose immunosuppressive therapy and autologous peripheral blood stem cell transplantation for severe multiple sclerosis.

There were 26 patients enrolled in a pilot study of high-dose immunosuppressive therapy (HDIT) for severe multiple sclerosis (MS). Median baseline expanded disability status scale (EDSS) was 7.0 (range, 5.0-8.0). HDIT consisted of total body irradiation, cyclophosphamide, and antithymocyte globulin (ATG) and was followed by transplantation of autologous, granulocyte colony-stimulating factor (G-CSF)-mobilized CD34-selected stem cells. Regimen-related toxicities were mild. Because of bladder dysfunction, there were 8 infectious events of the lower urinary tract. One patient died from Epstein-Barr virus (EBV)-related posttransplantation lymphoproliferative disorder (PTLD) associated with a change from horse-derived to rabbit-derived ATG in the HDIT regimen. An engraftment syndrome characterized by noninfectious fever with or without rash developed in 13 of the first 18 patients and was associated in some cases with transient worsening of neurologic symptoms. There were 2 significant adverse neurologic events that occurred, including a flare of MS during mobilization and an episode of irreversible neurologic deterioration after HDIT associated with fever. With a median follow-up of 24 (range, 3-36) months, the Kaplan-Meier estimate of progression (>/= 1.0 point EDSS) at 3 years was 27%. Of 12 patients who had oligoclonal bands in the cerebrospinal fluid at baseline, 9 had persistence after HDIT. After HDIT, 4 patients developed new enhancing lesions on magnetic resonance imaging of the brain. The estimate of survival at 3 years was 91%. Important clinical issues in the use of HDIT and stem cell transplantation for MS were identified; however, modifications of the initial approaches appear to reduce treatment risks. This was a heterogeneous high-risk group, and a phase 3 study is planned to fully assess efficacy.