Μm3 In Size Research Articles

Three-Dimensional Optical Imaging of Internal Deformations in Polymeric Microscale Mechanical Metamaterials.

Recent advances in two-photon polymerization fabrication processes are paving the way to creating macroscopic metamaterials with microscale architectures, which exhibit mechanical properties superior to their bulk material counterparts. These metamaterials typically feature lightweight, complex patterns such as lattice or minimal surface structures. Conventional tools for investigating these microscale structures, such as scanning electron microscopy, cannot easily probe the internal features of these structures, which are critical for a comprehensive assessment of their mechanical behavior. In turn, we demonstrate an optical confocal microscopy-based approach that allows for high-resolution optical imaging of internal deformations and fracture processes in microscale metamaterials under mechanical load. We validate this technique by investigating an exemplary metamaterial lattice structure of 80 × 80 × 80 μm3 in size. This technique can be extended to other metamaterial systems and holds significant promise to enhance our understanding of their real-world performance under loading conditions.

Formin-mediated nuclear actin at androgen receptors promotes transcription.

Steroid hormone receptors are ligand-binding transcription factors essential for mammalian physiology. The androgen receptor (AR) binds androgens mediating gene expression for sexual, somatic and behavioural functions, and is involved in various conditions including androgen insensitivity syndrome and prostate cancer1. Here we identified functional mutations in the formin and actin nucleator DAAM2in patients with androgen insensitivity syndrome. DAAM2 was enriched in the nucleus, where its localization correlated with that of the AR to form actin-dependent transcriptional droplets in response to dihydrotestosterone. DAAM2 AR droplets ranged from 0.02 to 0.06 µm3 in size and associated with active RNA polymerase II. DAAM2 polymerized actin directly at the AR to promote droplet coalescence in a highly dynamic manner, and nuclear actin polymerization is required for prostate-specific antigen expression in cancer cells. Our data uncover signal-regulated nuclear actin assembly at a steroid hormone receptor necessary for transcription.

Cationic Pb2 Dumbbells Stabilized in the Highly Covalent Lead Nitridosilicate Pb2Si5N8

Due to the weak oxidative force of N2 , nitrides are only typically formed with the less electronegative metals. Meeting this challenge, we here present Pb2 Si5 N8 , the first nitridosilicate containing highly electron-affine cations of a metal from the right side of the Zintl border. By using advanced synchrotron X-ray diffraction, the crystal structure was determined from a tiny single crystal of 1×3×3 μm3 in size, revealing a significantly different bonding situation compared to all other nitridosilicates known so far. Indeed, DFT calculations confirm distinct amounts of covalency not only between Pb and N but also between formal Pb2+ cations. Thus, unprecedented cationic Pb2 dumbbells with a stretching vibration at 117 cm-1 were found in Pb2 Si5 N8 , the first representative of a crystallographically elucidated lead nitride, stabilized by high amounts of covalency.

Cationic Pb2 Dumbbells Stabilized in the Highly Covalent Lead Nitridosilicate Pb2Si5N8

AbstractDue to the weak oxidative force of N2, nitrides are only typically formed with the less electronegative metals. Meeting this challenge, we here present Pb2Si5N8, the first nitridosilicate containing highly electron‐affine cations of a metal from the right side of the Zintl border. By using advanced synchrotron X‐ray diffraction, the crystal structure was determined from a tiny single crystal of 1×3×3 μm3 in size, revealing a significantly different bonding situation compared to all other nitridosilicates known so far. Indeed, DFT calculations confirm distinct amounts of covalency not only between Pb and N but also between formal Pb2+ cations. Thus, unprecedented cationic Pb2 dumbbells with a stretching vibration at 117 cm−1 were found in Pb2Si5N8, the first representative of a crystallographically elucidated lead nitride, stabilized by high amounts of covalency.

Preparation of fine single crystals of magnetic superconductor RuSr2GdCu2O8−δ by partial melting

In this study, fine uniform RuSr2GdCu2O8−δ (RuGd-1212) single crystals have been successfully prepared by partial melting. Synthesis temperature could be lowered to a value not exceeding the decomposition temperature of RuGd-1212 using the Sr–Gd–Cu–O flux. The crystals grown by alumina boats are cubic, which coincides with the result of a previous study of RuGd-1212 single crystals using platinum crucibles. The single crystals were up to 15 × 15 × 15 µm3 in size and their lattice constants were consistent with those of polycrystalline samples reported previously. Although the present size of single crystals is not sufficient for measurements, the partial melting technique will be beneficial for future progress of research using RuGd-1212 single crystals. Appropriate nominal composition, sintering atmosphere, and temperature are essential factors for growing RuGd-1212 single crystals.

3D imaging of the early embryonic chicken heart with focused ion beam scanning electron microscopy.

Early embryonic heart development is a period of dynamic growth and remodeling, with rapid changes occurring at the tissue, cell, and subcellular levels. A detailed understanding of the events that establish the components of the heart wall has been hampered by a lack of methodologies for three-dimensional (3D), high-resolution imaging. Focused ion beam scanning electron microscopy (FIB-SEM) is a novel technology for imaging 3D tissue volumes at the subcellular level. FIB-SEM alternates between imaging the block face with a scanning electron beam and milling away thin sections of tissue with a FIB, allowing for collection and analysis of 3D data. FIB-SEM was used to image the three layers of the day 4 chicken embryo heart: myocardium, cardiac jelly, and endocardium. Individual images obtained with FIB-SEM were comparable in quality and resolution to those obtained with transmission electron microscopy. Up to 1,100 serial images were obtained in 4 nm increments at 4.88 nm resolution, and image stacks were aligned to create volumes 800-1,500 μm3 in size. Segmentation of organelles revealed their organization and distinct volume fractions between cardiac wall layers. We conclude that FIB-SEM is a powerful modality for 3D subcellular imaging of the embryonic heart wall.

Mechanical failure begins preferentially near resorption cavities in human vertebral cancellous bone under compression

The amount of bone turnover in the body has been implicated as a factor that can influence fracture risk and bone strength. Here we test the idea that remodeling cavities promote local tissue failure by determining if microscopic tissue damage (microdamage) caused by controlled loading in vitro is more likely to form near resorption cavities. Specimens of human vertebral cancellous bone (L4, 7 male and 2 female, age 70±10, mean±SD) were loaded in compression to the yield point, stained for microscopic tissue damage and submitted to three-dimensional fluorescent imaging using serial milling (image voxel size 0.7×0.7×5.0μm). We found the resulting damage volume per bone volume (DV/BV) was correlated with percent eroded surface (p<0.01, r2=0.65), demonstrating that whole specimen measures of resorption cavities and microdamage are related. Locations of microdamage were more than two times as likely to have a neighboring resorption cavity than randomly selected sites without microdamage (relative risk 2.39, 95% confidence interval of relative risk: 2.09–2.73), indicating a spatial association between resorption cavities and microdamage at the local level. Individual microdamage sites were 48,700 (40,100; 62,700) μm3 in size (median, 25th and 75th percentiles). That microdamage was associated with resorption cavities when measured at the whole specimen level as well as at the local level provides strong evidence that resorption cavities play a role in mechanical failure processes of cancellous bone and therefore have the potential to influence resistance to clinical fracture.

Intrinsic magnetic properties of the superconductor NdFeAsO0.9F0.1 from local and global measurements

Magneto-optical imaging was used to study the local magnetization in polycrystalline NdFeAsO0.9F0.1 (NFAOF). Individual crystallites up to ∼200×100×30 μm3 in size could be mapped at various temperatures. The in-grain, persistent current density is about j∼105A cm−2 and the magnetic relaxation rate in a remanent state peaks at about Tm∼38 K. By comparison with the total magnetization measured in a bar-shaped, dense, polycrystalline sample, we suggest that NdFeAsO0.9F0.1 is similar to high-Tc cuprates, in between Bi2Sr2CaCu2O8+x and YBa2Cu3O7- x in terms of the vortex response in the mixed state. We find an apparent crossover in the pinning strength at ∼38 K that could be associated either with vortex decoupling or melting. Below this temperature the static and dynamic vortex behavior is consistent with the collective pinning and creep.

Micro-probe raman studies of the dynamics of liquid crystals

We present a modified version of a Raman microspectroscope designed for dynamical studies of thin liquid-crystalline films in glass cells. This system is based on a confocal geometry and a multi-channel liquid nitrogen cooled CCD detector. The confocal arrangement makes possible the study of volumes only a few μm3 in size within a liquid-crystal cell with an axial resolution of 14 μm. The multi-channel detector allows high quality spectra to be recorded in a few seconds with less than 10 mW of laser power at the sample. Using an electrooptic modulator, dynamic studies can be done on a microsecond time scale. We present results obtained during the electrical switching of a anti-ferroelectric liquid-crystalline low molar mass organosiloxane material.

A New Time-Resolved Raman Microspectrometer for the Study of Liquid-Crystalline Materials in Thin Cells

A new Raman microspectroscope was designed for the study of thin liquid-crystalline films in glass cells. This system is based on a confocal geometry and a multi-channel liquid nitrogen cooled CCD detector. The confocal arrangement makes possible the study of volumes only a few μm3 in size within a liquid-crystal cell with an axial resolution of 7 μm. The mutli-channel detector allows high quality spectra to be recorded in less than a second with only a few milliwatts of laser power at the sample. Using an electro-optic modulator, dynamic studies can be done on the millisecond scale or smaller. We present the first results obtained with this technique of the electrical switching of a ferroelectric liquid-crystalline low molar mass organosiloxane material.

In Situ Detection and Identification of Trace Explosives by Raman Microscopy

Abstract The innovative design of the newly developed Renishaw Raman Microscope system and its application to the in situ detection and identification of plastic explosives contained in fingerprint samples are presented. Raman microscopy is a nondestructive inspection method. Our experimental results show that Raman spectra and Raman band images can be obtained from explosive particles as small as 1 µm3 in size or 1 picogram in mass. After exploring the full potential of the Raman microscopic technique, the aim of this research is to develop a real-time and field-deployable plastic explosive detection system.

Thermal bubble powered microactuators

Thermal bubble powered micro mechanical actuators have been successfully demonstrated in working liquids. Micro mechanical plates which function as the mechanical actuators are 70×60×2 μm3 in size. They have been fabricated by surface-micromachining technology and suspended 2 μm above the substrate by the supports of cantilever beams. Micro thermal bubbles which are generated by heavily phosphorus doped polysilicon line resistive heaters have been used to lift the mechanical plates in a controllable manner. The typical current required to generate a single, spherical thermal bubble as the actuation source on top of the micro line resistors (60×2×0.3 μm3 in size) is 8.4 mA (80 m Watt) in FC 43 liquid (an inert, dielectrical fluid available from the 3M company). The thermal bubbles have been demonstrated to actuate the mechanical plate perpendicularly to the substrate with a maximum elevation distance of 140 μm and a maximum actuation force of 2 μN. This new actuation mechanism is expected to find applications for micro fluidic devices.

Viability of Heterotrophic Bacteria in Freshwater

The viabilities of planktonic bacteria from nine freshwaters and one raw sewage were compared. Viabilities estimated from microcolony formation in slide culture (18·4–48·7%) were higher than a conventional plate count method (1·8–14·9%). Microcolony viability was estimated in four ways; the one recommended was the ratio of the microcolony count and total count of microcolonies and single cells after 24 or 72 h incubation. Bacterial viability strongly correlated with the percentage of bacteria &lt;0·2 μm3 in size and the concentration of soluble carbohydrate in the water.