Discriminating schizophrenia and schizo-obsessive disorder: a structural MRI study combining VBM and machine learning methods

Schizo-obsessive disorder is characterized by the clinical syndrome in which comorbid obsessive–compulsive disorder accompanies schizophrenia. A substantial number of studies have investigated the neuropsychological and clinical differences between schizophrenia and schizo-obsessive disorder. However, the neurostructural differences between these two groups have not been adequately investigated. The aim of this study was to explore gray matter differences between schizophrenia and schizo-obsessive patients using voxel-based morphometry and support vector machines combined with feature selection algorithm. Twenty-three schizophrenia and 23 schizo-obsessive patients matched by age, gender and handedness were recruited. Clinical assessments were completed in addition to high-resolution structural MRI scanning. Group differences were investigated using contrast maps, and significant regions were subjected to a feature selection and support vector machine hybrid model. In addition, voxel-of-interest values for the commonly shared brain areas between schizophrenia and OCD reported in previous meta-analyses were also used as inputs in this step. The results showed that schizo-obsessive patients had greater gray matter densities in paracentral areas (including supplementary motor area) and middle cingulate gyrus than schizophrenia patients. These brain areas together with the fronto-subcortical areas could successfully discriminate two groups with an accuracy of 78.26 %. Our results provide the first neuroanatomical evidence that schizo-obsessive disorder and schizophrenia may be two distinct clinical entities. Based on these findings, considering schizo-obsessive disorder as a subtype of schizophrenia is discernible.

     

Annealing effects on the mechanical properties of near-frictionless carbon thin films

In this work, the near-frictionless carbon (NFC) thin films developed at Argonne National Laboratory were annealed at 100 °C, 150 °C, 200 °C, 400 °C, and 600 °C in nitrogen atmosphere. The changes of the NFC mechanical properties were measured with both static and dynamic nanoindentation methods. It was found that the Young's modulus and hardness decreased with increasing annealing temperatures. Raman spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the film's structural change before nanoindentation testing. Raman characterization indicated that the G peak shifted upwards as the annealing temperature was increased above 150 °C, which indicated decreasing sp³ content. The intensity of the D peak was shown to increase with annealing temperature indicating that the NFC film became more graphite-like. AFM analysis showed an increase of sp² clustering with annealing temperature, which resulted in an increase in surface roughness. SEM characterization indicated that as the films were annealed large cracks and numerous pinholes were generated. The characterization results were in good agreement with the measured mechanical properties.     

An adaptive angular sweep algorithm for value set construction

The generalized mapping theorem provides a means to synthesize convex-hull generator points for uncertain polynomials and transfer functions. However, its application requires maximizing a projection onto a unit ray over a uniform grid of angles, which is inefficient and ignores the errors associated with a finite grid. The algorithm developed in the paper addresses both of these issues by characterizing errors and synthesizing generator points only when needed to meet a given convergence tolerance     

Electrochemical boriding and characterization of AISI D2 tool steel

D2 is an air-hardening tool steel and due to its high chromium content provides very good protection against wear and oxidation, especially at elevated temperatures. Boriding of D2 steel can further enhance its surface mechanical and tribological properties. Unfortunately, it has been very difficult to achieve a very dense and uniformly thick boride layers on D2 steel using traditional boriding processes. In an attempt to overcome such a deficiency, we explored the suitability and potential usefulness of electrochemical boriding for achieving thick and hard boride layers on this tool steel in a molten borax electrolyte at 850, 900, 950 and 1000 °C for durations ranging from 15 min to 1 h. The microstructural characterization and phase analysis of the resultant boride layers were performed using optical, scanning electron microscopy and X-ray diffraction methods. Our studies have confirmed that a single phase Fe₂B layer or a composite layer consisting of FeB + Fe₂B is feasible on the surface of D2 steel depending on the length of boriding time. The boride layers formed after shorter durations (i.e., 15 min) mainly consisted of Fe₂B phase and was about 30 μm thick. The thickness of the layer formed in 60 min was about 60 μm and composed mainly of FeB and Fe₂B. The cross sectional micro-hardness values of the boride layers varied between 14 and 22 GPa, depending on the phase composition.     

The growth of single Fe2B phase on low carbon steel via phase homogenization in electrochemical boriding (PHEB)

In this study, we introduce a new electrochemical boriding method that results in the formation of a single-phase Fe₂B layer on low carbon steel substrates. Although FeB phase is much harder and more common than Fe₂B in all types of boriding operations, it has very poor fracture toughness; hence, it can fracture or delaminate easily from the surface under high normal or tangential loading. We call the new method “phase homogenization in electrochemical boriding” (PHEB), in which carbon steel samples undergo electrochemical boriding for about 15 min at 950 °C in a molten electrolyte consisting of 90% borax and 10% sodium carbonate, then after the electrical power to the electrodes is stopped, the samples are left in the bath for an additional 45 min without any polarization. The typical current density during the electrochemical boriding is about 200 mA/cm². The total original thickness of the resultant boride layer after 15 min boriding was about 60 μm (consisting of 20 μm FeB layer and 40 μm Fe₂B layer); however, during the additional phase homogenization period of 45 min, the thickness of the boride layer increased to 75 μm and consisted of only Fe₂B phase, as confirmed by glancing-angle x-ray diffraction and scanning electron microscopy in backscattering mode. The microscopic characterization of the boride layers revealed a dense, homogeneous, thick boride layer with microhardness of about 16 GPa. The fracture behavior and adhesion of the boride layer were evaluated by the Daimler-Benz Rockwell C test and found to be excellent, i.e., consistent with an HF1 rating.     

Paraoxonase 1-bound magnetic nanoparticles: preparation and characterizations

This is most probably the first time that covalently binding of Human serum paraoxonase 1 (PON1) to superparamagnetic magnetite nanoparticles via carbodiimide activation was investigated and presented in this study. PON1 was purified from human serum using ammonium sulfate precipitation and hydrophobic interaction chromatography (Sepharose 4B, L-tyrosine, 1-Napthylamine) and magnetic iron oxide nanoparticles were prepared by co-precipitation Fe(+2) and Fe(+3) ions in an ammonia solution at room temperature. X-ray diffraction (XRD) and the magnetic measurements showed that the nanoparticles are magnetite and superparamagnetic, respectively. Direct measurements by dynamic light scattering revealed that the hydrodynamic size was 16.76 nm with polydispersity index (PDI: 0.234). The analysis of Fourier transform infrared spectroscopy revealed that the PON1 was properly bound to magnetic nanoparticles replacing the characteristic band of -NH2 at 1629 cm(-1) with the protein characteristic band at 1744 cm(-1) and 1712 cm(-1). Magnetic measurements determined that PON1-bound nanoparticles have also favorable superparamagnetic properties with zero coercivity and remanence though a slightly smaller saturation magnetization due to the decrease of magnetic moment in the volume friction. The kinetic measurements indicated the PON1-bound nanoparticles retained 70% of its original activity and exhibited an improved stability than did the free enzyme. The PON1 enzyme is seen to be quite convenient to bind superparamagnetic nanoparticles as support material.     

Influence of tribofilm on superlubricity of highly-hydrogenated amorphous carbon films in inert gaseous environments

In this study, we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon (a-C:H) film in order to ascertain the underlying mechanisms for its superlubric behavior (i.e., less than 0.01 friction coefficient). Specifically, we achieved superlubricity (i.e., friction coefficients of down to 0.003) with this film in dry nitrogen and argon atmospheres especially when the tribo-pair is made of an a-C:H coated Si disk sliding against an a-C:H coated steel ball, while the a-C:H coated disk against uncoated ball does not provide superlubricity. We also found that the state of superlubricity is more stable in argon than in nitrogen and the formation of a smooth and uniformly-thick carbonaceous tribofilm appears to be one of the key factors for the realization of such superlubricity. Besides, the interfacial morphology of sliding test pairs and the atomic-scale bond structure of the carbon-based tribofilms also play an important role in the observed superlubric behavior of a-C:H films. Using Raman spectroscopy and high resolution transmission electron microscopy, we have compared the structural differences of the tribofilms produced on bare and a-C:H coated steel balls. For the a-C:H coated ball as mating material which provided superlow friction in argon, structural morphology of the tribofilm was similar or comparable to that of the original a-C:H coating; while for the bare steel ball, the sp²-bonded C fraction in the tribofilm increased and a fingerprint-like nanocrystalline structure was detected by high resolution transmission electron microscopy (HRTEM). We also calculated the shear stresses for different tribofilms, and established a relationship between the magnitude of the shear stresses and the extent of sp³-sp² phase transformation.     

Environmental effects on the friction of hydrogenated DLC films

We have investigated environmental effects on hydrogenated diamond-like carbon (H-DLC) films under various pressures of H₂O, O₂, and N₂ by ultrahigh vacuum (UHV) tribometry. The H-DLC film exhibits an ultralow coefficient of friction (μ = 0.004 in UHV). The μ value increases with increasing pressure of H₂O and O₂. Specifically, μ increases up to 0.07 under 10 Torr of H₂O, and up to 0.03 under 150 Torr of O₂; these are typical H₂O and O₂ contents respectively in ambient air. Our results are consistent with similar environmental effects previously reported. But, we have also discovered that these friction changes are reversible, returning to the ultralow value when UHV is restored. The reversibility of the friction behavior in both environments, coupled with the lack of evidence of tribochemical changes by Auger electron spectroscopy, suggest that the observed friction changes are due to the weakly adsorbed gas molecules that influence the friction property by physically separating the H-DLC interface. Speed-dependent tribometry also supports this argument. In addition, two DLC films with different hydrogen contents and with widely different friction coefficients in UHV are shown to exhibit identical μ values under humid environments, further demonstrating that the frictional properties of these DLC films are essentially determined by the surface layer of adsorbed gas molecules.     

Investigation of Initial and Steady-State Sliding Behavior of a Nearly Frictionless Carbon Film by Imaging 2- and 3-D TOF-SIMS

Using imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS), we investigated the initial and steady-state sliding behavior of a nearly frictionless carbon (NFC) film. Specifically, TOF-SIMS images (both 2-D and 3-D) of these surfaces were constructed to highlight the spatial distributions of ionized and molecular species that were present on as-received and friction-tested NFC surfaces and as a function of depth. As a complementary technique, we used X-ray photoelectron spectroscopy (XPS) to gain further insight into the chemical nature of the sliding surfaces. The NFC films were produced on Si wafers and steel substrates in a gas discharge plasma that consisted of 25 vol.% methane and 75 vol.% hydrogen using a plasma-enhanced chemical vapor deposition (PECVD) system. They were then subjected to sliding friction and wear experiments in a pin-on-disk machine under 5- and 10-N loads and at sliding velocities of 0.2–0.5 m/s in dry nitrogen. The initial friction coefficients of the NFC films were in the range of 0.05–0.1, but decreased rapidly to values less than 0.01 at steady state. Positive and negative TOF-SIMS spectra and 2- and 3-D images reconstructed from selected masses revealed that the elemental distribution of certain chemical species differs substantially between undisturbed and tribo-tested areas of the NFC films. Specifically, the tribo-tested areas are essentially made up of carbon and hydrogen, while undisturbed or as-received areas are covered by a layer that is rich in oxygen and other species. These findings correlate well with the initial and steady-state friction coefficients of these films and help further explain their superlubricity in inert test environments.