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  • Artikel  (31.489)
  • American Institute of Physics (AIP)  (31.489)
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  • 1
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    Development of array piezoelectric fingers towards in vivo breast tumor detection (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: We have investigated the development of a handheld 4 × 1 piezoelectric finger (PEF) array breast tumor detector system towards in vivo patient testing, particularly, on how the duration of the DC applied voltage, the depression depth of the handheld unit, and breast density affect the PEF detection sensitivity on 40 patients. The tests were blinded and carried out in four phases: with DC voltage durations 5, 3, 2, to 0.8 s corresponding to scanning a quadrant, a half, a whole breast, and both breasts within 30 min, respectively. The results showed that PEF detection sensitivity was unaffected by shortening the applied voltage duration from 5 to 0.8 s nor was it affected by increasing the depression depth from 2 to 6 mm. Over the 40 patients, PEF detected 46 of the 48 lesions (46/48)—with the smallest lesion detected being 5 mm in size. Of 28 patients (some have more than one lesion) with mammography records, PEF detected 31/33 of all lesions (94%) and 14/15 of malignant lesions (93%), while mammography detected 30/33 of all lesions (91%) and 12/15 of malignant lesions (80%), indicating that PEF could detect malignant lesions not detectable by mammography without significantly increasing false positives. PEF’s detection sensitivity is also shown to be independent of breast density, suggesting that PEF could be a potential tool for detecting breast cancer in young women and women with dense breasts.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 2
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    High repetition pump-and-probe photoemission spectroscopy based on a compact fiber laser system (2016)
    American Institute of Physics (AIP)
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    Publikationsdatum: 2016-12-09
    Beschreibung: The paper describes a time-resolved photoemission (TRPES) apparatus equipped with a Yb-doped fiber laser system delivering 1.2-eV pump and 5.9-eV probe pulses at the repetition rate of 95 MHz. Time and energy resolutions are 11.3 meV and ∼310 fs, respectively, the latter is estimated by performing TRPES on a highly oriented pyrolytic graphite (HOPG). The high repetition rate is suited for achieving high signal-to-noise ratio in TRPES spectra, thereby facilitating investigations of ultrafast electronic dynamics in the low pump fluence ( p ) region. TRPES of polycrystalline bismuth (Bi) at p as low as 30 nJ/mm 2 is demonstrated. The laser source is compact and is docked to an existing TRPES apparatus based on a 250-kHz Ti:sapphire laser system. The 95-MHz system is less prone to space-charge broadening effects compared to the 250-kHz system, which we explicitly show in a systematic probe-power dependency of the Fermi cutoff of polycrystalline gold. We also describe that the TRPES response of an oriented Bi(111)/HOPG sample is useful for fine-tuning the spatial overlap of the pump and probe beams even when p is as low as 30 nJ/mm 2 .
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 3
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    A sparsity-based iterative algorithm for reconstruction of micro-CT images from highly undersampled projection datasets obtained with a synchrotron X-ray source (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: Synchrotron X-ray Micro Computed Tomography (Micro-CT) is an imaging technique which is increasingly used for non-invasive in vivo preclinical imaging. However, it often requires a large number of projections from many different angles to reconstruct high-quality images leading to significantly high radiation doses and long scan times. To utilize this imaging technique further for in vivo imaging, we need to design reconstruction algorithms that reduce the radiation dose and scan time without reduction of reconstructed image quality. This research is focused on using a combination of gradient-based Douglas-Rachford splitting and discrete wavelet packet shrinkage image denoising methods to design an algorithm for reconstruction of large-scale reduced-view synchrotron Micro-CT images with acceptable quality metrics. These quality metrics are computed by comparing the reconstructed images with a high-dose reference image reconstructed from 1800 equally spaced projections spanning 180°. Visual and quantitative-based performance assessment of a synthetic head phantom and a femoral cortical bone sample imaged in the biomedical imaging and therapy bending magnet beamline at the Canadian Light Source demonstrates that the proposed algorithm is superior to the existing reconstruction algorithms. Using the proposed reconstruction algorithm to reduce the number of projections in synchrotron Micro-CT is an effective way to reduce the overall radiation dose and scan time which improves in vivo imaging protocols.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 4
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    Band alignment of MAPb(I1–xBrx)3 thin films by vacuum deposition (2016)
    American Institute of Physics (AIP)
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    Publikationsdatum: 2016-12-09
    Beschreibung: In this work, the mixed bromide iodide lead perovskites CH 3 NH 3 Pb(I 1– x Br x ) 3 (0 ≤  x  ≤ 0.67) thin films were prepared by co-evaporation of CH 3 NH 3 I, PbI 2 , and PbBr 2 . The electronic properties of CH 3 NH 3 Pb(I 1– x Br x ) 3 thin films were investigated by X-ray and ultraviolet photoelectron spectroscopy in-situ . The results of core level binding energy show that there is no chemical shift of the C1s, N1s, Br3d5, and I3d5 when the Br composition changes, while there is an approximately linear chemical shift of Pb4f7 to higher binding energy as the Br composition increases. The density functional theory calculation reveals that there is more charge transfer from Pb to Br than I, which results in the chemical shift of Pb4f states. On the other hand, the valence band maximum increases as the Br composition increases, while the work function shows no obvious change, because the conduction band is dominated by Pb 6 p orbitals while the valence band is dominated by halide p orbitals. Our work demonstrates the adjustability of the energy level alignment of MAPb(I 1– x Br x ) 3 by the Br composition.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
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  • 5
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    Gas viscosity measurement with diamagnetic-levitation viscometer based on electromagnetically spinning system (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: Utilizing a graphite-disk probe attached with a thin aluminum disk, we have developed a friction-free viscosity measurement system. The probe is levitated above a NdFeB magnet because of diamagnetic effect and rotated by an electromagnetically induced torque. The probe is absolutely free form mechanical friction, and therefore, the accurate measurements of the viscosity of gases can be achieved. To demonstrate the accuracy and sensitivity of our method, we measured the viscosity of 8 kinds of gases and its temperature change from 278 K to 318 K, and we confirmed a good agreement between the obtained values and literature values. This paper demonstrates that our method has the ability to measure the fluid viscosity in the order of μ Pa ⋅ s.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 6
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    An ultra-low noise, high-voltage piezo-driver (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: We present an ultra-low noise, high-voltage driver suited for use with piezoelectric actuators and other low-current applications. The architecture uses a flyback switching regulator to generate up to 250 V in our current design, with an output of 1 kV or more possible with small modifications. A high slew-rate op-amp suppresses the residual switching noise, yielding a total root-mean-square noise of ≈100 μ V (1 Hz–100 kHz). A low-voltage (±10 V), high bandwidth signal can be summed with unity gain directly onto the output, making the driver well-suited for closed-loop feedback applications. Digital control enables both repeatable setpoints and sophisticated control logic, and the circuit consumes less than 150 mA at ±15 V.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 7
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    Composition-tuning in a solid-state electrotransport furnace with active thermal expansion compensation (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: A new solid-state electrotransport (SSE) apparatus for refining ultra-pure single crystals of metallic compounds under ultra-high vacuum is described. The setup employs a novel thermal expansion compensation mechanism to minimize mechanical stress on the sample during refinement with cold clamps for contamination-less purification at elevated temperatures. The apparatus is designed to tune the composition of initially slightly off-stoichiometric samples. The expansion compensation and stress-free operation were tested by recording the thermal expansion of elemental cerium in a treatment up to 655 °C. SSE refinement was then performed on a high-quality single crystal of U 6 Fe resulting in a 50% increase of its residual resistivity ratio to the highest value obtained for a single crystal to date.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 8
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    Modulation axis performs circular motion in a 45° dual-drive symmetric photoelastic modulator (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: A 45° dual-drive symmetric photoelastic modulator is demonstrated. Two piezoelectric actuators are connected to a symmetric photoelastic crystal at an angle of 45°. When the amplitudes of the stress standing waves induced by the two piezoelectric actuators are equal and the phase difference between the two stress standing waves is π 2 , the modulation axis performs circular motion with a frequency of half of the photoelastic modulator’s resonant frequency, while the retardation remains a constant that is determined at the driving voltage amplitudes. This reveals a new polarization modulation method. We have theoretically analyzed and experimentally observed the new polarization modulation, and the retardation calibration is also reported.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Publiziert von American Institute of Physics (AIP)
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  • 9
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    Universality in freezing of an asymmetric drop (2016)
    American Institute of Physics (AIP)
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    Publikationsdatum: 2016-12-09
    Beschreibung: We present the evidence of universality in conical tip formation during the freezing of arbitrary-shaped sessile droplets. The focus is to demonstrate the relationship between this universality and the liquid drop shape. We observe that, in the case of asymmetric drops, this universal shape is achieved when the tip reconfigures by changing its location, which subsequently alters the frozen drop shape. The proposed “two-triangle” model quantifies the change in the tip configuration as a function of the asymmetry of the drop that shows a good agreement with the experimental evidence. Finally, based on the experimental and theoretical exercise, we propose the scaling dependence between the variations in the tip configuration and the asymmetry of the drop.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
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  • 10
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    Gain spectroscopy of a type-II VECSEL chip (2016)
    American Institute of Physics (AIP)
    Details
    Publikationsdatum: 2016-12-09
    Beschreibung: Using optical pump–white light probe spectroscopy, the gain dynamics is investigated for a vertical-external-cavity surface-emitting laser chip, which is based on a type-II heterostructure. The active region of the chip consists of a GaAs/(GaIn)As/Ga(AsSb)/(GaIn)As/GaAs multiple quantum well. For this structure, a fully microscopic theory predicts a modal room temperature gain at a wavelength of 1170 nm, which is confirmed by the experimental spectra. The results show a gain buildup on the type-II chip that is delayed relative to that of a type-I chip. This slower gain dynamics is attributed to a diminished cooling rate arising from the reduced electron–hole scattering.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
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