Μm In Period Research Articles

Multileveled tunable silicon grating array bonded on large scale integration substrate by polymers

A multileveled tunable silicon grating array is designed and fabricated on a large-scale-integration (LSI) substrate. The grating consists of 250 single crystalline silicon ribbons of 260 nm in thickness, 400 μm in length, and 10 μm in period. The LSI substrate generates voltages to vary the heights of respective grating ribbons addressed by digital signal input. Each grating ribbon is attracted by an electrostatic force generated by 6-bit applied voltage in the range from 0 to 5 V. In the fabrication, the LSI substrate and a silicon-on-insulator wafer are bonded by the two kinds of polymers. A photosensitive polyimide polymer is used for patterning the bonding pads and also for bonding the wafers at the pressure of 0.25 MPa and the temperature of 350°C. Another epoxy polymer fills the space underneath the grating ribbons for subsequent process, which is finally removed by sacrificial etching to make the grating ribbons freestanding. The tunability of the grating is examined experimentally under the basic operation conditions.

Abstract 3913: Evaluation of patient-derived cell lines and cancer organoids for the prediction of drug responses in patient-derived xenograft models

Abstract Cancer organoids are heterogeneous 3D cellular clusters with complexities that mimic some characteristics of tumors in situ. Thus, assays performed with cancer organoids might enable better predictions of in vivo drug responses than those performed with cell monolayers. The National Cancer Institute (NCI) is developing a national repository of Patient-Derived (PD) models comprised of clinically annotated and molecularly characterized PD xenografts (PDXs), PD tumor cell lines (PDCs), and PD cancer organoids (PDOrgs) (https://pdmr.cancer.gov/). We evaluated the therapeutic activity of a panel of FDA-approved and investigational anticancer agents, including carboplatin, gemcitabine, paclitaxel, SN38, 5-FU, adavosertib, erlotinib, trametinib, and vemurafenib, against a cohort of PDCs, PDOrgs, and PDXs from solid tumors including colon, gastroesophageal, head and neck, NSCLC, pancreatic, bladder, and uterine cancers. Our goal was to investigate whether drug sensitivities determined using PDCs and PDOrgs correlate with responses observed in the matching PDXs. Cultures were exposed to anticancer agents at concentrations ranging from 1 pM to 100 µM for periods of 4 or 6 days. The data indicated that the GI50 values for PDOrgs were in overall agreement with in vivo PDX drug responses measured as relative median to event free survival (RMEFS), where an event is the median time (days) from treatment initiation to tumor volume quadrupling, calculated as median time to tumor volume quadrupling for treated animals/median time to tumor volume quadrupling for control animals. For both paclitaxel and trametinib, responses in PDOrgs, from most sensitive to most resistant, were similar to the corresponding PDXs. Drug sensitivities determined in PDC monolayers were less clearly related to in vivo PDX responses; particularly for PDCs treated with carboplatin, gemcitabine, and SN-38. This work is part of a larger effort to provide a rigorous comparison between fully characterized and annotated PDCs-PDOrgs-PDXs to assess the value of different in vitro model systems for the prediction of PDX drug responses. This research was supported [in part] by the Developmental Therapeutics Program in the Division of Cancer Treatment and Diagnosis of the National Cancer Institute. Funded by NCI Contract No. HHSN261200800001E. Citation Format: Petreena Campbell, Curtis Hose, Lara El Touny, Erik Harris, John Connelly, Carrie Bonomi, Kelly Dougherty, Savanna Styers, Abigail Walke, Jenna Moyer, Mariah Baldwin, Anna Wade, Michael Mullendore, Kaitlyn Arthur, Matthew Murphy, Kevin Plater, Marion Gibson, Joseph Geraghty, Michelle Gottholm-Ahalt, Tara Grinnage-Pulley, Tiffanie Chase, John Carter, Howard Stotler, Debbie Trail, Luke Stockwin, Dianne Newton, Yvonne Evrard, Melinda Hollingshead, Ralph E. Parchment, Nathan P. Coussens, Beverly A. Teicher, James H. Doroshow, Annamaria Rapisarda. Evaluation of patient-derived cell lines and cancer organoids for the prediction of drug responses in patient-derived xenograft models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3913.

Revealing competitive columnar grain growth behavior and periodic microstructural banding in additively manufactured Ti-6Al-4 V parts by selective electron beam melting

Powder-bed fusion additive manufacturing of Ti-6Al-4 V has been of tremendous interest in both academia and industry. As the two ubiquitous microstructural features, columnar grain and microstructural banding in selective electron beam melting of Ti-6Al-4 V are systematically studied by experimental and simulation methods. Three basic build geometries (i.e. V-, I- and A-shaped parts) are employed to study the columnar grain growth behavior. We find that columnar prior β-Ti grains grow epitaxially and competitively by following the classic competitive grain growth model in additive manufacturing of Ti-6Al-4 V. It results in increasingly stronger crystallographic texture with the rising build height. We also observe the consistently occurring microstructural banding (∼100 µm in period) normal to build direction due to the overlapped heat affected zones that are formed in the layerwise thermal cyclic process. In addition, a large quantity of sub-columnar grains exist within the microstructure for selective electron beam melted Ti-6Al-4 V. It is demonstrated that the periodic microstructural banding determines the appearance of sub-columnar grains which may affect the competition behavior for the growth of columnar grains.

X-ray source with quasi-monochromatic parallel beam

In inertial confined fusion experiments, an excellent-performance and high-efficiency X-ray source plays an important role in X-ray radiography schemes. Indeed, it can be used in a variety of X-ray experimental techniques. The mono-chromaticity, flux intensity, degree of collimation (the radiation can be transported long distances without loss), and spot size of the X-ray source affect the quality of imaging. Ray-tracing simulations, which are validated by experimental results, demonstrate that high-intensity collimated X-ray beams can be produced from an isotropic X-ray source. Therefore, a method of improving the performance of an X-ray source from a laser-produced plasma is presented. A spherically bent crystal is used to collimate mono-chromatic X-rays emitted from a laser-produced plasma. Here we design a spherically bent crystal spectrometer system for collimating the laser-produced X-rays. The system performance is experimentally tested at the Shenguang Ⅱ (SGⅡ) laser facility located in Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. The beam divergence is measured by using a metal grid placed downstream from the crystal, the metal grid that possesses wires with 60 μm in diameter and 127 μm in period. An imaging plate (IP) is placed at various distances downstream from grid. The quality of the generated beam is monitored by measuring the dimensions of the grid image formed by the beam on IP. While the narrow range of wavelength is measured with a spherically bent crystal spectrometer. Experimental results show that the spherically bent crystal spectrometer system can produce quasi-monochromatic (10<sup>-3</sup> < △ <i>λ/λ</i> <10<sup>-2</sup>) X-ray beams with a high degree of collimation (less than 2 mrad divergence), uniform spot size (~500 μm), and a relative tenability in the wide spectral range. The influences of various experimental parameters on the quality of beam collimation are evaluated in two ways. They can be investigated in test experiments by representing the beam divergence distribution as a function of Bragg angle. In another study of the effect of the aberrations, when the incident beam on the spherically bent crystal is not normal, the beam is less collimated in the tangential plane, and out of collimation in the sagittal plane. Following the ray-tracing method, we analyze the diffracted beam divergence produced by the astigmatic aberration. The qualitative conclusion is that the good agreement with the experimental results is obtained. By fully utilizing limited Bragg angle range, the spherically bent crystal spectrometer system can realize collimated diffracted X-ray beams with divergence of less than 1 mrad by using a laser-produced plasma X-ray source under the appropriately experimental parameters.

Variation of anode grid surface morphology and its effect on operation of a triode virtual cathode oscillator

After repeatedly operation of a triode virtual cathode oscillator, the surface morphology of anode grid is studied by a scanning electron microscope. It is found that there are many quasi-periodic sawteeth formed on the anode grid, which are about 300-500 μm in height, ~200 μm in width, and 150-200 μm in period. The formation of this sawteeth implies that there is possible Rayleigh-Taylor-like instability on the anode grid during the irradiation by high-current relativistic electron beam. These sawteeth enhance the electric field on anode grid, leading to more feasible of anode plasma generation, and more rapidly expansion of that plasma. As a result, the electron transmissivity of anode grid is decreased, the output microwave power of the virtual cathode oscillator is lowered and its operational performance is degraded.

Design and simulation in GaN based light emitting diodes using focused ion beam generated photonic crystals

Two-dimensional photonic crystal (2D-PC) structures have been designed to increase the light extraction in GaN based semiconductor light-emitting devices (LED). The photonic crystals could be fabricated using the focused ion beam (FIB) in a dual-beam nanotechnology workstation system SMI 3050, both with and without platinum coating. The acceleration voltage of the Ga ion beam was fixed at 30 kV and the ion beam current was 6 nA. The LED area was 155 µm × 85 µm with both top and bottom pads. In addition, we developed Bandsolve simulation tools for the photonic crystal band structures, and the simulation results supported our experimental observations. It was based on the advanced implementation of the plane-wave expansion technique for periodic structures. The radius was varied from 0.05 µm to 0.5 µm and the period was from 0.1 µm to 1 µm. Both square lattice array and hexagonal lattice array patterns have been investigated. It showed the highest monitor intensity for the sample that has a hexagonal array structure, with 0.45 µm in radius and 0.9 µm in period. The optimized parameters would be used as design guides to fabricate 2D-PC air hole arrays on the p-GaN surface for LED structures.

Nitroglycerin as a Modulator of Hemoglobin Function.

Recent evidence suggests that oxygen acts as an allosteric modulator of nitric oxide (NO) binding to hemoglobin. This may have important physiological implications. Those effects, thought by some to be mediated by nitrosylation of the conserved cysteine β93 residues (S-nitrosohemoglobin; SNO-Hb), may also have therapeutic relevance in sickle cell disease and potentially be a useful strategy in controlling vasoactive effects of hemoglobin-based blood substitutes. Nitroglycerin (NTG), the classic vasodilator drug, acts in part through metabolism to NO. Normal (AA) and sickle (SS) blood suspensions were treated with nitroglycerin from 0.03 to 300 μM for periods up to 3.25 hours. Such treatment significantly lowered the oxygen affinity (increases P50, PO2 at which hemoglobin is half-saturated with O2) of both AA and SS red cells. The decrease in oxygen affinity is greater when oxygenated cells are treated than deoxygenated cells, with changes in P50 as great as 7.4 mm Hg in the AA cells and 9.9 mm Hg in the SS cells. Those shifts occur within 15 minutes, before significant increases in methemoglobin levels. This is opposite to what has been seen with other NO donors (2-(N,N-diethylamino)-diazenolate-2-oxide, S-nitrosocysteine, and sodium trioxodinitrate), where increased oxygen affinity occurs. Other classic NO donors also yielded significant methemoglobin formation within 15 minutes. In vivo effects of NTG infusion up to 1 μg/kg/min fail to demonstrate any change in P50 or methemoglobin in study subjects with normal AA erythrocytes. (Shigihara A. Masui1994;43:222) In addition, NTG has been shown to enhance oxygen release from erythrocytes without significantly increasing tissue blood flow in the hepatic microcirculation in a rat model. (Kosaka H, et al. Nat Med1997;3:456) Furthermore, a study in a dog model demonstrated NTG-induced enhanced oxygen unloading in the ischemic microcirculation. (Bin JP, et al. Circulation2006;113:2502) Elevated tandem erythrocyte S-nitrosothiol content, reflecting mainly SNO-Hb, was also noted. However, SNO-Hb increases oxygen affinity (Bonaventura C, et al. J Biol Chem1999;274:24742) and cannot explain the increased oxygen unloading. The effect of NTG on erythrocytes in our in vitro study model mimics in vivo results in the microcirculation (as opposed to the macrovascular circulation) and demonstrates that the reported enhanced oxygen unloading is due to a decrease in oxygen affinity of hemoglobin. Other biotransformation products of NTG may account for these effects as opposed to SNO-Hb. This study demonstrates that selective NO donors (i.e., NTG) may target erythrocytes for enhanced R (oxyhemoglobin) to T (deoxyhemoglobin) transformations specifically in the microcirculation and thereby improve tissue oxygenation.

Controlled composition modulation in potassium lithium tantalate niobate crystals grown by off-centered TSSG method

Off-centered top-seeded solution growth (TSSG) method is demonstrated as an effective and simple way to generate controlled composition modulation in potassium lithium tantalate niobate (KLTN) single crystals. The changes in concentration were measured by differential interference contrast (DIC) microscopy. Large length with periodic modulations ranging from 1 to 5 μm in period was grown along a KLTN sample with period dispersion lower than 2%.

Generation of 840 mW of red light by frequency doubling a diode-pumped 1342 nm Nd:YVO4 laser with periodically-poled LiTaO3

We report an efficient generation of red light in a periodically-poled LiTaO3 (PPLT) crystal by extracavity single-pass frequency doubling of a diode-pumped, Q-switched Nd:YVO4 laser at 1342 nm. The sample used in the experiment is 20 mm in length and 14.77 μm in period. An average power of 840 mW of the 671 nm red light is obtained with a 808 nm pump of 12.3 W, the overall optical-to-optical efficiency being 6.8%. The measured effective nonlinear coefficient of the sample is ∼3.8 pm/V. The high conversion efficiency and output power demonstrate that the periodically-poled crystal serving as a frequency conversion device may be used in practice to construct an all-solid-state red laser based on an extracavity single-pass quasi-continuous scheme.

Effect of surface topology of amorphous substrates on the growth mechanism and grain size of APCVD grown silicon for solar cells

In order to improve the crystallization of APCVD silicon on amorphous substrates we have investigated different techniques to grow films with sufficient average grain size. An experimental study of the influence of substrate surface topology on nucleation and grain size of APCVD grown silicon is reported here. Oxidized silicon wafers with a striation pattern and pyramidal structure are used as substrates for deposition. The size of the striation pattern varies from 8 to 128 μm in period and from 40 nm to 36 μm in height. The pyramids and inverted pyramids (2–40 μm high) have been made using selective etching of (100) oriented wafers. A 20–50 μm thick silicon film has been deposited on all substrate types at high temperature (1100–1200°C) and SiH 2Cl 2 partial pressure of 500 Pa. The structure of the deposited film strongly depends on the surface topology. To study the mechanism of this effect we have determined the nucleation densities on textured surfaces for a deposition time of 2 s. A value of 6–10 μm −2 was found. Although the free-energy change is lowered at the edges (E.I. Givargizov, Oriented Crystallization on Amorphous Substrates, Plenum, New York, 1991) there was no significant increase of nucleation density in these areas. Thus the effect observed is supposed to occur due to the change of geometry at competing grain growth. The described effect seems to be applicable to grow silicon films appropriate for solar cell production.

In Situ Measurements of the Resist Etch Rate for Submicron Patterns

A resist film is etched by oxygen-based plasmas, and fine grating patterns of the resist are fabricated. During etching, a laser beam is irradiated onto the sample and the reflection intensity from the sample is measured in order to determine the etching depth. The reflection intensities are calculated by solving the Maxwell equations for electromagnetic wave propagation. The dependence of the reflection intensity on the etching depth varies greatly with the ratio of the space width to the grating period. The absolute etch rate can be obtained by comparison between the experimental and simulated reflection intensities. The fabricated gratings are 0.5 µm in period and the ratios of the space width to the grating period are between 0.4 and 0.7. The reflection intensities obtained from the experiments agree very well with those from the simulations. The etch rate decreases as the etching depth increases, but it is almost independent of the aspect ratio of the fabricated patterns. The etch rate decrease is not caused by an increase in the aspect ratio of the etched pattern, but may be induced by the time variation of plasma conditions.

Effect of ?-naphthaleneacetic acid and sucrose levels on the development of cultured embryos of coconut

Mature coconut embryos were germinated in a modified Murashige and Skoog medium and then cultured on BMY3 medium incorporating sucrose in the range of 4 to 8%. α-Naphthaleneacetic acid (NAA) was added into the medium at concentrations ranging from 0 to 800 μM for periods of 4 to 24 weeks. Application of NAA for 4 weeks stimulated shoot growth, whereas application periods greater than 4 weeks had no significant effect. NAA in the range of 100–300 μM stimulated elongation of the primary root and the optimum concentration increased with increases in sucrose levels. Production of adventitious roots was stimulated by the addition of NAA with levels of 200 μM and above being the most effective. Increasing the sucrose concentration from 4% through to 8% stimulated root elongation in the absence of NAA and inhibited shoot growth whether NAA was present or absent.

Control of Grain Boundary Location By Selective Nucleation Over Amorphous Substrates

ABSTRACTA selective nucleation based crystal-growth-technique over amorphous substrates is originated. The method manipulates nucleation sites and periods and hence, controls the grain boundary location by modifing the substrate surface. In Si, small Si3 N4 nucleation sites are formed, 1–2 pm in diameter, 100 μm in period, over Sio2. One Si nucleus is formed exclusively in the small area of Si3 N4 by CVD. The highly faceted and periodically located nuclei grow over SiO2 up to 100 μm in diameter before impingement. A MOS-FET fabricated inside the island operates comparably to the bulk Si control