Giant Grains Research Articles

From nano to giant grains: Optimizing Pt thermistors for microbolometers

Pt is a suitable thermistor for use in microbolometers due to its high melting point, chemical inertness, and low 1/f noise. This work explores mechanisms of grain growth to fabricate Pt thin film thermistors for maximizing the temperature coefficient of resistance (TCR). The interplay between the microstructure and TCR is examined by varying Pt film deposition parameters, AlOX interlayer deposition technique, patterning technique, and annealing parameters. A smooth thin film morphology having giant grains of several hundreds of micrometers is achieved by abnormal grain growth, which is not attainable through normal grain growth. The fabrication of thermistor meanders is demonstrated through a combination of processes including Pt film deposition in O2/Ar environment, annealing at 1000 °C in Ar, and ion beam etching. Pt thermistors with a TCR (0 °C – 100 °C) of 0.371 ± 0.001 %/ °C are compatible with microbolometers utilizing carbon nanotube absorbers.

Centrifugation-Assisted Growth of Single-Crystalline Grains in Microcapsules.

Colloidal crystals have been tailored in a format of microspheres to use them as a building block to construct macroscopic photonic surfaces. However, the polycrystalline grains grown from the spherical surface usually exhibit low reflectivity. Although single-crystalline microspheres have been produced, it is difficult to control the crystal orientation. Here, we design spherical microcapsules with density anisotropy that contain single-crystalline grains along the heavy side. The microcapsules spontaneously align to have a heavy side down under the action of gravity and display a bright and uniform reflection color from the entire surface of the grains. Key to the success is the use of gentle centrifugal force to initiate nucleation and grow single-crystalline grains from the heavy side through depletion attraction. The microcapsules have density anisotropy due to the heterogeneity of the shell thickness, which causes them to self-align under centrifugation. At the same time, particles are accumulated on the heavy side, which produces many tiny grains on the heavy side immediately after the centrifugation. With controlled depletion attraction among particles, only a few grains survive during postincubation through Ostwald ripening, and one or a few giant single-crystalline grains are finally produced along the heavy side of each microcapsule.

甜樱桃对高温胁迫的生理响应

PDF HTML阅读 XML下载 导出引用 引用提醒 甜樱桃对高温胁迫的生理响应 DOI: 10.5846/stxb202103230764 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省科技厅公益技术研究项目（LGN21C150005）；杭州市农科院科技推广项目（2019HNCT-26） Physiological responses to high temperature stress in Prunus avium L. Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨甜樱桃对高温胁迫的响应机制，以1年生的甜樱桃嫁接盆栽苗为试材，研究了自然高温处理及胁迫后恢复对其叶片生理和超显微结构的影响。结果表明：经连续3d日最高气温均值达57.7℃胁迫后，甜樱桃叶片过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）活性、超氧阴离子（O2·-）产生速率、非光化学淬灭系数（qN）显著增加，渗透调节物质可溶性蛋白、可溶性糖及脯氨酸含量显著提高，谷胱甘肽还原酶（GR）活性、叶绿素含量、PSII最大光化学效率（Fv/Fm）和电子传递速率（ETR）显著下降，超氧化物歧化酶（SOD）和过氧化物酶（POD）活性及光化学淬灭系数（qP）变化不显著。同时对叶片显超微结构观察发现，胁迫引起叶绿体变性，基质内囊体发生扭曲，部分基粒类囊体片层消失，出现大量巨型淀粉粒及嗜锇颗粒。恢复2d后SOD、POD、CAT、APX活性以及可溶性糖、可溶性蛋白、叶绿素总含量均显著下降，而GR活性和脯氨酸含量显著升高。以上表明，连续3d自然最高气温达57.7℃对甜樱桃叶片抗氧化系统和光合特性等产生了显著影响，叶绿体超显微结构受到明显破坏，对叶片造成了不可逆伤害。 Abstract:Sweet cherry is the earliest fruit ripen tree in north China and mainly cultivated in Taian, Yantai and Dalian. In recent years, due to the early rise of spring temperature in south China and the rapid development of leisure and sightseeing agriculture, sweet cherry had gradually developed to the south. However, high temperature was more frequent in south China in summer. The influence of temperature on plant are various, which can lead to reactive oxygen species (ROS) in a large number of accumulation in plants and the stability of the biofilm fall and the permeability increases, large molecules such as proteins and nucleic acids, DNA rupture, enzymatic reaction efficiency drops, organelles such as chloroplasts and mitochondria structure was damaged and photosynthetic rate decreased significantly, growth and development, Eventually, the yield and quality of plants were severely reduced. Meanwhile high temperature was closely related to the double pistil rate of sweet cherry. The fruit setting rate of sweet cherry was affected, especially the commercial fruit rate. High temperature became a limiting factor for the southward development of sweet cherry. To investigate the response mechanism of sweet cherry to high temperature stress, the effects of natural high temperature treatment and stress recovery on physiological indexes and ultrastructure of grafted pot seedlings of 1-year sweet cherry were studied in this research. After the seedlings were treated at the average maximum temperature 57.7℃ in consecutive 3 days, the catalase (CAT) and ascorbic peroxidase (APX) activity, superoxide anion (O2·-) producing rate and coefficient of the photochemical quenching (qN) increased significantly in sweet cherry leaves. The osmotic regulation substances including soluble protein, soluble sugar and proline content increased significantly. The glutathione reductase (GR) activity, chlorophyll content, PSII maximum photochemical efficiency (Fv/Fm) and the electron transport rate (ETR) were significantly reduced. The activities of superoxide dismutase (SOD) and peroxidase (POD) and the photochemical quenching coefficient (qP) had no significant changes. The ultrastructure of the leaves was also observed. It was found that the stress caused the chloroplast properties change. The part of the grana thylakoid lamellae disappeared, and a large number of giant starch grains and osmiophilic globule appeared. After recovery for 2 days, the activities of SOD, POD, CAT, APX, soluble sugar, soluble protein and total chlorophyll contents decreased significantly, while the activities of GR and proline content increased significantly. The results indicated that the maximum temperature 57.7℃ for 3 days had significant effects on the antioxidant system and photosynthetic characteristics of sweet cherry leaves, and the chloroplast ultrastructure was significantly damaged, causing irreversible damage to the leaves. 参考文献 相似文献 引证文献

Identification of the biochemical characteristics of developing giant embryo rice grains using non-targeted metabolomics

Giant embryo rice is well known for its high content of nutrients, such as GABA. However, the biochemical characteristics of this grain remain un-elucidated, and little is known about whether additional types of nutritional chemicals accumulate in giant embryo rice. In this study, we compared the metabolome of the developing grain of giant embryo rice, namely, ‘Shangshida No. 5‘, to that of normal embryo rice, namely, ‘Chao2-10‘, using a non-targeted metabolomics approach. Our results showed that more additional nutrients and bioactive compounds that had not been reported previously in other giant embryo rice, such as reduced glutathione, β-alanine, VB6, arabinose, xylitol, and xylose, were present in ‘Shangshida No. 5’ than in ‘Chao2-10‘. Specifically, the amount of β-alanine in ‘Shangshida No. 5’ was 18.71 times that in ‘Chao2-10’ at 45 DAF. These analyses suggest that ‘Shangshida No. 5’ is a high-quality functional rice, and has potential applications in rice nutritional improvements.

Oxygen-induced giant grain growth in Ag films

Thin film crystallites typically exhibit normal or abnormal growth with maximum grain size limited by energetic and geometric constraints. Although epitaxial methods have been used to produce large single crystal regions, they impose limitations that preclude some compelling applications. The generation of giant grain thin film materials has broad implications for fundamental property analysis and applications. This work details the production of giant grains in Ag films (2.5 μm-thick), ranging in size from ≈50 μm to 1 mm, on silicon nitride films upon silicon substrates. The presence of oxygen during film deposition plays a critical role in controlling grain size and orientation.

Electrically Active and Inactive Single Grain Boundaries in Semiconducting BaTiO3

Bi‐crystal specimens were prepared from Nb and Mn‐doped BaTiO3 poly‐crystals with giant grains of millimeter order in size, and the resistance (R) versus temperature (T) characteristics of these individual grain boundaries was investigated. The electrically active grain boundaries that show normal positive temperature coefficient resistor (PTCR) behavior had no second phases or they were partially distributed along boundaries. On the other hand, electrically inactive grain boundaries that show flat R‐T characteristics were also observed, where continuous Ti‐rich second phases of Ba4Ti12O27 could be detected. Different interface state density and its resultant R–T characteristics were observed for each individual active boundary, which indicates the degree of oxidation and the formation of potential barrier can be different depending on the character of the grain‐boundary plane. The resistance of inactive boundaries was determined by that of insulating second phase showing negative temperature coefficient resistor (NTCR) behavior. These results demonstrate that continuous second phase surrounding a grain deactivates the electrical properties of grain boundary, and thus should be distinguished from insulating depletion layer near grain boundary.

Growth of wrinkle-free graphene on texture-controlled platinum films and thermal-assisted transfer of large-scale patterned graphene.

Growth of large-scale patterned, wrinkle-free graphene and the gentle transfer technique without further damage are most important requirements for the practical use of graphene. Here we report the growth of wrinkle-free, strictly uniform monolayer graphene films by chemical vapor deposition on a platinum (Pt) substrate with texture-controlled giant grains and the thermal-assisted transfer of large-scale patterned graphene onto arbitrary substrates. The designed Pt surfaces with limited numbers of grain boundaries and improved surface perfectness as well as small thermal expansion coefficient difference to graphene provide a venue for uniform growth of monolayer graphene with wrinkle-free characteristic. The thermal-assisted transfer technique allows the complete transfer of large-scale patterned graphene films onto arbitrary substrates without any ripples, tears, or folds. The transferred graphene shows high crystalline quality with an average carrier mobility of ∼ 5500 cm(2) V(-1) s(-1) at room temperature. Furthermore, this transfer technique shows a high tolerance to variations in types and morphologies of underlying substrates.

Cytomictic anomalous male meiosis and 2n pollen grain formation in Mertensia echioides Benth. (Boraginaceae) from Kashmir Himalaya.

Presently Mertensia echioides Benth. (Boraginaceae) collected from Kashmir Himalaya, India, is cytologically analyzed for the first time revealing 2n = 2x = 24 (diploid). Interestingly we found 4.3–6.2% syncytic meiocytes/PMCs with 2n = 4x = 48 (tetraploid) in addition to normal meiocytes (2n = 24) during male meiosis. These comparatively larger PMCs (pollen mother cells) lead to the formation of fertile giant 2n pollen grains. A frequency of 6.4–13.3% PMCs shows transfer of chromatin material at prophase-I and, therefore, results in aneuploid meiocytes. Whole chromatin transfer by the process of cytomixis could also have led to the formation of tetraploid cells. Translocation heterozygosity is also evident in the form of multivalents in 12–17% diploid (2x) meiocytes at diakinesis and metaphase-I and is reported for the first time in this species. The syncytes formed depict open chain hexavalent and quadrivalent formation in the three populations with different frequencies. Moreover chromatin stickiness at metaphase-I is observed in 45% of PMCs in population-1 (P-1). Syncyte or unreduced PMC formation leading to unreduced fertile gametes is here speculated to act as a possible way out for infraspecific polyploidization in the species.

Giant secondary grain growth in Cu films on sapphire

Single crystal metal films on insulating substrates are attractive for microelectronics and other applications, but they are difficult to achieve on macroscopic length scales. The conventional approach to obtaining such films is epitaxial growth at high temperature using slow deposition in ultrahigh vacuum conditions. Here we describe a different approach that is both simpler to implement and produces superior results: sputter deposition at modest temperatures followed by annealing to induce secondary grain growth. We show that polycrystalline as-deposited Cu on α-Al2O3(0001) can be transformed into Cu(111) with centimeter-sized grains. Employing optical microscopy, x-ray diffraction, and electron backscatter diffraction to characterize the films before and after annealing, we find a particular as-deposited grain structure that promotes the growth of giant grains upon annealing. To demonstrate one potential application of such films, we grow graphene by chemical vapor deposition on wafers of annealed Cu and obtain epitaxial graphene grains of 0.2 mm diameter.

Graphene growth with giant domains using chemical vapor deposition

We report the first demonstration of the growth of giant graphene domains on platinum (Pt), which results in a uniform bilayer graphene film with domain sizes of millimetre scale. These giant graphene domains are attributed to the giant Pt grains attained in post-deposition annealed Pt thin films that exhibit a strong dependency on the Pt film thickness. Giant grains have been claimed to occur in other metallic materials under appropriate film thicknesses and processing conditions. Our findings demonstrate a route towards rational large-scale uniform graphene synthesis for applications in nanoelectronics and sensing.

Giant grains of nocardia actinomycetoma

A 27-year-old woman presented to a tertiary centre for mycology in Mexico City, Mexico, with an 11-year history of progressive swelling and deformity of her right foot, and was no longer able to weight-bear. Clinically, there were draining sinuses and giant, white grains with a seropurulent discharge (fi gure, A). A radiograph of her foot showed marked soft tissue enlargement and bony lytic lesions (fi gure, B). Direct microscopy of the grains showed characteristic features of nocardia (fi gure, C). Histopathology of a skin biopsy showed grains together with a granulomatous infl ammatory reaction (fi gure, D). Culture confi rmed the presence of Nocardia brasiliensis. The patient had previously been treated unsuccessfully with oral penicillin, which is not a recommended treatment for actinomycetomas. Given the incapacitating nature of her disease and bony involvement, she was treated parenterally with amikacin (500 mg twice daily) and imipenem (500 mg three-times daily) for 3 weeks after which she was given oral co-trimoxazole (800 mg sulfamethoxazole and 160 mg trimethoprim daily) and dapsone (100 mg daily). She was cured both clinically and microbiologically (negative microscopy and culture), with complete resolution of sinuses after 6 months of oral treatment. Oral treatment was continued for a further year after cure to prevent relapse, and she remains disease-free 2 years and 10 months later. The clinical features of this case, especially the presence of discharging white grains, are highly suggestive of a mycetoma. Additionally, mycetomas characteristically aff ect the extremities as a result of traumatic inoculation of the causative organism. Despite mycetomas being endemic in Mexico, cases are frequently unrecognised and incorrectly managed medically or inappropriately excised surgically. The presence of giant grains is unusual and cannot be accounted for by disease severity or chronicity. Giant grains are probably a feature of a distinct subspecies of nocardia. Molecular tests can be used to identify subspecies, although they were not done in this case.

Nanoindentation of BaTiO3: dislocation nucleation and mechanical twinning

This paper presents a study of the deformation mechanisms of barium titanate under nanoindentation. The (0 0 1) and (1 1 0) crystallographic orientations of BaTiO3 giant grains were indented and critical mean contact pressures for dislocation nucleation were extracted from the indentation curves. The orientation of the dislocation slip lines was identified by atomic force microscopy, showing that the ⟨1 1 0⟩{1 1 0} glide systems were activated. Twin bands, observed on both orientations, also occur on the {1 1 0} habit planes and actively participate in the accommodation of the plastic deformation. Furthermore, dislocation pile-ups introduced by spherical indentations have shown a close relation between dislocations and twinning formation.

Grain Growth and Magnetic Properties of Nb2O5-Doped NiZn Ferrites

The grain growth and magnetic properties of Nb2O5 doped NiZn ferrites prepared by a solid-state reaction method have been investigated. X-ray diffraction (XRD) patterns indicated that a single phase spinel structure was observed when the content of Nb2O5 was less than 1.00 wt %. While 1.00 wt % of Nb2O5 added, besides the spinel phase, an orthorhombic phase of FeNb2O6 appeared which resulted in the (440) diffraction peak to be enhanced as the main peak. In addition, as the content of Nb2O5 increased, the diffraction intensities of the samples increased gradually. The microstructure observation revealed that Nb2O5 addition remarkably retarded grain growth when it below 0.85 wt %. And the addition of 0.85 wt % Nb2O5 induced the formation of a microstructure composed of giant grains with trapped pores embedded in a normal microstructure. Up to a content of 1.00 wt %, grain growth was obviously enhanced. The initial permeability (µi) initially increased up to a content of 0.40 wt % and showed a decrease at higher content up to 1.00 wt %. However, losses (PL) changed contrarily. Saturation induction (Bs) decreased monotonously with increasing Nb2O5 content.

Location control of giant silicon grains using organic lenses

We studied the location control of a giant grain of polycrystalline silicon produced by Ni-mediated crystallization of amorphous silicon (a-Si) using a cap layer. An organic lens made of acryl was used for the focusing of light for the seed formation and subsequent crystallization. A single grain 62μm in diameter was made using an 80-μm-square SiNx cap layer on the a-Si. The position of a thin-film transistor (TFT) on a grain can be controlled, so that a single grain TFT can be fabricated at a predetermined position without use of the laser annealing technique.

Induction of 2n pollen in tulips by arresting the meiotic process with nitrous oxide gas

Triploid tulips have agronomically desirable traits such as vigorous growth and large flower size, but only a portion of all cultivated tulips is triploid. To apply 2n pollen to polyploid breeding of tulips, the polyploidizing agent, nitrous oxide gas (N2O), was applied to bulbs. In tulips, meiosis in anthers occurs inside the bulbs from mid- to late-October. When meiosis in anthers (excised from bulbs) reached metaphase I, we treated other bulbs of the same clones with N2O for 24–48 h. Most of the treated plants produced pollen grains with a wide-ranging or bimodal size distribution, indicating a mixture of n, 2n and aneuploid pollen grains. The use of pollen containing a relatively high proportion of giant pollen grains tended to yield larger numbers of triploids in the progeny. The number of giant pollen grains could be increased when N2O-treated pollen grains were suspended in 10% sucrose and then sieved through a nylon mesh. Very few polyploids were observed in some cross combinations, even those involving pollen with a relatively high proportion of giant grains. Even so, this low polyploid yield most likely is due to a triploid block, because the capsules obtained in the crosses of the diploid×N2O-treated plants contained some abnormal seeds, which were mostly triploid. Embryo culture was useful in rescuing abnormal embryos. The present study reveals that 2n pollen can be produced at high frequency using N2O during tulip breeding.

90° Domain Configuration and Lateral Domain Wall Motion in BaTiO3 Evaluated by Secondary Electron Microscopy

We report on the investigation of domain imaging in (001) oriented BaTiO3 giant grains studied by means of secondary electron microscopy. Samples were prepared by the modified exaggerated growth method, polished, etched and finally mechanically affected by a uniaxial in situ compression test in scanning force microscopy. Samples were characterized in the absence of applied mechanical stress by scanning electron microscopy. A back-switching process is proposed to be induced due to the electron beam causing compensation of the excess of positive surface charges inside the ferroelastic switched C + domain.

Origin of Tetraploid Progenies in 4x*2x Crosses of Cyclamen(Cyclamen persicum Mill.).

The origin of tetraploids from 4x × 2x cyclamen crosses was examined by using the diploid pollen parents with and without giant pollen grains, and by pollinating tetraploid cultivars with sieved giant and normal-sized pollen grains borne on diploid plants. The developing pollen mother cells were observed after the second meiotic division in the diploids with and without the giant pollen grains. Tetraploid progeny production in the crosses was obviously related to the giant pollen grains. Tetraploid F1 progenies were produced in the crosses by using pollen from diploid plants that produce giant pollen ; no seed was obtained in the crosses by using pollen from diploids, which produce no giant pollen. More seeds were obtained when sieved giant pollen grains were used for the crosses than when non-sieved pollen grains with giant pollen were used, whereas no seed was obtained in the crosses using only normal-size pollen grains from diploids. Thirteen to 27% of pollen mother cells in the diploids with giant pollen grains formed pollen dyads or triads after the second meiotic division, whereas few pollen dyads and triads were formed in those without giant pollen grains. These observations suggest that most giant pollen grains in diploid cyclamen are unreduced male gametes. Therefore, the origin of tetraploids derived from 4x × 2x cyclamen crosses is the results of fertilization between an unreduced pollen grain from the diploid plant and a normally reduced egg cell from the tetraploid. Furthermore, the use of sieved giant pollen grains was efficient for the production of tetraploid progenies.

A New Sample Structure for Position-Controlled Giant-Grain Growth of Silicon using Phase-Modulated Excimer-Laser Annealing

A new sample structure has been proposed for position-controlled growth of giant Si grains by a phase-modulated excimer-laser annealing method. The sample consists of a layered structure with an organic silica underlayer at the bottom for reducing the heat removal rate from the Si layer placed on it, and a thick silica capping-layer on the top, for enlarging the amount of excess stored heat. These layers effectively elongated the grain growth time, resulting in the long lateral grain growth to 24 µm. In addition, a sample having a buried silica island array in the Si layer has also been proposed for achieving two-dimensional position control, where the island determines the starting position of the lateral grain growth. By combining these technologies, we have grown single crystals of Si grains as large as 12 µm at pre-designated positions by single-shot irradiation.

Evolution of high aspect ratio grains in a TiAl-based alloy by directional grain growth

A concept of microstructural control named “directional grain growth” (DGG) has been proposed. In this method, local phase transition and grain growth are utilized for controlling grain shape and grain orientation in a restricted region for an inhomogeneous material in chemical composition which is given directionality by plastic deformation. In heat treatment for DGG, a seed grain grows preferentially in a shaped region without precipitates by being held at a relatively low temperature and then enlarges further by encroaching the surrounding region where precipitates vanish gradually with temperature elevating at a slow rate. Such a DGG heat treatment was applied to a Ti–45.6at %Al–1.7at.%Mn alloy fabricated by reactive sintering of an extruded mixture of elemental powders and contained inevitably directional inhomogeneity. As a result, a structure was obtained consisting of giant columnar grains of Al-bearing αTi phase of several mm in length, 6.0–7.0 in aspect ratio and a preferred orientation. The axis of the columnar grains was approximately perpendicular to [0001] α .

Transmission electron microscopy analysis of crystallographic transition from fcc to fct on PtMn spin valves

The structural changes during the crystallographic transition from fcc to fct of antiferromagnetic PtMn layers with postdeposition annealing, in spin-valve multilayers constructed by Ta/PtMn/CoFe/Cu/CoFe/NiFe/Ta/Si, were investigated using transmission electron microscopy and energy dispersive x-ray spectroscopy. We determined that the crystallographic orientation of the PtMn layers after postdeposition annealing depends on the initial size of the columnar grains in as-deposited spin valves. For spin valves with an initial grain size of 10 nm, the fcc→fct transition of PtMn layers was completed with the crystallographic orientation on the (111) texture. In contrast, spin valves with an initial grain size of 50 nm brought about a crystallographic reconstruction of the PtMn layer due to the tensile stress from neighboring grains during the fcc→fct transition. This results in a transformation from a fcc(111) to a fct(101) texture and a recombination of grains to form giant grains of 300–500 nm in the PtMn layer. This dynamic reconstruction promotes the interlayer diffusion of constituent atoms in spin-valve multilayers, leading to an increase in the interlayer coupling field between the pinned and free layers (Hin) and a promotion of thermal degradation of magnetoresistance (ΔR).