Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Effects of Maternal Retinoic Acid Administration on Lung Angiogenesis in Oligohydramnios-Exposed Fetal Rats

All-trans retinoic acid (ATRA) induces in vitro angiogenesis and vascular endothelial growth factor (VEGF) secretion. Prenatal administration of vitamin A tends to increase the pulmonary and plasma levels of VEGF in the developing mouse. The aims of this study were to examine the effects of maternal retinoic acid treatment on lung VEGF expression and angiogenesis in oligohydramnios-exposed fetal rats. Methods: On day 16 of gestation, pregnant Sprague–Dawley rats were randomly assigned to either the retinoic acid group (intragastric ATRA at 10 mg/kg body weight) or the vehicle group. We punctured each uterine sac to produce oligohydramnios, and fetuses in the opposite uterine horn served as controls. On day 21 of gestation, the fetuses were delivered by cesarean section. Results: Rats exposed to oligohydramnios exhibited lower lung weights and lung/body weight ratios, and ATRA exhibited no effects on the body or lung weights of oligohydramnios-exposed rats. Lung microvessel density decreased in oligohydramnios-exposed rats of maternal vehicle-treated dams. Microvessel density was comparable between the oligohydramnios + retinoic acid group and the control + retinoic acid group. VEGF expression was comparable among control and oligohydramnios-exposed rats of maternal vehicle- or retinoic acid-treated dams. Conclusion: Maternal retinoic acid treatment did not increase lung VEGF expression or enhance lung development in oligohydramnios-exposed fetal rats. These results do not support the use of maternal retinoic acid to prevent oligohydramnios-induced pulmonary hypoplasia in the pseudoglandular stage

Neonatal Hyperoxia Exposure Induces Kidney Fibrosis in Rats

Human and animal studies have demonstrated that neonatal hyperoxia increases oxidative stress and adversely affects glomerular and tubular maturity. This study was undertaken to determine how exposure to neonatal hyperoxia affected kidney morphology and fibrosis and to elucidate the relationship between connective tissue growth factor (CTGF) and collagen expression in rat kidneys. Methods: Sprague–Dawley rat pups were exposed to either hyperoxia or ambient air. The control groups were maintained in ambient air for 1 week and 3 weeks. The hyperoxia groups were exposed to >95% O2 for 1 week and subsequently placed in an environment of 60% O2 for an additional 2 weeks. The animals were euthanized on Postnatal Day 7 or 21 and the kidneys underwent histological analyses and oxidative stress and total collagen measurements. Results: The rats reared in O2-enriched air exhibited significantly higher tubular injury scores (1.4 ± 0.5 vs. 0.7 ± 0.7 on Day 7; 1.4 ± 0.5 vs. 0.6 ± 0.5 on Day 21), a larger proportion of the cortex occupied by glomeruli (25.5 ± 4.1 vs. 21.3 ± 3.1% on Day 7; 20.1 ± 3.5 vs. 17.1 ± 1.7% on Day 21), larger glomerular sizes (84.7 ± 5.8 vs. 77.5 ± 6.1 μm on Day 7; 88.4 ± 2.9 vs. 84.9 ± 3.1 μm on Day 21), and higher total collagen content (54.1 ± 27.5 vs. 18.3 ± 6.3 μg/mg protein on Day 7; 397.4 ± 32.8 vs. 289.5 ± 80.0 μg/mg protein on Day 21) than did rats reared in ambient air. Immunohistochemical expressions of oxidative stress marker 8-hydroxy-2′-deoxyguanosine and CTGF immunoreactivities were significantly higher in the rats reared in O2-enriched air compared with the rats reared in ambient air on Postnatal Days 7 and 21. Conclusion: Neonatal hyperoxia exposure contributes to kidney fibrosis, which is probably caused by activated CTGF expression

Effect of Surfactant and Budesonide on the Pulmonary Distribution of Fluorescent Dye in Mice

Surfactant is a useful vehicle for the intratracheal delivery of medicine to the distal lung. The aim of this study was to analyze the effect of intratracheal surfactant and budesonide instillation on the pulmonary distribution of fluorescent dye in mice. Methods: Male athymic nude mice were assigned randomly as controls, fluorescent dye, fluorescent dye + surfactant (50 mg/kg), fluorescent dye + budesonide (0.25 mg/kg), and fluorescent dye + surfactant + budesonide groups. A total volume of 60 μL fluorescent solutions was intratracheally injected and followed by 60 μL of air. We photographed and measured fluorescence in the lungs, from the back, 15 minutes after intratracheal administration using an IVIS Xenogen imaging instrument. Results: The fluorescent dye (1,1′-dioctadecyltetramethyl indotricarbocyanine iodide) was most strongly detected near the trachea and weakly detected in the lungs in mice administered with fluorescent solutions. Almost no fluorescence was seen in the lung region of control mice. Intratracheal administration of surfactant or budesonide increased fluorescent intensity compared with control mice. Combined administration of surfactant and budesonide further increased fluorescent intensity compared with mice given surfactant or budesonide alone. Conclusion: Surfactant and budesonide enhance the pulmonary distribution of fluorescent dye in mice

Dinuclear and Trinuclear Nickel Complexes as Effective Catalysts for Alternating Copolymerization on Carbon Dioxide and Cyclohexene Oxide

A series of novel nickel complexes 1-9 supported by NNO-tridentate Schiff-base derivatives have been synthesized and characterized. Treatment of the pro-ligands [L(1)-H = 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)imino)methyl)phenol, L(2)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4,6-bis(2-phenylpropan-2-yl)phenol, L(3)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)phenol] with Ni(OAc)2·4H2O in refluxing ethanol afforded mono- or bimetallic nickel complexes {[(L(1))Ni(OAc)] (1); (L(2))Ni(OAc)] (2); (L(3))2Ni2(OAc)2(H2O)] (3)}. Alcohol-solvated trimetallic nickel acetate complexes {[(L(3))2Ni3(OAc)4(MeOH)2] (4); (L(3))2Ni3(OAc)4(EtOH)2] (5)} could be generated from the reaction of L(3)-H and anhydrous nickel(II) acetate with a ratio of 2:3 in refluxing anhydrous MeOH or EtOH. The reaction of nickel acetate tetrahydrate and L(4)-H to L(6)-H [L(4)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-5-methoxyphenol, L(5)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4-methoxy-phenol, L(6)-H = 2-(((2-(dimethylamino)ethyl)imino)(phenyl)methyl)phenol] produced, respectively, the alcohol-free trinuclear nickel complexes {[(L(4))2Ni3(OAc)4] (7); [(L(5))2Ni3(OAc)4] (8); [(L(6))2Ni3(OAc)4] (9)} with the same ratio in refluxing EtOH under the atmospheric environment. Interestingly, recrystallization of [(L(3))2Ni3(OAc)4(MeOH)] (4) or [(L(3))2Ni3(OAc)4(EtOH)] (5) in the mixed solvent of CH2Cl2/hexane gives [(L(3))2Ni3(OAc)4] (6), which is isostructural with analogues 7-9. All bi- and trimetallic nickel complexes exhibit efficient activity and good selectivity for copolymerization of CO2 with cyclohexene oxide, resulting in copolymers with a high alternating microstructure possessing ≥99% carbonate-linkage content. This is the first example to apply well-defined trinuclear nickel complexes as efficient catalysts for the production of perfectly alternating poly(cyclohexene carbonate)

Fabrication of Silica-Coated Hollow Carbon Nanospheres Encapsulating Fe₃O₄ Cluster for Magnetical and MR Imaging Guided NIR Light Triggering Hyperthermia and Ultrasound Imaging

Iron oxide nanoparticles (IONPs)-carbon (C) hybrid zero-dimensional nanostructures normally can be categorized into core–shell and yolk–shell architectures. Although IONP-C is a promising theranostic nanoagent, the in vivo study has surprisingly been less described. In addition, little effort has strived toward the fabrication of yolk–shell compared to the core–shell structures. In this context, we synthesized a yolk–shell type of the silica-coated hollow carbon nanospheres encapsulating IONPs cluster, which can be dispersed in aqueous solution for systemic studies in vivo, via the preparation involving the mixed micellization, polymerization/hollowing, sol–gel (hydration–condensation), and pyrolysis processes. Through a surface modification of the polyethylenimine followed by the sol–gel process, the silica shell coating was able to escape from condensing and sintering courses resulting in aggregation, due to the annealing. Not limited to the well-known functionalities in magnetical targeting and magnetic resonance (MR) imaging for IONP-C hybrid structures, we expanded this yolk–shell NPs as a near-infrared (NIR) light-responsive echogenic nanoagent giving an enhanced ultrasound imaging. Overall, we fabricated the NIR sensitive yolk–shell IONP-C to activate ultrasound imaging and photothermal ablation under magnetically and MR imaging guided therapy

Synthesis and Evaluation of Small Molecule Drug Conjugates Harnessing Thioester-Linked Maytansinoids

Ligand-targeting drug conjugates are a class of clinically validated biopharmaceutical drugs constructed by conjugating cytotoxic drugs with specific disease antigen targeting ligands through appropriate linkers. The integrated linker-drug motif embedded within such a system can prevent the premature release during systemic circulation, thereby allowing the targeting ligand to engage with the disease antigen and selective accumulation. We have designed and synthesized new thioester-linked maytansinoid conjugates. By performing in vitro cytotoxicity, targeting ligand binding assay, and in vivo pharmacokinetic studies, we investigated the utility of this new linker-drug moiety in the small molecule drug conjugate (SMDC) system. In particular, we conjugated the thioester-linked maytansinoids to the phosphatidylserine-targeting small molecule zinc dipicolylamine and showed that Zn8_DM1 induced tumor regression in the HCC1806 triple-negative breast cancer xenograft model. Moreover, in a spontaneous sorafenib-resistant liver cancer model, Zn8_DM1 exhibited potent antitumor growth efficacy. From quantitative mRNA analysis of Zn8_DM1 treated-tumor tissues, we observed the elevation of gene expressions associated with a “hot inflamed tumor” state. With the identification and validation of a plethora of cancer-associated antigens in the “omics” era, this work provided the insight that antibody- or small molecule-based targeting ligands can be conjugated similarly to generate new ligand-targeting drug conjugates