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2.
Clinics (Sao Paulo) ; 76: e1816, 2021.
Article in English | MEDLINE | ID: mdl-33787653

ABSTRACT

OBJECTIVE: This study aimed to identify the most useful ultrasound (US) features associated with definite neonatal necrotizing enterocolitis (NEC) and their prognostic values, particularly the calculated markers combined with important features. METHODS: A total of 213 suspected NEC cases were collected from the neonatal department of our hospital from January 2015 to August 2017. Each infant received both X-ray and US examinations. RESULTS: No differences were found in sex composition and delivery modes between groups. NEC-positive neonates had poorer prognosis compared to negative ones. The NEC group showed a higher frequency of abnormal signals. US showed higher NEC-related frequencies in different parameters. A variable (named predictor in US [PUS]) with five features was constructed. For NEC diagnosis, this variable provided a much higher area under the curve Q2 (AUC) (0.965) than other parameters. In this model, PUS had a cutoff value of 0.376 with a 0.900 sensitivity and 0.922 specificity. In prognosis, the closest factors were selected to draw a receiver operating characteristic curve, as well as a novel calculated variable US prognostic (USPro) marker. USPro had a much higher AUC (0.86) than other single features and showed a cutoff value of 0.18145, with 0.75 sensitivity and 0.84 specificity. This variable had a weaker power in prognosis when compared with PUS in diagnosis. CONCLUSIONS: The application of abdominal color Doppler US can provide high accuracy and sensitivity in NEC diagnosis and also contribute to its prognosis, without induction of radiation. Suspected neonates should be examined using this technique as early as possible.


Subject(s)
Enterocolitis, Necrotizing , Infant, Newborn, Diseases , Enterocolitis, Necrotizing/diagnostic imaging , Humans , Infant , Infant, Newborn , Prognosis , ROC Curve , Ultrasonography
3.
BMC Med Imaging ; 21(1): 35, 2021 02 23.
Article in English | MEDLINE | ID: mdl-33622261

ABSTRACT

BACKGROUND: Long-term exposure to coal dust causes respiratory disease. In chest computer tomography (CT), pulmonary nodules, pulmonary interstitial fibrosis and emphysema manifest themselves. However, tracheal foreign bodies caused by coal dust are rarely reported. In this study, we report a special case of a tracheal coal foreign body, in which the patient has neither a history of coal work nor foreign body inhalation. CASE PRESENTATION: A 49-year-old man was diagnosed with chronic obstructive pulmonary disease (COPD) due to chronic cough and exertional dyspnoea. His symptoms gradually worsened despite treatment for COPD. Chest radiograph and CT images showed an irregular high-density nodule inserting fromthe trachea into the right thyroid at approximately the level of the 7th cervical vertebra. Fiberoptic bronchoscopy revealed that the tracheal lumen was mostly blocked. After the surgery, the energy spectrum CT quantitative analysis showed that the foreign body was likely that of a bituminous coal specimen. CONCLUSIONS: For cases in which a foreign body in the airway is highly suspected, early fiberoptic bronchoscopy and radiographic examinations should be performed as soon as possible to avoid misdiagnosis and ensure timely treatment.


Subject(s)
Coal , Dust , Foreign Bodies/diagnostic imaging , Trachea/diagnostic imaging , Tracheal Stenosis/etiology , Bronchoscopy , Dyspnea/etiology , Foreign Bodies/complications , Foreign Bodies/diagnosis , Humans , Male , Middle Aged , Radiography, Thoracic , Tomography, X-Ray Computed , Tracheal Stenosis/diagnosis , Tracheal Stenosis/diagnostic imaging
4.
Clinics ; 76: e1816, 2021. tab, graf
Article in English | LILACS | ID: biblio-1153936

ABSTRACT

OBJECTIVE: This study aimed to identify the most useful ultrasound (US) features associated with definite neonatal necrotizing enterocolitis (NEC) and their prognostic values, particularly the calculated markers combined with important features. METHODS: A total of 213 suspected NEC cases were collected from the neonatal department of our hospital from January 2015 to August 2017. Each infant received both X-ray and US examinations. RESULTS: No differences were found in sex composition and delivery modes between groups. NEC-positive neonates had poorer prognosis compared to negative ones. The NEC group showed a higher frequency of abnormal signals. US showed higher NEC-related frequencies in different parameters. A variable (named predictor in US [PUS]) with five features was constructed. For NEC diagnosis, this variable provided a much higher area under the curve Q2 (AUC) (0.965) than other parameters. In this model, PUS had a cutoff value of 0.376 with a 0.900 sensitivity and 0.922 specificity. In prognosis, the closest factors were selected to draw a receiver operating characteristic curve, as well as a novel calculated variable US prognostic (USPro) marker. USPro had a much higher AUC (0.86) than other single features and showed a cutoff value of 0.18145, with 0.75 sensitivity and 0.84 specificity. This variable had a weaker power in prognosis when compared with PUS in diagnosis. CONCLUSIONS: The application of abdominal color Doppler US can provide high accuracy and sensitivity in NEC diagnosis and also contribute to its prognosis, without induction of radiation. Suspected neonates should be examined using this technique as early as possible.


Subject(s)
Humans , Infant, Newborn , Infant , Enterocolitis, Necrotizing/diagnostic imaging , Infant, Newborn, Diseases , Prognosis , ROC Curve , Ultrasonography
5.
Mol Med Rep ; 19(6): 4727-4734, 2019 Jun.
Article in English | MEDLINE | ID: mdl-31059065

ABSTRACT

The aim of the present study was to investigate the protective effect of integrin ß1 in the treatment of stress urinary incontinence (SUI) by electrical stimulation, and the underlying mechanisms by which electrical stimulation regulates the collagen metabolism of female vaginal wall fibroblasts (FVWFs). FVWFs obtained from the vaginal wall tissue of patients with (Ingelman­Sundberg scale; grade II, n=8; grade III, n=10) or without (n=8) SUI during gynecological operations were isolated by enzymatic digestion and subsequently identified by immunocytochemistry. Following this, cultured FVWFs were treated with an inhibitor of integrin ß1, recombinant human integrin ß1 and electrical stimulation (100 mv/mm, 2 h, 20 Hz), followed by total mRNA and protein extraction. mRNA and protein expression levels of integrin ß1, transforming growth factor (TGF)­ß1 and collagen (COL) I and III in FVWFs were quantified by reverse transcription­quantitative PCR (RT­qPCR) and western blot analysis respectively. Integrin ß1, TGF­ß1 and COL I and III expression levels were decreased in patients with SUI compared with healthy controls, and the grade III group had lower levels than the grade II group. Following electrical stimulation treatment, the expression levels of TGF­ß1, COL I and III were enhanced in the grade II group, but not in the grade III group. Nevertheless, the inhibitor of integrin ß1 reduced the protective effect of electrical stimulation in the grade II group. In addition, electrical stimulation combined with recombinant human integrin ß1 could also protect cells from SUI in the grade III group. The present study provides evidence for the increased degradation of the extracellular matrix and integrin ß1 in the vaginal wall tissues of patients with SUI, and the protective effect of electrical stimulation against SUI via integrin ß1. These results provide a novel mechanism for the treatment of SUI using electrical stimulation.


Subject(s)
Electric Stimulation/methods , Integrin beta1/pharmacology , Integrin beta1/therapeutic use , Urinary Incontinence, Stress/drug therapy , Collagen Type I/metabolism , Collagen Type III/metabolism , Extracellular Matrix/metabolism , Female , Fibroblasts/metabolism , Fibroblasts/pathology , Humans , Transforming Growth Factor beta1 , Urinary Incontinence , Vagina/metabolism , Vagina/pathology
6.
Oncol Rep ; 41(2): 917-927, 2019 Feb.
Article in English | MEDLINE | ID: mdl-30483796

ABSTRACT

Metastasis is the most common cause of death in ovarian cancer patients but remains largely untreated. Epithelial­mesenchymal transition (EMT) is critical for the conversion of early­stage ovarian tumors into metastatic malignancies. Thus, investigating the signaling pathways promoting EMT may identify potential targets for the treatment of metastatic ovarian cancer. Lysine demethylase 2A (KDM2A), also known as FBXL11 and JHDM1A, is a histone H3 lysine 36 (H3K36) demethylase that regulates EMT and the metastasis of ovarian cancer. However, the function and underlying mechanisms of EMT suppression in ovarian cancer have not been thoroughly elucidated to date. In the present study, we used Gene Expression Omnibus (GEO) databases to determine that KDM2A is significantly upregulated in human ovarian cancers. KDM2A expression was assessed by immunohistochemistry of epithelial ovarian cancer (EOC) borderline ovarian tumors and normal ovary tissues. Seven fresh EOC tissues and 3 fresh normal ovary tissues were collected for western blot analysis. Kaplan­Meier survival curves were constructed to identify genes related to EOC prognosis from the TCGA data portal. Stable KDM2A­knockdown cell lines were established to study the biological functions and underlying mechanisms of KDM2A in EMT in vitro. GEO database analysis revealed that KDM2A was highly upregulated in EOC tissues; this analysis was accompanied by immunochemistry and western blot analysis using samples of human tissues. High expression of KDM2A was associated with poor survival in EOC patients. KDM2A knockdown promoted apoptosis and suppressed the proliferation, migration and invasion of tumor cells in vitro. EMT and the PI3K/AKT/mTOR signaling pathway were suppressed in KDM2A­silenced cells. Inactivation of the PI3K/AKT/mTOR signaling pathway in A2780 cells induced EMT inhibition. Our data revealed that KDM2A functions as a tumor oncogene, and the downregulation of KDM2A expression regulates EMT and EOC progression, providing a valuable prognostic marker and potential target for the treatment of EOC patients.


Subject(s)
Biomarkers, Tumor/metabolism , Carcinoma, Ovarian Epithelial/genetics , Epithelial-Mesenchymal Transition/genetics , F-Box Proteins/metabolism , Jumonji Domain-Containing Histone Demethylases/metabolism , Oncogene Proteins/metabolism , Ovarian Neoplasms/genetics , Adult , Aged , Biomarkers, Tumor/genetics , Carcinoma, Ovarian Epithelial/mortality , Carcinoma, Ovarian Epithelial/pathology , Cell Line, Tumor , Cell Proliferation/genetics , Datasets as Topic , Disease Progression , Down-Regulation , F-Box Proteins/genetics , Female , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Humans , Jumonji Domain-Containing Histone Demethylases/genetics , Kaplan-Meier Estimate , Middle Aged , Oncogene Proteins/genetics , Ovarian Neoplasms/mortality , Ovarian Neoplasms/pathology , Ovary/pathology , Phosphatidylinositol 3-Kinases/metabolism , Prognosis , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction/genetics , TOR Serine-Threonine Kinases/metabolism , Up-Regulation , Young Adult
7.
Sci Rep ; 8(1): 10938, 2018 Jul 19.
Article in English | MEDLINE | ID: mdl-30026578

ABSTRACT

Intrinsic defects give rise to scattering processes governing the transport properties of mesoscopic systems. We investigate analytically and numerically the local density of states in Bernal stacking bilayer graphene with a point defect. With Bernal stacking structure, there are two types of lattice sites. One corresponds to connected sites, where carbon atoms from each layer stack on top of each other, and the other corresponds to disconnected sites. From our theoretical study, a picture emerges in which the pronounced zero-energy peak in the local density of states does not attribute to zero-energy impurity states associated to two different types of defects but to a collective phenomenon of the low-energy resonant states induced by the defect. To corroborate this description, we numerically show that at small system size N, where N is the number of unit cells, the zero-energy peak near the defect scales as 1/lnN for the quasi-localized zero-energy state and as 1/N for the delocalized zero-energy state. As the system size approaches to the thermodynamic limit, the former zero-energy peak becomes a power-law singularity 1/|E| in low energies, while the latter is broadened into a Lorentzian shape. A striking point is that both types of zero-energy peaks decay as 1/r2 away from the defect, manifesting the quasi-localized character. Based on our results, we propose a general formula for the local density of states in low-energy and in real space. Our study sheds light on this fundamental problem of defects.

8.
Sci Rep ; 8(1): 3333, 2018 02 20.
Article in English | MEDLINE | ID: mdl-29463902

ABSTRACT

Recent molecularly targeted approaches have gained advances in nasopharyngeal carcinoma treatment. However, the estimated five-year survival rate has not met the desired degree of improvement. Here, we report that upregulation of the expression of the SOX2-activated lncRNA ANRIL is involved in nasopharyngeal carcinoma. ANRIL has been found to be upregulated in clinical nasopharyngeal carcinoma. Using genetic approaches targeting ANRIL in nasopharyngeal carcinoma cells, we found that the knockdown of ANRIL inhibits cell proliferation in vitro and in vivo. Mechanistically, SOX2 binds with ANRIL and increases its RNA level, which upregulates ß-catenin signalling, resulting in enhanced nasopharyngeal carcinoma tumourigenesis. Expression levels of ANRIL are positively correlated with SOX2 and ß-catenin in clinical nasopharyngeal carcinoma samples. Our findings demonstrate that the SOX2-ANRIL-ß-catenin axis plays a critical role in nasopharyngeal carcinoma proliferation and provide a potential therapeutic approach for nasopharyngeal carcinoma patients.


Subject(s)
Biomarkers, Tumor/metabolism , Cell Transformation, Neoplastic/pathology , Gene Expression Regulation, Neoplastic , Nasopharyngeal Carcinoma/pathology , RNA, Long Noncoding/genetics , SOXB1 Transcription Factors/metabolism , Animals , Apoptosis , Biomarkers, Tumor/genetics , Case-Control Studies , Cell Proliferation , Cell Transformation, Neoplastic/genetics , Cell Transformation, Neoplastic/metabolism , Female , Follow-Up Studies , Humans , Mice , Mice, Inbred BALB C , Mice, Nude , Nasopharyngeal Carcinoma/genetics , Nasopharyngeal Carcinoma/metabolism , Prognosis , SOXB1 Transcription Factors/genetics , Survival Rate , Tumor Cells, Cultured , Xenograft Model Antitumor Assays , beta Catenin/genetics , beta Catenin/metabolism
9.
Int J Mol Med ; 40(2): 347-356, 2017 Aug.
Article in English | MEDLINE | ID: mdl-28656271

ABSTRACT

The present study aimed to reveal the metabolic alterations of the extracellular matrix (ECM) in uterosacral ligament (USL) with pelvic organ prolapse (POP) and to explore the role of transforming growth factor­ß1 (TGF­ß1) in pathogenesis of POP. For this purpse, 60 participants who underwent hysterectomy for benign indications were enrolled, 30 of which had symptomatic POP (grade II, III or IV) and composed the POP group, and the other 30 had asymptomatic POP (grade I or less) and served as the controls. Collagen fibers, elastin,matrix metalloproteinase (MMP)­2/9, tissue inhibitor of matrix metalloproteinases (TIMP)­2 and TGF­ß1 were examined by Masson's trichrome staining, immunohistochemistry and RT-qPCR using USL biopsies. In vitro, human USL fibroblasts (hUSLFs) were primary cultured, pre-treated with recombinant TGF­ß1 (0, 5, or 10 ng/ml) and then subjected to cyclic mechanical stretching (CMS; 0 or 5,333 µÎµ strain). Changes in the expression levels of collagen type I/III, elastin, TIMP­2, MMP­2/9 and Smad were detected. Our results revealed that at the tissue level, the expression of collagen fibers, elastin, TIMP­2 and TGF­ß1 was significantly reduced in the POP group, while the activities of MMP­2/9 were significantly upregulated, compared with the control group. Statistical analysis indicated that the mRNA expression of TGF­ß1 inversely correlated with the severity of POP partially. Our in vitro experimental data demonstrated that a CMS of 5333 µÎµ strain promoted the degradation of ECM proteins, inhibited the synthesis of TIMP­2, and upregulated the proteolytic activities of MMP­2/9. Pre-treatment with TGF­ß1 attenuated the loss of ECM by stimulating the synthesis of TIMP­2 and inhibiting the activities of MMP­2/9 through the TGF­ß1/Smad3 signaling pathway. On the whole, our data indicate that the reduced anabolism and increased catabolism of ECM proteins in USL are the pathological characteristics of POP. TGF­ß1 not only has a specific value in predicting the severity of POP, but should also be considered as a novel therapeutic target for POP.


Subject(s)
Extracellular Matrix/pathology , Pelvic Organ Prolapse/pathology , Signal Transduction , Transforming Growth Factor beta1/metabolism , Cells, Cultured , Collagen/analysis , Collagen/metabolism , Elastin/analysis , Elastin/metabolism , Extracellular Matrix/metabolism , Female , Humans , Matrix Metalloproteinase 2/analysis , Matrix Metalloproteinase 2/metabolism , Matrix Metalloproteinase 9/analysis , Matrix Metalloproteinase 9/metabolism , Middle Aged , Pelvic Organ Prolapse/metabolism , Pelvic Organ Prolapse/therapy , Proteolysis , Smad Proteins/analysis , Smad Proteins/metabolism , Tissue Inhibitor of Metalloproteinase-2/analysis , Tissue Inhibitor of Metalloproteinase-2/metabolism , Transforming Growth Factor beta1/analysis , Transforming Growth Factor beta1/therapeutic use
10.
Int J Gynecol Cancer ; 26(9): 1557-1563, 2016 11.
Article in English | MEDLINE | ID: mdl-27540692

ABSTRACT

AIM: The aim of this study was to investigate the effects of punicalagin, a polyphenol isolated from Punica granatum, on human A2780 ovarian cancer cells in vitro. METHODS: The viability of human A2780 ovarian cells was evaluated using Cell Counting Kit-8 assay. Cell cycle was detected with flow cytometry analysis. The protein expression levels of Bcl-2, Bax, ß-catenin, cyclin D1, survivin, tissue inhibitor of metalloproteinase (TIMP)-2, and TIMP-3 were measured using Western blot analysis. Matrix metalloproteinase (MMP)-2 and MMP-9 activity was determined with gelatin zymography. Wound healing assay was used to determine cell migration. RESULTS: Punicalagin inhibited the cell viability of A2780 cells in a dose- and time-dependent manner, and the cell cycle of A2780 cells was arrested in G1/S phase transition. The treatment also induced apoptosis as shown by the up-regulation of Bax and down-regulation of Bcl-2. On the other hand, punicalagin treatment increased the expressions of TIMP-2 and TIMP-3, decreased the activities of MMP-2 and MMP-9, and inhibited cell migration. In addition, the ß-catenin pathway was suppressed as shown by the down-regulations of ß-catenin and its downstream factors including cyclin D1 and survivin. CONCLUSIONS: Punicalagin may have cancer-chemopreventive as well as cancer-chemotherapeutic effects against human ovarian cancer in humans through the inhibition of ß-catenin signaling pathway.


Subject(s)
Carcinoma/drug therapy , Hydrolyzable Tannins/therapeutic use , Ovarian Neoplasms/drug therapy , Carcinoma/metabolism , Cell Cycle/drug effects , Cell Line, Tumor , Cell Movement/drug effects , Drug Screening Assays, Antitumor , Female , Humans , Hydrolyzable Tannins/pharmacology , Matrix Metalloproteinases/metabolism , Ovarian Neoplasms/metabolism , Signal Transduction/drug effects , Tissue Inhibitor of Metalloproteinases/metabolism , bcl-2-Associated X Protein/metabolism , beta Catenin/metabolism
11.
J Chem Phys ; 142(6): 064708, 2015 Feb 14.
Article in English | MEDLINE | ID: mdl-25681936

ABSTRACT

We have studied the growth of S layers adsorbed on Au(100) with low-energy electron diffraction (LEED), X-ray photoemission spectra (XPS), and scanning tunneling microscope (STM). Three phases of S/Au(100)-(2 × 2), trimer, and c(2 × 4)-are identified; the latter two are not previously reported. A dose of S2 at 300 K transformed Au(100)-(5 × 20) initially into the (2 × 2) phase and formed the c(2 × 4) phase at a saturation coverage. The STM results show that monolayer Au islands formed during the initial S dose and remained throughout the growth, resulting in a rough c(2 × 4) surface. We show that a highly ordered c(2 × 4) phase can be obtained with a flat (2 × 2) phase as an intermediate step during growth. Based on the evolution of XPS and STM images with varied S2 dose, the components of S 2p are assigned and structural models for the various S/Au(100) phases are proposed. In the (2 × 2) phase, one S atom resides on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.25 ML; in the trimer phase, three S atoms form a trimer residing on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.75 ML; in the c(2 × 4) phase, there are five S atoms in each primitive unit cell of c(2 × 4); three of them form a trimer residing on a four-fold hollow site, and the other two form a dimer located on the top of the trimer, corresponding to a nominal S coverage of 1.25 ML. With the proposed structural models, the growth of S on Au(100) at 300 K is described in detail.

12.
Front Biosci (Elite Ed) ; 4(4): 1303-13, 2012 01 01.
Article in English | MEDLINE | ID: mdl-22201956

ABSTRACT

Tanshinone IIA (Tan IIA), an active component derived from Salvia miltiorrhiza root, has been used to treat various ischemic cardiovascular and cerebrovascular diseases. However, its impact on hepatic ischemia/reperfusion (I/R) injury remains unclear. Here, we addressed this issue by using a 90-minute partial liver ischemia model. Mice were administered Tan IIA intragastrically for 3 days before ischemia and were assessed for liver damage 6-h after reperfusion. Tan IIA pretreatment significantly inhibited serum aminotransferases and proinflammatory cytokine levels along with reduced inflammatory infiltration and liver damage. Mechanistic studies revealed that Tan IIA suppressed TLR4 expression in nonparenchymal cells (NPCs) and induced heme oxygenase-1 (HO-1) production in both parenchymal and NPCs. Moreover, the phosphorylation of AKT and ERK1/2 in the liver was enhanced, while the phosphorylation of JNK, p38 and p65 was suppressed. These results suggest Tan IIA can suppress TLR4 signaling which then enhances HO-1 expression along with reduced proinflammatory cytokine expressions in the liver, and Tan IIA could be a useful candidate drug in clinic for prevention and treatment of hepatic I/R injury.


Subject(s)
Abietanes/therapeutic use , Liver/blood supply , Reperfusion Injury/drug therapy , Animals , Base Sequence , Blotting, Western , DNA Primers , Immunohistochemistry , Male , Mice , Mice, Inbred C57BL , Real-Time Polymerase Chain Reaction
13.
ACS Nano ; 5(3): 1792-7, 2011 Mar 22.
Article in English | MEDLINE | ID: mdl-21319850

ABSTRACT

Defining pathways to assemble long-range-ordered 2D nanostructures of specifically designed organic molecules is required in order to optimize the performance of organic thin-film electronic devices. We report on the rapid fabrication of a nearly perfect self-assembled monolayer (SAM) composed of a single-domain 6,13-dichloropentacene (DCP) brick-wall pattern on Au(788). Scanning tunneling microscopy (STM) results show the well-ordered DCP SAM extends over hundreds of nanometers. Combining STM results with insights from density functional theory, we propose that a combination of unique intermolecular and molecule-step interactions drives the DCP SAM formation.


Subject(s)
Crystallization/methods , Gold/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Naphthacenes/chemistry , Adsorption , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Surface Properties
14.
Phys Rev Lett ; 101(15): 157203, 2008 Oct 10.
Article in English | MEDLINE | ID: mdl-18999634

ABSTRACT

The magnetic circular dichroism of III-V diluted magnetic semiconductors, calculated within a theoretical framework suitable for highly disordered materials, is shown to be dominated by optical transitions between the bulk bands and an impurity band formed from magnetic dopant states. The real-space Green's functions incorporate spatial correlations in the disordered conduction band and valence-band electronic structure, and include extended and localized states on an equal basis. Our findings reconcile unusual trends in the experimental magnetic circular dichroism in III-V diluted magnetic semiconductors with the antiferromagnetic p-d exchange interaction between a magnetic dopant spin and its host.

15.
Phys Rev Lett ; 100(2): 027603, 2008 Jan 18.
Article in English | MEDLINE | ID: mdl-18232926

ABSTRACT

The transition from disorder to order in Ag film grown on Au(111) was investigated by monitoring the quantum well states using angle-resolved photoelectron spectroscopy. Our results show that the binding energies do not alter, but the in-plane dispersion alters from flat to parabolic when the film is annealed. We suggest that there are isolated and ordered patches scattered across the film at an early stage of the transition and that atoms inside the patches are fully ordered along the surface normal. These ordered patches grow and merge together as the annealing temperature increases.

17.
Phys Rev Lett ; 97(10): 106803, 2006 Sep 08.
Article in English | MEDLINE | ID: mdl-17025843

ABSTRACT

We propose a method for all-electrical manipulation of single ion spins substituted into a semiconductor. Mn ions with a bound hole in GaAs form a natural example. Direct electrical manipulation of the ion spin is possible, because electric fields manipulate the orbital wave function of the hole, and through the spin-orbit coupling the spin is reoriented as well. Coupling ion spins can be achieved using gates to control the size of the hole wave function. Coherent manipulation of ionic spins may find applications in high-density storage and in scalable coherent or quantum information processing.

19.
Nature ; 442(7101): 436-9, 2006 Jul 27.
Article in English | MEDLINE | ID: mdl-16871214

ABSTRACT

The discovery of ferromagnetism in Mn-doped GaAs has ignited interest in the development of semiconductor technologies based on electron spin and has led to several proof-of-concept spintronic devices. A major hurdle for realistic applications of Ga(1-x)Mn(x)As, or other dilute magnetic semiconductors, remains that their ferromagnetic transition temperature is below room temperature. Enhancing ferromagnetism in semiconductors requires us to understand the mechanisms for interaction between magnetic dopants, such as Mn, and identify the circumstances in which ferromagnetic interactions are maximized. Here we describe an atom-by-atom substitution technique using a scanning tunnelling microscope (STM) and apply it to perform a controlled study at the atomic scale of the interactions between isolated Mn acceptors, which are mediated by holes in GaAs. High-resolution STM measurements are used to visualize the GaAs electronic states that participate in the Mn-Mn interaction and to quantify the interaction strengths as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga(1-x)Mn(x)As structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples.

20.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(5 Pt 2): 055401, 2004 May.
Article in English | MEDLINE | ID: mdl-15244872

ABSTRACT

We study the width-amplitude relation for three-dimensional Bernstein-Greene-Kruskal (BGK) electrostatic solitary waves in magnetized plasmas, taking into account the dynamics of both electrons and ions. We obtain two coupled inequalities that constrain the amplitude and the widths parallel and perpendicular to the magnetic field for a Gaussian potential, and demonstrate how the solution space is further constrained by the finite temperature ratio between electrons and ions. The description is valid for both the electron and ion mode solitary waves. Our results provide a quantitative basis for understanding the ubiquity of BGK waves in widely different classes of collisionless plasmas.

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