A Comparison of Antibacterial Activity of Selected Thyme (Thymus) Species by Means of the Dot Blot Test with Direct Bioautographic Detection.

PubMed

Orłowska, Marta; Kowalska, Teresa; Sajewicz, Mieczysław; Jesionek, Wioleta; Choma, Irena M; Majer-Dziedzic, Barbara; Szymczak, Grażyna; Waksmundzka-Hajnos, Monika

2015-01-01

Bioautography carried out with the aid of thin-layer chromatographic adsorbents can be used to assess antibacterial activity in samples of different origin. It can either be used as a simple and cost-effective detection method applied to a developed chromatogram, or to the dot blot test performed on a chromatographic plate, where total antibacterial activity of a sample is scrutinized. It was an aim of this study to compare antibacterial activity of 18 thyme (Thymus) specimens and species (originating from the same gardening plot and harvested in the same period of time) by means of a dot blot test with direct bioautography. A two-step extraction of herbal material was applied, and at step two the polar fraction of secondary metabolites was obtained under the earlier optimized extraction conditions [methanol-water (27+73, v/v), 130°C]. This fraction was then tested for its antibacterial activity against Bacillus subtilis bacteria. It was established that all investigated extracts exhibited antibacterial activity, yet distinct differences were perceived in the size of the bacterial growth inhibition zones among the compared thyme species. Based on the results obtained, T. citriodorus "golden dwarf" (sample No. 5) and T. marschallianus (sample No. 6) were selected as promising targets for further investigations and possible inclusion in a herbal pharmacopeia, which is an essential scientific novelty of this study.

[Analytic study of dot blotting for the detection of anti-Jo-1, anti-M2, anti-ribosomes and anti-LKM].

PubMed

Huguet, S; Sghiri, R; Ballot, E; Johanet, C

2004-01-01

The Cyto-Dot 4 HM043 kit commercialised by BMD, has replaced the Cyto-Dot HM010 kit that allowed three auto-antibodies detection (anti-Jo-1, anti-M2 and anti-ribosomal protein). Detection of anti-LKM1 auto-antibody was added. These four auto-antibodies have in common only the intracytoplasmic localisation of their respective antigen. The aim of our study was to evaluate this new kit using 104 sera and to compare our results with reference techniques (indirect immunofluorescence IF for anti-M2, anti-ribosomal protein and anti-LKM1, double immunodiffusion ID for anti-Jo-1 and anti-LKM1, western blotting WB for anti-M2) and with Cyto-Dot HM010. The one hundred and four sera were divided into five groups: Group I (n = 12) with anti-Jo-1 detected by ID; Group II (n = 28) with 26 anti-M2 positive by IF and WB, 2 anti-M2 positive only by WB; Group III (n = 10) with anti-ribosomal protein detected by IF 5 of which precipitated by ID; Group IV (n = 32) with anti-LKM1 by IF and ID divided into 18 AIH2 and 14 HCV; Group V (n = 22) consisting of 14 healthy individuals and 8 patients with hypergammaglobulinemia. Results of this study are similar to those of Cyto-Dot HM010 for the three auto-antibodies already in use. Cyto-Dot 4 is a very good anti-LKM1 confirmation method as it is ID. Copyright John Libbey Eurotext 2003.

[Preparation and application of monoclonal antibodies against DR region of Na+-K+-ATPase α1 subunit].

PubMed

Yan, Xiaofei; Wu, Litao; DU, Xiaojuan; Li, Jing; Zhang, Fujun; Han, Yan; Lyu, Shemin; Li, Dongmin

2016-12-01

Objective To prepare monoclonal antibodies against DR region (897DVEDSYGQQWTYEQR911) of Na + -K + -ATPase α1 subunit and identify their properties. Methods BALB/c mice were immunized with DR-keyholelimpet hemocyanin (KLH). Splenocytes from the immunized mice were collected and subsequently fused with SP2/0 mouse myeloma cells. Positive hybridoma clones were obtained after cell fusion and selection. ELISA was used to detect DR antibody titer in the cell supernatants. DR region-specific monoclonal antibodies were analyzed by dot blotting, Western blotting and immunofluorescence assay. Na + -K + -ATPase activity was detected by SensoLyte R FDP Protein Phosphatase Assay Kit and the protective effect of the monoclonal antibody against high glucose-induced cell injury was assessed in H9c2 cells. Results Three hybridoma cell lines which secreted stable DR monoclonal antibody were obtained. The strongest positive cell line, named DRm217, was selected to prepare ascites. Dot blotting, Western blotting and immunofluorescence assay showed that DRm217 recognized specially DR region of Na + -K + -ATPase and bound on H9c2 cell membranes. DRm217 stimulated Na + -K + -ATPase activity and alleviated high glucose-induced H9c2 cells injury. Conclusion The monoclonal antibodies against DR region of Na + -K + -ATPase α1 subunit is prepared.

Resveratrol inhibits beta-amyloid oligomeric cytotoxicity but does not prevent oligomer formation.

PubMed

Feng, Ying; Wang, Xiao-ping; Yang, Shi-gao; Wang, Yu-jiong; Zhang, Xi; Du, Xue-ting; Sun, Xiao-xia; Zhao, Min; Huang, Lei; Liu, Rui-tian

2009-11-01

Beta-amyloid (Abeta) aggregation has been strongly associated with the neurodegenerative pathology and a cascade of harmful event rated to Alzheimer's disease (AD). Inhibition of Abeta assembly, destabilization of preformed Abeta aggregates and attenuation of the cytotoxicity of Abeta oligomers and fibrils could be valuable therapeutics of patients with AD. Recent studies suggested that moderate consumption of red wine and intake of dietary polyphenols, such as resveratrol, may benefit AD phenotypes in animal models and reduce the relative risk for AD clinical dementia. To understand the mechanism of this neuroprotection, we studied the effects of resveratrol, an active ingredient of polyphenols in wine and many plants, on the polymerization of Abeta42 monomer, the destabilization of Abeta42 fibril and the cell toxicity of Abeta42 in vitro using fluorescence spectroscopic analysis with thioflavin T (ThT), transmission electron microscope (TEM), circular dichroism (CD) and MTT assay. The results showed that resveratrol could dose-dependently inhibit Abeta42 fibril formation and cytotoxicity but could not prevent Abeta42 oligomerization. The studies by Western-blot, dot-blot and ELISA confirmed that the addition of resveratrol resulted in numerous Abeta42 oligomer formation. In conjunction with the concept that Abeta oligomers are linked to Abeta toxicity, we speculate that aside from potential antioxidant activities, resveratrol may directly bind to Abeta42, interfere in Abeta42 aggregation, change the Abeta42 oligomer conformation and attenuate Abeta42 oligomeric cytotoxicity.

Isolation of RNA for dot hybridization by heparin-DNase I treatment of whole cell lysate.

PubMed

Krawczyk, Z; Wu, C

1987-08-15

We have developed a new procedure for the rapid preparation of undegraded total RNA from cultured cells for specific quantitation by dot blotting analysis. Pelleted cells are resuspended in hypotonic solution containing a ribonuclease inhibitor and heparin and disrupted by freeze-thaw. Heparin is employed as an agent for nuclear lysis, dissociation of chromosomal protein, and release of mRNA from rough endoplasmic reticulum. We eliminate chromosomal DNA by digestion with DNase I and denature the RNA in the lysate with formaldehyde. After centrifugation to remove debris, the supernatant is used directly for dot blotting. All manipulations are performed in the same microfuge tube and recovery of RNA is quantitative. The procedure is especially useful for processing large numbers of samples. We illustrate its versatility by analysis of specific RNAs in Drosophila, rat, and human cell lines. In reconstruction experiments, less than 80 molecules per cell of a small RNA (beta-globin) can be detected under highly stringent hybridization conditions, using only moderately labeled double-stranded plasmid DNA probes and short film exposures.

Application of a Dot Blot Hybridization Platform to Assess Streptococcus uberis Population Structure in Dairy Herds

PubMed Central

Albuquerque, Pedro; Ribeiro, Niza; Almeida, Alexandre; Panschin, Irena; Porfirio, Afonso; Vales, Marta; Diniz, Francisca; Madeira, Helena; Tavares, Fernando

2017-01-01

Streptococcus uberis is considered one of the most important pathogens associated with bovine mastitis. While traditionally acknowledged as an environmental pathogen, S. uberis has been shown to adopt a contagious epidemiological pattern in several dairy herds. Since different control strategies are employed depending on the mode of transmission, in-depth studies of S. uberis populations are essential to determine the best practices to control this pathogen. In this work, we optimized and validated a dot blot platform, combined with automatic image analysis, to rapidly assess the population structure of infective S. uberis, and evaluated its efficiency when compared to multilocus sequence analysis (MLSA) genotyping. Two dairy herds with prevalent S. uberis infections were followed in a 6 month period, in order to collect and characterize isolates from cows with persistent infections. These herds, located in Portugal (Barcelos and Maia regions), had similar management practices, with the herd from Barcelos being smaller and having a better milking parlor management, since infected cow segregation was immediate. A total of 54 S. uberis isolates were obtained from 24 different cows from the two herds. To overcome operator-dependent analysis of the dot blots and increase the technique's consistency and reliability, the hybridization signals were converted into probability values, with average probabilities higher than 0.5 being considered positive results. These data allowed to confirm the isolates' identity as S. uberis using taxa-specific markers and to determine the presence of virulence- and antibiotic resistance-related genes. In addition, MLSA allowed to disclose the most prevalent S. uberis clonal lineages in both herds. Seven different clusters were identified, with Barcelos showing a high clonal diversity and Maia a dominant lineage infecting most cows, suggesting distinct epidemiological patterns, with S. uberis displaying an environmental or contagious transmission pattern depending on the herd. Overall, this work showed the utility of dot blot and MLSA to characterize population structure and epidemiological patterns of mastitis-causing S. uberis. This approach allowed to disclose prevalent virulence patterns and clonal lineages of S. uberis in two distinct herds, and gain insights on the impact of herd management practices on pathogen population structure. PMID:28174566

Enzyme-linked immunosorbent assays for Z-DNA.

PubMed

Thomas, M J; Strobl, J S

1988-10-01

Dot blot and transblot enzyme-linked immunosorbent assays (e.l.i.s.a.) are described which provide sensitive non-radioactive methods for screening Z-DNA-specific antisera and for detecting Z-DNA in polydeoxyribonucleotides and supercoiled plasmids. In the alkaline phosphatase dot blot e.l.i.s.a., Z-DNA, Br-poly(dG-dC).poly(dG-dC), or B-DNA, poly(dG-dC).poly(dG-dC), poly(dA-dT).poly(dA-dT), Br-poly(dI-dC).poly(dI-dC), or salmon sperm DNA were spotted onto nitrocellulose discs and baked. The e.l.i.s.a. was conducted in 48-well culture dishes at 37 degrees C using a rabbit polyclonal antiserum developed against Br-poly(dG-dC).poly(dG-dC), an alkaline phosphatase-conjugated second antibody, and p-nitrophenol as the substrate. Under conditions where antibody concentrations were not limiting, alkaline phosphatase activity was linear for 2 h. Dot blot e.l.i.s.a. conditions are described which allow quantification of Z-DNA [Br-poly(dG-dC).poly(dG-dC)] within the range 5-250 ng. Dot blot and transblot horseradish peroxidase e.l.i.s.a. are described that detect Z-DNA within supercoiled plasmid DNAs immobilized on diazophenylthioether (DPT) paper. In the transblot e.l.i.s.a., plasmid pUC8 derivatives containing 16, 24, or 32 residues of Z-DNA were electrophoresed in agarose gels and electrophoretically transferred to DPT paper. Z-DNA-antibody complexes were detected by the horseradish peroxidase-catalysed conversion of 4-chloro-1-naphthol to a coloured product that was covalently bound to the DPT paper. Z-DNA antibody reactivity was specific for supercoiled Z-DNA containing plasmids after removal of the antibodies cross-reactive with B-DNA by absorption onto native DNA-cellulose. The transblot e.l.i.s.a. was sensitive enough to detect 16 base pairs of alternating G-C residues in 100 ng of pUC8 DNA.

Development of a biotinylated DNA probe for detection of infectious hematopoietic necrosis virus

USGS Publications Warehouse

Deering, R.E.; Arakawa, C.K.; Oshima, K.H.; O'Hara, P.J.; Landolt, M.L.; Winton, J.R.

1991-01-01

A nonrad~oact~ve DNA probe assay was developed to detect and ~dent~fy infect~ous hernatopoiet~c necrosls virus (IHNV) uslng a dot blot format The probe a synthet~c DNA oligonucleot~de labeled enzymatlcally w~th biotln hybnd~zed spec~f~cally w~th nucleocaps~d mRNA extracted from Infected cells early In the vlrus repl~cation cycle A rap~d guan~dln~um th~ocyanate based RNA extraction method uslng RNAzol B and rn~crocentrifuge tubes eff~c~ently pioduced h~gh qual~ty RNA from 3 commonly used f~sh cell llnes, CHSE-214, CHH-1, and EPC The probe reacted with 6 d~verse ~solates of IHNV, but d~d not react \

Application of a reverse dot blot DNA-DNA hydridization method to quantify host-feeding tendencies of two sibling species in the Anopheles gambiae complex.

PubMed

Fritz, M L; Miller, J R; Bayoh, M N; Vulule, J M; Landgraf, J R; Walker, E D

2013-12-01

A DNA-DNA hybridization method, reverse dot blot analysis (RDBA), was used to identify Anopheles gambiae s.s. and Anopheles arabiensis (Diptera: Culicidae) hosts. Of 299 blood-fed and semi-gravid An. gambiae s.l. collected from Kisian, Kenya, 244 individuals were identifiable to species; of these, 69.5% were An. arabiensis and 29.5% were An. gambiae s.s. Host identifications with RDBA were comparable with those of conventional polymerase chain reaction (PCR) followed by direct sequencing of amplicons of the vertebrate mitochondrial cytochrome b gene. Of the 174 amplicon-producing samples used to compare these two methods, 147 were identifiable by direct sequencing and 139 of these were identifiable by RDBA. Anopheles arabiensis bloodmeals were mostly (94.6%) bovine in origin, whereas An. gambiae s.s. fed upon humans more than 91.8% of the time. Tests by RDBA detected that two of 112 An. arabiensis contained blood from more than one host species, whereas PCR and direct sequencing did not. Recent use of insecticide-treated bednets in Kisian is likely to have caused the shift in the dominant vector species from An. gambiae s.s. to An. arabiensis. Reverse dot blot analysis provides an opportunity to study changes in host-feeding by members of the An. gambiae complex in response to the broadening distribution of vector control measures targeting host-selection behaviours. © 2013 The Royal Entomological Society.

Analysis of differentially expressed genes in two immunologically distinct strains of Eimeria maxima using suppression subtractive hybridization and dot-blot hybridization

PubMed Central

2014-01-01

Background It is well known that different Eimeria maxima strains exhibit significant antigenic variation. However, the genetic basis of these phenotypes remains unclear. Methods Total RNA and mRNA were isolated from unsporulated oocysts of E. maxima strains SH and NT, which were found to have significant differences in immunogenicity in our previous research. Two subtractive cDNA libraries were constructed using suppression subtractive hybridization (SSH) and specific genes were further analyzed by dot-blot hybridization and qRT-PCR analysis. Results A total of 561 clones were selected from both cDNA libraries and the length of the inserted fragments was 0.25–1.0 kb. Dot-blot hybridization revealed a total of 86 differentially expressed clones (63 from strain SH and 23 from strain NT). Nucleotide sequencing analysis of these clones revealed ten specific contigs (six from strain SH and four from strain NT). Further analysis found that six contigs from strain SH and three from strain NT shared significant identities with previously reported proteins, and one contig was presumed to be novel. The specific differentially expressed genes were finally verified by RT-PCR and qRT-PCR analyses. Conclusions The data presented here suggest that specific genes identified between the two strains may be important molecules in the immunogenicity of E. maxima that may present potential new drug targets or vaccine candidates for coccidiosis. PMID:24894832

Magnetic bead-quantum dot assay for detection of a biomarker for traumatic brain injury

NASA Astrophysics Data System (ADS)

Kim, Chloe; Searson, Peter C.

2015-10-01

Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level.Current diagnostic methods for traumatic brain injury (TBI), which accounts for 15% of all emergency room visits, are limited to neuroimaging modalities. The challenges of accurate diagnosis and monitoring of TBI have created the need for a simple and sensitive blood test to detect brain-specific biomarkers. Here we report on an assay for detection of S100B, a putative biomarker for TBI, using antibody-conjugated magnetic beads for capture of the protein, and antibody-conjugated quantum dots for optical detection. From Western Blot, we show efficient antigen capture and concentration by the magnetic beads. Using magnetic bead capture and quantum dot detection in serum samples, we show a wide detection range and detection limit below the clinical cut-off level. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05608j

A rapid and sensitive dot-blot hybridization assay for the detection of citrus exocortis viroid in Citrus medica with digoxigenin-labelled RNA probes.

PubMed

Fonseca, M E; Marcellino, L H; Gander, E

1996-04-05

A rapid and sensitive dot-blot hybridization assay using in vitro-transcribed digoxigenin-labelled RNA probes (riboprobes) was developed aiming at detection of citrus exocortis viroid (CEVd) in crude sap of infected Citrus medica plants. The protocol includes a very quick and simple preparation of RNA extracts from samples using a denaturation step with formaldehyde. From our results, the employment of this step is highly recommended because the hybridization signals in formaldehyde-denatured samples were significantly stronger when compared with that of extracts without formaldehyde treatment. The assay was found to be sensitive enough to detect 0.1 ng of purified CEVd RNA and was able to detect viroid in 0.2 mg of symptomatic Citrus medica leaves. The use of riboprobes also allowed hybridization under high temperature conditions, avoiding non-specific background.

Evaluation of enzyme-linked immunosorbent and alternative assays for detection of HIV antibodies using panels of Brazilian sera.

PubMed

Ivo-Dos-Santos, J; Mello, D L; Couto-Fernandez, J C; Passos, R M; Dias-Carneiro, L A; Castilho, E A; Galvão-Castro, B

1990-01-01

Sera from 472 Brazilian subjects, confirmed to be either positive or negative for HIV antibodies and comprising the total clinical spectrum of HIV infection, were utilized in the evaluation of six commercially available enzyme-linked immunosorbent assays (ELISA), as well as of four alternative assays, namely indirect immunofluorescence (IIF), passive hemagglutination (PHA), dot blot and Karpas AIDS cell test. The sensitivities ranged from 100% (Abbott and Roche ELISA) to 84.2% (PHA) and the specificities ranged from 99.3% (IIF) to 80.2% (PHA). The sensitivity and specificity of the PHA and the sensitivity of the Karpas cell test were significantly lower than those of the other tests. Although the IFF and dot blot had good sensitivities and specificities, the six ELISA were more attractive than those tests when other parameters such as ease of reading and duration of assay were considered.

Overcoming the errors of in-house PCR used in the clinical laboratory for the diagnosis of extrapulmonary tuberculosis.

PubMed

Kunakorn, M; Raksakai, K; Pracharktam, R; Sattaudom, C

1999-03-01

Our experiences from 1993 to 1997 in the development and use of IS6110 base PCR for the diagnosis of extrapulmonary tuberculosis in a routine clinical setting revealed that error-correcting processes can improve existing diagnostic methodology. The reamplification method initially used had a sensitivity of 90.91% and a specificity of 93.75%. The concern was focused on the false positive results of this method caused by product-carryover contamination. This method was changed to single round PCR with carryover prevention by uracil DNA glycosylase (UDG), resulting in a 100% specificity but only 63% sensitivity. Dot blot hybridization was added after the single round PCR, increasing the sensitivity to 87.50%. However, false positivity resulted from the nonspecific dot blot hybridization signal, reducing the specificity to 89.47%. The hybridization of PCR was changed to a Southern blot with a new oligonucleotide probe giving the sensitivity of 85.71% and raising the specificity to 99.52%. We conclude that the PCR protocol for routine clinical use should include UDG for carryover prevention and hybridization with specific probes to optimize diagnostic sensitivity and specificity in extrapulmonary tuberculosis testing.

A single polyprobe for detecting simultaneously eight pospiviroids infecting ornamentals and vegetables.

PubMed

Torchetti, Enza Maria; Navarro, Beatriz; Di Serio, Francesco

2012-12-01

The spread of viroids belonging to the genus Pospiviroid (family Pospiviroidae), recorded recently in ornamentals and vegetables in several European countries, calls for fast, efficient and sensitive detection methods. Based on bioinformatics analyses of sequence identity among all pospiviroids, a digoxigenin-labeled polyprobe (POSPIprobe) was developed that, when tested by dot-blot and Northern-blot hybridization, detected Potato spindle tuber viroid, Citrus exocortis viroid, Columnea latent viroid, Mexican papita viroid, Tomato planta macho viroid, Tomato apical stunt viroid, Pepper chat fruit viroid and Chrysanthemum stunt viroid. The end-point detection limits of the POSPIprobe ranged from 5(-2) to 5(-4), and from 5(-1) to 5(-3) for nucleic acid preparations obtained by phenol extraction and silica-capture, respectively, similar to those of single probes. Based on sequence identity, the POSPIprobe is expected to detect also the two pospiviroid species not tested in this study (Tomato chlorotic dwarf viroid and Iresine viroid-1). Dot-blot assays with the POSPIprobe were validated by testing 68 samples from tomato, chrysanthemum and argyranthemum infected by different pospiviroids as revealed by RT-PCR, thus confirming the potential of this polyprobe for quarantine, certification and survey programs. Copyright © 2012 Elsevier B.V. All rights reserved.

Novel diagnostic procedure for determining metastasis to sentinel lymph nodes in breast cancer using a semi-dry dot-blot method.

PubMed

Otsubo, Ryota; Oikawa, Masahiro; Hirakawa, Hiroshi; Shibata, Kenichiro; Abe, Kuniko; Hayashi, Tomayoshi; Kinoshita, Naoe; Shigematsu, Kazuto; Hatachi, Toshiko; Yano, Hiroshi; Matsumoto, Megumi; Takagi, Katsunori; Tsuchiya, Tomoshi; Tomoshige, Koichi; Nakashima, Masahiro; Taniguchi, Hideki; Omagari, Takeyuki; Itoyanagi, Noriaki; Nagayasu, Takeshi

2014-02-15

We developed an easy, quick and cost-effective detection method for lymph node metastasis called the semi-dry dot-blot (SDB) method, which visualizes the presence of cancer cells with washing of sectioned lymph nodes by anti-pancytokeratin antibody, modifying dot-blot technology. We evaluated the validity and efficacy of the SDB method for the diagnosis of lymph node metastasis in a clinical setting (Trial 1). To evaluate the validity of the SDB method in clinical specimens, 180 dissected lymph nodes from 29 cases, including breast, gastric and colorectal cancer, were examined. Each lymph node was sliced at the maximum diameter and the sensitivity, specificity and accuracy of the SDB method were determined and compared with the final pathology report. Metastasis was detected in 32 lymph nodes (17.8%), and the sensitivity, specificity and accuracy of the SDB method were 100, 98.0 and 98.3%, respectively (Trial 2). To evaluate the efficacy of the SDB method in sentinel lymph node (SLN) biopsy, 174 SLNs from 100 cases of clinically node-negative breast cancer were analyzed. Each SLN was longitudinally sliced at 2-mm intervals and the sensitivity, specificity, accuracy and time required for the SDB method were determined and compared with the intraoperative pathology report. Metastasis was detected in 15 SLNs (8.6%), and the sensitivity, specificity, accuracy and mean required time of the SDB method were 93.3, 96.9, 96.6 and 43.3 min, respectively. The SDB method is a novel and reliable modality for the intraoperative diagnosis of SLN metastasis. © 2013 UICC.

Molecular detection of HpmA and HlyA hemolysin of uropathogenic Proteus mirabilis.

PubMed

Cestari, Silvia Emanoele; Ludovico, Marilucia Santos; Martins, Fernando Henrique; da Rocha, Sérgio Paulo Dejato; Elias, Waldir Pereira; Pelayo, Jacinta Sanchez

2013-12-01

Urinary tract infection (UTI) is one of the bacterial infections frequently documented in humans. Proteus mirabilis is associated with UTI mainly in individuals with urinary tract abnormality or related with vesicular catheterism and it can be difficult to treat because of the formation of stones in the bladder and kidneys. These stones are formed due to the presence of urease synthesized by the bacteria. Another important factor is that P. mirabilis produces hemolysin HpmA, used by the bacteria to damage the kidney tissues. Proteus spp. samples can also express HlyA hemolysin, similar to that found in Escherichia coli. A total of 211 uropathogenic P. mirabilis isolates were analyzed to detect the presence of the hpmA and hpmB genes by the techniques of polymerase chain reaction (PCR) and dot blot and hlyA by PCR. The hpmA and hpmB genes were expressed by the RT-PCR technique and two P. mirabilis isolates were sequenced for the hpmA and hpmB genes. The presence of the hpmA and hpmB genes was confirmed by PCR in 205 (97.15 %) of the 211 isolates. The dot blot confirmed the presence of the hpmA and hpmB genes in the isolates that did not amplify in the PCR. None of the isolates studied presented the hlyA gene. The hpmA and hpmB genes that were sequenced presented 98 % identity with the same genes of the HI4320 P. mirabilis sample. This study showed that the PCR technique has good sensitivity for detecting the hpmA and hpmB genes of P. mirabilis.

Activation of Ran GTPase by a Legionella Effector Promotes Microtubule Polymerization, Pathogen Vacuole Motility and Infection

PubMed Central

Rothmeier, Eva; Pfaffinger, Gudrun; Hoffmann, Christine; Harrison, Christopher F.; Grabmayr, Heinrich; Repnik, Urska; Hannemann, Mandy; Wölke, Stefan; Bausch, Andreas; Griffiths, Gareth; Müller-Taubenberger, Annette; Itzen, Aymelt; Hilbi, Hubert

2013-01-01

The causative agent of Legionnaires' disease, Legionella pneumophila, uses the Icm/Dot type IV secretion system (T4SS) to form in phagocytes a distinct “Legionella-containing vacuole” (LCV), which intercepts endosomal and secretory vesicle trafficking. Proteomics revealed the presence of the small GTPase Ran and its effector RanBP1 on purified LCVs. Here we validate that Ran and RanBP1 localize to LCVs and promote intracellular growth of L. pneumophila. Moreover, the L. pneumophila protein LegG1, which contains putative RCC1 Ran guanine nucleotide exchange factor (GEF) domains, accumulates on LCVs in an Icm/Dot-dependent manner. L. pneumophila wild-type bacteria, but not strains lacking LegG1 or a functional Icm/Dot T4SS, activate Ran on LCVs, while purified LegG1 produces active Ran(GTP) in cell lysates. L. pneumophila lacking legG1 is compromised for intracellular growth in macrophages and amoebae, yet is as cytotoxic as the wild-type strain. A downstream effect of LegG1 is to stabilize microtubules, as revealed by conventional and stimulated emission depletion (STED) fluorescence microscopy, subcellular fractionation and Western blot, or by microbial microinjection through the T3SS of a Yersinia strain lacking endogenous effectors. Real-time fluorescence imaging indicates that LCVs harboring wild-type L. pneumophila rapidly move along microtubules, while LCVs harboring ΔlegG1 mutant bacteria are stalled. Together, our results demonstrate that Ran activation and RanBP1 promote LCV formation, and the Icm/Dot substrate LegG1 functions as a bacterial Ran activator, which localizes to LCVs and promotes microtubule stabilization, LCV motility as well as intracellular replication of L. pneumophila. PMID:24068924

Seroprevalence of Fasciola gigantica infection in bovines using cysteine proteinase dot enzyme-linked immunosorbent assay

PubMed Central

Kumar, Niranjan; Varghese, Anju; Solanki, J. B.

2017-01-01

Aim: The objective of the present study was to know the seroprevalence status of Fasciola gigantica infection in cattle and buffaloes using cysteine proteinase (CP) antigen in dot enzyme-linked immunosorbent assay (ELISA) format under field conditions. Materials and Methods: As per the standard protocol, the sera were collected from the blood of 112 cattle and 38 buffaloes of coastal areas of Navsari district, South Gujarat, India. The indirect ELISA was performed on the strip of nitrocellulose paper blotted with 1 µl of CP antigen, to detect F. gigantica seropositive animals. Results: The native CP of F. gigantica revealed a single visible band on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There was no any noted cross-reaction between the selected antigen and sera of Gastrothylax crumenifer-infected animals in ELISA. Out of 150 screened bovines, the sera of 47 (31.33%) were found to be reactive in dot-ELISA, with a prevalence rate of 31.25% and 31.58% in cattle and buffaloes, respectively. The seropositive bovines with heavy, moderate, and light level of infection were 44.68%, 34.04%, and 21.28%, respectively (p<0.05 between heavy and light; p>0.05 between moderate and heavy or light). The share of F. gigantica seropositive and negative animals was 31% and 69%, respectively. The optical density at 450 nm of pooled sera of seropositive bovines with heavy, moderate, and light reactivity in plate-ELISA was significantly higher with field or reference ­negative sera. Conclusion: The CP-based dot-ELISA can be useful for field veterinarians for quick and timely isolation of the animals requiring urgent flukicide therapy. PMID:29184364

Formation of uniform high-density and small-size Ge/Si quantum dots by scanning pulsed laser annealing of pre-deposited Ge/Si film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qayyum, Hamza; Chen, Szu-yuan, E-mail: sychen@ltl.iams.sinica.edu.tw; Department of Physics, National Central University, Zhongli, Taoyuan 320, Taiwan

2016-05-15

The capability to fabricate Ge/Si quantum dots with small dot size and high dot density uniformly over a large area is crucial for many applications. In this work, we demonstrate that this can be achieved by scanning a pre-deposited Ge thin layer on Si substrate with a line-focused pulsed laser beam to induce formation of quantum dots. With suitable setting, Ge/Si quantum dots with a mean height of 2.9 nm, a mean diameter of 25 nm, and a dot density of 6×10{sup 10} cm{sup −2} could be formed over an area larger than 4 mm{sup 2}. The average size ofmore » the laser-induced quantum dots is smaller while their density is higher than that of quantum dots grown by using Stranski-Krastanov growth mode. Based on the dependence of the characteristics of quantum dots on the laser parameters, a model consisting of laser-induced strain, surface diffusion, and Ostwald ripening is proposed for the mechanism underlying the formation of the Ge/Si quantum dots. The technique demonstrated could be applicable to other materials besides Ge/Si.« less

S genotyping in Japanese plum and sweet cherry by allele-specific hybridization using streptavidin-coated magnetic beads.

PubMed

Wang, Chun-Lei; Zhang, Zhi-Ping; Tonosaki, Kaoru; Kitashiba, Hiroyasu; Nishio, Takeshi

2013-04-01

We report a rapid and reliable method for S genotyping of Rosaceae fruit trees, which would to be useful for successful planting of cross-compatible cultivars in orchards. Japanese plum (Prunus salicina) and sweet cherry (Prunus avium), belonging to the family Rosaceae, possess gametophytic self-incompatibility controlled by a single polymorphic locus containing at least two linked genes, S-RNase and SFB (S-haplotype-specific F-box gene). For successful planting of cross-compatible cultivars of Rosaceae fruit trees in commercial orchards, it is necessary to obtain information on S genotypes of cultivars. Recently, a method of dot-blot analysis utilizing allele-specific oligonucleotides having sequences of SFB-HVa region has been developed for identification of S haplotypes in Japanese plum and sweet cherry. However, dot-blot hybridization requires considerable time and skill for analysis even of a small number of plant samples. Thus, a quick and efficient method for S genotyping was developed in this study. In this method, instead of a nylon membrane used for dot-blot hybridization, streptavidin-coated magnetic beads are used to immobilize PCR products, which are hybridized with allele-specific oligonucleotide probes. Our improved method allowed us to identify 10 S haplotypes (S-a, S-b, S-c, S-d, S-e, S-f, S-h, S-k, S-7 and S-10) of 13 Japanese plum cultivars and 10 S haplotypes (S-1, S-2, S-3, S-4, S-4', S-5, S-6, S-7, S-9 and S-16) of 13 sweet cherry cultivars utilizing SFB or S-RNase gene polymorphism. This method would be suitable for identification of S genotypes of a small number of plant samples.

[Scientific Evaluation of Crude Drugs and Kampo Medicines Using the Eastern Blotting Method and Its Application to Biological Metabolic Studies].

PubMed

Morinaga, Osamu

2018-01-01

　The scientific evaluation of crude drugs and kampo medicines (KMs) was demonstrated using the eastern blotting method with monoclonal antibodies (MAbs) against bioactive natural compounds. Scutellariae radix is one of the most important crude drugs used in KMs. Part of its pharmaceutical properties is due to the flavone glycoside baicalin (BI). A quantitative analysis method based on eastern blotting was developed for BI using an anti-BI MAb. A rapid, simple, sensitive, specific analytical system was subsequently established for BI with the eastern blotting technique using dot-blot and chemiluminescent methods. This system was useful as a high-throughput analytical method for the determination of BI in KMs as well as HPLC and enzyme-linked immunosorbent assay systems. Furthermore, an eastern blotting method was applied to the biological metabolic study of glycyrrhizic acid (GL), the major active constituent of licorice, for investigation of metabolites of GL such as 3-monoglucuronyl-glycyrrhetinic acid (3MGA) because licorice causes pseudoaldosteronism as a side effect. This approach may make it possible to determine the pathogenic agents of licorice-induced pseudoaldosteronism.

Purification and immunolocalization of an annexin-like protein in pea seedlings

NASA Technical Reports Server (NTRS)

Clark, G. B.; Dauwalder, M.; Roux, S. J.

1992-01-01

As part of a study to identify potential targets of calcium action in plant cells, a 35-kDa, annexin-like protein was purified from pea (Pisum sativum L.) plumules by a method used to purify animal annexins. This protein, called p35, binds to a phosphatidylserine affinity column in a calcium-dependent manner and binds 45Ca2+ in a dot-blot assay. Preliminary sequence data confirm a relationship for p35 with the annexin family of proteins. Polyclonal antibodies have been raised which recognize p35 in Western and dot blots. Immunofluorescence and immunogold techniques were used to study the distribution and subcellular localization of p35 in pea plumules and roots. The highest levels of immunostain were found in young developing vascular cells producing wall thickenings and in peripheral root-cap cells releasing slime. This localization in cells which are actively involved in secretion is of interest because one function suggested for the animal annexins is involvement in the mediation of exocytosis.

Further characterization and independent validation of a DNA aptamer-quantum dot-based magnetic sandwich assay for Campylobacter.

PubMed

Bruno, John G; Sivils, Jeffrey C

2017-11-01

Previously reported DNA aptamers developed against surface proteins extracted from Campylobacter jejuni were further characterized by aptamer-based Western blotting and shown to bind epitopes on proteins weighing ~16 and 60 kD from reduced C. jejuni and Campylobacter coli lysates. Proteins of these approximate weights have also been identified in traditional antibody-based Western blots of Campylobacter spp. Specificity of the capture and reporter aptamers from the previous report was further validated by aptamer-based ELISA-like (ELASA) colorimetric microplate assay. Finally, the limit of detection of the previously reported plastic-adherent aptamer-magnetic bead and aptamer-quantum dot sandwich assay (PASA) was validated by an independent food safety testing laboratory to lie between 5 and 10 C. jejuni cells per milliliter in phosphate buffered saline and repeatedly frozen and thawed chicken rinsate. Such ultrasensitive and rapid (30 min) aptamer-based assays could provide alternative or additional screening tools to enhance food safety testing for Campylobacter and other foodborne pathogens.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandler, D.P.; Welt, M.; Leung, F.C.

An efficient one-step injection technique for gene insertion into fertilized rainbow trout (Oncorhynchus mykiss) eggs is described, and basic parameters affecting egg survival are reported. Freshly fertilized rainbow trout eggs were injected in the perivitelline space with a recombinant mouse metallothionein-genomic bovine growth hormone (bGH) DNA construct using a 30-gauge hypodermic needle and a standard microinjection system. Relative to control, site of injection and DNA concentration did not affect the egg survival, but injections later than 3--4 hours post fertilization were detrimental. The injection technique permitted treatment of 100 eggs/hr with survivals up to 100%, resulting in a 4% DNAmore » uptake rate as indicated by DNA dot blot analysis. Positive dot blot results also indicated that the injected DNA is able to cross the vitelline membrane and persist for 50--60 days post hatching, obviating the need for direct injection into the germinal disk. Results are consistent with previous transgenic fish work, underscoring the usefulness of the technique for generating transgenic trout and salmonids. 24 refs., 6 figs., 3 tabs.« less

"Mini-array" transcriptional analysis of the Listeria monocytogenes lecithinase operon as a class project: A student investigative molecular biology laboratory experience*.

PubMed

Christensen, Douglas; Jovic, Marko

2006-05-01

This report describes a molecular biotechnology-based laboratory curriculum developed to accompany an undergraduate genetics course. During the course of a semester, students researched the pathogen, developed a research question, designed experiments, and performed transcriptional analysis of a set of genes that confer virulence to the food-borne pathogen, Listeria monocytogenes. Gene fragments were amplified via PCR and utilized in "mini-arrays," a dot-blot-based format suitable for the simultaneous transcriptional analysis of multiple genes. The project provides exposure to a wide range of molecular techniques and can be easily modified for variations in class size. Data are generated at various steps of the process, allowing for student interpretation, troubleshooting, and assessment opportunities. Copyright © 2006 International Union of Biochemistry and Molecular Biology, Inc.

Self-organization of quantum-dot pairs by high-temperature droplet epitaxy

PubMed Central

Holmes, Kyland; Mazur, Yuriy I; Ramsey, Kimberly A; Salamo, Gregory J

2006-01-01

The spontaneously formation of epitaxial GaAs quantum-dot pairs was demonstrated on an AlGaAs surface using Ga droplets as a Ga nano-source. The dot pair formation was attributed to the anisotropy of surface diffusion during high-temperature droplet epitaxy.

DOT1L histone methyltransferase regulates the expression of BCAT1 and is involved in sphere formation and cell migration of breast cancer cell lines.

PubMed

Oktyabri, Dulamsuren; Ishimura, Akihiko; Tange, Shoichiro; Terashima, Minoru; Suzuki, Takeshi

2016-04-01

DOT1L is a histone H3 lysine 79 (H3K79) methyltransferase mainly implicated in leukemia. Here we analyzed the function of DOT1L in breast cancer cells. The expression of DOT1L was up-regulated in malignant breast cancer tissues. Over-expression of DOT1L significantly increased the sphere formation and the cell migration activities of MCF7 breast cancer cell line. In contrast, knockdown of DOT1L reduced the cell migration activity of MDA-MB-231 breast cancer cell line. BCAT1, which encodes a branched-chain amino acid transaminase, was identified as one of the target genes controlled by DOT1L through the regulation of H3K79 methylation. Mechanistic investigation revealed that BCAT1 might be an important regulator responsible for DOT1L-mediated sphere formation and cell migration in breast cancer cells. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Fish β-parvalbumin acquires allergenic properties by amyloid assembly.

PubMed

Martínez, Javier; Sánchez, Rosa; Castellanos, Milagros; Fernández-Escamilla, Ana M; Vázquez-Cortés, Sonia; Fernández-Rivas, Montserrat; Gasset, María

2015-01-01

Amyloids are highly cross-β-sheet-rich aggregated states that confer protease resistance, membrane activity and multivalence properties to proteins, all essential features for the undesired preservation of food proteins transiting the gastrointestinal tract and causing type I allergy. Amyloid propensity of β-parvalbumin, the major fish allergen, was theoretically analysed and assayed under gastrointestinal-relevant conditions using the binding of thioflavin T, the formation of sodium dodecyl sulphate- (SDS-) resistant aggregates, circular dichroism spectroscopy and atomic force microscopy fibril imaging. Impact of amyloid aggregates on allergenicity was assessed with dot blot. Sequences of β-parvalbumin from species with commercial value contain several adhesive hexapeptides capable of driving amyloid formation. Using Atlantic cod β-parvalbumin (rGad m 1) displaying high IgE cross-reactivity, we found that formation of amyloid fibres under simulated gastrointestinal conditions accounts for the resistance to acid and neutral proteases, for the presence of membrane active species under gastrointestinal relevant conditions and for the IgE-recognition in the sera of allergic patients. Incorporation of the anti-amyloid compound epigallocatechin gallate prevents rGad m 1 fibrillation, facilitates its protease digestion and impairs its recognition by IgE. the formation of amyloid by rGad m 1 explains its degradation resistance, its facilitated passage across the intestinal epithelial barrier and its epitope architecture as allergen.

Quantitative characterization of nanoparticle agglomeration within biological media

NASA Astrophysics Data System (ADS)

Hondow, Nicole; Brydson, Rik; Wang, Peiyi; Holton, Mark D.; Brown, M. Rowan; Rees, Paul; Summers, Huw D.; Brown, Andy

2012-07-01

Quantitative analysis of nanoparticle dispersion state within biological media is essential to understanding cellular uptake and the roles of diffusion, sedimentation, and endocytosis in determining nanoparticle dose. The dispersion of polymer-coated CdTe/ZnS quantum dots in water and cell growth medium with and without fetal bovine serum was analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. Characterization by TEM of samples prepared by plunge freezing the blotted solutions into liquid ethane was sensitive to the dispersion state of the quantum dots and enabled measurement of agglomerate size distributions even in the presence of serum proteins where DLS failed. In addition, TEM showed a reduced packing fraction of quantum dots per agglomerate when dispersed in biological media and serum compared to just water, highlighting the effect of interactions between the media, serum proteins, and the quantum dots. The identification of a heterogeneous distribution of quantum dots and quantum dot agglomerates in cell growth medium and serum by TEM will enable correlation with the previously reported optical metrology of in vitro cellular uptake of this quantum dot dispersion. In this paper, we present a comparative study of TEM and DLS and show that plunge-freeze TEM provides a robust assessment of nanoparticle agglomeration state.

A Model of Risk Analysis in Analytical Methodology for Biopharmaceutical Quality Control.

PubMed

Andrade, Cleyton Lage; Herrera, Miguel Angel De La O; Lemes, Elezer Monte Blanco

2018-01-01

One key quality control parameter for biopharmaceutical products is the analysis of residual cellular DNA. To determine small amounts of DNA (around 100 pg) that may be in a biologically derived drug substance, an analytical method should be sensitive, robust, reliable, and accurate. In principle, three techniques have the ability to measure residual cellular DNA: radioactive dot-blot, a type of hybridization; threshold analysis; and quantitative polymerase chain reaction. Quality risk management is a systematic process for evaluating, controlling, and reporting of risks that may affects method capabilities and supports a scientific and practical approach to decision making. This paper evaluates, by quality risk management, an alternative approach to assessing the performance risks associated with quality control methods used with biopharmaceuticals, using the tool hazard analysis and critical control points. This tool provides the possibility to find the steps in an analytical procedure with higher impact on method performance. By applying these principles to DNA analysis methods, we conclude that the radioactive dot-blot assay has the largest number of critical control points, followed by quantitative polymerase chain reaction, and threshold analysis. From the analysis of hazards (i.e., points of method failure) and the associated method procedure critical control points, we conclude that the analytical methodology with the lowest risk for performance failure for residual cellular DNA testing is quantitative polymerase chain reaction. LAY ABSTRACT: In order to mitigate the risk of adverse events by residual cellular DNA that is not completely cleared from downstream production processes, regulatory agencies have required the industry to guarantee a very low level of DNA in biologically derived pharmaceutical products. The technique historically used was radioactive blot hybridization. However, the technique is a challenging method to implement in a quality control laboratory: It is laborious, time consuming, semi-quantitative, and requires a radioisotope. Along with dot-blot hybridization, two alternatives techniques were evaluated: threshold analysis and quantitative polymerase chain reaction. Quality risk management tools were applied to compare the techniques, taking into account the uncertainties, the possibility of circumstances or future events, and their effects upon method performance. By illustrating the application of these tools with DNA methods, we provide an example of how they can be used to support a scientific and practical approach to decision making and can assess and manage method performance risk using such tools. This paper discusses, considering the principles of quality risk management, an additional approach to the development and selection of analytical quality control methods using the risk analysis tool hazard analysis and critical control points. This tool provides the possibility to find the method procedural steps with higher impact on method reliability (called critical control points). Our model concluded that the radioactive dot-blot assay has the larger number of critical control points, followed by quantitative polymerase chain reaction and threshold analysis. Quantitative polymerase chain reaction is shown to be the better alternative analytical methodology in residual cellular DNA analysis. © PDA, Inc. 2018.

Expression of the Tpanxb1 gene from Taenia pisiformis and its potential diagnostic value by dot-ELISA.

PubMed

Yang, Deying; Chen, Lin; Wu, Xuhang; Zhou, Xuan; Li, Mei; Chen, Zuqin; Nong, Xiang; Gu, Xiaobin; Peng, Xuerong; Yang, Guangyou

2014-04-01

Cysticercosis, caused by the larvae of Taenia pisiformis, is a common disease in rabbits that results in economic losses. To date, there has been limited information available on the early detection of infection by this parasite. This study describes a dot-ELISA method based on an autologous antigen annexin B1 (Tpanxb1). Its potential for serodiagnosis of rabbit cysticercosis was also evaluated. Western blot analysis revealed that the recombinant Tpanxb1 (rTpanxb1) protein could be specifically recognized by rabbit anti-sera. In serum trials, the antibodies could be detected by dot-ELISA using rTpanxb1 at 14 days post-infection. The positive response was present for up to 49 days post-infection. Based on the necropsy results of 169 rabbit samples, the relative sensitivity and specificity of the dot-ELISA were 94.55% and 92.86%, respectively. This study provides a foundation for studying the immunological function of annexin and its application to control Taenia cestodes.

Fabrication and characterization of silicon quantum dots in Si-rich silicon carbide films.

PubMed

Chang, Geng-Rong; Ma, Fei; Ma, Dayan; Xu, Kewei

2011-12-01

Amorphous Si-rich silicon carbide films were prepared by magnetron co-sputtering and subsequently annealed at 900-1100 degrees C. After annealing at 1100 degrees C, this configuration of silicon quantum dots embedded in amorphous silicon carbide formed. X-ray photoelectron spectroscopy was used to study the chemical modulation of the films. The formation and orientation of silicon quantum dots were characterized by glancing angle X-ray diffraction, which shows that the ratio of silicon and carbon significantly influences the species of quantum dots. High-resolution transmission electron microscopy investigations directly demonstrated that the formation of silicon quantum dots is heavily dependent on the annealing temperatures and the ratio of silicon and carbide. Only the temperature of about 1100 degrees C is enough for the formation of high-density and small-size silicon quantum dots due to phase separation and thermal crystallization. Deconvolution of the first order Raman spectra shows the existence of a lower frequency peak in the range 500-505 cm(-1) corresponding to silicon quantum dots with different atom ratio of silicon and carbon.

Quantification of protein carbonylation.

PubMed

Wehr, Nancy B; Levine, Rodney L

2013-01-01

Protein carbonylation is the most commonly used measure of oxidative modification of proteins. It is most often measured spectrophotometrically or immunochemically by derivatizing proteins with the classical carbonyl reagent 2,4 dinitrophenylhydrazine (DNPH). We present protocols for the derivatization and quantification of protein carbonylation with these two methods, including a newly described dot blot with greatly increased sensitivity.

Physical mapping withing the tuberous sclerosis linkage group in region 9q32-q34

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, R.M.; Carter, N.P.; Griffiths, B.

1993-02-01

Pulsed-field gel electrophoresis and flow dot-blot analysis have been used to construct a physical map of the q32-q34 region of chromosome 9, where one of the loci responsible for tuberous sclerosis (TSC1) has been mapped by genetic linkage. Five linked groups of markers have been defined by pulsed-field gel electrophoresis. The orientation of these groups and the order of markers within them were determined by hybridization to flow-sorted dot blots derived from a panel of cell lines of chromosome 9 translocations to place probes proximal or distal to each breakpoint. The local map order 9q32-q34 derived by application of thismore » combination of techniques is as follows: centromere - ALAD-1.3 Mb-ORM/20 kb/D9S16-GSN-250 kb-C5-HXB-1.9 Mb-D9S21-AK1-1.4 Mb-SPTAN1-ASS-800-kb-ABL-2 Mb-D0S10/350 Kb/DBH-telomere. 48 refs., 6 figs., 4 figs.« less

Semiquantitative Dot Blot with the GRA8 antigen to differentiate the stages of toxoplasmosis infection.

PubMed

Costa, Juan Gabriel; Vilariño, María Julia

2018-06-01

In this work we present a novel methodology to differentiate the phases of toxoplasmosis infection: the "semiquantitative Dot Blot". It is a simple technique that does not require expensive equipment, does not involve a long technique development, and can be used in a low-complexity laboratory. In this study, two recombinant sequences of Toxoplasma gondii GRA8 antigen were used, and specific IgG antibodies were detected in selected patient samples. This method makes it possible to obtain a score for each serum and define whether the patient is in the acute or chronic phase of the infection. The sensitivity and specificity results varied depending on the antigenic sequence used. With GRA8A, 62.1% and 72.7% were obtained, while with GRA8B, 82.8% and 72.1% were obtained, respectively. Although the sensitivity and specificity values were not close to 100%, they were similar to those reported with the same antigens in ELISA. Therefore, this quantitative technique would be a good alternative to ELISA. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of the Maillard Reaction on the Immunoreactivity of Amandin in Food Matrices.

PubMed

Chhabra, Guneet S; Liu, Changqi; Su, Mengna; Venkatachalam, Mahesh; Roux, Kenneth H; Sathe, Shridhar K

2017-10-01

Amandin is the major storage protein and allergen in almond seeds. Foods, containing almonds, subjected to thermal processing typically experience Maillard browning reaction. The resulting destruction of amino groups, protein glycation, and/or denaturation may alter amandin immunoreactivity. Amandin immunoreactivity of variously processed almond containing foods was therefore the focus of the current investigation. Commercial and laboratory prepared foods, including those likely to have been subjected to Maillard browning, were objectively assessed by determining Hunter L * , a * , b * values. The L * values for the tested samples were in the range of 31.75 to 85.28 consistent with Maillard browning. Three murine monoclonal antibodies, 4C10, 4F10, and 2A3, were used to determine the immunoreactivity of the targeted samples using immunoassays (ELISA, Western blot, dot blot). The tested foods did not exhibit cross-reactivity indicating that the immunoassays were amandin specific. For sandwich ELISAs, ratio (R) of sample immunoreactivity to reference immunoreactivity was calculated. The ranges of R values were 0.67 to 15.19 (4C10), 1.00 to 11.83 (4F10), and 0.77 to 23.30 (2A3). The results of dot blot and Western blot were consistent with those of ELISAs. Results of these investigations demonstrate that amandin is a stable marker protein for almond detection regardless of the degree of amandin denaturation and/or destruction as a consequence of Maillard reaction encountered under the tested processing conditions. Foods containing almond are often subjected to processing prior to consumption. Amandin, the major allergen in almond, may experience Maillard reaction. Understanding the change in amandin immunoreactivity as a result of Maillard reaction is important for amandin detection and production of hypoallergenic food products. © 2017 Institute of Food Technologists®.

Chemically Triggered Formation of Two-Dimensional Epitaxial Quantum Dot Superlattices.

PubMed

Walravens, Willem; De Roo, Jonathan; Drijvers, Emile; Ten Brinck, Stephanie; Solano, Eduardo; Dendooven, Jolien; Detavernier, Christophe; Infante, Ivan; Hens, Zeger

2016-07-26

Two dimensional superlattices of epitaxially connected quantum dots enable size-quantization effects to be combined with high charge carrier mobilities, an essential prerequisite for highly performing QD devices based on charge transport. Here, we demonstrate that surface active additives known to restore nanocrystal stoichiometry can trigger the formation of epitaxial superlattices of PbSe and PbS quantum dots. More specifically, we show that both chalcogen-adding (sodium sulfide) and lead oleate displacing (amines) additives induce small area epitaxial superlattices of PbSe quantum dots. In the latter case, the amine basicity is a sensitive handle to tune the superlattice symmetry, with strong and weak bases yielding pseudohexagonal or quasi-square lattices, respectively. Through density functional theory calculations and in situ titrations monitored by nuclear magnetic resonance spectroscopy, we link this observation to the concomitantly different coordination enthalpy and ligand displacement potency of the amine. Next to that, an initial ∼10% reduction of the initial ligand density prior to monolayer formation and addition of a mild, lead oleate displacing chemical trigger such as aniline proved key to induce square superlattices with long-range, square micrometer order; an effect that is the more pronounced the larger the quantum dots. Because the approach applies to PbS quantum dots as well, we conclude that it offers a reproducible and rational method for the formation of highly ordered epitaxial quantum dot superlattices.

Publisher Correction: N6-methyladenosine RNA modification regulates embryonic neural stem cell self-renewal through histone modifications.

PubMed

Wang, Yang; Li, Yue; Yue, Minghui; Wang, Jun; Kumar, Sandeep; Wechsler-Reya, Robert J; Zhang, Zhaolei; Ogawa, Yuya; Kellis, Manolis; Duester, Gregg; Zhao, Jing Crystal

2018-06-07

In the version of this article initially published online, there were errors in URLs for www.southernbiotech.com, appearing in Methods sections "m6A dot-blot" and "Western blot analysis." The first two URLs should be https://www.southernbiotech.com/?catno=4030-05&type=Polyclonal#&panel1-1 and the third should be https://www.southernbiotech.com/?catno=6170-05&type=Polyclonal. In addition, some Methods URLs for bioz.com, www.abcam.com and www.sysy.com were printed correctly but not properly linked. The errors have been corrected in the PDF and HTML versions of this article.

Evidence for the formation of a novel nitrosothiol from the gaseous mediators nitric oxide and hydrogen sulphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whiteman, Matthew; Li Ling; Kostetski, Iouri

The gaseous mediators hydrogen sulphide (H{sub 2}S) and nitric oxide ( {sup {center_dot}}NO) are synthesised in the body from L-cysteine and L-arginine, respectively. In the cardiovascular system, {sup {center_dot}}NO is an important regulator of vascular tone and its over- or under-production has been linked to a variety of diseases. The physiological significance of H{sub 2}S is not yet clear but, like {sup {center_dot}}NO, it exhibits vasodilator activity and may play a part in septic and haemorrhagic shock, hypertension, regulation of cardiac contractility, and in inflammation. To date, there have been no reports of a chemical interaction between H{sub 2}S andmore » {sup {center_dot}}NO. Here we show that incubation of the H{sub 2}S donor, sodium hydrosulphide, with a range of {sup {center_dot}}NO donors and {sup {center_dot}}NO gas in vitro leads to the formation of a nitrosothiol molecule as determined by a combination of techniques; electron paramagnetic resonance, amperometry, and measurement of nitrite. We further show that this nitrosothiol did not induce cGMP accumulation in cultured RAW264.7 cells unless {sup {center_dot}}NO was released with Cu{sup 2+}. Finally, using liver homogenates from LPS treated rats we present evidence for the endogenous formation of this nitrosothiol. These findings provide First evidence for the formation of a novel nitrosothiol generated by reaction between H{sub 2}S and {sup {center_dot}}NO. We propose that generation of this nitrosothiol in the body may regulate the physiological effects of both {sup {center_dot}}NO and H{sub 2}S.« less

Real-time observation of FIB-created dots and ripples on GaAs

NASA Astrophysics Data System (ADS)

Rose, F.; Fujita, H.; Kawakatsu, H.

2008-01-01

We report a phenomenological study of Ga dots and ripples created by a focused ion beam (FIB) on the GaAs(001) surface. Real-time observation of dot diffusion and ripple formation was made possible by recording FIB movies. In the case of FIB irradiation with a 40 nA current of Ga+ ions accelerated under 40 kV with an incidence angle of θ = 30°, increasing ion dose gives rise to three different regimes. In Regime 1, dots with lateral sizes in the range 50-460 nm are formed. Dots diffuse under continuous sputtering. In Regime 2, dots self-assemble into Bradley and Harper (BH) type ripples with a pseudo-period of λ = 1150 ± 25 nm. In Regime 3, ripples are eroded and the surface topology evolves into microplanes. In the case of normal incidence, FIB sputtering leads only to the formation of dots, without surface rippling.

Detection of Listeria monocytogenes by using the polymerase chain reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bessesen, M.T.; Luo, Q.; Blaser, M.J.

1990-09-01

A method was developed for detection of Listeria monocytogens by polymerase chain reaction amplification followed by agarose gel electrophoresis or dot blot analysis with {sup 32}P-labeled internal probe. The technique identified 95 of 95 L. monocytogenes strains, 0 of 12 Listeria strains of other species, and 0 of 12 non-Listeria strains.

Strain-induced formation of fourfold symmetric SiGe quantum dot molecules.

PubMed

Zinovyev, V A; Dvurechenskii, A V; Kuchinskaya, P A; Armbrister, V A

2013-12-27

The strain field distribution at the surface of a multilayer structure with disklike SiGe nanomounds formed by heteroepitaxy is exploited to arrange the symmetric quantum dot molecules typically consisting of four elongated quantum dots ordered along the [010] and [100] directions. The morphological transition from fourfold quantum dot molecules to continuous fortresslike quantum rings with an increasing amount of deposited Ge is revealed. We examine key mechanisms underlying the formation of lateral quantum dot molecules by using scanning tunneling microscopy and numerical calculations of the strain energy distribution on the top of disklike SiGe nanomounds. Experimental data are well described by a simple thermodynamic model based on the accurate evaluation of the strain dependent part of the surface chemical potential. The spatial arrangement of quantum dots inside molecules is attributed to the effect of elastic property anisotropy.

Satellitesimal Formation via Collisional Dust Growth in Steady Circumplanetary Disks

NASA Astrophysics Data System (ADS)

Shibaike, Yuhito; Okuzumi, Satoshi; Sasaki, Takanori; Ida, Shigeru

2017-09-01

The icy satellites around Jupiter are considered to have formed in a circumplanetary disk. While previous models have focused on the formation of the satellites starting from satellitesimals, the question of how satellitesimals themselves form from smaller dust particles has not yet been addressed. In this work, we study the possibility that satellitesimals form in situ in a circumplanetary disk. We calculate the radial distribution of the surface density and representative size of icy dust particles that grow by colliding with each other and drift toward the central planet in a steady circumplanetary disk with a continuous supply of gas and dust from the parent protoplanetary disk. The radial drift barrier is overcome if the ratio of the dust-to-gas accretion rates onto the circumplanetary disk, {\\dot{M}}{{d}}/{\\dot{M}}{{g}}, is high and the strength of turbulence, α, is not too low. The collision velocity is lower than the critical velocity of fragmentation when α is low. Taken together, we find that the conditions for satellitesimal formation via dust coagulation are given by {\\dot{M}}{{d}}/{\\dot{M}}{{g}}≥slant 1 and {10}-4≤slant α < {10}-2. The former condition is generally difficult to achieve, suggesting that the in situ satellitesimal formation via particle sticking is viable only under extreme conditions. We also show that neither satellitesimal formation via the collisional growth of porous aggregates nor via streaming instability is viable as long as {\\dot{M}}{{d}}/{\\dot{M}}{{g}} is low.

Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

NASA Technical Reports Server (NTRS)

Qiu, Y.; Uhl, D.

2002-01-01

InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

Evaporation-Induced Assembly of Quantum Dots into Nanorings

PubMed Central

Chen, Jixin; Liao, Wei-Ssu; Chen, Xin; Yang, Tinglu; Wark, Stacey E.; Son, Dong Hee; Batteas, James D.; Cremer, Paul S.

2011-01-01

Herein, we demonstrate the controlled formation of two-dimensional periodic arrays of ring-shaped nanostructures assembled from CdSe semiconductor quantum dots (QDs). The patterns were fabricated by using an evaporative templating method. This involves the introduction of an aqueous solution containing both quantum dots and polystyrene microspheres onto the surface of a planar hydrophilic glass substrate. The quantum dots became confined to the meniscus of the microspheres during evaporation, which drove ring assembly via capillary forces at the polystyrene sphere/glass substrate interface. The geometric parameters for nanoring formation could be controlled by tuning the size of the microspheres and the concentration of the QDs employed. This allowed hexagonal arrays of nanorings to be formed with thicknesses ranging from single dot necklaces to thick multilayer structures over surface areas of many square millimeters. Moreover, the diameter of the ring structures could be simultaneously controlled. A simple model was employed to explain the forces involved in the formation of nanoparticle nanorings. PMID:19206264

An Immunological Assay for Detection and Enumeration of Thermophilic Biomining Microorganisms

PubMed Central

Amaro, Ana M.; Hallberg, Kevin B.; Lindström, E. Börje; Jerez, Carlos A.

1994-01-01

A specific, fast, and sensitive nonradioactive immunobinding assay for the detection and enumeration of the moderate thermophile Thiobacillus caldus and the thermophilic archaeon Sulfolobus acidocaldarius was developed. It employs enhanced chemiluminescence or peroxidase-conjugated immunoglobulins in a dot or slot blotting system and is very convenient for monitoring thermophilic bioleaching microorganisms in effluents from industrial bioleaching processes. Images PMID:16349398

An immunological assay for detection and enumeration of thermophilic biomining microorganisms.

PubMed

Amaro, A M; Hallberg, K B; Lindström, E B; Jerez, C A

1994-09-01

A specific, fast, and sensitive nonradioactive immunobinding assay for the detection and enumeration of the moderate thermophile Thiobacillus caldus and the thermophilic archaeon Sulfolobus acidocaldarius was developed. It employs enhanced chemiluminescence or peroxidase-conjugated immunoglobulins in a dot or slot blotting system and is very convenient for monitoring thermophilic bioleaching microorganisms in effluents from industrial bioleaching processes.

Healthcare Worker Seroconversion in SARS Outbreak

PubMed Central

Ooi, Eng-Eong; Tan, Hiang-Khoon; Ong, Kong-Wee; Sil, Bijon Kumar; Teo, Melissa; Ng, Timothy; Soo, Khee-Chee

2004-01-01

Serum samples were obtained from healthcare workers 5 weeks after exposure to an outbreak of severe acute respiratory syndrome (SARS). A sensitive dot blot enzyme-linked immunosorbent assay, complemented by a specific neutralization test, shows that only persons in whom probable SARS was diagnosed had specific antibodies and suggests that subclinical SARS is not an important feature of the disease. PMID:15030691

Detection of 98. 5% of the mutations in 200 Belgian cystic fibrosis alleles by reverse dot-blot and sequencing of the complete coding region and exon/intron junctions of the CFTR gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cuppens, H.; Marynen, P.; Cassiman, J.J.

1993-12-01

The authors have previously shown that about 85% of the mutations in 194 Belgian cystic fibrosis alleles could be detected by a reverse dot-blot assay. In the present study, 50 Belgian chromosomes were analyzed for mutations in the cystic fibrosis transmembrane conductance regulator gene by means of direct solid phase automatic sequencing of PCR products of individual exons. Twenty-six disease mutations and 14 polymorphisms were found. Twelve of these mutations and 3 polymorphisms were not described before. With the exception of one mutant allele carrying two mutations, these mutations were the only mutations found in the complete coding region andmore » their exon/intron boundaries. The total sensitivity of mutant CF alleles that could be identified was 98.5%. Given the heterogeneity of these mutations, most of them very rare, CFTR mutation screening still remains rather complex in the population, and population screening, whether desirable or not, does not appear to be technically feasible with the methods currently available. 24 refs., 1 fig., 2 tabs.« less

Nonisotopic detection of human papillomavirus DNA in clinical specimens using a consensus PCR and a generic probe mix in an enzyme-linked immunosorbent assay format.

PubMed

Kornegay, J R; Shepard, A P; Hankins, C; Franco, E; Lapointe, N; Richardson, H; Coutleé, F

2001-10-01

We assessed the value of a new digoxigenin (DIG)-labeled generic probe mix in a PCR-enzyme-linked immunosorbent assay format to screen for the presence of human papillomavirus (HPV) DNA amplified from clinical specimens. After screening with this new generic assay is performed, HPV DNA-positive samples can be directly genotyped using a reverse blotting method with product from the same PCR amplification. DNA from 287 genital specimens was amplified via PCR using biotin-labeled consensus primers directed to the L1 gene. HPV amplicons were captured on a streptavidin-coated microwell plate (MWP) and detected with a DIG-labeled HPV generic probe mix consisting of nested L1 fragments from types 11, 16, 18, and 51. Coamplification and detection of human DNA with biotinylated beta-globin primers served as a control for both sample adequacy and PCR amplification. All specimens were genotyped using a reverse line blot assay (13). Results for the generic assay using MWPs and a DIG-labeled HPV generic probe mix (DIG-MWP generic probe assay) were compared with results from a previous analysis using dot blots with a radiolabeled nested generic probe mix and type-specific probes for genotyping. The DIG-MWP generic probe assay resulted in high intralaboratory concordance in genotyping results (88% versus 73% agreement using traditional methods). There were 207 HPV-positive results using the DIG-MWP method and 196 positives using the radiolabeled generic probe technique, suggesting slightly improved sensitivity. Only one sample failed to test positive with the DIG-MWP generic probe assay in spite of a positive genotyping result. Concordance between the two laboratories was nearly 87%. Approximately 6% of samples that were positive or borderline when tested with the DIG-MWP generic probe assay were not detected with the HPV type-specific panel, perhaps representing very rare or novel HPV types. This new method is easier to perform than traditional generic probe techniques and uses more objective interpretation criteria, making it useful in studies of HPV natural history.

Production of three-dimensional quantum dot lattice of Ge/Si core-shell quantum dots and Si/Ge layers in an alumina glass matrix.

PubMed

Buljan, M; Radić, N; Sancho-Paramon, J; Janicki, V; Grenzer, J; Bogdanović-Radović, I; Siketić, Z; Ivanda, M; Utrobičić, A; Hübner, R; Weidauer, R; Valeš, V; Endres, J; Car, T; Jerčinović, M; Roško, J; Bernstorff, S; Holy, V

2015-02-13

We report on the formation of Ge/Si quantum dots with core/shell structure that are arranged in a three-dimensional body centered tetragonal quantum dot lattice in an amorphous alumina matrix. The material is prepared by magnetron sputtering deposition of Al2O3/Ge/Si multilayer. The inversion of Ge and Si in the deposition sequence results in the formation of thin Si/Ge layers instead of the dots. Both materials show an atomically sharp interface between the Ge and Si parts of the dots and layers. They have an amorphous internal structure that can be crystallized by an annealing treatment. The light absorption properties of these complex materials are significantly different compared to films that form quantum dot lattices of the pure Ge, Si or a solid solution of GeSi. They show a strong narrow absorption peak that characterizes a type II confinement in accordance with theoretical predictions. The prepared materials are promising for application in quantum dot solar cells.

Compact and highly stable quantum dots through optimized aqueous phase transfer

NASA Astrophysics Data System (ADS)

Tamang, Sudarsan; Beaune, Grégory; Poillot, Cathy; De Waard, Michel; Texier-Nogues, Isabelle; Reiss, Peter

2011-03-01

A large number of different approaches for the aqueous phase transfer of quantum dots have been proposed. Surface ligand exchange with small hydrophilic thiols, such as L-cysteine, yields the lowest particle hydrodynamic diameter. However, cysteine is prone to dimer formation, which limits colloidal stability. We demonstrate that precise pH control during aqueous phase transfer dramatically increases the colloidal stability of InP/ZnS quantum dots. Various bifunctional thiols have been applied. The formation of disulfides, strongly diminishing the fluorescence QY has been prevented through addition of appropriate reducing agents. Bright InP/ZnS quantum dots with a hydrodynamic diameter <10 nm and long-term stability have been obtained. Finally we present in vitro studies of the quantum dots functionalized with the cell-penetrating peptide maurocalcine.

Production and characterization of egg yolk antibody (IgY) against recombinant VP8-S2 antigen.

PubMed

Nasiri, K; Nassiri, M R; Tahmoorespur, M; Haghparast, A; Zibaee, S

2016-01-01

Bovine Rotavirus and Bovine Coronavirus are the most important causes of diarrhea in newborn calves and in some other species such as pigs and sheep. VP8 subunit of rotavirus is the major determinant of the viral infectivity and neutralization. Spike glycoprotein of coronavirus is responsible for induction of neutralizing antibody response. Studies showed that immunoglobulin of egg yolk (IgY) from immunized hens has been identified to be a convenient source for specific antibodies for using in immunotherapy and immunodiagnostic to limit the infections. In this study, chimeric VP8-S2 gene was designed using by computational techniques. The chimeric VP8-S2 gene was cloned and sub-cloned into pGH and pET32a (+) vectors. Then, recombinant pET32a-VP8-S2 vector was transferred into E. coli BL21 CodonPlus (DE3). The expressed protein was purified by Ni-NTA chromatography column. Hens were immunized with the purified VP8-S2 protein three times. IgY was purified from egg yolks using polyethylene glycol precipitation method. Activity and specificity of anti-VP8-S2 IgY were detected by dot-blotting, Western-blotting and indirect ELISA. We obtained anti-VP8-S2 IgY by immunizing hens with the recombinant VP8-S2 protein. The anti-VP8-S2 IgY was showed to bind specifically to the chimeric VP8-S2 protein by dot-blotting, Western-blotting analyses and indirect ELISA. The result of this study indicated that such construction can be useful to investigate as candidates for development of detection methods for simultaneous diagnosis of both infections. Specific IgY against the recombinant VP8-S2 could be recommended as a candidate for passive immunization against bovine rotavirus and bovine coronavirus.

Hubble's View of Little Blue Dots

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-02-01

The recent discovery of a new type of tiny, star-forming galaxy is the latest in a zoo of detections shedding light on our early universe. What can we learn from the unique little blue dots found in archival Hubble data?Peas, Berries, and DotsGreen pea galaxies identified by citizen scientists with Galaxy Zoo. [Richard Nowell Carolin Cardamone]As telescope capabilities improve and we develop increasingly deeper large-scale surveys of our universe, we continue to learn more about small, faraway galaxies. In recent years, increasing sensitivity first enabled the detection of green peas luminous, compact, low-mass (10 billion solar masses; compare this to the Milky Ways 1 trillion solar masses!) galaxies with high rates of star formation.Not long thereafter, we discovered galaxies that form stars similarly rapidly, but are even smaller only 330 million solar masses, spanning less than 3,000 light-years in size. These tiny powerhouses were termed blueberries for their distinctive color.Now, scientists Debra and Bruce Elmegreen (of Vassar College and IBM Research Division, respectively) report the discovery of galaxies that have even higher star formation rates and even lower masses: little blue dots.Exploring Tiny Star FactoriesThe Elmegreens discovered these unique galaxies by exploring archival Hubble data. The Hubble Frontier Fields data consist of deep images of six distant galaxy clusters and the parallel fields next to them. It was in the archival data for two Frontier Field Parallels, those for clusters Abell 2744 and MAS J0416.1-2403, that the authors noticed several galaxies that stand out as tiny, bright, blue objects that are nearly point sources.Top: a few examples of the little blue dots recently identified in two Hubble Frontier Field Parallels. Bottom: stacked images for three different groups of little blue dots. [Elmegreen Elmegreen 2017]The authors performed a search through the two Frontier Field Parallels, discovering a total of 55 little blue dots with masses spanning 105.8107.4solar masses, specific star formation rates of 10-7.4, and redshifts of 0.5 z 5.4.Exploring these little blue dots, the Elmegreens find that the galaxies sizes tend to be just a few hundred light-years across. They are gas-dominated; gas currently outweighs stars in these galaxies by perhaps a factor of five. Impressively, based on the incredibly high specific star formation rates observed in these little blue dots, they appear to have formed all of their stars in the last 1% of the age of the universe for them.An Origin for Globulars?Log-log plot of star formation rate vs. mass for the three main groups of little blue dots (red, green, and blue markers), a fourth group of candidates with different properties (brown markers), and previously discovered local blueberry galaxies. The three main groups of little blue dots appear to be low-mass analogs of blueberries. [Elmegreen Elmegreen 2017]Intriguingly, this rapid star formation might be the key to answering a long-standing question: where do globular clusters come from? The Elmegreens propose that little blue dots might actually be an explanation for the origin of these orbiting, spherical, low-metallicity clusters of stars.The authors demonstrate that, if the current star formation rates observed in little blue dots were to persist for another 50 Myr before feedback or gas exhaustion halted star production, the little blue dots could form enough stars to create clusters of roughly a million solar masses which is large enough to explain the globular clusters we observe today.If little blue dots indeed rapidly produced such star clusters in the past, the clusters could later be absorbed into the halos of todays spiral and elliptical galaxies, appearing to us as the low-metallicity globular clusters that orbit large galaxies today.CitationDebra Meloy Elmegreen and Bruce G. Elmegreen 2017 ApJL 851 L44. doi:10.3847/2041-8213/aaa0ce

Storage and stability of IgG and IgM monoclonal antibodies dried on filter paper and utility in Neisseria meningitidis serotyping by Dot-blot ELISA.

PubMed

Ferraz, Aline S; Belo, Elza F T; Coutinho, Ligia M C C; Oliveira, Ana P; Carmo, Andréia M S; Franco, Daniele L; Ferreira, Tatiane; Yto, André Y; Machado, Marta S F; Scola, Monica C G; De Gaspari, Elizabeth

2008-03-06

A simple filter paper method was developed for, the transport and storage of monoclonal antibodies (Mabs) at room temperature or -20 degrees C after spotting on filter paper, for subsequent serotyping of outer membrane antigens of N.meningitidis by dot-blot ELISA. Monoclonal antibodies (Mabs) were spotted within a 0.5-1 cm diameter area of Whatman grade 903 paper, which were stored individually at room temperature or at -20 degrees C. These MAbs were stored and analyzed after periods of one week, 4 weeks, 12 months, or 13 years in the case of frozen Mab aliquots, or after 4 weeks at -20 degrees C or at room temperature (RT) in the case of Mabs dried on filter paper strips. Assays were performed in parallel using dot-blot ELISA. In addition to the MAbs specific for serotyping class 1, 2 or 3, we used a larger number of Mabs for polysaccharides, lipooligosaccharides (LOS), class 5 and cross-reactive antigens for native outer membrane of N.meningitidis. The Mabs dried on filter paper were eluted with phosphate-buffered saline (PBS) containing 0.2% gelatin. Mabs of the isotypes IgG and IgM dried on filter papers were not affected by duration of storage. The detection by serotyping Mabs was generally consistent for dried filter paper MAb samples stored frozen for over 1 year at -20 degrees C, and although decreased reactive antibody titers were found after storage, this did not interfere with the specificity of the Mabs used after 13 years as dry spots on filter paper. The use of filter paper is an inexpensive and convenient method for collecting, storing, and transporting Mab samples for serotyping studies. In addition, the samples occupy little space and can be readily transported without freezing. The efficiency of using immunoglobulin G (IgG) or M (IgM) eluted was found to be consistent with measurement of IgG or IgM titers in most corresponding, ascites Mabs stored frozen for over 1 year. The application of meningococcal typing methods and designations depend on the question being asked.

Improved Low Temperature Performance of Supercapacitors

NASA Technical Reports Server (NTRS)

Brandon, Erik J.; West, William C.; Smart, Marshall C.; Gnanaraj, Joe

2013-01-01

Low temperature double-layer capacitor operation enabled by: - Base acetonitrile / TEATFB salt formulation - Addition of low melting point formates, esters and cyclic ethers center dot Key electrolyte design factors: - Volume of co-solvent - Concentration of salt center dot Capacity increased through higher capacity electrodes: - Zeolite templated carbons - Asymmetric cell designs center dot Continuing efforts - Improve asymmetric cell performance at low temperature - Cycle life testing Motivation center dot Benchmark performance of commercial cells center dot Approaches for designing low temperature systems - Symmetric cells (activated carbon electrodes) - Symmetric cells (zeolite templated carbon electrodes) - Asymmetric cells (lithium titanate/activated carbon electrodes) center dot Experimental results center dot Summary

Design optimization of large-size format edge-lit light guide units

NASA Astrophysics Data System (ADS)

Hastanin, J.; Lenaerts, C.; Fleury-Frenette, K.

2016-04-01

In this paper, we present an original method of dot pattern generation dedicated to large-size format light guide plate (LGP) design optimization, such as photo-bioreactors, the number of dots greatly exceeds the maximum allowable number of optical objects supported by most common ray-tracing software. In the proposed method, in order to simplify the computational problem, the original optical system is replaced by an equivalent one. Accordingly, an original dot pattern is splitted into multiple small sections, inside which the dot size variation is less than the ink dots printing typical resolution. Then, these sections are replaced by equivalent cells with continuous diffusing film. After that, we adjust the TIS (Total Integrated Scatter) two-dimensional distribution over the grid of equivalent cells, using an iterative optimization procedure. Finally, the obtained optimal TIS distribution is converted into the dot size distribution by applying an appropriate conversion rule. An original semi-empirical equation dedicated to rectangular large-size LGPs is proposed for the initial guess of TIS distribution. It allows significantly reduce the total time needed to dot pattern optimization.

Gate tunable parallel double quantum dots in InAs double-nanowire devices

NASA Astrophysics Data System (ADS)

Baba, S.; Matsuo, S.; Kamata, H.; Deacon, R. S.; Oiwa, A.; Li, K.; Jeppesen, S.; Samuelson, L.; Xu, H. Q.; Tarucha, S.

2017-12-01

We report fabrication and characterization of InAs nanowire devices with two closely placed parallel nanowires. The fabrication process we develop includes selective deposition of the nanowires with micron scale alignment onto predefined finger bottom gates using a polymer transfer technique. By tuning the double nanowire with the finger bottom gates, we observed the formation of parallel double quantum dots with one quantum dot in each nanowire bound by the normal metal contact edges. We report the gate tunability of the charge states in individual dots as well as the inter-dot electrostatic coupling. In addition, we fabricate a device with separate normal metal contacts and a common superconducting contact to the two parallel wires and confirm the dot formation in each wire from comparison of the transport properties and a superconducting proximity gap feature for the respective wires. With the fabrication techniques established in this study, devices can be realized for more advanced experiments on Cooper-pair splitting, generation of Parafermions, and so on.

Self-organized formation of quantum dots of a material on a substrate

DOEpatents

Zhang, Zhenyu; Wendelken, John F.; Chang, Ming-Che; Pai, Woei Wu

2001-01-01

Systems and methods are described for fabricating arrays of quantum dots. A method for making a quantum dot device, includes: forming clusters of atoms on a substrate; and charging the clusters of atoms such that the clusters of atoms repel one another. The systems and methods provide advantages because the quantum dots can be ordered with regard to spacing and/or size.

Diagnosis of AIDS-Related Intestinal Parasites

DTIC Science & Technology

1988-01-07

malnutrition or with certain concomitant illnesses such as measles or chicken pox , may be susceptible to more severe clinical manifestations with cure only...above) and Homero Martinez, M.D., Instituto National de la Nutricion, Mexico City. In this study, 53 children with at least one microscopic stool...outlined or using nitrocellulose "DOT-blot" technology. In addition, plans are underway to begin field testing the Entamoeba histolytica ELISA in Mexico

Rosette Assay: Highly Customizable Dot-Blot for SH2 Domain Screening.

PubMed

Ng, Khong Y; Machida, Kazuya

2017-01-01

With a growing number of high-throughput studies, structural analyses, and availability of protein-protein interaction databases, it is now possible to apply web-based prediction tools to SH2 domain-interactions. However, in silico prediction is not always reliable and requires experimental validation. Rosette assay is a dot blot-based reverse-phase assay developed for the assessment of binding between SH2 domains and their ligands. It is conveniently customizable, allowing for low- to high-throughput analysis of interactions between various numbers of SH2 domains and their ligands, e.g., short peptides, purified proteins, and cell lysates. The binding assay is performed in a 96-well plate (MBA or MWA apparatus) in which a sample spotted membrane is incubated with up to 96 labeled SH2 domains. Bound domains are detected and quantified using a chemiluminescence or near-infrared fluorescence (IR) imaging system. In this chapter, we describe a practical protocol for rosette assay to assess interactions between synthesized tyrosine phosphorylated peptides and a library of GST-tagged SH2 domains. Since the methodology is not confined to assessment of SH2-pTyr interactions, rosette assay can be broadly utilized for ligand and drug screening using different protein interaction domains or antibodies.

A rat genetic map constructed by representational difference analysis markers with suitability for large-scale typing.

PubMed Central

Toyota, M; Canzian, F; Ushijima, T; Hosoya, Y; Kuramoto, T; Serikawa, T; Imai, K; Sugimura, T; Nagao, M

1996-01-01

Representational difference analysis (RDA) was applied to isolate chromosomal markers in the rat. Four series of RDA [restriction enzymes, BamHI and HindIII; subtraction of ACI/N (ACI) amplicon from BUF/Nac (BUF) amplicon and vice versa] yielded 131 polymorphic markers; 125 of these markers were mapped to all chromosomes except for chromosome X. This was done by using a mapping panel of 105 ACI x BUF F2 rats. To complement the relative paucity of chromosomal markers in the rat, genetically directed RDA, which allows isolation of polymorphic markers in the specific chromosomal region, was performed. By changing the F2 driver-DNA allele frequency around the region, four markers were isolated from the D1Ncc1 locus. Twenty-five of 27 RDA markers were informative regarding the dot blot analysis of amplicons, hybridizing only with tester amplicons. Dot blot analysis at a high density per unit of area made it possible to process a large number of samples. Quantitative trait loci can now be mapped in the rat genome by processing a large number of samples with RDA markers and then by isolating markers close to the loci of interest by genetically directed RDA. Images Fig. 1 Fig. 3 Fig. 4 PMID:8632989

Selection of DNA aptamers against Human Cardiac Troponin I for colorimetric sensor based dot blot application.

PubMed

Dorraj, Ghamar Soltan; Rassaee, Mohammad Javad; Latifi, Ali Mohammad; Pishgoo, Bahram; Tavallaei, Mahmood

2015-08-20

Troponin T and I are ideal markers which are highly sensitive and specific for myocardial injury and have shown better efficacy than earlier markers. Since aptamers are ssDNA or RNA that bind to a wide variety of target molecules, the purpose of this research was to select an aptamer from a 79bp single-stranded DNA (ssDNA) random library that was used to bind the Human Cardiac Troponin I from a synthetic nucleic acids library by systematic evolution of ligands exponential enrichment (Selex) based on several selection and amplification steps. Human Cardiac Troponin I protein was coated onto the surface of streptavidin magnetic beads to extract specific aptamer from a large and diverse random ssDNA initial oligonucleotide library. As a result, several aptamers were selected and further examined for binding affinity and specificity. Finally TnIApt 23 showed beast affinity in nanomolar range (2.69nM) toward the target protein. A simple and rapid colorimetric detection assay for Human Cardiac Troponin I using the novel and specific aptamer-AuNPs conjugates based on dot blot assay was developed. The detection limit for this protein using aptamer-AuNPs-based assay was found to be 5ng/ml. Copyright © 2015 Elsevier B.V. All rights reserved.

Identification and characterization of jute LTR retrotransposons:

PubMed Central

Ahmed, Salim; Shafiuddin, MD; Azam, Muhammad Shafiul; Islam, Md. Shahidul; Ghosh, Ajit

2011-01-01

Long Terminal Repeat (LTR) retrotransposons constitute a significant part of eukaryotic genomes and play an important role in genome evolution especially in plants. Jute is an important fiber crop with a large genome of 1,250 Mbps. This genome is still mostly unexplored. In this study we aimed at identifying and characterizing the LTR retrotransposons of jute with a view to understanding the jute genome better. In this study, the Reverse Transcriptase domain of Ty1-copia and Ty3-gypsy LTR retrotransposons of jute were amplified by degenerate primers and their expressions were examined by reverse transcription PCR. Copy numbers of reverse transcriptase (RT) genes of Ty1-copia and Ty3-gypsy elements were determined by dot blot analysis. Sequence analysis revealed higher heterogeneity among Ty1-copia retrotransposons than Ty3-gypsy and clustered each of them in three groups. Copy number of RT genes in Ty1-copia was found to be higher than that of Ty3-gypsy elements from dot blot hybridization. Cumulatively Ty1-copia and Ty3-gypsy may constitute around 19% of the jute genome where two groups of Ty1-copia were found to be transcriptionally active. Since the LTR retrotransposons constitute a large portion of jute genome, these findings imply the importance of these elements in the evolution of jute genome. PMID:22016842

Genetic relatedness of orbiviruses by RNA-RNA blot hybridization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bodkin, D.K.

1985-01-01

RNA-RNA blot hybridization was developed in order to identify type-specific genes among double-stranded (ds) RNA viruses, to assess the genetic relatedness of dsRNA viruses and to classify new strains. Viral dsRNA segments were electrophoresed through 10% polyacrylamide gels, transferred to membranes, and hybridized to (5'/sup 32/P)-pCp labeled genomic RNA from a related strain. Hybridization was performed at 52/sup 0/C, 50% formamide, 5X SSC. Under these conditions heterologous RNA species must share greater than or equal to 74% sequence homology in order to form stable dsRNA hybrids. Cognate genes of nine members of the Palyam serogroup of orbiviruses were identified andmore » their sequence relatedness to the prototype. Palyam virus, was determined. Reciprocal blot hybridizations were performed using radiolabeled genomic RNA of all members of the Palyam serogroup. Unique and variant genes were identified by lack of cross-homology or by weak homology between segments. Since genes 2 and 6 exhibited the highest degree of sequence variability, response to the vertebrate immune system may be a major cause of sequence divergence among members of a single serogroup. Changuinola serogroup isolates were compared by dot-blot hybridization, while Colorado tick fever (CTF) serogroup isolates were compared by the RNA-RNA blot hybridization procedure described for reovirus and Palyam serogroup isolates. Preliminary blot hybridization data were also obtained on the relatedness of members of different Orbivirus serogroups.« less

Category Formation in Autism: Can Individuals with Autism Form Categories and Prototypes of Dot Patterns?

ERIC Educational Resources Information Center

Gastgeb, Holly Zajac; Dundas, Eva M.; Minshew, Nancy J.; Strauss, Mark S.

2012-01-01

There is a growing amount of evidence suggesting that individuals with autism have difficulty with categorization. One basic cognitive ability that may underlie this difficulty is the ability to abstract a prototype. The current study examined prototype and category formation with dot patterns in high-functioning adults with autism and matched…

Facile fabrication of luminescent organic dots by thermolysis of citric acid in urea melt, and their use for cell staining and polyelectrolyte microcapsule labelling.

PubMed

Zholobak, Nadezhda M; Popov, Anton L; Shcherbakov, Alexander B; Popova, Nelly R; Guzyk, Mykhailo M; Antonovich, Valeriy P; Yegorova, Alla V; Scrypynets, Yuliya V; Leonenko, Inna I; Baranchikov, Alexander Ye; Ivanov, Vladimir K

2016-01-01

Luminescent organic dots (O-dots) were synthesized via a one-pot, solvent-free thermolysis of citric acid in urea melt. The influence of the ratio of the precursors and the duration of the process on the properties of the O-dots was established and a mechanism of their formation was hypothesized. The multicolour luminescence tunability and toxicity of synthesized O-dots were extensively studied. The possible applications of O-dots for alive/fixed cell staining and labelling of layer-by-layer polyelectrolyte microcapsules were evaluated.

Facile fabrication of luminescent organic dots by thermolysis of citric acid in urea melt, and their use for cell staining and polyelectrolyte microcapsule labelling

PubMed Central

Zholobak, Nadezhda M; Popov, Anton L; Shcherbakov, Alexander B; Popova, Nelly R; Guzyk, Mykhailo M; Antonovich, Valeriy P; Yegorova, Alla V; Scrypynets, Yuliya V; Leonenko, Inna I; Baranchikov, Alexander Ye

2016-01-01

Luminescent organic dots (O-dots) were synthesized via a one-pot, solvent-free thermolysis of citric acid in urea melt. The influence of the ratio of the precursors and the duration of the process on the properties of the O-dots was established and a mechanism of their formation was hypothesized. The multicolour luminescence tunability and toxicity of synthesized O-dots were extensively studied. The possible applications of O-dots for alive/fixed cell staining and labelling of layer-by-layer polyelectrolyte microcapsules were evaluated. PMID:28144539

Detection of DNA via the fluorescence quenching of Mn-doped ZnSe D-dots/doxorubicin/DNA ternary complexes system.

PubMed

Gao, Xue; Niu, Lu; Su, Xingguang

2012-01-01

This manuscript reports a method for the detection of double-stranded DNA, based on Mn:ZnSe d-dots and intercalating agent doxorubicin (DOX). DOX can quench the photoluminescence (PL) of Mn:ZnSe d-dots through photoinduced electron transfer process, after binding with Mn:ZnSe d-dots. The addition of DNA can result in the formation of the Mn:ZnSe d-dots-DOX-DNA ternary complexes, the fluorescence of the Mn:ZnSe d-dots-DOX complexes would be further quenched by the addition of DNA, thus allowing the detection of DNA. The formation mechanism of the Mn:ZnSe d-dots-DOX-DNA ternary complexes was studied in detail in this paper. Under optimal conditions, the quenched fluorescence intensity of Mn:ZnSe d-dots-DOX system are perfectly described by Stern-Volmer equation with the concentration of hsDNA ranging from 0.006 μg mL(-1) to 6.4 μg mL(-1). The detection limit (S/N = 3) for hsDNA is 0.5 ng mL(-1). The proposed method was successfully applied to the detection of DNA in synthetic samples and the results were satisfactory.

Diagnostic potential of Western blot analysis of sera from dogs with leishmaniasis in endemic areas and significance of the pattern.

PubMed

Aisa, M J; Castillejo, S; Gallego, M; Fisa, R; Riera, M C; de Colmenares, M; Torras, S; Roura, X; Sentis, J; Portus, M

1998-02-01

Serum samples collected from 237 dogs in Catalonia (northeastern Spain) were screened by Western blot analysis to detect the presence of antibodies specific to different Leishmania infantum polypeptide fractions. Leishmaniasis was confirmed in 72 of these dogs by direct examination and/or culture. Another 165 animals from the Priorat region were studied periodically for 2-8 years between 1987 and 1995, giving a total of 565 determinations. A control group of 93 dogs from nonendemic areas was also studied. Sera from dogs with leishmaniasis recognized antigens with molecular weights ranging from 12 to 85 kD. The most sensitive antigens were those of 70, 65, 46, 30, 28, 14, and 12 kD, which were recognized by 75%, 75%, 78%, 75%, 81%, 79%, and 75%, respectively, of the sera from dogs with positive parasitologic examination results. Antigens of 70 and 65 kD were also recognized by two dogs from nonendemic areas. Antigens of 14 and 12 kD were the first to be recognized by sera of asymptomatic dogs with titers less than the cut-off value of the dot-ELISA that increased during the longitudinal study, and the presence of antibodies specific for these fractions was observed for up to six years before seroconversion observed by dot-ELISA. These antibodies were also the first to disappear in dogs in which the disease was self-limited. The study corroborates the high sensitivity and specificity of Western blots in the diagnosis of canine leishmaniasis when the bands of low molecular weight (less than 46 kD) are considered, and indicates that fractions of 14 and 12 kD are useful in detecting early forms of the disease.

Inhibitory effects of magnolol and honokiol on human calcitonin aggregation

PubMed Central

Guo, Caiao; Ma, Liang; Zhao, Yudan; Peng, Anlin; Cheng, Biao; Zhou, Qiaoqiao; Zheng, Ling; Huang, Kun

2015-01-01

Amyloid formation is associated with multiple amyloidosis diseases. Human calcitonin (hCT) is a typical amyloidogenic peptide, its aggregation is associated with medullary carcinoma of the thyroid (MTC), and also limits its clinical application. Magnolia officinalis is a traditional Chinese herbal medicine; its two major polyphenol components, magnolol (Mag) and honokiol (Hon), have displayed multiple functions. Polyphenols like flavonoids and their derivatives have been extensively studied as amyloid inhibitors. However, the anti-amyloidogenic property of a biphenyl backbone containing polyphenols such as Mag and Hon has not been reported. In this study, these two compounds were tested for their effects on hCT aggregation. We found that Mag and Hon both inhibited the amyloid formation of hCT, whereas Mag showed a stronger inhibitory effect; moreover, they both dose-dependently disassembled preformed hCT aggregates. Further immuno-dot blot and dynamic light scattering studies suggested Mag and Hon suppressed the aggregation of hCT both at the oligomerization and the fibrillation stages, while MTT-based and dye-leakage assays demonstrated that Mag and Hon effectively reduced cytotoxicity caused by hCT aggregates. Furthermore, isothermal titration calorimetry indicated Mag and Hon both interact with hCT. Together, our study suggested a potential anti-amyloidogenic property of these two compounds and their structure related derivatives. PMID:26324190

Non-adiabatic molecular dynamics investigation of photoionization state formation and lifetime in Mn²⁺-doped ZnO quantum dots.

PubMed

Fischer, Sean A; Lingerfelt, David B; May, Joseph W; Li, Xiaosong

2014-09-07

The unique electronic structure of Mn(2+)-doped ZnO quantum dots gives rise to photoionization states that can be used to manipulate the magnetic state of the material and to generate zero-reabsorption luminescence. Fast formation and long non-radiative decay of this photoionization state is a necessary requirement for these important applications. In this work, surface hopping based non-adiabatic molecular dynamics are used to demonstrate the fast formation of a metal-to-ligand charge transfer state in a Mn(2+)-doped ZnO quantum dot. The formation occurs on an ultrafast timescale and is aided by the large density of states and significant mixing of the dopant Mn(2+) 3dt2 levels with the valence-band levels of the ZnO lattice. The non-radiative lifetime of the photoionization states is also investigated.

Three-Dimensional Control of Self-Assembled Quantum Dot Configurations

DTIC Science & Technology

2010-06-17

Lateral Quantum Dot Molecules Around Self-Assembled Nanoholes . Appl. Phys. Lett. 2003, 82, 2892–2894. 7. Alonso-Gonzalez, P.; Martin-Sanchez, J.; Gonzalez...Y.; Alen, B.; Fuster, D.; Gonzalez, L. Formation of Lateral Low Density In(Ga)As Quantum Dot Pairs in GaAs Nanoholes . Cryst. Growth Des. 2009, 9

The Battle of the Printers.

ERIC Educational Resources Information Center

Muller, Douglas; Pettibone, Timothy

This paper compares the characteristics of dot-matrix and daisy wheel printers using a two-column format. In the first section, the left column is used to point out the advantages of dot-matrix printers, while the daisy wheel printer is praised in the right-hand column. Examples of various capabilities are included. Advantages of the dot-matrix…

Atmospheric pressure-MOVPE growth of GaSb/GaAs quantum dots

NASA Astrophysics Data System (ADS)

Tile, Ngcali; Ahia, Chinedu C.; Olivier, Jaco; Botha, Johannes Reinhardt

2018-04-01

This study focuses on the growth of GaSb/GaAs quantum dots (QD) using an atmospheric pressure MOVPE system. For the best uncapped dots, the average dot height, base diameter and density are 5 nm, 45 nm and 4.5×1010 cm-2, respectively. Capping of GaSb QDs at high temperatures caused flattening and formation of thin inhomogeneous GaSb layer inside GaAs resulting in no obvious QD PL peak. Capping at low temperatures lead to the formation of dot-like features and a wetting layer (WL) with distinct PL peaks for QD and WL at 1097 nm and 983 nm respectively. Some of the dot-like features had voids. An increase in excitation power caused the QD and WL peaks to shift to higher energies. This is attributed to electrostatic band bending leading to triangular potential wells, typical of type-II alignment between GaAs and strained GaSb. Variable temperature PL measurements of the QD sample showed the decrease in the intensity of the WL peak to be faster than that of the QD peak as the temperature increased.

Do Circumnuclear Dense Gas Disks Drive Mass Accretion onto Supermassive Black Holes?

NASA Astrophysics Data System (ADS)

Izumi, Takuma; Kawakatu, Nozomu; Kohno, Kotaro

2016-08-01

We present a positive correlation between the mass of dense molecular gas ({M}{{dense}}) of ˜100 pc scale circumnuclear disks (CNDs) and the black hole mass accretion rate ({\\dot{M}}{{BH}}) in a total of 10 Seyfert galaxies, based on data compiled from the literature and an archive (median aperture θ med = 220 pc). A typical {M}{{dense}} of CNDs is 107-8 {M}⊙ , estimated from the luminosity of the dense gas tracer, the HCN(1-0) emission line. Because dense molecular gas is the site of star formation, this correlation is virtually equivalent to the one between the nuclear star-formation rate and {\\dot{M}}{{BH}} revealed previously. Moreover, the {M}{{dense}}{--}{\\dot{M}}{{BH}} correlation was tighter for CND-scale gas than for the gas on kiloparsec or larger scales. This indicates that CNDs likely play an important role in fueling black holes, whereas greater than kiloparesec scale gas does not. To demonstrate a possible approach for studying the CND-scale accretion process with the Atacama Large Millimeter/submillimeter Array, we used a mass accretion model where angular momentum loss due to supernova explosions is vital. Based on the model prediction, we suggest that only the partial fraction of the mass accreted from the CND ({\\dot{M}}{{acc}}) is consumed as {\\dot{M}}{{BH}}. However, {\\dot{M}}{{acc}} agrees well with the total nuclear mass flow rate (I.e., {\\dot{M}}{{BH}} + outflow rate). Although these results are still tentative with large uncertainties, they support the view that star formation in CNDs can drive mass accretion onto supermassive black holes in Seyfert galaxies.

Topography evolution of 500 keV Ar(4+) ion beam irradiated InP(100) surfaces - formation of self-organized In-rich nano-dots and scaling laws.

PubMed

Sulania, Indra; Agarwal, Dinesh C; Kumar, Manish; Kumar, Sunil; Kumar, Pravin

2016-07-27

We report the formation of self-organized nano-dots on the surface of InP(100) upon irradiating it with a 500 keV Ar(4+) ion beam. The irradiation was carried out at an angle of 25° with respect to the normal at the surface with 5 different fluences ranging from 1.0 × 10(15) to 1.0 × 10(17) ions per cm(2). The morphology of the ion-irradiated surfaces was examined by atomic force microscopy (AFM) and the formation of the nano-dots on the irradiated surfaces was confirmed. The average size of the nano-dots varied from 44 ± 14 nm to 94 ± 26 nm with increasing ion fluence. As a function of the ion fluence, the variation in the average size of the nano-dots has a great correlation with the surface roughness, which changes drastically up to the ion fluence of 1.0 × 10(16) ions per cm(2) and attains almost a saturation level for further irradiation. The roughness and the growth exponent values deduced from the scaling laws suggest that the kinetic sputtering and the large surface diffusion steps of the atoms are the primary reasons for the formation of the self-organized nanodots on the surface. X-ray photo-electron spectroscopy (XPS) studies show that the surface stoichiometry changes with the ion fluence. With irradiation, the surface becomes more indium (In)-rich owing to the preferential sputtering of the phosphorus atoms (P) and the pure metallic In nano-dots evolve at the highest ion fluence. The cross-sectional scanning electron microscopy (SEM) analysis of the sample irradiated with the highest fluence showed the absence of the nanostructuring beneath the surface. The surface morphological changes at this medium energy ion irradiation are discussed in correlation with the low and high energy experiments to shed more light on the mechanism of the well separated nano-dot formation.

An Improved Method for Generating Consistent Soluble Amyloid-beta Oligomer Preparations for In Vitro Neurotoxicity Studies

PubMed Central

Ryan, Deborah A.; Narrow, Wade C.; Federoff, Howard J.; Bowers, William J.

2010-01-01

Soluble Aβ oligomers are recognized as playing a key role in Alzheimer’s disease (AD) pathophysiology. Despite their significance, many investigators encounter difficulty generating reliable preparations for in vitro and in vivo experiments. Solutions of Aβ are often unstable and soluble conformer profiles inconsistent. In this study we describe detailed methods for preparing Aβ oligomers that are stable for several weeks and are enriched for low and high molecular weight oligomeric forms, including the 56-kDa form, a conformer implicated in AD-related cognitive impairment. We characterize their structural and functional properties using Western blot, dot blot, atomic force microscopy, Thioflavine T fluorescence, and primary neuronal culture toxicity assays. These synthetic preparations should prove valuable to many studying Aβ-mediated mechanisms underlying AD. PMID:20452375

Fabrication of (In,Ga)As quantum-dot chains on GaAs(100)

NASA Astrophysics Data System (ADS)

Wang, Z. M.; Holmes, K.; Mazur, Yu. I.; Salamo, G. J.

2004-03-01

Nanostructure evolution during the growth of multilayers of In0.5Ga0.5As/GaAs (100) by molecular-beam epitaxy is investigated to control the formation of lines of quantum dots called quantum-dot chains. It is found that the dot chains can be substantially increased in length by the introduction of growth interruptions during the initial stages of growth of the GaAs spacer layer. Quantum-dot chains that are longer than 5 μm are obtained by adjusting the In0.5Ga0.5As coverage and growth interruptions. The growth procedure is also used to create a template to form InAs dots into chains with a predictable dot density. The resulting dot chains offer the possibility to engineer carrier interaction among dots for novel physical phenomena and potential devices.

Solid-state thermal behavior and stability studies of theophylline-citric acid cocrystals prepared by neat cogrinding or thermal treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Po-Chun; Lin, Hong-Liang; Wang, Shun-Li, E-mail: wangshunli@mail.ncyu.edu.tw

To investigate the thermal behavior of cocrystal formed between anhydrous theophylline (TP) and anhydrous citric acid (CA) by neat manual cogrinding or thermal treatment, DSC and FTIR microspectroscopy with curve-fitting analysis were applied. The physical mixture and 60-min ground mixture were stored at 55{+-}0.5 Degree-Sign C/40{+-}2% RH condition to determine their stability behavior. Typical TP-CA cocrystals were prepared by slow solvent evaporation method. Results indicate that the cogrinding process could gradually induce the cocrystal formation between TP and CA. The IR spectral peak shift from 3495 to 3512 cm{sup -1} and the stepwise appearance of several new IR peaks atmore » 1731, 1712, 1676, 1651, 1557 and 1265 cm{sup -1} with cogrinding time suggest that the mechanism of TP-CA cocrystal formation was evidenced by interacting TP with CA through the intermolecular O-H{center_dot}{center_dot}{center_dot}O hydrogen bonding. The stability of 60-min ground mixture of TP-CA was confirmed at 55{+-}0.5 Degree-Sign C/40{+-}2% RH condition over a storage time of 60 days. - Garphical abstract: Cogrinding, thermal and solvent-evaporation methods might easily induce the theophylline-citric acid cocrystal formation. Highlights: Black-Right-Pointing-Pointer Cogrinding process could gradually induce the cocrystal formation between TP and CA. Black-Right-Pointing-Pointer The TP-CA cocrystal was formed through the intermolecular O-H{center_dot}{center_dot}{center_dot}O hydrogen bonding. Black-Right-Pointing-Pointer The 60-min TP-CA ground mixture was similar to the solvent-evaporated cocrystal. Black-Right-Pointing-Pointer The thermal-induced TP-CA cocrystal formation was confirmed by pre-heating the physical mixture to 152 Degree-Sign C. Black-Right-Pointing-Pointer The 60-min TP-CA ground mixture was stable at accelerated condition over a storage time of 60 days.« less

49 CFR 92.41 - Requesting recovery when the Department is not the paying agency.

Code of Federal Regulations, 2010 CFR

2010-10-01

... processs of separating. If the employee is in the process of separating, the DOT creditor operating element... paying agency. (a) Format of the request for recovery. (1) Where the DOT operating element is the..., attach a copy of the decision of the administrative law judge or other hearing official. The DOT creditor...

Synthesis and characterization of graphene quantum dots-silver nanocomposites

NASA Astrophysics Data System (ADS)

Vandana, M.; Ashokkumar, S. P.; Vijeth, H.; Niranjana, M.; Yesappa, L.; Devendrappa, H.

2018-04-01

A facile microwave assisted hydrothermal method is used to synthesise glucose derived water soluble crystalline graphene quantum dots (GQDs) andcitrate reduction method was used to synthesized silver nanoparticles (SNPs). The formation of graphene quantum dots-silver nanocomposites (GSC) was synthesized through a simple refluxing process and characterised using Fourier Transform Infrared (FT-IR) to study the chemical interaction, Surface morphology using FESEM, Optical properties were studied using UV-Visible spectroscopy. The absorption band shows at 249, 306 and 447 nm confirms the formation of GQDs and GSC. The electrochemical performance of GSC tested to determine the oxidation/reduction processes by cyclic voltammetry and linear sweep voltammetry.

A non-genetic approach to labelling acute myeloid leukemia and bone marrow cells with quantum dots.

PubMed

Zheng, Yanwen; Tan, Dongming; Chen, Zheng; Hu, Chenxi; Mao, Zhengwei J; Singleton, Timothy P; Zeng, Yan; Shao, Xuejun; Yin, Bin

2014-06-01

The difficulty in manipulation of leukemia cells has long hindered the dissection of leukemia pathogenesis. We have introduced a non-genetic approach of marking blood cells, using quantum dots. We compared quantum dots complexed with different vehicles, including a peptide Tat, cationic polymer Turbofect and liposome. Quantum dots-Tat showed the highest efficiency of marking hematopoietic cells among the three vehicles. Quantum dots-Tat could also label a panel of leukemia cell lines at varied efficiencies. More uniform intracellular distributions of quantum dots in mouse bone marrow and leukemia cells were obtained with quantum dots-Tat, compared with the granule-like formation obtained with quantum dots-liposome. Our results suggest that quantum dots have provided a photostable and non-genetic approach that labels normal and malignant hematopoietic cells, in a cell type-, vehicle-, and quantum dot concentration-dependent manner. We expect for potential applications of quantum dots as an easy and fast marking tool assisting investigations of various types of blood cells in the future.

222 Aerobiological and Immunological Studies on Coconut Pollen Allergy

PubMed Central

Saha, Bodhisattwa; Bhattacharya, Swati Gupta

2012-01-01

Background Pollen grains constitute a significant portion of the aerobiological flora. The plant Coccos nucifera (commonly known as coconut) is found in huge quantities in the tropical coastal areas of the world and is very common in Kolkata, India. A 2 years aerobiological survey was carried out using Burkard Volumetric Sampler to know the seasonal variation of Cocos nucifera pollen. The plant flower through out the year but maximum concentration was found in the month of August. Allergenicity of Cocos nucifera pollen has been reported from the Skin Prick Test, Lung function test, ELISA from a 400 susceptible patients in and around West Bengal in India. An immunobiological study was conducted to identify major allergens from Coccos nucifera pollen causing hay fever, skin allergy and allergic asthma in Kolkata population. Methods Proteins from pollen grains were obtained by initially defatting and then extracted with sodium phosphate buffer with 10 mM PMSF. Total protein was divided into 4 fractions by ammonium sulfate at 25%, 50 %, 75% and 100% respectively. SDS PAGE was done with the 25% fraction (result obtained from dot blotting) and subsequently western blotting was performed. Two dimensional gel electrophoresis and immunoblotting was also done from the crude protein. Results The total protein was separated on a SDS PAGE gel showed 21 prominent bands by Coomassie Blue staining. Dot -blotting the different fractions from ammonium sulfate cut, showed a positive result in the 25% fraction. Western blot with patient specific sera gave 3 bands out of which a major band was obtained at 60Kd. This result was obtained in more than 65% of the patients from whom Sera was isolated. 2D gel electrophoresis of the crude protein sample was performed which showed 120 protein spots in the PI range of 3 to 10 and molecular weight 14Kd to 97Kd. Immunoblotting the 2D gel with pooled patient specific sera showed 20 spots thus implying IgE reactivity. Conclusions It can thus be inferred that Coccos nucifera pollen grains are very common in the air and are important to cause allergy to susceptible persons. More over the 60 Kd protein is responsible for allergenicity.

Sub-inhibitory tigecycline concentrations induce extracellular matrix binding protein Embp dependent Staphylococcus epidermidis biofilm formation and immune evasion.

PubMed

Weiser, Julian; Henke, Hanae A; Hector, Nina; Both, Anna; Christner, Martin; Büttner, Henning; Kaplan, Jeffery B; Rohde, Holger

2016-09-01

Biofilm-associated Staphylococcus epidermidis implant infections are notoriously reluctant to antibiotic treatment. Here we studied the effect of sub-inhibitory concentrations of penicillin, oxacillin, vancomycin, daptomycin, linezolid and tigecycline on S. epidermidis 1585 biofilm formation, expression of extracellular matrix binding protein (Embp) and potential implications for S. epidermidis - macrophage interactions. Penicillin, vancomycin, daptomycin, and linezolid had no biofilm augmenting effect at any of the concentrations tested. In contrast, at sub-inhibitory concentrations tigecycline and oxacillin exhibited significant biofilm inducing activity. In S. epidermidis 1585, SarA is a negative regulator of giant 1 MDa Embp, and down regulation of sarA induces Embp-dependent assembly of a multi-layered biofilm architecture. Dot blot immune assays, confocal laser scanning microscopy, and qPCR showed that under biofilm inducing conditions, tigecycline augmented embp expression compared to the control grown without antibiotics. Conversely, expression of regulator sarA was suppressed, suggesting that tigecycline exerts its effects on embp expression through SarA. Tigecycline failed to induce biofilm formation in embp transposon mutant 1585-M135, proving that under these conditions Embp up-regulation is necessary for biofilm accumulation. As a functional consequence, tigecycline induced biofilm formation significantly impaired the up-take of S. epidermidis by mouse macrophage-like cell line J774A.1. Our data provide novel evidence for the molecular basis of antibiotic induced biofilm formation, a phenotype associated with inherently increased antimicrobial tolerance. While this could explain failure of antimicrobial therapies, persistence of S. epidermidis infections in the presence of sub-inhibitory antimicrobials is additionally propelled by biofilm-related impairment of macrophage-mediated pathogen eradication. Copyright © 2016 Elsevier GmbH. All rights reserved.

Universal Immunoprobe for (Per)Chlorate-Reducing Bacteria

PubMed Central

O'Connor, Susan M.; Coates, John D.

2002-01-01

Recent studies in our lab have demonstrated the ubiquity and diversity of microorganisms which couple growth to the reduction of chlorate or perchlorate [(per)chlorate] under anaerobic conditions. We identified two taxonomic groups, the Dechloromonas and the Dechlorosoma groups, which represent the dominant (per)chlorate-reducing bacteria (ClRB) in the environment. As part of these studies we demonstrated that chlorite dismutation is a central step in the reductive pathway of (per)chlorate that is common to all ClRB and which is mediated by the enzyme chlorite dismutase (CD). Initial studies on CD suggested that this enzyme is highly conserved among the ClRB, regardless of their phylogenetic affiliation. As such, this enzyme makes an ideal target for a probe specific for these organisms. Polyclonal antibodies were commercially raised against the purified CD from the ClRB Dechloromonas agitata strain CKB. The obtained antiserum was deproteinated by ammonium sulfate precipitation, and the antigen binding activity was assessed using dot blot analysis of a serial dilution of the antiserum. The titers obtained with purified CD indicated that the antiserum had a high affinity for the CD enzyme, and activity was observed in dilutions as low as 10−6 of the original antiserum. The antiserum was active against both cell lysates and whole cells of D. agitata, but only if the cells were grown anaerobically with (per)chlorate. No response was obtained with aerobically grown cultures. In addition to D. agitata, dot blot analysis employed with both whole-cell suspensions and cell lysates of several diverse ClRB representing the alpha, beta, and gamma subclasses of Proteobacteria tested positive regardless of phylogenetic affiliation. Interestingly, the dot blot response obtained for each of the ClRB cell lysates was different, suggesting that there may be some differences in the antigenic sites of the CD protein produced in these organisms. In general, no reactions were observed with cells or cell lysates of the organisms closely related to the ClRB which could not grow by (per)chlorate reduction. These studies have resulted in the development of a highly specific and sensitive immunoprobe based on the commonality of the CD enzyme in ClRB which can be used to assess dissimilatory (per)chlorate-reducing populations in environmental samples regardless of their phylogenetic affiliations. PMID:12039773

Manipulating surface diffusion and elastic interactions to obtain quantum dot multilayer arrangements over different length scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Placidi, E., E-mail: ernesto.placidi@ism.cnr.it; Arciprete, F.; Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome

2014-09-15

An innovative multilayer growth of InAs quantum dots on GaAs(100) is demonstrated to lead to self-aggregation of correlated quantum dot chains over mesoscopic distances. The fundamental idea is that at critical growth conditions is possible to drive the dot nucleation only at precise locations corresponding to the local minima of the Indium chemical potential. Differently from the known dot multilayers, where nucleation of new dots on top of the buried ones is driven by the surface strain originating from the dots below, here the spatial correlations and nucleation of additional dots are mostly dictated by a self-engineering of the surfacemore » occurring during the growth, close to the critical conditions for dot formation under the fixed oblique direction of the incoming As flux, that drives the In surface diffusion.« less

Usefulness of in-house obtained recombinant proteins Yop of Yersinia enterocolitica as highly specific antigens in ELISA and recom-dot performed in the serodiagnosis of yersiniosis.

PubMed

Rastawicki, Waldemar; Smietafiska, Karolina; Chrost, Anna; Wolkowicz, Tomasz; Rokosz-Chudziak, Natalia

Proper analysis of the human immune response is crucial in the laboratory diagnosis of many bacterial infections-The current serological diagnosis of yersiniosis often is carried out using ELISA with native antigens. However, recombinant proteins increase the specificity of the serological assays, particularly in patients with chronic, non- specific infections. The aim of the present study was to evaluate the usefulness of in-house obtained recombinant proteins Yop of Yersinia enterocolitica as highly specific antigens in ELISA and recom-dot performed in the serodiagnosis of yersiniosis. Recombinant YopD, YopB, YopE and V-Ag proteins of Y enterocolitica were expressing in E. coli BL21 (DE3) using the pET-30 Ek/LIC expression vector (Novagen). Purification was accomplished by immobilized metal (Ni2) affinity column chromatography (His-trap). The proteins were used as antigens in standard ELISA and recom-dot assay, which was performed on nitrocellulose strips. The study population, used for characterization of the humoral immune response to the recombinant proteins, consisted of 74 patients suspected for Y enterocolitica infection and 41 clinically healthy blood donors. Some of the results obtained by ELISA and recom-dot were compared with results obtained by commercial western-blot Yersinia (Virotech). In the group of patients suspected for yersiniosis in clinical investigation the most positive results were obtained in ELISA with the recombinant protein YopD (IgA respectively 25 (42.4%), IgG 41 (69.5%), IgM 24 (40.7%). The percentage ofpositive results in the group of blood donors did not exceed 10.0% in IgG and 5.0% in IgA/IgM classes of immunoglobulin. The results obtained in the recom-dot assay showed that among 74 tested serum samples obtained from individuals suspected of yersiniosis the most common IgA, IgG and IgM antibodies were found for recombinant protein YopD (respectively IgG in 60.8%, IgA in 37.8% and IgM in 33.8% of serum samples). IgG antibodies to the protein V-Ag were observed in 32.4%, protein YopB in 27.0% and for the protein YopE in 18.9% serum samples. Immunoglobulin A, and M for the recombinant proteins were found much less frequently than IgG antibodies (respectively 12.2% and 10.8% for V protein-Ag in 10.8% and 14.9% protein and_YopB 2,7% and 10.8% for the protein YopE). Further studies showed that results obtained in recom-dot assay with recombinant protein YopD were comparable with the results of commercial western-blot Yersinia. The study showed that in-house obtained recombinant proteins can be used as highly specific antigens in ELISA and recom-dot performed in the serodiagnosis of yersiniosis. The most useful was the protein YopD.

Lipid A binding proteins in macrophages detected by ligand blotting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hampton, R.Y.; Golenbock, D.T.; Raetz, C.R.H.

1987-05-01

Endotoxin (LPS) stimulates a variety of eukaryotic cells. These actions are involved in the pathogenesis of Gram-negative septicemia. The site of action of the LPS toxic moiety, lipid A (LA), is unclear. Their laboratory has previously identified a bioactive LA precursor lipid IV/sub A/, which can be enzymatically labeled with /sup 32/P/sub i/ (10/sup 9/ dpm/nmole) and purified (99%). They now show that this ligand binds to specific proteins immobilized on nitrocellulose (NC) from LPS-sensitive RAW 264.7 cultured macrophages. NC blots were incubated with (/sup 32/P)-IV/sub A/ in a buffer containing BSA, NaCl, polyethylene glycol, and azide. Binding was assessedmore » using autoradiography or scintillation counting. Dot blot binding of the radioligand was inhibited by excess cold IV/sub A/, LA, or ReLPS but not by phosphatidylcholine, cardiolipin, phosphatidylinositol, or phosphatidic acid. Binding was trypsin-sensitive and dependent on protein concentration. Particulate macrophage proteins were subjected to SDS-PAGE and then electroblotted onto NC. Several discrete binding proteins were observed. Identical treatment of fetal bovine serum or molecular weight standards revealed no detectable binding. By avoiding high nonspecific binding of intact membranes, this ligand blotting assay may be useful in elucidating the molecular actions of LPS.« less

Impact of stress relaxation in GaAsSb cladding layers on quantum dot creation in InAs/GaAsSb structures grown on GaAs (001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bremner, S. P.; Ban, K.-Y.; Faleev, N. N.

2013-09-14

We describe InAs quantum dot creation in InAs/GaAsSb barrier structures grown on GaAs (001) wafers by molecular beam epitaxy. The structures consist of 20-nm-thick GaAsSb barrier layers with Sb content of 8%, 13%, 15%, 16%, and 37% enclosing 2 monolayers of self-assembled InAs quantum dots. Transmission electron microscopy and X-ray diffraction results indicate the onset of relaxation of the GaAsSb layers at around 15% Sb content with intersected 60° dislocation semi-loops, and edge segments created within the volume of the epitaxial structures. 38% relaxation of initial elastic stress is seen for 37% Sb content, accompanied by the creation of amore » dense net of dislocations. The degradation of In surface migration by these dislocation trenches is so severe that quantum dot formation is completely suppressed. The results highlight the importance of understanding defect formation during stress relaxation for quantum dot structures particularly those with larger numbers of InAs quantum-dot layers, such as those proposed for realizing an intermediate band material.« less

DNA probe for lactobacillus delbrueckii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delley, M.; Mollet, B.; Hottinger, H.

1990-06-01

From a genomic DNA library of Lactobacillus delbrueckii subsp. bulgaricus, a clone was isolated which complements a leucine auxotrophy of an Escherichia coli strain (GE891). Subsequent analysis of the clone indicated that it could serve as a specific DNA probe. Dot-blot hybridizations with over 40 different Lactobacillus strains showed that this clone specifically recognized L. delbrueckii subsp. delbrueckii, bulgaricus, and lactis. The sensitivity of the method was tested by using an {alpha}-{sup 32}P-labeled probe.

DNA Probe for Lactobacillus delbrueckii

PubMed Central

Delley, Michèle; Mollet, Beat; Hottinger, Herbert

1990-01-01

From a genomic DNA library of Lactobacillus delbrueckii subsp. bulgaricus, a clone was isolated which complements a leucine auxotrophy of an Escherichia coli strain (GE891). Subsequent analysis of the clone indicated that it could serve as a specific DNA probe. Dot-blot hybridizations with over 40 different Lactobacillus strains showed that this clone specifically recognizes L. delbrueckii subsp. delbrueckii, bulgaricus, and lactis. The sensitivity of the method was tested by using an α-32P-labeled DNA probe. Images PMID:16348233

Rapid detection of rifampin-resistant clinical isolates of Mycobacterium tuberculosis by reverse dot blot hybridization.

PubMed

Guo, Qian; Yu, Yan; Zhu, Yan Ling; Zhao, Xiu Qin; Liu, Zhi Guang; Zhang, Yuan Yuan; Li, Gui Lian; Wei, Jian Hao; Wu, Yi Mou; Wan, Kang Lin

2015-01-01

A PCR-reverse dot blot hybridization (RDBH) assay was developed for rapid detection of rpoB gene mutations in 'hot mutation region' of Mycobacterium tuberculosis (M. tuberculosis). 12 oligonucleotide probes based on the wild-type and mutant genotype rpoB sequences of M. tuberculosis were designed to screen the most frequent wild-type and mutant genotypes for diagnosing RIF resistance. 300 M. tuberculosis clinical isolates were detected by RDBH, conventional drug-susceptibility testing (DST) and DNA sequencing to evaluate the RDBH assay. The sensitivity and specificity of the RDBH assay were 91.2% (165/181) and 98.3% (117/119), respectively, as compared to DST. When compared with DNA sequencing, the accuracy, positive predictive value (PPV) and negative predictive value (NPV) of the RDBH assay were 97.7% (293/300), 98.2% (164/167), and 97.0% (129/133), respectively. Furthermore, the results indicated that the most common mutations were in codons 531 (48.6%), 526 (25.4%), 516 (8.8%), and 511 (6.6%), and the combinative mutation rate was 15 (8.3%). One and two strains of insertion and deletion were found among all strains, respectively. Our findings demonstrate that the RDBH assay is a rapid, simple and sensitive method for diagnosing RIF-resistant tuberculosis. Copyright © 2015 The Editorial Board of Biomedical and Environmental Sciences. Published by China CDC. All rights reserved.

Search for a Novel Allergen in Hen's Egg Allergy Using an IgE Immunoblotting Assay.

PubMed

Sogawa, Kazuyuki; Takahashi, Yuria; Shibata, Yui; Satoh, Mamoru; Kodera, Yoshio; Nomura, Fumio; Tanaka, Toshio; Sato, Hironori; Yamaide, Fumiya; Nakano, Taiji; Iwahashi, Kazuhiko; Sugita-Konishi, Yoshiko; Shimada, Akinori; Shimojo, Naoki

2018-04-18

Food allergy is a serious health issue affecting roughly 4% of children, with a substantial effect on quality of life. Chicken egg allergy is frequently observed in infants. Therefore, some of them have to exclude hen's eggs from their daily diet to avoid allergenic symptoms. Hen's egg is composed of 2 soluble parts; one is egg white, which has been characterized as the major source of allergenicity, while the other is egg yolk, which is estimated as a miner source. Only 2 allergens from egg yolk, α-livetin (Gal d 5) and YGP42 (Gal d 6), have been described to date. Sera from 53 patients allergic to hen's eggs and 2 patients allergic to sesame were obtained from the Department of Pediatrics, Chiba University Hospital. The study was performed using SDS-PAGE, IgE immunoblotting, and dot blotting. Seven bands of egg yolk were detected by IgE immunoblotting. Out of these bands, a possible new allergen was further characterized by LC-MS/MS. The 33-kDa band was identified as yolk glycoprotein (YGP40) by LC-MS/MS. A total of 21 of the 53 patients (47%) had YGP40 detected by dot blotting. We identified YGP40 as a new hen's egg yolk allergen and detected 4 sites of YGP40 as linear epitopes. © 2018 S. Karger AG, Basel.

Burden of major diarrheagenic protozoan parasitic co-infection among amoebic dysentery cases from North East India: a case report.

PubMed

Nath, Joyobrato; Hussain, Gulzar; Singha, Baby; Paul, Jaishree; Ghosh, Sankar Kumar

2015-09-01

Intestinal diarrheagenic polyparasitic infections are among the major public health concerns in developing countries. Here we examined stool specimens by microscopy, DNA dot blot and polymerase chain reaction (PCR) to evaluate the co-infection of four principal protozoans among amoebic dysentery cases from Northeast Indian population. The multiplex PCR confirmed Entamoeba histolytica (8.1%), Entamoeba dispar (4.8%) and mixed infection of both the parasites (3.4%) in 68 of 356 stool specimens that were positive in microscopy and/or HMe probe based DNA dot blot screening. The prevailing parasite that co-exists with E. histolytica was Giardia duodenalis (34.1%), followed by Enterocytozoon bieneusi (22.0%), Cryptosporidium parvum (14.6%) and Cyclospora cayetanensis (7.3%, P = 0.017). Symptomatic participants (odds ratio (OR) = 4.07; 95% confidence interval (CI) = 1.06, 15.68; P = 0.041), monsoon season (OR = 7.47; 95% CI = 1.40, 39.84; P = 0.046) and participants with family history of parasitic infection (OR = 4.50; 95% CI = 1.16, 17.51; P = 0.030) have significant association with overall co-infection rate. According to molecular consensus, comprehensive microscopy yielded 3.4% (12/356) false-negative and 7.6% (27/356) false-positive outcome, suggesting an improved broad-spectrum PCR-based diagnostic is required to scale down the poor sensitivity and specificity as well as implementation of integrated control strategy.

Application of a reverse dot blot, DNA-DNA hydridization method to quantify host-feeding tendencies of two sibling species in the Anopheles gambiae complex

PubMed Central

Fritz, Megan L; Miller, James R; Bayoh, M Nabie; Vulule, John M; Landgraf, Jeffrey R; Walker, Edward D

2012-01-01

A DNA-DNA hybridization method, reverse dot blot analysis (RDBA), was used for identification of Anopheles gambiae s.s. and An. arabiensis hosts. Of 299 blood fed and half gravid An. gambiae s.l. collected from Kisian, Kenya, 244 individuals were identifiable to species; 69.5% were An. arabiensis, and 29.5% were An. gambiae s.s. Host identifications with RDBA were comparable to conventional PCR followed by direct sequencing of amplicons of the vertebrate mitochondrial cytochrome B gene. Of the 174 amplicon-producing samples used for comparison of these two methods, 147 were identifiable by direct sequencing, and 139 of these same by RDBA. An. arabiensis blood meals were mostly (>90%) bovine in origin, whereas An. gambiae s.s. fed upon humans > 90% of the time. RDBA detected that 2 of 112 An. arabiensis had blood from more than one host species, whereas PCR and direct sequencing did not. Recent insecticide-treated bednet (ITN) use in Kisian has likely caused the shift in the dominant vector species from An. gambiae s.s. to An. arabiensis. RDBA provides an opportunity to study changes in host-feeding by members of the An. gambiae complex as a response to the broadening distribution of vector control measures targeting host-selection behaviors. PMID:24188164

Development of Prevotella intermedia-specific PCR primers based on the nucleotide sequences of a DNA probe Pig27.

PubMed

Kim, Min Jung; Hwang, Kyung Hwan; Lee, Young-Seok; Park, Jae-Yoon; Kook, Joong-Ki

2011-03-01

The aim of this study was to develop Prevotella intermedia-specific PCR primers based on the P. intermedia-specific DNA probe. The P. intermedia-specific DNA probe was screened by inverted dot blot hybridization and confirmed by Southern blot hybridization. The nucleotide sequences of the species-specific DNA probes were determined using a chain termination method. Southern blot analysis showed that the DNA probe, Pig27, detected only the genomic DNA of P. intermedia strains. PCR showed that the PCR primers, Pin-F1/Pin-R1, had species-specificity for P. intermedia. The detection limits of the PCR primer sets were 0.4pg of the purified genomic DNA of P. intermedia ATCC 49046. These results suggest that the PCR primers, Pin-F1/Pin-R1, could be useful in the detection of P. intermedia as well as in the development of a PCR kit in epidemiological studies related to periodontal diseases. Crown Copyright © 2010. Published by Elsevier B.V. All rights reserved.

Whole genomic DNA probe for detection of Porphyromonas endodontalis.

PubMed

Nissan, R; Makkar, S R; Sela, M N; Stevens, R

2000-04-01

The purpose of the present study was to develop a DNA probe for Porphyromonas endodontalis. Pure cultures of P. endodontalis were grown in TYP medium, in an anaerobic chamber. DNA was extracted from the P. endodontalis and labeled using the Genius System by Boehringer Mannheim. The labeled P. endodontalis DNA was used in dot-blot hybridization reactions with homologous (P. endodontalis) and unrelated bacterial samples. To determine specificity, strains of 40 other oral bacterial species (e.g. Porphyromonas gingivalis, Porphyromonas asaccharolytica, and Prevotella intermedia) were spotted and reacted with the P. endodontalis DNA probe. None of the panel of 40 oral bacteria hybridized with the P. endodontalis probe, whereas the blot of the homologous organism showed a strong positive reaction. To determine the sensitivity of the probe, dilutions of a P. endodontalis suspension of known concentration were blotted onto a nylon membrane and reacted with the probe. The results of our investigation indicate that the DNA probe that we have prepared specifically detects only P. endodontalis and can detect at least 3 x 10(4) cells.

Nf-GH, a glycosidase secreted by Naegleria fowleri, causes mucin degradation: an in vitro and in vivo study.

PubMed

Martínez-Castillo, Moisés; Cárdenas-Guerra, Rosa Elena; Arroyo, Rossana; Debnath, Anjan; Rodríguez, Mario Alberto; Sabanero, Myrna; Flores-Sánchez, Fernando; Navarro-Garcia, Fernando; Serrano-Luna, Jesús; Shibayama, Mineko

2017-07-01

The aim of this work was to identify, characterize and evaluate the pathogenic role of mucinolytic activity released by Naegleria fowleri. Zymograms, protease inhibitors, anion exchange chromatography, MALDI-TOF-MS, enzymatic assays, Western blot, and confocal microscopy were used to identify and characterize a secreted mucinase; inhibition assays using antibodies, dot-blots and mouse survival tests were used to evaluate the mucinase as a virulence factor. A 94-kDa protein with mucinolytic activity was inducible and abolished by p-hydroxymercuribenzoate. MALDI-TOF-MS identified a glycoside hydrolase. Specific antibodies against N. fowleri-glycoside hydrolase inhibit cellular damage and MUC5AC degradation, and delay mouse mortality. Our findings suggest that secretory products from N. fowleri play an important role in mucus degradation during the invasion process.

Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection

PubMed Central

Damalakiene, Leona; Karabanovas, Vitalijus; Bagdonas, Saulius; Valius, Mindaugas; Rotomskis, Ricardas

2013-01-01

Background: The purpose of this study was to elucidate the mechanism of natural uptake of nonfunctionalized quantum dots in comparison with microinjected quantum dots by focusing on their time-dependent accumulation and intracellular localization in different cell lines. Methods: The accumulation dynamics of nontargeted CdSe/ZnS carboxyl-coated quantum dots (emission peak 625 nm) was analyzed in NIH3T3, MCF-7, and HepG2 cells by applying the methods of confocal and steady-state fluorescence spectroscopy. Intracellular colocalization of the quantum dots was investigated by staining with Lysotracker®. Results: The uptake of quantum dots into cells was dramatically reduced at a low temperature (4°C), indicating that the process is energy-dependent. The uptake kinetics and imaging of intracellular localization of quantum dots revealed three accumulation stages of carboxyl-coated quantum dots at 37°C, ie, a plateau stage, growth stage, and a saturation stage, which comprised four morphological phases: adherence to the cell membrane; formation of granulated clusters spread throughout the cytoplasm; localization of granulated clusters in the perinuclear region; and formation of multivesicular body-like structures and their redistribution in the cytoplasm. Diverse quantum dots containing intracellular vesicles in the range of approximately 0.5–8 μm in diameter were observed in the cytoplasm, but none were found in the nucleus. Vesicles containing quantum dots formed multivesicular body-like structures in NIH3T3 cells after 24 hours of incubation, which were Lysotracker-negative in serum-free medium and Lysotracker-positive in complete medium. The microinjected quantum dots remained uniformly distributed in the cytosol for at least 24 hours. Conclusion: Natural uptake of quantum dots in cells occurs through three accumulation stages via a mechanism requiring energy. The sharp contrast of the intracellular distribution after microinjection of quantum dots in comparison with incubation as well as the limited transfer of quantum dots from vesicles into the cytosol and vice versa support the endocytotic origin of the natural uptake of quantum dots. Quantum dots with proteins adsorbed from the culture medium had a different fate in the final stage of accumulation from that of the protein-free quantum dots, implying different internalization pathways. PMID:23429995

Long-range spin coherence in a strongly coupled all-electronic dot-cavity system

NASA Astrophysics Data System (ADS)

Ferguson, Michael Sven; Oehri, David; Rössler, Clemens; Ihn, Thomas; Ensslin, Klaus; Blatter, Gianni; Zilberberg, Oded

2017-12-01

We present a theoretical analysis of spin-coherent electronic transport across a mesoscopic dot-cavity system. Such spin-coherent transport has been recently demonstrated in an experiment with a dot-cavity hybrid implemented in a high-mobility two-dimensional electron gas [C. Rössler et al., Phys. Rev. Lett. 115, 166603 (2015), 10.1103/PhysRevLett.115.166603] and its spectroscopic signatures have been interpreted in terms of a competition between Kondo-type dot-lead and molecular-type dot-cavity singlet formation. Our analysis brings forward all the transport features observed in the experiments and supports the claim that a spin-coherent molecular singlet forms across the full extent of the dot-cavity device. Our model analysis includes (i) a single-particle numerical investigation of the two-dimensional geometry, its quantum-coral-type eigenstates, and associated spectroscopic transport features, (ii) the derivation of an effective interacting model based on the observations of the numerical and experimental studies, and (iii) the prediction of transport characteristics through the device using a combination of a master-equation approach on top of exact eigenstates of the dot-cavity system, and an equation-of-motion analysis that includes Kondo physics. The latter provides additional temperature scaling predictions for the many-body phase transition between molecular- and Kondo-singlet formation and its associated transport signatures.

In-plane nuclear field formation investigated in single self-assembled quantum dots

NASA Astrophysics Data System (ADS)

Yamamoto, S.; Matsusaki, R.; Kaji, R.; Adachi, S.

2018-02-01

We studied the formation mechanism of the in-plane nuclear field in single self-assembled In0.75Al0.25As /Al0.3Ga0.7As quantum dots. The Hanle curves with an anomalously large width and hysteretic behavior at the critical transverse magnetic field were observed in many single quantum dots grown in the same sample. In order to explain the anomalies in the Hanle curve indicating the formation of a large nuclear field perpendicular to the photo-injected electron spin polarization, we propose a new model based on the current phenomenological model for dynamic nuclear spin polarization. The model includes the effects of the nuclear quadrupole interaction and the sign inversion between in-plane and out-of-plane components of nuclear g factors, and the model calculations reproduce successfully the characteristics of the observed anomalies in the Hanle curves.

Morphological evolution of Ge/Si(001) quantum dot rings formed at the rim of wet-etched pits.

PubMed

Grydlik, Martyna; Brehm, Moritz; Schäffler, Friedrich

2012-10-30

We demonstrate the formation of Ge quantum dots in ring-like arrangements around predefined {111}-faceted pits in the Si(001) substrate. We report on the complex morphological evolution of the single quantum dots contributing to the rings by means of atomic force microscopy and demonstrate that by careful adjustment of the epitaxial growth parameters, such rings containing densely squeezed islands can be grown with large spatial distances of up to 5 μm without additional nucleation of randomly distributed quantum dots between the rings.

Development of a Rapid Qualitative Assay for Determining Elevated Antibody Levels to Periodontopathic Organisms

DTIC Science & Technology

1990-01-01

Titers 31 1. Collection of samples 31 2. Enzyme-linkedimmunosorbent assay 31 B. Development of Dot-Blot Assay 32 1. Selection of en2yme-sUbstrate system...ELISA results 39 2., Selection -of appropriate serum dilution 46 3. Selection -of appropriate antigen diltion 59 4. Selection of blockina concentration 64 5... Selection of incubation time for antibody-containing 65 fluid .6. Selection -of enn’me Conitumate reation. time . 6 7. Selection of svbstrate

Diversity, Replication, Pathogenicity and Cell Biology of Crimean Congo Hemorrhagic Fever Virus

DTIC Science & Technology

2006-10-01

recombinant protein produced and purified in E . coli was able to bind to ssRNA in a dot blot filter binding assay. In order to identify domains in the N...Fig. 1. RNA binding domains of the N protein of CCHFV. The depicted GST-fusion proteins were expressed in E . coli and purified using a...detected and NSm protein produced after cleavage of the glycoprotein precursor in virus infected cells. The NSm is stable and transported to the Golgi

A carboxylated Zn-phthalocyanine inhibits fibril formation of Alzheimer's amyloid β peptide.

PubMed

Tabassum, Shatera; Sheikh, Abdullah M; Yano, Shozo; Ikeue, Takafumi; Handa, Makoto; Nagai, Atsushi

2015-02-01

Amyloid β (Aβ), a 39-42 amino acid peptide derived from amyloid precursor protein, is deposited as fibrils in Alzheimer's disease brains, and is considered to play a major role in the pathogenesis of the disease. We have investigated the effects of a water-soluble Zn-phthalocyanine, ZnPc(COONa)₈, a macrocyclic compound with near-infrared optical properties, on Aβ fibril formation in vitro. A thioflavin T fluorescence assay showed that ZnPc(COONa)₈ significantly inhibited Aβ fibril formation, increasing the lag time and dose-dependently decreasing the plateau level of fibril formation. Moreover, it destabilized pre-formed Aβ fibrils, resulting in an increase in low-molecular-weight species. After fibril formation in the presence of ZnPc(COONa)₈, immunoprecipitation of Aβ₁₋₄₂ using Aβ-specific antibody followed by near-infrared scanning demonstrated binding of ZnPc(COONa)₈ to Aβ₁₋₄₂. A study using the hydrophobic fluorescent probe 8-anilino-1-naphthalenesulfonic acid showed that ZnPc(COONa)8 decreased the hydrophobicity during Aβ₁₋₄₂ fibril formation. CD spectroscopy showed an increase in the α helix structure and a decrease in the β sheet structure of Aβ₁₋₄₀ in fibril-forming buffer containing ZnPc(COONa)₈. SDS/PAGE and a dot-blot immunoassay showed that ZnPc(COONa)₈ delayed the disappearance of low-molecular-weight species and the appearance of higher-molecular-weight oligomeric species of Aβ₁₋₄₂. A cell viability assay showed that ZnPc(COONa)₈ was not toxic to a neuronal cell line (A1), but instead protected A1 cells against Aβ₁₋₄₂-induced toxicity. Overall, our results indicate that ZnPc(COONa)₈ binds to Aβ and decreases the hydrophobicity, and this change is unfavorable for Aβ oligomerization and fibril formation. © 2014 FEBS.

Dislocation-induced Charges in Quantum Dots: Step Alignment and Radiative Emission

NASA Technical Reports Server (NTRS)

Leon, R.; Okuno, J.; Lawton, R.; Stevens-Kalceff, M.; Phillips, M.; Zou, J.; Cockayne, D.; Lobo, C.

1999-01-01

A transition between two types of step alignment was observed in a multilayered InGaAs/GaAs quantum-dot (QD) structure. A change to larger QD sizes in smaller concentrations occurred after formation of a dislocation array.

Water as a promoter and catalyst for dioxygen electrochemistry in aqueous and organic media.

DOE PAGES

Staszak-Jirkovsky, Jakub; Subbaraman, Ram; Strmcnik, Dusan; ...

2015-11-01

Water and oxygen electrochemistry lies at the heart of interfacial processes controlling energy transformations in fuel cells, electrolyzers, and batteries. Here, by comparing results for the ORR obtained in alkaline aqueous media to those obtained in ultradry organic electrolytes with known amounts of H2O added intentionally, we propose a new rationale in which water itself plays an important role in determining the reaction kinetics. This effect derives from the formation of HOad center dot center dot center dot H2O (aqueous solutions) and LiO2 center dot center dot center dot H2O (organic solvents) complexes that place water in a configurationally favorablemore » position for proton transfer to weakly adsorbed intermediates. We also find that, even at low concentrations (<10 ppm), water acts simultaneously as a promoter and as a catalyst in the production of Li2O2, regenerating itself through a sequence of steps that include the formation and recombination of H+ and OH-. We conclude that, although the binding energy between metal surfaces and oxygen intermediates is an important descriptor in electrocatalysis, understanding the role of water as a proton-donor reactant may explain many anomalous features in electrocatalysis at metal-liquid interfaces.« less

45th Annual Targets, UAVs and Range Operations Symposium and Exhibition - Tools and Technologies for the Warfighter. Volume 1

DTIC Science & Technology

2007-10-30

Flight Test wmv format Joint Ground Robotics Program, Mr. Duane Gotvald, Deputy Project Manager , PEO GCS Robotic Systems Joint Program 1...Mr. Al Brown, TMO Deputy Director, PMITTS, PEO STRI 1. Targets Management Office wmv format Strength through Industry & Technology National...Ferguson, RCN, NDHQ 10:20AM DTRMC, OSD Strategic Plan Jerry Christensen, DOT&E 10:40 Target Management Initiative Ken McCormick, DOT&E 11:10AM

Production and characterisation of a novel chicken IgY antibody raised against C-terminal peptide from human thymidine kinase 1.

PubMed

Wu, Chuanjing; Yang, Rongjiang; Zhou, Ji; Bao, Shing; Zou, Li; Zhang, Pinggan; Mao, Yongrong; Wu, Jianping; He, Qimin

2003-06-01

Egg yolk is a good source of highly specific antibodies against mammalian antigens because of the phylogenetic distance between birds and mammals. Chicken egg yolk immunoglobulins (IgY) were generated to a synthetic 31-amino acid peptide from the C-terminal of human HeLa thymidine kinase 1 (TK1) enzyme. The anti-TK1 IgY antibody was purified using affinity chromatography against the 31-amino acid peptide. The purified antibody inhibited the catalytic activity of the TK1 enzyme in the CEM TK1(+) cells and recognized the 25-kDa subunit and tetrameric form of TK1, which has a pI value of 8.3. No immunoreaction was observed in CEM TK1(-) cells. Western blot of the serum TK1 (S-TK1) also showed that only a single band was found in the serum of patients with malignancies. No band was seen in healthy serum. Furthermore, dot blots and enhanced chemiluminescence (ECL) detection of S-TK1 performed on sera of preoperative patients with gastric cancer (GC) (n=31) and healthy controls (n=62) showed that the levels of S-TK1 in the sera of cancer patients were significantly different (P<0.01). Using ECL dot blots, 0.1 pg of TK1 in 3 microl sera could be detected. Immunohistostaining of tissues in the 11 advanced-stage cancer patients (four breast carcinomas, three hepatocarcinomas and four thyroid carcinomas) indicated that a strong staining of TK1 enzyme was found in the cytoplasm of malignant cells. No staining or weak staining was seen in normal tissues. We suggest that screening for TK1 using anti-TK1 IgY may be potentially useful for serological and immunohistochemical detection of TK1 as an early prognosis and for monitoring patients undergoing treatment.

Immunolocalization and immunodetection of the excretory/secretory (ES) antigens of Fasciola gigantica.

PubMed

Khan, M A Hannan; Ullah, Rizwan; Rehman, Abdur; Rehman, Lubna; P A, Ahammed Shareef; Abidi, S M A

2017-01-01

The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance. Along with Fasciola hepatica, F. gigantica incurs huge economic losses to the agricultural sector. Because of unavailability of an effective and commercial vaccine, the earliest diagnosis of the disease is the only way to control the disease. The conventional coprological techniques are able to detect the disease only after the parasites get matured and starts releasing their eggs with the faeces of host, therefore prepatent infection remain undiagnosed. The alternative method is by serological tests that uses circulatory antigens. Despite high sensitivity, their reliability is quite low because of the common antigens shared between different helminth parasites. To overcome this, investigation was shifted to identify the copro-antigens which could be more sensitive and reliable. In the present study, we tried to identify some of the immunodominant proteins from the Excretory Secretory (ES) product of F. gigantica which can be further characterized and used for early detection of infection and also as drug and vaccine candidates. The ES products of F. gigantica were collected and used for raising the polyclonal antibody in rabbit. The polypeptide profile was generated as well as immunogenic polypeptides were identified. The Source of ES antigen was immunolocalized using confocal microscopy and dot blot assay was performed to diagnose field infection. The polypeptide profile of ES products revealed a total of 24 polypeptides out of which 12 immunogenic polypeptides were identified by western blotting. Confocal micrographs showed the immunolocalization of antigens in the intestinal caecae, vitalline glands, gonads as well as in the tegument of the worm. The dot blot assay confirmed the utility of ES products for the detection of field infection. Subsequently, cross reactivity was found negative with Gigantocotyle explanatum; an amphitome parasite of same habitat. However, the cross reactivity with other helminths needs to be worked out.

Immunolocalization and immunodetection of the excretory/secretory (ES) antigens of Fasciola gigantica

PubMed Central

Ullah, Rizwan; Rehman, Abdur; Rehman, Lubna; P. A., Ahammed Shareef; Abidi, S. M. A.

2017-01-01

The digenetic trematode Fasciola gigantica is a parasite of great agricultural and economic importance. Along with Fasciola hepatica, F. gigantica incurs huge economic losses to the agricultural sector. Because of unavailability of an effective and commercial vaccine, the earliest diagnosis of the disease is the only way to control the disease. The conventional coprological techniques are able to detect the disease only after the parasites get matured and starts releasing their eggs with the faeces of host, therefore prepatent infection remain undiagnosed. The alternative method is by serological tests that uses circulatory antigens. Despite high sensitivity, their reliability is quite low because of the common antigens shared between different helminth parasites. To overcome this, investigation was shifted to identify the copro-antigens which could be more sensitive and reliable. In the present study, we tried to identify some of the immunodominant proteins from the Excretory Secretory (ES) product of F. gigantica which can be further characterized and used for early detection of infection and also as drug and vaccine candidates. The ES products of F. gigantica were collected and used for raising the polyclonal antibody in rabbit. The polypeptide profile was generated as well as immunogenic polypeptides were identified. The Source of ES antigen was immunolocalized using confocal microscopy and dot blot assay was performed to diagnose field infection. The polypeptide profile of ES products revealed a total of 24 polypeptides out of which 12 immunogenic polypeptides were identified by western blotting. Confocal micrographs showed the immunolocalization of antigens in the intestinal caecae, vitalline glands, gonads as well as in the tegument of the worm. The dot blot assay confirmed the utility of ES products for the detection of field infection. Subsequently, cross reactivity was found negative with Gigantocotyle explanatum; an amphitome parasite of same habitat. However, the cross reactivity with other helminths needs to be worked out. PMID:28973017

Phosphine-free synthesis and characterization of type-II ZnSe/CdS core-shell quantum dots

NASA Astrophysics Data System (ADS)

Ghasemzadeh, Roghayyeh; Armanmehr, Mohammad Hasan; Abedi, Mohammad; Fateh, Davood Sadeghi; Bahreini, Zaker

2018-01-01

A phosphine-free route for synthesis of type-II ZnSe/CdS core-shell quantum dots, using green, low cost and environmentally friendly reagents and phosphine-free solvents such as 1-octadecene (ODE) and liquid paraffin has been reported. Hot-injection technique has been used for the synthesis of ZnSe core quantum dots. The CdS shell quantum dots prepared by reaction of CdO precursor and S powder in 1-octadecene (ODE). The ZnSe/CdS core-shell quantum dots were synthesized via successive ion layer adsorption and reaction (SILAR) technique. The characterization of produced quantum dots were performed by absorption and fluorescence spectroscopy, X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results showed the formation of type-II ZnSe/CdS core-shell quantum dots with FWHM 32 nm and uniform size distribution.

Formation mechanism of dot-line square superlattice pattern in dielectric barrier discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Weibo; Dong, Lifang, E-mail: donglfhbu@163.com, E-mail: pyy1616@163.com; Wang, Yongjie

We investigate the formation mechanism of the dot-line square superlattice pattern (DLSSP) in dielectric barrier discharge. The spatio-temporal structure studied by using the intensified-charge coupled device camera shows that the DLSSP is an interleaving of three different subpatterns in one half voltage cycle. The dot square lattice discharges first and, then, the two kinds of line square lattices, which form square grid structures discharge twice. When the gas pressure is varied, DLSSP can transform from square superlattice pattern (SSP). The spectral line profile method is used to compare the electron densities, which represent the amounts of surface charges qualitatively. Itmore » is found that the amount of surface charges accumulated by the first discharge of DLSSP is less than that of SSP, leading to a bigger discharge area of the following discharge (lines of DLSSP instead of halos of SSP). The spatial distribution of the electric field of the surface charges is simulated to explain the formation of DLSSP. This paper may provide a deeper understanding for the formation mechanism of complex superlattice patterns in DBD.« less

Effect of protein concentrates, emulsifiers on textural and sensory characteristics of gluten free cookies and its immunochemical validation.

PubMed

Sarabhai, Swati; Indrani, D; Vijaykrishnaraj, M; Milind; Arun Kumar, V; Prabhasankar, P

2015-06-01

The effect of 5, 7.5 and 10 % protein concentrates namely soya protein isolate (SPI), whey protein concentrate (WPC) and addition of 0.5 % emulsifiers such as glycerol monostearate (GMS), sodium stearoyl- 2- lactylate (SSL) and lecithin (LEC) on the rheological, sensory and textural characteristics of cookies with rice flour and its immunochemical validation was studied. The results showed that the use of 7.5 % SPI/WPC along with GMS significantly improved the quality characteristics of cookies with rice flour. Dot-Blot and Western-blot studies of cookies with 7.5 % of SPI or WPC confirmed that the anti-gliadin did not recognize these proteins. Carry- through process using ELISA kit confirmed that gluten was within the permissible limit in all the stages of processing and hence these cookies can be consumed by people suffering from celiac disease.

cDNA cloning and analysis of RNA 2 of a Prunus stem pitting isolate of tomato ringspot virus.

PubMed

Hadidi, A; Powell, C A

1991-10-01

Recombinant plasmids containing sequences derived from the genome of a tomato ringspot virus (TomRSV) isolate associated with both stem pitting disease of stone fruits and apple union necrosis and decline were constructed. Selected inserts were subcloned into the polylinker region of the SP6 transcription vector pSP64. Using the SP6 promoter flanking this region, high specific activity 32P-labelled cRNA probes were generated by SP6 RNA polymerase. cRNA probes were specific for TomRSV RNA 2 present in purified virions or in extracts from woody and herbacous hosts. No sequence relatedness was detected between TomRSV RNA 2 and genomic RNA from tobacco ringspot, arabis mosaic, strawberry latent ringspot, or cucumber mosaic virus in Northern blot analysis using TomRSV cRNA probes. These probes detected TomRSV infection in woody and herbaceous hosts in dot-blot hybridization assays.

Spatiotemporal alterations of autophagy marker LC3 in rat skin fibroblasts during wound healing process

PubMed Central

Asai, Emiko; Yamamoto, Masaya; Ueda, Kazuki; Waguri, Satoshi

2018-01-01

Abstract To investigate the possible implications of autophagy, one of the degradation pathways induced by metabolic stress, in the dynamic reconstructive process of wound healing, the appearance and changes of punctate structures for microtubule-associated protein 1 light chain 3 (LC3), an autophagosome marker, were examined in a rat skin wound healing model. Although the ratio of LC3-II/LC3-I in Western blotting was not evidently changed during the wound healing process, LC3-positive dots were clearly observed in fibroblasts and myofibroblasts, and occasionally in macrophages, by immunohistofluorescence microscopy. Some of the LC3-positive dots were colocalized with Atg16L signal, an isolation membrane marker, and electron microscopy revealed the presence of typical autophagosomes in fibroblasts near the margin of the wound. The number of LC3-positive dots per fibroblast increased during the later period of the proliferation phase, and interestingly, it was higher in the margin than the center of the wound. It was also high in the periwound skin area. These results suggest that drastic functional changes in fibroblasts during wound healing process are accompanied by the alteration of the autophagy-lysosomal degradation system. PMID:29343655

Spatiotemporal alterations of autophagy marker LC3 in rat skin fibroblasts during wound healing process.

PubMed

Asai, Emiko; Yamamoto, Masaya; Ueda, Kazuki; Waguri, Satoshi

2018-04-17

To investigate the possible implications of autophagy, one of the degradation pathways induced by metabolic stress, in the dynamic reconstructive process of wound healing, the appearance and changes of punctate structures for microtubule-associated protein 1 light chain 3 (LC3), an autophagosome marker, were examined in a rat skin wound healing model. Although the ratio of LC3-II/LC3-I in Western blotting was not evidently changed during the wound healing process, LC3-positive dots were clearly observed in fibroblasts and myofibroblasts, and occasionally in macrophages, by immunohistofluorescence microscopy. Some of the LC3-positive dots were colocalized with Atg16L signal, an isolation membrane marker, and electron microscopy revealed the presence of typical autophagosomes in fibroblasts near the margin of the wound. The number of LC3-positive dots per fibroblast increased during the later period of the proliferation phase, and interestingly, it was higher in the margin than the center of the wound. It was also high in the periwound skin area. These results suggest that drastic functional changes in fibroblasts during wound healing process are accompanied by the alteration of the autophagy-lysosomal degradation system.

InAs Colloidal Quantum Dots Synthesis via Aminopnictogen Precursor Chemistry.

PubMed

Grigel, Valeriia; Dupont, Dorian; De Nolf, Kim; Hens, Zeger; Tessier, Mickael D

2016-10-05

Despite their various potential applications, InAs colloidal quantum dots have attracted considerably less attention than more classical II-VI materials because of their complex syntheses that require hazardous precursors. Recently, amino-phosphine has been introduced as a cheap, easy-to-use and efficient phosphorus precursor to synthesize InP quantum dots. Here, we use aminopnictogen precursors to implement a similar approach for synthesizing InAs quantum dots. We develop a two-step method based on the combination of aminoarsine as the arsenic precursor and aminophosphine as the reducing agent. This results in state-of-the-art InAs quantum dots with respect to the size dispersion and band-gap range. Moreover, we present shell coating procedures that lead to the formation of InAs/ZnS(e) core/shell quantum dots that emit in the infrared region. This innovative synthesis approach can greatly facilitate the research on InAs quantum dots and may lead to synthesis protocols for a wide range of III-V quantum dots.

Electrically tunable g factors in quantum dot molecular spin states.

PubMed

Doty, M F; Scheibner, M; Ponomarev, I V; Stinaff, E A; Bracker, A S; Korenev, V L; Reinecke, T L; Gammon, D

2006-11-10

We present a magnetophotoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g factors of different spin states that have molecular wave functions distributed over both quantum dots. We propose a phenomenological model for the change in g factor based on resonant changes in the amplitude of the wave function in the barrier due to the formation of bonding and antibonding orbitals.

Electrically Tunable g Factors in Quantum Dot Molecular Spin States

NASA Astrophysics Data System (ADS)

Doty, M. F.; Scheibner, M.; Ponomarev, I. V.; Stinaff, E. A.; Bracker, A. S.; Korenev, V. L.; Reinecke, T. L.; Gammon, D.

2006-11-01

We present a magnetophotoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g factors of different spin states that have molecular wave functions distributed over both quantum dots. We propose a phenomenological model for the change in g factor based on resonant changes in the amplitude of the wave function in the barrier due to the formation of bonding and antibonding orbitals.

Room temperature deposition of silicon nanodot clusters by plasma-enhanced chemical vapor deposition.

PubMed

Kim, Jae-Kwan; Kim, Jun Young; Yoon, Jae-Sik; Lee, Ji-Myon

2013-10-01

The formation of nanometer-scale (ns)-Si dots and clusters on p-GaN layers has been studied by controlling the early stage of growth during plasma-enhanced chemical vapor deposition (PECVD) at room temperature. We found that ns-Si dots and clusters formed on the p-GaN surface, indicating that growth was the Volmer-Weber mode. The deposition parameters such as radio frequency (RF) power and processing time mainly influenced the size of the ns-Si dots (40 nm-160 nm) and the density of the ns-Si dot clusters.

Rapid diagnosis of pulmonary tuberculosis and detection of drug resistance by combined simultaneous amplification testing and reverse dot blot.

PubMed

Chen, Yiwen; Zhang, Lahong; Hong, Liquan; Luo, Xian; Chen, Juping; Tang, Leiming; Chen, Jiahuan; Liu, Xia; Chen, Zhaojun

2018-06-01

Making a correct and rapid diagnosis is essential for managing pulmonary tuberculosis (PTB), particularly multidrug-resistant tuberculosis. We aimed to evaluate the efficacy of the combination of simultaneous amplification testing (SAT) and reverse dot blot (RDB) for the rapid detection of Mycobacterium tuberculosis (MTB) and drug-resistant mutants in respiratory samples. 225 suspected PTB and 32 non-TB pulmonary disease samples were collected. All sputum samples were sent for acid-fast bacilli smear, SAT, culture and drug susceptibility testing (DST) by the BACTEC TM MGIT TM 960 system. 53 PTB samples were tested by both RDB and DNA sequencing to identify drug resistance genes and mutated sites. The SAT positive rate (64.9%) was higher than the culture positive rate (55.1%), with a coincidence rate of 83.7%. The sensitivity and specificity of SAT for diagnosing PTB were 66.7% and 100%, respectively, while those for culture were 53.9% and 84.2%, respectively. RDB has high sensitivity and specificity in identifying drug resistance genes and mutated sites. The results of RDB correlated well with those of DST and DNA sequencing, with coincidence rates of 92.5% and 98.1%, respectively. The combination of SAT and RDB is promising for rapidly detecting PTB and monitoring drug resistance in clinical laboratories. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Antigenic topology of chlamydial PorB protein and identification of targets for immune neutralization of infectivity.

PubMed

Kawa, Diane E; Stephens, Richard S

2002-05-15

The outer membrane protein PorB is a conserved chlamydial protein that functions as a porin and is capable of eliciting neutralizing Abs. A topological antigenic map was developed using overlapping synthetic peptides representing the Chlamydia trachomatis PorB sequence and polyclonal immune sera. To identify which antigenic determinants were surface accessible, monospecific antisera were raised to the PorB peptides and were used in dot-blot and ELISA-based absorption studies with viable chlamydial elementary bodies (EBs). The ability of the surface-accessible antigenic determinants to direct neutralizing Ab responses was investigated using standardized in vitro neutralization assays. Four major antigenic clusters corresponding to Phe(34)-Leu(59) (B1-2 and B1-3), Asp(112) -Glu(145) (B2-3 and B2-4), Gly(179)-Ala(225) (B3-2 to B3-4), and Val(261)-Asn(305) (B4-4 to B5-2) were identified. Collectively, the EB absorption and dot-blot assays established that the immunoreactive PorB Ags were exposed on the surface of chlamydial EBs. Peptide-specific antisera raised to the surface-accessible Ags neutralized chlamydial infectivity and demonstrated cross-reactivity to synthetic peptides representing analogous C. pneumoniae PorB sequences. Furthermore, neutralization of chlamydial infectivity by C. trachomatis PorB antisera was inhibited by synthetic peptides representing the surface-exposed PorB antigenic determinants. These findings demonstrate that PorB Ags may be useful for development of chlamydial vaccines.

Screening differentially expressed genes in an amphipod (Hyalella azteca) exposed to fungicide vinclozolin by suppression subtractive hybridization.

PubMed

Wu, Yun H; Wu, Tsung M; Hong, Chwan Y; Wang, Yei S; Yen, Jui H

2014-01-01

Vinclozolin, a dicarboximide fungicide, is an endocrine disrupting chemical that competes with an androgenic endocrine disruptor compound. Most research has focused on the epigenetic effect of vinclozolin in humans. In terms of ecotoxicology, understanding the effect of vinclozolin on non-target organisms is important. The expression profile of a comprehensive set of genes in the amphipod Hyalella azteca exposed to vinclozolin was examined. The expressed sequence tags in low-dose vinclozolin-treated and -untreated amphipods were isolated and identified by suppression subtractive hybridization. DNA dot blotting was used to confirm the results and establish a subtracted cDNA library for comparing all differentially expressed sequences with and without vinclozolin treatment. In total, 494 differentially expressed genes, including hemocyanin, heatshock protein, cytochrome, cytochrome oxidase and NADH dehydrogenase were detected. Hemocyanin was the most abundant gene. DNA dot blotting revealed 55 genes with significant differential expression. These genes included larval serum protein 1 alpha, E3 ubiquitin-protein ligase, mitochondrial cytochrome c oxidase, mitochondrial protein, proteasome inhibitor, hemocyanin, zinc-finger-containing protein, mitochondrial NADH-ubiquinone oxidoreductase and epididymal sperm-binding protein. Vinclozolin appears to upregulate stress-related genes and hemocyanin, related to immunity. Moreover, vinclozolin downregulated NADH dehydrogenase, related to respiration. Thus, even a non-lethal concentration of vinclozolin still has an effect at the genetic level in H. azteca and presents a potential risk, especially as it would affect non-target organism hormone metabolism.

Detection of Zika virus using reverse-transcription LAMP coupled with reverse dot blot analysis in saliva

PubMed Central

Yasmin, Rubina; Barber, Cheryl A.; Castro, Talita; Malamud, Daniel; Kim, Beum Jun; Zhu, Hui; Montagna, Richard A.; Abrams, William R.

2018-01-01

In recent years, there have been increasing numbers of infectious disease outbreaks that spread rapidly to population centers resulting from global travel, population vulnerabilities, environmental factors, and ecological disasters such as floods and earthquakes. Some examples of the recent outbreaks are the Ebola epidemic in West Africa, Middle East respiratory syndrome coronavirus (MERS-Co) in the Middle East, and the Zika outbreak through the Americas. We have created a generic protocol for detection of pathogen RNA and/or DNA using loop-mediated isothermal amplification (LAMP) and reverse dot-blot for detection (RDB) and processed automatically in a microfluidic device. In particular, we describe how a microfluidic assay to detect HIV viral RNA was converted to detect Zika virus (ZIKV) RNA. We first optimized the RT-LAMP assay to detect ZIKV RNA using a benchtop isothermal amplification device. Then we implemented the assay in a microfluidic device that will allow analyzing 24 samples simultaneously and automatically from sample introduction to detection by RDB technique. Preliminary data using saliva samples spiked with ZIKV showed that our diagnostic system detects ZIKV RNA in saliva. These results will be validated in further experiments with well-characterized ZIKV human specimens of saliva. The described strategy and methodology to convert the HIV diagnostic assay and platform to a ZIKV RNA detection assay provides a model that can be readily utilized for detection of the next emerging or re-emerging infectious disease. PMID:29401479

Naked-eye fingerprinting of single nucleotide polymorphisms on psoriasis patients

NASA Astrophysics Data System (ADS)

Valentini, Paola; Marsella, Alessandra; Tarantino, Paolo; Mauro, Salvatore; Baglietto, Silvia; Congedo, Maurizio; Paolo Pompa, Pier

2016-05-01

We report a low-cost test, based on gold nanoparticles, for the colorimetric (naked-eye) fingerprinting of a panel of single nucleotide polymorphisms (SNPs), relevant for the personalized therapy of psoriasis. Such pharmacogenomic tests are not routinely performed on psoriasis patients, due to the high cost of standard technologies. We demonstrated high sensitivity and specificity of our colorimetric test by validating it on a cohort of 30 patients, through a double-blind comparison with two state-of-the-art instrumental techniques, namely reverse dot blotting and sequencing, finding 100% agreement. This test offers high parallelization capabilities and can be easily generalized to other SNPs of clinical relevance, finding broad utility in diagnostics and pharmacogenomics.We report a low-cost test, based on gold nanoparticles, for the colorimetric (naked-eye) fingerprinting of a panel of single nucleotide polymorphisms (SNPs), relevant for the personalized therapy of psoriasis. Such pharmacogenomic tests are not routinely performed on psoriasis patients, due to the high cost of standard technologies. We demonstrated high sensitivity and specificity of our colorimetric test by validating it on a cohort of 30 patients, through a double-blind comparison with two state-of-the-art instrumental techniques, namely reverse dot blotting and sequencing, finding 100% agreement. This test offers high parallelization capabilities and can be easily generalized to other SNPs of clinical relevance, finding broad utility in diagnostics and pharmacogenomics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02200f

Detection of Zika virus using reverse-transcription LAMP coupled with reverse dot blot analysis in saliva.

PubMed

Sabalza, Maite; Yasmin, Rubina; Barber, Cheryl A; Castro, Talita; Malamud, Daniel; Kim, Beum Jun; Zhu, Hui; Montagna, Richard A; Abrams, William R

2018-01-01

In recent years, there have been increasing numbers of infectious disease outbreaks that spread rapidly to population centers resulting from global travel, population vulnerabilities, environmental factors, and ecological disasters such as floods and earthquakes. Some examples of the recent outbreaks are the Ebola epidemic in West Africa, Middle East respiratory syndrome coronavirus (MERS-Co) in the Middle East, and the Zika outbreak through the Americas. We have created a generic protocol for detection of pathogen RNA and/or DNA using loop-mediated isothermal amplification (LAMP) and reverse dot-blot for detection (RDB) and processed automatically in a microfluidic device. In particular, we describe how a microfluidic assay to detect HIV viral RNA was converted to detect Zika virus (ZIKV) RNA. We first optimized the RT-LAMP assay to detect ZIKV RNA using a benchtop isothermal amplification device. Then we implemented the assay in a microfluidic device that will allow analyzing 24 samples simultaneously and automatically from sample introduction to detection by RDB technique. Preliminary data using saliva samples spiked with ZIKV showed that our diagnostic system detects ZIKV RNA in saliva. These results will be validated in further experiments with well-characterized ZIKV human specimens of saliva. The described strategy and methodology to convert the HIV diagnostic assay and platform to a ZIKV RNA detection assay provides a model that can be readily utilized for detection of the next emerging or re-emerging infectious disease.

Sialic acid content in human saliva and anti-influenza activity against human and avian influenza viruses.

PubMed

Limsuwat, Nattavatchara; Suptawiwat, Ornpreya; Boonarkart, Chompunuch; Puthavathana, Pilaipan; Wiriyarat, Witthawat; Auewarakul, Prasert

2016-03-01

It was shown previously that human saliva has higher antiviral activity against human influenza viruses than against H5N1 highly pathogenic avian influenza viruses, and that the major anti-influenza activity was associated with sialic-acid-containing molecules. To further characterize the differential susceptibility to saliva among influenza viruses, seasonal influenza A and B virus, pandemic H1N1 virus, and 15 subtypes of avian influenza virus were tested for their susceptibility to human and chicken saliva. Human saliva showed higher hemagglutination inhibition (HI) and neutralization (NT) titers against seasonal influenza A virus and the pandemic H1N1 viruses than against influenza B virus and most avian influenza viruses, except for H9N2 and H12N9 avian influenza viruses, which showed high HI and NT titers. To understand the nature of sialic-acid-containing anti-influenza factors in human saliva, α2,3- and α2,6-linked sialic acid was measured in human saliva samples using a lectin binding and dot blot assay. α2,6-linked sialic acid was found to be more abundant than α2,3-linked sialic acid, and a seasonal H1N1 influenza virus bound more efficiently to human saliva than an H5N1 virus in a dot blot analysis. These data indicated that human saliva contains the sialic acid type corresponding to the binding preference of seasonal influenza viruses.

Development and evaluation of hexaplex PCR for rapid detection of methicillin, cadmium/zinc and antiseptic-resistant staphylococci, with simultaneous identification of PVL-positive and -negative Staphylococcus aureus and coagulase negative staphylococci.

PubMed

Panda, Sasmita; Kar, Sarita; Choudhury, Ranginee; Sharma, Savitri; Singh, Durg V

2014-03-01

We developed a multiplex PCR to detect the presence of methicillin- (mecA), cadmium/zinc-(czrC) and antiseptic-resistant (qacA/B) staphylococci and to identify Panton-Valentine leukocidin (PVL)-positive and -negative Staphylococcus aureus and coagulase-negative staphylococci (CoNS) from infected and healthy eyes. The assay was validated on 177 staphylococci comprising of 55 each of S. aureus and CoNS isolated from infected eyes and five S. aureus and 62 CoNS isolated from healthy eyes and nine direct ocular samples. Nine direct ocular samples for in situ testing consisted of corneal scrapings (4), conjunctiva swabs (2) and others (3). Multiplex PCR result was correlated with genotype data obtained with single PCR and dot-blot assay. The control strains that were positive in multiplex PCR for 16S rRNA, nuc, mecA, pvl, czrC and qacA/B genes were also positive in the dot-blot assay. The specificity of amplified genes obtained with reference strains was further confirmed by DNA sequencing. The single step-hexaplex PCR method can be used for rapid detection of mecA, nuc, pvl, czrC and qacA/B genes in staphylococci with simultaneous identification of PVL-positive and -negative S. aureus and CoNS from a variety of ocular samples. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Investigation of structural, morphological and opto-electronic properties of CdS quantum dot thin film

NASA Astrophysics Data System (ADS)

Ibrahim Mohammed S., M.; Gubari, Ghamdan M. M.; Huse, Nanasaheb P.; Dive, Avinash S.; Sharma, Ramphal

2018-05-01

We have successfully deposited CdS quantum dot thin film on the glass substrate by simple and economic chemical bath deposition method at ˜50 ˚C. The X-ray diffraction study confirms the formation of CdS when compared with standard JCPDS data with average crystallite size ˜3 nm. The morphology of the film was studied by FE-SEM, which suggests the homogeneous and uniform deposition of the CdS material over the entire glass substrate with a porous structure. From UV absorption spectra we observed that the sample exhibited a band edge near ˜400 nm with a slight deviation with the presence of excitonic peak for the sample. The presence of excitonic peak may be attributed to the formation of quantum dots. The calculated band gap energy of CdS quantum dot thin film was found to be ˜3.136 eV. The thin film further characterized to study electrical parameters and the sample show a drastic increase in current after light illumination.

A fluorescent nanosensor based on graphene quantum dots-aptamer probe and graphene oxide platform for detection of lead (II) ion.

PubMed

Qian, Zhao Sheng; Shan, Xiao Yue; Chai, Lu Jing; Chen, Jian Rong; Feng, Hui

2015-06-15

The sensitive detection of heavy metal ions in the organism and aquatic ecosystem using nanosensors based on environment friendly and biocompatible materials still remains a challenge. A fluorescent turn-on nanosensor for lead (II) detection based on biocompatible graphene quantum dots and graphene oxide by employment of Pb(2+)-induced G-quadruplex formation was reported. Graphene quantum dots with high quantum yield, good biocompatibility were prepared and served as the fluorophore of Pb(2+) probe. Fluorescence turn-off of graphene quantum dots is easily achieved through efficient photoinduced electron transfer between graphene quantum dots and graphene oxide, and subsequent fluorescence turn-on process is due to the formation of G-quadraplex aptamer-Pb(2+) complex triggered by the addition of Pb(2+). This nanosensor can distinguish Pb(2+) ion from other ions with high sensitivity and good reproducibility. The detection method based on this nanosensor possesses a fast response time of one minute, a broad linear span of up to 400.0 nM and ultralow detection limit of 0.6 nM. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of an IP-Free Biotechnology Platform for Constitutive Production of HPV16 L1 Capsid Protein Using the Pichia pastoris PGK1 Promoter.

PubMed

Mariz, F C; Coimbra, E C; Jesus, A L S; Nascimento, L M; Torres, F A G; Freitas, A C

2015-01-01

The human papillomavirus (HPV) L1 major capsid protein, which forms the basis of the currently available vaccines against cervical cancer, self-assembles into virus-like particles (VLPs) when expressed heterologously. We report the development of a biotechnology platform for HPV16 L1 protein expression based on the constitutive PGK1 promoter (PPGK1) from the methylotrophic yeast Pichia pastoris. The L1 gene was cloned under regulation of PPGK1 into pPGKΔ3 expression vector to achieve intracellular expression. In parallel, secretion of the L1 protein was obtained through the use of an alternative vector called pPGKΔ3α, in which a codon optimized α-factor signal sequence was inserted. We devised a work-flow based on the detection of the L1 protein by dot blot, colony blot, and western blot to classify the positive clones. Finally, intracellular HPV VLPs assembly was demonstrated for the first time in yeast cells. This study opens up perspectives for the establishment of an innovative platform for the production of HPV VLPs or other viral antigens for vaccination purposes, based on constitutive expression in P. pastoris.

How do closed-compact multi-lamellar droplets form under shear flow? A possible mechanism

NASA Astrophysics Data System (ADS)

Courbin, L.; Pons, R.; Rouch, J.; Panizza, P.

2003-01-01

The formation of closed-compact multi-lamellar droplets obtained upon shearing both a lamellar phase (Lα) and a two-phase separated lamellar-sponge (Lα-L3) mixture is investigated as a function of the shear rate dot gamma, using small-angle light scattering (SALS) and cross-polarized optical microscopy. In both systems the formation of droplets occurs homogeneously in the cell at a well-defined wave vector qe propto dot gamma1/3 via a strain-controlled process. These results suggest that the formation of droplets may be monitored in both systems by a buckling instability of the lamellae as predicted from a recent theory.

Formation of plasmon pulses in the cooperative decay of excitons of quantum dots near a metal surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shesterikov, A. B.; Gubin, M. Yu.; Gladush, M. G.

The formation of pulses of surface electromagnetic waves at a metal–dielectric boundary is considered in the process of cooperative decay of excitons of quantum dots distributed near a metal surface in a dielectric layer. It is shown that the efficiency of exciton energy transfer to excited plasmons can, in principle, be increased by selecting the dielectric material with specified values of the complex permittivity. It is found that in the mean field approximation, the semiclassical model of formation of plasmon pulses in the system under study is reduced to the pendulum equation with the additional term of nonlinear losses.

Multi-Excitonic Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

Scheibner, M.; Stinaff, E. A.; Doty, M. F.; Ware, M. E.; Bracker, A. S.; Gammon, D.; Ponomarev, I. V.; Reinecke, T. L.; Korenev, V. L.

2006-03-01

With the ability to create coupled pairs of quantum dots, the next step towards the realization of semiconductor based quantum information processing devices can be taken. However, so far little knowledge has been gained on these artificial molecules. Our photoluminescence experiments on single InAs/GaAs quantum dot molecules provide the systematics of coupled quantum dots by delineating the spectroscopic features of several key charge configurations in such quantum systems, including X, X^+,X^2+, XX, XX^+ (with X being the neutral exciton). We extract general rules which determine the formation of molecular states of coupled quantum dots. These include the fact that quantum dot molecules provide the possibility to realize various spin configurations and to switch the electron hole exchange interaction on and off by shifting charges inside the molecule. This knowledge will be valuable in developing implementations for quantum information processing.

Role of surface states and defects in the ultrafast nonlinear optical properties of CuS quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mary, K. A. Ann; Unnikrishnan, N. V., E-mail: nvu100@yahoo.com; Philip, Reji

2014-07-01

We report facile preparation of water dispersible CuS quantum dots (2–4 nm) and nanoparticles (5–11 nm) through a nontoxic, green, one-pot synthesis method. Optical and microstructural studies indicate the presence of surface states and defects (dislocations, stacking faults, and twins) in the quantum dots. The smaller crystallite size and quantum dot formation have significant effects on the high energy excitonic and low energy plasmonic absorption bands. Effective two-photon absorption coefficients measured using 100 fs laser pulses employing open-aperture Z-scan in the plasmonic region of 800 nm reveal that CuS quantum dots are better ultrafast optical limiters compared to CuS nanoparticles.

Comparison of two quantum dots for bioluminescence resonance energy transfer based on nucleic acid detection

NASA Astrophysics Data System (ADS)

Zhang, Daohong

2017-05-01

The performance of two commercially available quantum dots, quantum dot 605 (Qd605) and quantum dot 625 (Qd625), was tested and compared in the sensing system developed by our group previously. The sandwich format sensing system employed Renilla luciferase (Rluc) and quantum dots (Qds), could report the presence of targets with increasing bioluminescent resonance energy transfer (BRET) signal. The best spacing between the Rluc and Qds probes were 15 nucleotides. Both of Qd605 and Qd625 sensing system could quantify nucleic acid targets through 1-min hybridization from 0.2 picomoles. However, the Qd625 system showed higher BRET signal and better selectivity. Therefore, Qd625 is a better choice in this system compared to Qd605.

Highly sensitive serological methods for detecting tomato yellow leaf curl virus in tomato plants and whiteflies.

PubMed

Xie, Yan; Jiao, Xiaoyang; Zhou, Xueping; Liu, Huan; Ni, Yuequn; Wu, Jianxiang

2013-05-06

Tomato yellow leaf curl virus (TYLCV) is a member of the genus Begomovirus in the family Geminiviridae, which causes severe losses in tomato production in tropic and subtropic regions. The purified TYLCV virions were used as the immunogen to produce monoclonal antibodies (MAbs) using the hybridoma technology. MAb-based dot enzyme-linked immunosorbent assay (dot-ELISA) and direct tissue blot immunoassay (DTBIA) were developed for sensitive, simple, and rapid detection of TYLCV in field tomato and whitefly (Bemisia tabaci) samples collected from TYLCV prevalent provinces in China. Using the hybridoma technology, six murine MAbs (1C4, 8D10, 6E3, 2F2, 3F4 and 4G3) against TYLCV were prepared. Using the MAb 1C4, dot-ELISA and DTBIA were then established for detecting TYLCV in field tomato and whitefly samples collected from TYLCV prevalent provinces in China. The dot-ELISA could detect TYLCV in infected tissue crude extract diluted at 1:5,120 (w/v, g mL-1), and in viruliferous whitefly homogenate diluted at 1:128 (individual whitefly/μL), respectively. Field tomato samples (n=487) and whitefly samples (n=110) from TYLCV prevalent districts in China were screened for the presence of TYLCV using the two developed methods, and the results were further confirmed by PCR and nucleotide sequencing. The survey revealed that TYLCV is widespread on tomato plants in Zhejiang, Shandong and Henan provinces in China. The developed dot-ELISA is very suitable for the routine detection of TYLCV in field tomato and whitefly samples, and the DTBIA is more suitable for the routine detection of TYLCV in large-scale tomato plant samples collected from TYLCV prevalent areas.

Evaluation of a novel Dot-ELISA assay utilizing a recombinant protein for the effective diagnosis of Taenia pisiformis larval infections.

PubMed

Chen, Lin; Yang, Deying; Gu, Xiaobin; Peng, Xuerong; Yang, Guangyou

2014-08-29

Cysticercosis, caused by the larvae of Taenia pisiformis, is a common disease in domestic breeds of the rabbit Oryctolagus cuniculus that results in economic losses. At present, there is no convenient and effective method for the rapid detection of T. pisiformis larvae. Here, we developed and tested the efficacy of a Dot-ELISA assay for the diagnosis of T. pisiformis larval infections in rabbits, based on the expression of the recombinant fusion protein (rTp1) from the Tp1 gene. Rapid amplification of cDNA ends (RACE) was used to amplify the 3' ends of the Tp1 gene, based on the unigene similar to Ts1 gene (EU009656.1) which comes from transcriptome sequencing of T. pisiformis. The Tp1 gene was successfully amplified, cloned and expressed in BL21 (DE3). Western blot analysis revealed that the recombinant Tp1 protein is specifically recognized by rabbit T. pisiformis cysticercosis antisera. This purified recombinant fusion protein, rTp1, was probed by Dot-ELISA with sera from rabbits infected with T. pisiformis larvae and with other parasitic infections. Results showed that this Dot-ELISA assay had both high sensitivity (92.9-97.6%) and specificity (95.2-98.4%) to detect T. pisiformis larval infections. We also found very low levels of cross-reaction with other parasitic infections. This study has revealed that our novel Dot-ELISA assay utilizing the recombinant fusion protein, rTp1, has a strong potential for the effective diagnosis of T. pisiformis infections in rabbits. Copyright © 2014 Elsevier B.V. All rights reserved.

Self-aligned periodic Ni nano dots embedded in nano-oxide layer

NASA Astrophysics Data System (ADS)

Doi, M.; Izumi, M.; Kawasaki, S.; Miyake, K.; Sahashi, M.

The Ni nano constriction dots embedded in the Ta-nano-oxide layer (NOL) was prepared by the ion beam sputtering (IBS) method. After the various conditions of the oxidations, the structural analyses of the NOL were performed by RHEED, AES and in situ STM/AFM observations. From the current image of the conductive AFM for NOL, the periodically aligned metallic dots with the size around 5-10 nm were successfully observed. The mechanism of the formation of the self-organized aligned Ni nano constriction dots is discussed from the standpoint of the grain size, the crystal orientation, the preferred oxidation of Ta at the diffused interface.

Nanosilicon dot arrays with a bit pitch and a track pitch of 25 nm formed by electron-beam drawing and reactive ion etching for 1 Tbit/in.{sup 2} storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosaka, Sumio; Sano, Hirotaka; Shirai, Masumi

2006-11-27

The formation of very fine Si dots with a bit pitch and a track pitch of less than 25 nm using electron-beam (EB) lithography on ZEP520 and calixarene EB resists and CF{sub 4} reactive ion etching has been demonstrated. The experimental results indicate that the calixarene resist is very suitable for forming an ultrahigh-packed bit array pattern of Si dots. This result promises to open the way toward 1 Tbit/in.{sup 2} storage using patterned media with a dot size of <15 nm.

Self-assembled indium arsenide quantum dots: Structure, formation dynamics, optical properties

NASA Astrophysics Data System (ADS)

Lee, Hao

1998-12-01

In this dissertation, we investigate the properties of InAs/GaAs quantum dots grown by molecular beam epitaxy. The structure and formation dynamics of InAs quantum dots are studied by a variety of structural characterization techniques. Correlations among the growth conditions, the structural characteristics, and the observed optical properties are explored. The most fundamental structural characteristic of the InAs quantum dots is their shape. Through detailed study of the reflection high energy electron diffraction patterns, we determined that self-assembled InAs islands possess a pyramidal shape with 136 bounding facets. Cross-sectional transmission electron microscopy images and atomic force microscopy images strongly support this model. The 136 model we proposed is the first model that is consistent with all reported shape features determined using different methods. The dynamics of coherent island formation is also studied with the goal of establishing the factors most important in determining the size, density, and the shape of self- organized InAs quantum dots. Our studies clearly demonstrate the roles that indium diffusion and desorption play in InAs island formation. An unexpected finding (from atomic force microscopy images) was that the island size distribution bifurcated during post- growth annealing. Photoluminescence spectra of the samples subjected to in-situ annealing prior to the growth of a capping layer show a distinctive double-peak feature. The power-dependence and temperature-dependence of the photoluminescence spectra reveals that the double- peak emission is associated with the ground-state transition of islands in two different size branches. These results confirm the island size bifurcation observed from atomic force microscopy images. The island size bifurcation provides a new approach to the control and manipulation of the island size distribution. Unexpected dependence of the photoluminescence line-shape on sample temperature and pump intensity was observed for samples grown at relatively high substrate temperatures. The behavior is modeled and explained in terms of competition between two overlapping transitions. The study underscores that the growth conditions can have a dramatic impact on the optical properties of the quantum dots. This dissertation includes both my previously published and unpublished authored materials.

Development of a one-step immunochromatographic strip test using gold nanoparticles for the rapid detection of Salmonella typhi in human serum.

PubMed

Preechakasedkit, Pattarachaya; Pinwattana, Kulwadee; Dungchai, Wijitar; Siangproh, Weena; Chaicumpa, Wanpen; Tongtawe, Pongsri; Chailapakul, Orawon

2012-01-15

An immunochromatographic strip test using gold nanoparticles was developed for the rapid detection of Salmonella typhi (S. typhi) in human serum. The strip test based on the principle of sandwich immunoassay by the specific binding of antigens from S. typhi O901 and antibody of S. typhi O901 on a nitrocellulose membrane. Antibody-gold nanoparticle conjugate was used as the label and was coated onto a glass fiber membrane, which was used as a conjugate pad. To create a test and control zone, antibody of S. typhi O901 and an anti-IgG were dotted on the nitrocellulose membrane, respectively. Positive samples were displayed as red dots at the test and control zones of the nitrocellulose membrane, while negative samples resulted in a red dot only in the control zone. The limit of detection (LOD) was found to be 1.14×10(5) cfu mL(-1), which could be visually detected by the naked eye within 15 min. This strip test provided a lower detection limit and analysis time than a dot blot immunoassay (8.88×10(6) cfu mL(-1) for LOD and 110 min for reaction time). In addition, our immunochromatographic strip test was employed to detect S. typhi in human serum effectively, with high accuracy. This strip test offers great promise for a rapid, simple and low-cost analysis of S. typhi. Copyright © 2011 Elsevier B.V. All rights reserved.

Dot enzyme-linked immunosorbent assay (ELISA) for the detection of Toxocara infection using a rat model.

PubMed

Paller, Vachel Gay V; Besana, Cyrelle M; Valdez, Isabel Kristine M

2017-12-01

Toxocariasis is a zoonotic disease usually caused by dog and cat roundworms, Toxocara canis and T. cati. Detection and diagnosis is difficult in paratenic and accidental hosts, including humans, as they cannot be detected through conventional methods such as fecal examination. Diagnosis therefore relies on immunological methods and molecular methods such as enzyme-linked immunosorbent assay (ELISA) and Western Blot, which are both time-consuming and requires sophisticated equipment. In the Philippines, only a few studies are available on Toxocara seroprevalence. Therefore, there is a need to adapt methods for serodiagnosis of Toxocara infection in humans for the Philippine setting. A dot enzyme linked immunosorbent assay (dot-ELISA) was standardized using T. canis excretory-secretory antigens. Test sera were collected from laboratory rats (Sprague-Dawley strain) experimentally infected with embryonated eggs of T. canis and Ascaris suum as well as rice field rats naturally infected with Taenia taeniaeformis and Nippostrongylus sp. Optimum conditions used were 20 µg/ml antigen concentration and 1:10 serum dilution. The sensitivity, specificity, positive, and negative predictive values were 90% (95% CI 55.5-99.7%), 100% (95% CI 69.2-100.0%), 100% (95% CI 66.4-100%), and 90.9% (95% CI 58.7-99.8%), respectively. Dot-ELISA has the potential to be developed as a cheaper, simpler, and more practical method for detection of anti- Toxocara antibodies on accidental hosts. This is a preliminary study conducted on experimental animals before optimization and standardization for human serum samples.

Antigenic characterisation of yeast-expressed lyssavirus nucleoproteins.

PubMed

Kucinskaite, Indre; Juozapaitis, Mindaugas; Serva, Andrius; Zvirbliene, Aurelija; Johnson, Nicholas; Staniulis, Juozas; Fooks, Anthony R; Müller, Thomas; Sasnauskas, Kestutis; Ulrich, Rainer G

2007-12-01

In Europe, three genotypes of the genus Lyssavirus, family Rhabdoviridae, are present, classical rabies virus (RABV, genotype 1), European bat lyssavirus type 1 (EBLV-1, genotype 5) and European bat lyssavirus type 2 (EBLV-2, genotype 6). The entire authentic nucleoprotein (N protein) encoding sequences of RABV (challenge virus standard, CVS, strain), EBLV-1 and EBLV-2 were expressed in yeast Saccharomyces cerevisiae at high level. Purification of recombinant N proteins by caesium chloride gradient centrifugation resulted in yields between 14-17, 25-29 and 18-20 mg/l of induced yeast culture for RABV-CVS, EBLV-1 and EBLV-2, respectively. The purified N proteins were evaluated by negative staining electron microscopy, which revealed the formation of nucleocapsid-like structures. The antigenic conformation of the N proteins was investigated for their reactivity with monoclonal antibodies (mAbs) directed against different lyssaviruses. The reactivity pattern of each mAb was virtually identical between immunofluorescence assay with virus-infected cells, and ELISA and dot blot assay using the corresponding recombinant N proteins. These observations lead us to conclude that yeast-expressed lyssavirus N proteins share antigenic properties with naturally expressed virus protein. These recombinant proteins have the potential for use as components of serological assays for lyssaviruses.

Electrochemical Study and Applications of Selective Electrodeposition of Silver on Quantum Dots.

PubMed

Martín-Yerga, Daniel; Rama, Estefanía Costa; Costa-García, Agustín

2016-04-05

In this work, selective electrodeposition of silver on quantum dots is described. The particular characteristics of the nanostructured silver thus obtained are studied by electrochemical and microscopic techniques. On one hand, quantum dots were found to catalyze the silver electrodeposition, and on the other hand, a strong adsorption between electrodeposited silver and quantum dots was observed, indicated by two silver stripping processes. Nucleation of silver nanoparticles followed different mechanisms depending on the surface (carbon or quantum dots). Voltammetric and confocal microscopy studies showed the great influence of electrodeposition time on surface coating, and high-resolution transmission electron microscopy (HRTEM) imaging confirmed the initial formation of Janus-like Ag@QD nanoparticles in this process. By use of moderate electrodeposition conditions such as 50 μM silver, -0.1 V, and 60 s, the silver was deposited only on quantum dots, allowing the generation of localized nanostructured electrode surfaces. This methodology can also be employed for sensing applications, showing a promising ultrasensitive electrochemical method for quantum dot detection.

Rhizopus stolonifer mediated biosynthesis of biocompatible cadmium chalcogenide quantum dots.

PubMed

Mareeswari, P; Brijitta, J; Harikrishna Etti, S; Meganathan, C; Kaliaraj, Gobi Saravanan

2016-12-01

We report an efficient method to biosynthesize biocompatible cadmium telluride and cadmium sulphide quantum dots from the fungus Rhizopus stolonifer. The suspension of the quantum dots exhibited purple and greenish-blue luminescence respectively upon UV light illumination. Photoluminescence spectroscopy, X-ray diffraction, and transmission electron microscopy confirms the formation of the quantum dots. From the photoluminescence spectrum the emission maxima is found to be 424 and 476nm respectively. The X-ray diffraction of the quantum dots matches with results reported in literature. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay for cell viability evaluation carried out on 3-days transfer, inoculum 3×10 5 cells, embryonic fibroblast cells lines shows that more than 80% of the cells are viable even after 48h, indicating the biocompatible nature of the quantum dots. A good contrast in imaging has been obtained upon incorporating the quantum dots in human breast adenocarcinoma Michigan Cancer Foundation-7 cell lines. Copyright © 2016 Elsevier Inc. All rights reserved.

Characteristic Behavior and Scaling Studies of Self Organized InP Nano-dots formed via keV and MeV irradiations

NASA Astrophysics Data System (ADS)

Paramanik, Dipak; Varma, Shikha

2008-04-01

The controlled formation of nano-dots, using ion beams as tool, has become important as it offers a unique method to generate non-equilibrium phases with novel physical properties and structures with nano-dimensions. We have investigated the creation of self assembled nano- dots on InP(111) surfaces after 3 keV as well as 1.5 MeV ion beams at a large range of fluences. We have studied the Scaling exponents of the evolved surfaces by utilizing the technique of Scanning Probe Microscopy (SPM). At keV energies ripening of the nano-dots is seen below a critical time whereas an inverse ripening is observed for longer durations. At the critical time square shaped array of nano --dots are observed. The dots are characterized by narrow height and size distributions. Nano dots have also been observed at MeV ion irradiations. Their size distribution though broad at lowest fluence decreases for larger fluences.

RKKY interaction in a chirally coupled double quantum dot system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heine, A. W.; Tutuc, D.; Haug, R. J.

2013-12-04

The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtainedmore » Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region.« less

Large-area ordered Ge-Si compound quantum dot molecules on dot-patterned Si (001) substrates

NASA Astrophysics Data System (ADS)

Lei, Hui; Zhou, Tong; Wang, Shuguang; Fan, Yongliang; Zhong, Zhenyang

2014-08-01

We report on the formation of large-area ordered Ge-Si compound quantum dot molecules (CQDMs) in a combination of nanosphere lithography and self-assembly. Truncated-pyramid-like Si dots with {11n} facets are readily formed, which are spatially ordered in a large area with controlled period and size. Each Si dot induces four self-assembled Ge-rich dots at its base edges that can be fourfold symmetric along <110> directions. A model based on surface chemical potential accounts well for these phenomena. Our results disclose the critical effect of surface curvature on the diffusion and the aggregation of Ge adatoms and shed new light on the unique features and the inherent mechanism of self-assembled QDs on patterned substrates. Such a configuration of one Si QD surrounded by fourfold symmetric Ge-rich QDs can be seen as a CQDM with unique features, which will have potential applications in novel devices.

The Effect of Temperature on Photoluminescence Enhancement of Quantum Dots in Brain Slices.

PubMed

Zhao, Fei; Kim, Jongsung

2017-04-01

In this paper, we investigated the effect of temperature on photoluminescence of quantum dots immobilized on the surface of an optical fiber in a rat brain slice. The optical fiber was silanized with 3-aminopropyl trimethoxysilane (APTMS), following which quantum dots with carboxyl functional group were immobilized on the optical fiber via amide bond formation. The effect of temperature on the fluorescence intensity of the quantum dots in rat brain slices was studied. This report shows that the fluorescence intensity of quantum dots increases with the increase of temperature of the brain slice. The fluorescence enhancement phenomenon appears to take place via electron transfer related to pH increase. With the gradual increase of temperature, the fluorescence intensity of quantum dots in solution decreased, while that in the brain slice increased. This enhanced thermal performance of QDs in brain slice makes suggestion for the study of QDs-based brain temperature sensors.

In situ growth of ceramic quantum dots in polyaniline host via water vapor flow diffusion as potential electrode materials for energy applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mombrú, Dominique; Romero, Mariano, E-mail: mromero@fq.edu.uy; Faccio, Ricardo, E-mail: rfaccio@fq.edu.uy

In situ preparation of polyaniline-ceramic nanocomposites has recently demonstrated that the electrical properties are highly improved with respect to the typical ex situ preparations. In this report, we present for the first time, to the best of our knowledge, the in situ growth of titanium oxide quantum dots in polyaniline host via water vapor flow diffusion as an easily adaptable route to prepare other ceramic-polymer nanocomposites. The main relevance of this method is the possibility to prepare ceramic quantum dots from alkoxide precursors using water vapor flow into any hydrophobic polymer host and to achieve good homogeneity and size-control. Inmore » addition, we perform full characterization by means of high-resolution transmission electron microscopy, X-ray powder diffraction, small angle X-ray scattering, thermogravimetric and calorimetric analyses, confocal Raman microscopy and impedance spectroscopy analyses. The presence of the polymer host and interparticle Coulomb repulsive interactions was evaluated as an influence for the formation of ~3–8 nm equally-sized quantum dots independently of the concentration. The polyaniline polaron population showed an increase for the quantum dots diluted regime and the suppression at the concentrated regime, ascribed to the formation of chemical bonds at the interface, which was confirmed by theoretical simulations. In agreement with the previous observation, the in situ growth of ceramic quantum dots in polyaniline host via water vapor flow diffusion could be very useful as a novel approach to prepare electrode materials for energy conversion and storage applications. - Highlights: • In situ growth of titanium oxide quantum dots in polyaniline host via water vapor flow diffusion. • Polyaniline charge carriers at the interface and charge interactions between quantum dots. • Easy extrapolation to sol-gel derived quantum dots into polymer host as potential electrode materials.« less

Making comparative performance information more comprehensible: an experimental evaluation of the impact of formats on consumer understanding

PubMed Central

Damman, Olga C; De Jong, Anco; Hibbard, Judith H; Timmermans, Danielle R M

2016-01-01

Study objectives We aimed to investigate how different presentation formats influence comprehension and use of comparative performance information (CPI) among consumers. Methods An experimental between-subjects and within-subjects design with manipulations of CPI presentation formats. We enrolled both consumers with lower socioeconomic status (SES)/cognitive skills and consumers with higher SES/cognitive skills, recruited through an online access panel. Respondents received fictitious CPI and completed questions about interpretation and information use. Between subjects, we tested (1) displaying an overall performance score (yes/no); (2) displaying a small number of quality indicators (5 vs 9); and (3) displaying different types of evaluative symbols (star ratings, coloured dots and word icons vs numbers and bar graphs). Within subjects, we tested the effect of a reduced number of healthcare providers (5 vs 20). Data were analysed using descriptive analysis, analyses of variance and paired-sampled t tests. Results A total of 902 (43%) respondents participated. Displaying an overall performance score and the use of coloured dots and word icons particularly enhanced consumer understanding. Importantly, respondents provided with coloured dots most often correctly selected the top three healthcare providers (84.3%), compared with word icons (76.6% correct), star ratings (70.6% correct), numbers (62.0%) and bars (54.2%) when viewing performance scores of 20 providers. Furthermore, a reduced number of healthcare providers appeared to support consumers, for example, when provided with 20 providers, 69.5% correctly selected the top three, compared with 80.2% with five providers. Discussion Particular presentation formats enhanced consumer understanding of CPI, most importantly the use of overall performance scores, word icons and coloured dots, and a reduced number of providers displayed. Public report efforts should use these formats to maximise impact on consumers. PMID:26543066

Specificity rates for non-clinical, bilingual, Mexican Americans on three popular performance validity measures.

PubMed

Gasquoine, Philip G; Weimer, Amy A; Amador, Arnoldo

2017-04-01

To measure specificity as failure rates for non-clinical, bilingual, Mexican Americans on three popular performance validity measures: (a) the language format Reliable Digit Span; (b) visual-perceptual format Test of Memory Malingering; and (c) visual-perceptual format Dot Counting, using optimal/suboptimal effort cut scores developed for monolingual, English-speakers. Participants were 61 consecutive referrals, aged between 18 and 65 years, with <16 years of education who were subjectively bilingual (confirmed via formal assessment) and chose the language of assessment, Spanish or English, for the performance validity tests. Failure rates were 38% for Reliable Digit Span, 3% for the Test of Memory Malingering, and 7% for Dot Counting. For Reliable Digit Span, the failure rates for Spanish (46%) and English (31%) languages of administration did not differ significantly. Optimal/suboptimal effort cut scores derived for monolingual English-speakers can be used with Spanish/English bilinguals when using the visual-perceptual format Test of Memory Malingering and Dot Counting. The high failure rate for Reliable Digit Span suggests it should not be used as a performance validity measure with Spanish/English bilinguals, irrespective of the language of test administration, Spanish or English.

A fabrication guide for planar silicon quantum dot heterostructures

NASA Astrophysics Data System (ADS)

Spruijtenburg, Paul C.; Amitonov, Sergey V.; van der Wiel, Wilfred G.; Zwanenburg, Floris A.

2018-04-01

We describe important considerations to create top-down fabricated planar quantum dots in silicon, often not discussed in detail in literature. The subtle interplay between intrinsic material properties, interfaces and fabrication processes plays a crucial role in the formation of electrostatically defined quantum dots. Processes such as oxidation, physical vapor deposition and atomic-layer deposition must be tailored in order to prevent unwanted side effects such as defects, disorder and dewetting. In two directly related manuscripts written in parallel we use techniques described in this work to create depletion-mode quantum dots in intrinsic silicon, and low-disorder silicon quantum dots defined with palladium gates. While we discuss three different planar gate structures, the general principles also apply to 0D and 1D systems, such as self-assembled islands and nanowires.

Entanglement in a quantum neural network based on quantum dots

NASA Astrophysics Data System (ADS)

Altaisky, M. V.; Zolnikova, N. N.; Kaputkina, N. E.; Krylov, V. A.; Lozovik, Yu E.; Dattani, N. S.

2017-05-01

We studied the quantum correlations between the nodes in a quantum neural network built of an array of quantum dots with dipole-dipole interaction. By means of the quasiadiabatic path integral simulation of the density matrix evolution in a presence of the common phonon bath we have shown the coherence in such system can survive up to the liquid nitrogen temperature of 77 K and above. The quantum correlations between quantum dots are studied by means of calculation of the entanglement of formation in a pair of quantum dots with the typical dot size of a few nanometers and interdot distance of the same order. We have shown that the proposed quantum neural network can keep the mixture of entangled states of QD pairs up to the above mentioned high temperatures.

Origins of interlayer formation and misfit dislocation displacement in the vicinity of InAs/GaAs quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, S.; Kim, S. J.; Pan, X. Q.

We have examined the origins of interlayer formation and misfit dislocation (MD) displacement in the vicinity of InAs/GaAs quantum dots (QDs). For QDs formed by the Stranski-Krastanov mode, regularly spaced MDs nucleate at the interface between the QD and the GaAs buffer layer. In the droplet epitaxy case, both In island formation and In-induced “nano-drilling” of the GaAs buffer layer are observed during In deposition. Upon annealing under As flux, the In islands are converted to InAs QDs, with an InGaAs interlayer at the QD/buffer interface. Meanwhile, MDs nucleate at the QD/interlayer interface.

Formation of Size- and Position-Controlled Nanometer Size Pt Dots on GaAs and InP Substrates by Pulsed Electrochemical Deposition

NASA Astrophysics Data System (ADS)

Sato, Taketomo; Kaneshiro, Chinami; HiroshiOkada, HiroshiOkada; Hasegawa, Hideki

1999-04-01

Attempts were made to form regular arrays of size- andposition-controlled Pt-dots on GaAs and InP by combining an insitu electrochemical process with the electron beam (EB)lithography. This utilizes the precipitation of Pt nano-particles atthe initial stage of electrodeposition. First, electrochemicalconditions were optimized in the mode of self-assembled dot arrayformation on unpatterned substrates. Minimum in-plane dot diameters of22 nm and 26 nm on GaAs and InP, respectively, were obtained underthe optimal pulsed mode. Then, Pt dots were selectively formed onpatterned substrates with open circular windows formed by EBlithography, thereby realizing dot-position control. The Pt dot wasfound to have been deposited at the center of each open window, andthe in-plane diameter of the dot could be controlled by the number,width and period of the pulse-waveform applied to substrates. Aminimum diameter of 20 nm was realized in windows with a diameter of100 nm, using a single pulse. Current-voltage (I-V)measurements using an atomic force microscopy (AFM) system with aconductive probe indicated that each Pt dot/n-GaAs contact possessed ahigh Schottky barrier height of about 1 eV.

Photofragment slice imaging studies of pyrrole and the Xe{center_dot}{center_dot}{center_dot}pyrrole cluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubio-Lago, L.; Zaouris, D.; Sakellariou, Y.

The photolysis of pyrrole has been studied in a molecular beam at wavelengths of 250, 240, and 193.3 nm, using two different carrier gases, He and Xe. A broad bimodal distribution of H-atom fragment velocities has been observed at all wavelengths. Near threshold at both 240 and 250 nm, sharp features have been observed in the fast part of the H-atom distribution. Under appropriate molecular beam conditions, the entire H-atom loss signal from the photolysis of pyrrole at both 240 and 250 nm (including the sharp features) disappear when using Xe as opposed to He as the carrier gas. Wemore » attribute this phenomenon to cluster formation between Xe and pyrrole, and this assumption is supported by the observation of resonance enhanced multiphoton ionization spectra for the (Xe{center_dot}{center_dot}{center_dot}pyrrole) cluster followed by photofragmentation of the nascent cation cluster. Ab initio calculations are presented for the ground states of the neutral and cationic (Xe{center_dot}{center_dot}{center_dot}pyrrole) clusters as a means of understanding their structural and energetic properties.« less

Investigation of trypsin-CdSe quantum dot interactions via spectroscopic methods and effects on enzymatic activity.

PubMed

Kaur, Gurvir; Tripathi, S K

2015-01-05

The paper presents the interactions between trypsin and water soluble cadmium selenide (CdSe) quantum dots investigated by spectrophotometric methods. CdSe quantum dots have strong ability to quench the intrinsic fluorescence of trypsin by a static quenching mechanism. The quenching has been studied at three different temperatures where the results revealed that electrostatic interactions exist between CdSe quantum dots and trypsin and are responsible to stabilize the complex. The Scatchard plot from quenching revealed 1 binding site for quantum dots by trypsin, the same has been confirmed by making isothermal titrations of quantum dots against trypsin. The distance between donor and acceptor for trypsin-CdSe quantum dot complexes is calculated to be 2.8 nm by energy transfer mechanisms. The intrinsic fluorescence of CdSe quantum dots has also been enhanced by the trypsin, and is linear for concentration of trypsin ranging 1-80 μl. All the observations evidence the formation of trypsin-CdSe quantum dot conjugates, where trypsin retains the enzymatic activity which in turn is temperature and pH dependent. Copyright © 2014 Elsevier B.V. All rights reserved.

Complementarity determining regions and frameworks contribute to the disulfide bond independent folding of intrinsically stable scFv

PubMed Central

Gąciarz, Anna

2017-01-01

CyDisCo is a system facilitating disulfide bond formation in recombinant proteins in the cytoplasm of Escherichia coli. Previously we screened for soluble expression of single chain antibody fragments (scFv) in the cytoplasm of E. coli in the presence and absence of CyDisCo, with >90% being solubly expressed. Two scFv, those derived from natalizumab and trastuzumab, were solubly produced in high amounts even in the absence of folding catalysts i.e. disulfide bond formation is not critical for their folding. Here we investigate the contribution of the framework and the complementarity determining regions (CDRs) of scFv to the disulfide-independence of folding. We swapped CDRs between four scFv that have different properties, including two scFv that can efficiently fold independently from disulfide bonds and two more disulfide-dependent scFv. To confirm disulfide-independence we generated cysteine to alanine mutants of the disulfide-independent scFv. All of the scFv were tested for soluble expression in the cytoplasm of E. coli in the presence and absence of the oxidative folding catalysts Erv1p and PDI. Eight of the hybrid scFv were solubly produced in the presence of CyDisCo, while seven were solubly produced in the absence of CyDisCo, though the yields were often much lower when CyDisCo was absent. Soluble expression was also observed for scFv natalizumab and trastuzumab containing no cysteines. We compared yields, thermal stability and secondary structure of solubly produced scFv and undertook binding studies by western blotting, dot blotting or surface plasmon resonance of those produced in good yields. Our results indicate that both the CDRs and the framework contribute to the disulfide-dependence of soluble production of scFv, with the CDRs having the largest effect. In addition, there was no correlation between thermal stability and disulfide-dependence of folding and only a weak correlation between the yield of protein and the thermal stability of the protein. PMID:29253024

Complementarity determining regions and frameworks contribute to the disulfide bond independent folding of intrinsically stable scFv.

PubMed

Gąciarz, Anna; Ruddock, Lloyd W

2017-01-01

CyDisCo is a system facilitating disulfide bond formation in recombinant proteins in the cytoplasm of Escherichia coli. Previously we screened for soluble expression of single chain antibody fragments (scFv) in the cytoplasm of E. coli in the presence and absence of CyDisCo, with >90% being solubly expressed. Two scFv, those derived from natalizumab and trastuzumab, were solubly produced in high amounts even in the absence of folding catalysts i.e. disulfide bond formation is not critical for their folding. Here we investigate the contribution of the framework and the complementarity determining regions (CDRs) of scFv to the disulfide-independence of folding. We swapped CDRs between four scFv that have different properties, including two scFv that can efficiently fold independently from disulfide bonds and two more disulfide-dependent scFv. To confirm disulfide-independence we generated cysteine to alanine mutants of the disulfide-independent scFv. All of the scFv were tested for soluble expression in the cytoplasm of E. coli in the presence and absence of the oxidative folding catalysts Erv1p and PDI. Eight of the hybrid scFv were solubly produced in the presence of CyDisCo, while seven were solubly produced in the absence of CyDisCo, though the yields were often much lower when CyDisCo was absent. Soluble expression was also observed for scFv natalizumab and trastuzumab containing no cysteines. We compared yields, thermal stability and secondary structure of solubly produced scFv and undertook binding studies by western blotting, dot blotting or surface plasmon resonance of those produced in good yields. Our results indicate that both the CDRs and the framework contribute to the disulfide-dependence of soluble production of scFv, with the CDRs having the largest effect. In addition, there was no correlation between thermal stability and disulfide-dependence of folding and only a weak correlation between the yield of protein and the thermal stability of the protein.

Comparative analysis of germanium-silicon quantum dots formation on Si(100), Si(111) and Sn/Si(100) surfaces

NASA Astrophysics Data System (ADS)

Lozovoy, Kirill; Kokhanenko, Andrey; Voitsekhovskii, Alexander

2018-02-01

In this paper theoretical modeling of formation and growth of germanium-silicon quantum dots in the method of molecular beam epitaxy (MBE) on different surfaces is carried out. Silicon substrates with crystallographic orientations (100) and (111) are considered. Special attention is paid to the question of growth of quantum dots on the silicon surface covered by tin, since germanium-silicon-tin system is extremely important for contemporary nano- and optoelectronics: for creation of photodetectors, solar cells, light-emitting diodes, and fast-speed transistors. A theoretical approach for modeling growth processes of such semiconductor compounds during the MBE is presented. Both layer-by-layer and island nucleation stages in the Stranski-Krastanow growth mode are described. A change in free energy during transition of atoms from the wetting layer to an island, activation barrier of the nucleation, critical thickness of 2D to 3D transition, as well as surface density and size distribution function of quantum dots in these systems are calculated with the help of the established model. All the theoretical speculations are carried out keeping in mind possible device applications of these materials. In particular, it is theoretically shown that using of the Si(100) surface covered by tin as a substrate for Ge deposition may be very promising for increasing size homogeneity of quantum dot array for possible applications in low-noise selective quantum dot infrared photodetectors.

Comparative analysis of germanium-silicon quantum dots formation on Si(100), Si(111) and Sn/Si(100) surfaces.

PubMed

Lozovoy, Kirill; Kokhanenko, Andrey; Voitsekhovskii, Alexander

2018-02-02

In this paper theoretical modeling of formation and growth of germanium-silicon quantum dots in the method of molecular beam epitaxy (MBE) on different surfaces is carried out. Silicon substrates with crystallographic orientations (100) and (111) are considered. Special attention is paid to the question of growth of quantum dots on the silicon surface covered by tin, since germanium-silicon-tin system is extremely important for contemporary nano- and optoelectronics: for creation of photodetectors, solar cells, light-emitting diodes, and fast-speed transistors. A theoretical approach for modeling growth processes of such semiconductor compounds during the MBE is presented. Both layer-by-layer and island nucleation stages in the Stranski-Krastanow growth mode are described. A change in free energy during transition of atoms from the wetting layer to an island, activation barrier of the nucleation, critical thickness of 2D to 3D transition, as well as surface density and size distribution function of quantum dots in these systems are calculated with the help of the established model. All the theoretical speculations are carried out keeping in mind possible device applications of these materials. In particular, it is theoretically shown that using of the Si(100) surface covered by tin as a substrate for Ge deposition may be very promising for increasing size homogeneity of quantum dot array for possible applications in low-noise selective quantum dot infrared photodetectors.

Ferulic acid enhances IgE binding to peanut allergens in western blots.

USDA-ARS?s Scientific Manuscript database

Phenolic compounds at high concentrations are known to form insoluble complexes with proteins. We hypothesized that this complex formation could interfere with Western blot and ELISA assays for peanut allergens. To verify this, three simple phenolic compounds (ferulic, caffeic, and chlorogenic acids...

Making The Invisible Visible

NASA Technical Reports Server (NTRS)

1978-01-01

In public and private archives throughout the world there are many historically important documents that have become illegible with the passage of time. They have faded, been erased, acquired mold, water and dirt stain, suffered blotting or lost readability in other ways. While ultraviolet and infrared photography are widely used to enhance deteriorated legibility, these methods are more limited in their effectiveness than the space-derived image enhancement technique. The aim of the JPL effort with Caltech and others is to better define the requirements for a system to restore illegible information for study at a low page-cost with simple operating procedures. The investigators' principle tools are a vidicon camera and an image processing computer program, the same equipment used to produce sharp space pictures. The camera is the same type as those on NASA's Mariner spacecraft which returned to Earth thousands of images of Mars, Venus and Mercury. Space imagery works something like television. The vidicon camera does not take a photograph in the ordinary sense; rather it "scans" a scene, recording different light and shade values which are reproduced as a pattern of dots, hundreds of dots to a line, hundreds of lines in the total picture. The dots are transmitted to an Earth receiver, where they are assembled line by line to form a picture like that on the home TV screen.

Correlative Light- and Electron Microscopy Using Quantum Dot Nanoparticles.

PubMed

Killingsworth, Murray C; Bobryshev, Yuri V

2016-08-07

A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of human pathology tissue using widefield fluorescence light microscopy and transmission electron microscopy (TEM). To demonstrate the protocol we have immunolabeled ultrathin epoxy sections of human somatostatinoma tumor using a primary antibody to somatostatin, followed by a biotinylated secondary antibody and visualization with streptavidin conjugated 585 nm cadmium-selenium (CdSe) quantum dots (QDs). The sections are mounted on a TEM specimen grid then placed on a glass slide for observation by widefield fluorescence light microscopy. Light microscopy reveals 585 nm QD labeling as bright orange fluorescence forming a granular pattern within the tumor cell cytoplasm. At low to mid-range magnification by light microscopy the labeling pattern can be easily recognized and the level of non-specific or background labeling assessed. This is a critical step for subsequent interpretation of the immunolabeling pattern by TEM and evaluation of the morphological context. The same section is then blotted dry and viewed by TEM. QD probes are seen to be attached to amorphous material contained in individual secretory granules. Images are acquired from the same region of interest (ROI) seen by light microscopy for correlative analysis. Corresponding images from each modality may then be blended to overlay fluorescence data on TEM ultrastructure of the corresponding region.

Spatial distribution of osteoblast activating peptide in the rat stomach.

PubMed

Noreldin, Ahmed E; Sogabe, Maina; Yamano, Yoshiaki; Uehara, Masato; Mahdy, Mohamed A A; Elnasharty, Mohamed A; Sayed-Ahmed, Ahmed; Warita, Katsuhiko; Hosaka, Yoshinao Z

2016-03-01

Osteoblast activating peptide (OBAP) was previously reported to be expressed in the rat stomach and to have a vital role in osteogenesis, but its distribution in rat stomach has not been determined. Thus, the aim of the present study was to identify the cell types expressing OBAP in the rat stomach. The stomachs of twelve 10-to-11-week-old male Jc1:SD rats were used. Samples were collected for immunohistochemistry, immunoelectron microscopy and dot blot assay. Immunohistochemical investigation revealed that OBAP was distributed mainly in parietal cells without any expression in chief cells, X/A-like cells or enterochromaffin-like cells. Moreover, OBAP-immunopositive cells were observed mainly in the upper and lower parts of the gastric gland. Significantly high optical density of immunopositive cells was observed in the upper and lower gastric gland regions. The dot blot assay confirmed that OBAP is secreted by parietal cells and that it is present in the gastric gland lumen. Immunoelectron microscopy demonstrated that OBAP was confined to the mitochondrial inner membrane within parietal cells and that the number of mitochondria in the upper and lower parts of the gastric epithelium was significantly larger than the number in the middle part of the gastric epithelium. Based on the results, it was concluded that OBAP is mainly produced by mitochondria of parietal cells in the upper and lower parts of the gastric epithelium. Moreover, the presence of OBAP in the gastric gland lumen suggests an exocrine mechanism of release. Copyright © 2015 Elsevier GmbH. All rights reserved.

Fructose 1,6-Bisphosphate Aldolase, a Novel Immunogenic Surface Protein on Listeria Species

PubMed Central

Conceição, Fabricio Rochedo; Hust, Michael; Mendonça, Karla Sequeira; Moreira, Ângela Nunes; França, Rodrigo Correa; da Silva, Wladimir Padilha; Aleixo, José Antonio G.

2016-01-01

Listeria monocytogenes is a ubiquitous food-borne pathogen, and its presence in food or production facilities highlights the importance of surveillance. Increased understanding of the surface exposed antigens on Listeria would provide potential diagnostic and therapeutic targets. In the present work, using mass spectrometry and genetic cloning, we show that fructose-1,6-bisphosphate aldolase (FBA) class II in Listeria species is the antigen target of the previously described mAb-3F8. Western and dot blot assays confirmed that the mAb-3F8 could distinguish all tested Listeria species from close-related bacteria. Localization studies indicated that FBA is present in every fraction of Listeria cells, including supernatant and the cell wall, setting Listeria spp. as one of the few bacteria described to have this protein on their cell surface. Epitope mapping using ORFeome display and a peptide membrane revealed a 14-amino acid peptide as the potential mAb-3F8 epitope. The target epitope in FBA allowed distinguishing Listeria spp. from closely-related bacteria, and was identified as part of the active site in the dimeric enzyme. However, its function in cell surface seems not to be host cell adhesion-related. Western and dot blot assays further demonstrated that mAb-3F8 together with anti-InlA mAb-2D12 could differentiate pathogenic from non-pathogenic Listeria isolated from artificially contaminated cheese. In summary, we report FBA as a novel immunogenic surface target useful for the detection of Listeria genus. PMID:27489951

Cloning and characterization of profilin (Pru du 4), a cross-reactive almond (Prunus dulcis) allergen.

PubMed

Tawde, Pallavi; Venkatesh, Yeldur P; Wang, Fang; Teuber, Suzanne S; Sathe, Shridhar K; Roux, Kenneth H

2006-10-01

The identity of allergenic almond proteins is incomplete. Our objective was to characterize patient IgE reactivity to a recombinant and corresponding native almond allergen. An almond cDNA library was screened with sera from patients with allergy for IgE binding proteins. Two reactive clones were sequenced, and 1 was expressed. The expressed recombinant allergen and its native counterpart (purified from unprocessed almond flour) were assayed by 1-dimensional and 2-dimensional gel electrophoresis, dot blot, and ELISA, and screened for cross-reactivity with grass profilin. The 2 selected clones encoded profilin (designated Pru du 4) sequences that differed by 2 silent mutations. By dot-blot analyses, 6 of 18 patient sera (33%) reacted with the recombinant Pru du 4 protein, and 8 of 18 (44%) reacted with the native form. ELISA results were similar. Almond and ryegrass profilins were mutually inhibitable. Two-dimensional immunoblotting revealed the presence of more than 1 native almond profilin isoform. The strength of reactivity of some patients' serum IgE differed markedly between assays and between native and recombinant profilins. Almond nut profilin is an IgE-binding food protein that is cross-reactive with grass pollen profilin and is susceptible to denaturation, resulting in variable reactivity between assay types and between patients. Serum IgE of nearly half of the tested patients with almond allergy reacts with almond nut profilin. Because most patients also had pollinosis, the well-known cross-reactivity between pollen and food profilins could account for this pattern of reactivity.

Cloning and characterization of 2S albumin, Car i 1, a major allergen in pecan.

PubMed

Sharma, Girdhari M; Irsigler, Andre; Dhanarajan, Pushparani; Ayuso, Rosalia; Bardina, Luda; Sampson, Hugh A; Roux, Kenneth H; Sathe, Shridhar K

2011-04-27

Although pecans are associated with IgE-mediated food allergies, the allergens responsible remain to be identified and characterized. The 2S albumin gene was amplified from the pecan cDNA library. Dot-blots were used to screen the recombinant protein with pecan allergic patients' serum. The affinity purified native protein was analyzed by Edman sequencing and mass spectrometry/mass spectrometry (MS/MS) analysis. Cross-reactivity with walnut was determined by inhibition enzyme-linked immunosorbent assay (ELISA). Sequential epitopes were determined by probing the overlapping peptides with three different patients' serum pool. The 3-dimensional homology model was generated, and the locations of the pecan epitopes were compared with those of known sequential epitopes on other allergenic tree nut homologues. Of 28 patients tested by dot-blot, 22 (79%) bound to 2S albumin, designated as Car i 1. Edman sequencing and the MS/MS sequencing of native 2S albumin confirmed the identity of recombinant (r) Car i 1. Both pecan and walnut protein extracts inhibited the IgE-binding to rCar i 1. Sequential epitope mapping indicated weak, moderate, and strong reactivity against 12, 7, and 5 peptides, respectively. Of the 11 peptides recognized by all serum pools, 5 peptides were strongly reactive and located in 3 discrete regions of the Car i 1 (amino acids 43-57, 67-78, and 106-120). Three-dimensional modeling revealed IgE-reactive epitopes to be solvent accessible and share significant homology with other tree nuts providing a possible basis for previously observed cross-reactivity.

Fructose 1,6-Bisphosphate Aldolase, a Novel Immunogenic Surface Protein on Listeria Species.

PubMed

Mendonça, Marcelo; Moreira, Gustavo Marçal Schmidt Garcia; Conceição, Fabricio Rochedo; Hust, Michael; Mendonça, Karla Sequeira; Moreira, Ângela Nunes; França, Rodrigo Correa; da Silva, Wladimir Padilha; Bhunia, Arun K; Aleixo, José Antonio G

2016-01-01

Listeria monocytogenes is a ubiquitous food-borne pathogen, and its presence in food or production facilities highlights the importance of surveillance. Increased understanding of the surface exposed antigens on Listeria would provide potential diagnostic and therapeutic targets. In the present work, using mass spectrometry and genetic cloning, we show that fructose-1,6-bisphosphate aldolase (FBA) class II in Listeria species is the antigen target of the previously described mAb-3F8. Western and dot blot assays confirmed that the mAb-3F8 could distinguish all tested Listeria species from close-related bacteria. Localization studies indicated that FBA is present in every fraction of Listeria cells, including supernatant and the cell wall, setting Listeria spp. as one of the few bacteria described to have this protein on their cell surface. Epitope mapping using ORFeome display and a peptide membrane revealed a 14-amino acid peptide as the potential mAb-3F8 epitope. The target epitope in FBA allowed distinguishing Listeria spp. from closely-related bacteria, and was identified as part of the active site in the dimeric enzyme. However, its function in cell surface seems not to be host cell adhesion-related. Western and dot blot assays further demonstrated that mAb-3F8 together with anti-InlA mAb-2D12 could differentiate pathogenic from non-pathogenic Listeria isolated from artificially contaminated cheese. In summary, we report FBA as a novel immunogenic surface target useful for the detection of Listeria genus.

Biosafety of parenteral Brucella abortus RB51 vaccine in bison calves

USGS Publications Warehouse

Roffe, T.J.; Olsen, S.C.; Gidlewski, T.; Jensen, A.E.; Palmer, M.V.; Huber, R.

1999-01-01

Vaccination is considered among the primary management tools for reducing brucellosis prevalence in Greater Yellowstone Area (GYA) ungulates. Before their use, however, vaccine safety and efficacy must be demonstrated. Twenty-seven female bison (Bison bison) calves (approx 5 months old) were vaccinated with Brucella abortus Strain RB51 (1.5 x 1010 colony forming units [CFU], subcutaneously) as part of routine management. We assessed the persistence, pathology, shedding, and transmission associated with RB51 by serial necropsy, bacteriology, histopathology, and serology of 20 of these 27 vaccinated calves, and RB51 serology of 10 nonvaccinated, commingling adult females. With the exception of 1 calf, RB51 dot-blot titers at necropsy were <1:80. Strain RB51 was cultured from lymph nodes in 4 of 4 calves at 14 weeks postvaccination (PV), 4 of 4 calves at 18 weeks PV, 1 of 4 calves at 22 weeks PV, 3 of 4 at 26 weeks PV, and 0 of 4 calves at 30 weeks PV. No gross lesions were observed. Mild histologic changes occurred only in a few draining lymph nodes early in sampling. Adverse clinical effects were not observed in vaccinates. Swabs from nasopharynx, conjunctiva, rectum, and vagina were uniformly culture negative for RB51. Strain RB51 dot-blot assays of bison cows were negative at a 1:20 dilution at 26 weeks PV. Our results suggest that RB51 persists longer in bison calves than in domestic cattle and is systemically distributed within lymphatic tissues. However, bison apparently clear the RB51 vaccine strain without shedding, transmission, or significant adverse reactions.

Quantum dot impregnated-chitosan film for heavy metal ion sensing and removal.

PubMed

Jaiswal, Amit; Ghsoh, Siddhartha Sankar; Chattopadhyay, Arun

2012-11-06

We report the use of biopolymer-stabilized ZnS quantum dots (Q-dots) for cation exchange reaction-based easy sensing and removal of heavy metal ions such as Hg(2+), Ag(+), and Pb(2+) in water. Chitosan-stabilized ZnS Q-dots were synthesized in aqueous medium and were observed to have been converted to HgS, Ag(2)S, and PbS Q-dots in the presence of corresponding ions. The transformed Q-dots showed characteristic color development, with Hg(2+) being exceptionally identifiable due to the visible bright yellow color formation, while brown coloration was observed in other metal ions. The cation exchange was driven by the difference in the solubility product of the reactant and the product Q-dots. The cation exchanged Q-dots preserved the morphology of the reactant Q-dots and displayed volume increase based on the bulk crystal lattice parameters. The band gap of the transformed Q-dots showed a major increase from the corresponding bulk band gap of the material, demonstrating the role of quantum confinement. Next, we fabricated ZnS Q-dot impregnated chitosan film which was used to remove heavy metal ions from contaminated water as measured using atomic absorption spectroscopy (AAS). The present system could suitably be used as a simple dipstick for elimination of heavy metal ion contamination in water.

Femtosecond laser induced nanostructuring of graphite for the fabrication of quasi-periodic nanogratings and novel carbon nanostructures

NASA Astrophysics Data System (ADS)

Saikiran, V.; Dar, Mudasir H.; Rao, D. Narayana

2018-01-01

Here we have experimentally studied ultrafast femtosecond laser ablation of graphite in air and water environments for the fabrication of promising nanostructures on the graphite surface and also nanographite flakes, graphene quantum dots in water. After the fs laser irradiation in air quasi-periodic nanogratings were found on the graphite surface and when the irradiation is done in water we observed graphene quantum dots (GQDs) and graphitic flakes dispersed in the solution. The sheets consist of few layers of spongy kind of porous graphene, which form an irregular 3D porous structure. The field emission scanning electron microscopy reveals the formation of fluence dependent quasi-periodic deep-subwavelength nanogratings (Ʌ = 130-230 nm) on the surface. Several characterization methods have confirmed the formation of layered graphene and quantum dots. The studies on the solution confirmed the presence of GQDs with dimensions ranging about 2-4 nm. It is found that the formation of subwavelength structures and GQDs depends on the fs-laser energy and vary with different laser parameters such as fluence, energy, laser polarization.

Quantum Well and Quantum Dot Modeling for Advanced Infrared Detectors and Focal Plane Arrays

NASA Technical Reports Server (NTRS)

Ting, David; Gunapala, S. D.; Bandara, S. V.; Hill, C. J.

2006-01-01

This viewgraph presentation reviews the modeling of Quantum Well Infrared Detectors (QWIP) and Quantum Dot Infrared Detectors (QDIP) in the development of Focal Plane Arrays (FPA). The QWIP Detector being developed is a dual band detector. It is capable of running on two bands Long-Wave Infrared (LWIR) and Medium Wavelength Infrared (MWIR). The same large-format dual-band FPA technology can be applied to Quantum Dot Infrared Photodetector (QDIP) with no modification, once QDIP exceeds QWIP in single device performance. Details of the devices are reviewed.

Transient expression of CCL21as recombinant protein in tomato.

PubMed

Beihaghi, Maria; Marashi, Hasan; Bagheri, Abdolreza; Sankian, Mojtaba

2018-03-01

The main goal of this study was to investigate the possibility of expressing recombinant protein of C-C chemokine ligand 21 (CCL21) in Solanum lycopersicum via agroinfiltration. CCL21 is a chemokine can be used for anti-metastatic of cancer cell lines. To examine the expression of CCL21 protein in S. lycopersicum , the construct of ccl21 was synthesized. This construct was cloned into pBI121 and the resulting CCL21 plasmid was agro-infiltrated into S. lycopersicum leaves. Within three days after infiltration, Expression of the foreign gene was confirmed by quantitative Real-time PCR. A recombinant CCL21 protein was immunogenically detected by western blot, dot blot and ELISA assay. And results showed that the foreign gene was expressed in the transformed leaves in high level. Also scratch assay was used to investigate the role of this protein in anti-metastatic function. The results demonstrated anti-metastatic of cancer cells in the presence of this protein.

Plastid genome structure and loss of photosynthetic ability in the parasitic genus Cuscuta.

PubMed

Revill, Meredith J W; Stanley, Susan; Hibberd, Julian M

2005-09-01

The genus Cuscuta (dodder) is composed of parasitic plants, some species of which appear to be losing the ability to photosynthesize. A molecular phylogeny was constructed using 15 species of Cuscuta in order to assess whether changes in photosynthetic ability and alterations in structure of the plastid genome relate to phylogenetic position within the genus. The molecular phylogeny provides evidence for four major clades within Cuscuta. Although DNA blot analysis showed that Cuscuta species have smaller plastid genomes than tobacco, and that plastome size varied significantly even within one Cuscuta clade, dot blot analysis indicated that the dodders possess homologous sequence to 101 genes from the tobacco plastome. Evidence is provided for significant rates of DNA transfer from plastid to nucleus in Cuscuta. Size and structure of Cuscuta plastid genomes, as well as photosynthetic ability, appear to vary independently of position within the phylogeny, thus supporting the hypothesis that within Cuscuta photosynthetic ability and organization of the plastid genome are changing in an unco-ordinated manner.

Optical and structural properties of ensembles of colloidal Ag{sub 2}S quantum dots in gelatin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ovchinnikov, O. V., E-mail: Ovchinnikov-O-V@rambler.ru; Smirnov, M. S.; Shapiro, B. I.

2015-03-15

The size dependences of the absorption and luminescence spectra of ensembles of hydrophilic colloidal Ag{sub 2}S quantum dots produced by the sol-gel method and dispersed in gelatin are analyzed. By X-ray diffraction analysis and transmission electron microscopy, the formation of core/shell nanoparticles is detected. The characteristic feature of the nanoparticles is the formation of crystalline cores, 1.5–2.0 nm in dimensions, and shells of gelatin and its complexes with the components of synthesis. The observed slight size dependence of the position of infrared photoluminescence bands (in the range 1000–1400 nm) in the ensembles of hydrophilic colloidal Ag{sub 2}S quantum dots ismore » explained within the context of the model of the radiative recombination of electrons localized at structural and impurity defects with free holes.« less

The (Un)Lonely Planet Guide: Formation and Evolution of Planetary Systems from a ``Blue Dots'' Perspective

NASA Astrophysics Data System (ADS)

Meyer, M. R.

2010-10-01

In this contribution I summarize some recent successes, and focus on remaining challenges, in understanding the formation and evolution of planetary systems in the context of the Blue Dots initiative. Because our understanding is incomplete, we cannot yet articulate a design reference mission engineering matrix suitable for an exploration mission where success is defined as obtaining a spectrum of a potentially habitable world around a nearby star. However, as progress accelerates, we can identify observational programs that would address fundamental scientific questions through hypothesis testing such that the null result is interesting.

Biological sensing and control of emission dynamics of quantum dot bioconjugates using arrays of long metallic nanorods.

PubMed

Sadeghi, Seyed M; Gutha, Rithvik R; Wing, Waylin J; Sharp, Christina; Capps, Lucas; Mao, Chuanbin

2017-01-01

We study biological sensing using plasmonic and photonic-plasmonic resonances of arrays of ultralong metallic nanorods and analyze the impact of these resonances on emission dynamics of quantum dot bioconjugates. We demonstrate that the LSPRs and plasmonic lattice modes of such array can be used to detect a single self-assembled monolayer of alkanethiol at the visible (550 nm) and near infrared (770 nm) range with well resolved shifts. We study adsorption of streptavidin-quantum dot conjugates to this monolayer, demonstrating that formation of nearly two dimensional arrays of quantum dots with limited emission blinking can lead to extra well-defined wavelength shifts in these modes. Using spectrally-resolved lifetime measurements we study the emission dynamics of such quantum dot bioconjugates within their monodispersed size distribution. We show that, despite their close vicinity to the nanorods, the rate of energy transfer from these quantum dots to nanorods is rather weak, while the plasmon field enhancement can be strong. Our results reveal that the nanorods present a strongly wavelength or size-dependent non-radiative decay channel to the quantum dot bioconjugates.

Pistachio vicilin, Pis v 3, is immunoglobulin E-reactive and cross-reacts with the homologous cashew allergen, Ana o 1.

PubMed

Willison, L N; Tawde, P; Robotham, J M; Penney, R M; Teuber, S S; Sathe, S K; Roux, K H

2008-07-01

Patients allergic to cashew nuts often report allergy to pistachio, which could be a result of cross-reactivity between the two as both are members of the Anacardiaceae family. Because cashew 7S globulin (vicilin, Ana o 1) is a recognized major allergen, we cloned the pistachio homologue and assayed it for IgE reactivity and cross-reactivity with Ana o 1. Degenerate primers for 7S globulin were used in PCR to amplify DNA from a pistachio cDNA library. An isolate was sequenced, cloned and expressed in Escherichia coli. Reactivity to the allergen was screened by dot blot using 19 pistachio and/or cashew-allergic patients' sera. Cross-reactivity was investigated by inhibition dot- and Western immunoblot assays using pistachio/cashew-allergic patients' sera, and monoclonal antibodies (MAbs) raised against recombinant Ana o 1 (rAna o 1). An isolate was found that coded for a 7S vicilin-like protein, designated Pis v 3. IgE reactivity to Pis v 3 was found in the serum of seven of the 19 (37%) patients with histories of allergy to both pistachio and cashew or who were allergic to cashew but had never eaten pistachio. The seven patients with IgE that recognized rPis v 3 also recognized rAna o 1. Six of nine anti-rAna o 1 MAbs also showed reactivity to rPis v 3 on dot blots. Of the 37% of pistachio/cashew-allergic patients' sera that recognized the pistachio allergen, rPis v 3, all showed complete cross-reactivity with rAna o 1. The data does not identify the primary sensitizing agent but suggests that IgE reactivity to rPis v 3 and rAna o 1 is focused on the most conserved regions of the proteins. Clinical histories suggest that in some cases, cashew was the sensitizing agent. rPis v 3 is a likely contributor to the observed co-sensitivity to pistachio and cashew in some patients.

Effects of multiple organic ligands on size uniformity and optical properties of ZnSe quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archana, J., E-mail: archana.jayaram@yahoo.com; Navaneethan, M.; Hayakawa, Y.

2012-08-15

Highlights: ► Highly monodispersed ZnSe quantum dots have been synthesized by wet chemical route. ► Strong quantum confinement effect have been observed in ∼ 4 nm ZnSe quantum dots. ► Enhanced ultraviolet near band emission have been obtained using long chain polymer. -- Abstract: The effects of multi-ligands on the formation and optical transitions of ZnSe quantum dots have been investigated. The dots are synthesized using 3-mercapto-1,2-propanediol and polyvinylpyrrolidone ligands, and have been characterized by X-ray diffraction, transmission electron microscopy (TEM), UV–visible absorption spectroscopy, photoluminescence spectroscopy, and Fourier transform infrared spectroscopy. TEM reveals high monodispersion with an average size ofmore » 4 nm. Polymer-stabilized, organic ligand-passivated ZnSe quantum dots exhibit strong UV emission at 326 nm and strong quantum confinement in the UV–visible absorption spectrum. Uniform size and suppressed surface trap emission are observed when the polymer ligand is used. The possible growth mechanism is discussed.« less

Resonant energy transfer and trace-level sensing using branched Ag-rod-supported carbon dots

NASA Astrophysics Data System (ADS)

Nair, Radhika V.; Arya, M.; Vijayan, C.

2018-05-01

We report on the resonant energy transfer in branched Ag rod-supported carbon dots (C-dots) and its applications for the trace-level sensing of highly reactive oxygen species and organic pollutants based on surface plasmon enhanced energy transfer (SPEET) and surface enhanced Raman spectroscopy (SERS). The branched morphology of Ag is found to significantly enhance visible light absorption and thus increases the spectral overlap with C-dot emission. In addition, branched morphology results in the formation of a large number of plasmonic hotspots and efficient propagation of plasmons through the interconnections, as also supported by finite-difference time-domain simulations. Branched Ag-rod—C-dot composite is found to be able to detect 0.02 µM of hydrogen peroxide based on SPEET. The efficient transfer of electrons from C-dots to the Ag rod enhances the SERS efficiency of Ag resulting in an enhancement factor of the order of 108 and enables the composite to detect 10‑10 M of the organic pollutant Rhodamine 6G.

The diskmass survey. VIII. On the relationship between disk stability and star formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westfall, Kyle B.; Verheijen, Marc A. W.; Andersen, David R.

2014-04-10

We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability parameter from Romeo and Wiegert (Q {sub RW}), incorporating stellar kinematic data for the first time, and the star-formation rate estimated from 21 cm continuum emission. We determine the stability level of each disk probabilistically using a Bayesian analysis of our data and a simple dynamical model. Our method incorporates the shape of the stellar velocity ellipsoid (SVE) and yields robust SVE measurements for over 90% of our sample. Averagingmore » over this subsample, we find a meridional shape of σ{sub z}/σ{sub R}=0.51{sub −0.25}{sup +0.36} for the SVE and, at 1.5 disk scale lengths, a stability parameter of Q {sub RW} = 2.0 ± 0.9. We also find that the disk-averaged star-formation-rate surface density ( Σ-dot {sub e,∗}) is correlated with the disk-averaged gas and stellar mass surface densities (Σ {sub e,} {sub g} and Σ {sub e,} {sub *}) and anti-correlated with Q {sub RW}. We show that an anti-correlation between Σ-dot {sub e,∗} and Q {sub RW} can be predicted using empirical scaling relations, such that this outcome is consistent with well-established statistical properties of star-forming galaxies. Interestingly, Σ-dot {sub e,∗} is not correlated with the gas-only or star-only Toomre parameters, demonstrating the merit of calculating a multi-component stability parameter when comparing to star-formation activity. Finally, our results are consistent with the Ostriker et al. model of self-regulated star-formation, which predicts Σ-dot {sub e,∗}/Σ{sub e,g}∝Σ{sub e,∗}{sup 1/2}. Based on this and other theoretical expectations, we discuss the possibility of a physical link between disk stability level and star-formation rate in light of our empirical results.« less

Carbon nanodots prepared from o-phenylenediamine for sensing of Cu2+ ions in cells

NASA Astrophysics Data System (ADS)

Vedamalai, Mani; Periasamy, Arun Prakash; Wang, Chia-Wei; Tseng, Yu-Ting; Ho, Lin-Chen; Shih, Chung-Chien; Chang, Huan-Tsung

2014-10-01

A simple hydrothermal method was applied to prepare carbon nanodots (C dots) from o-phenylenediamine (OPD). The C dots exhibit photoluminescence at 567 nm when excited at 420 nm. In the presence of Cu2+ ions, the colour of C dots changes from yellow to orange, with an increased PL intensity as a result of the formation of Cu(OPD)2 complexes on the surfaces of C dots. The D-band to G-band ratios of C dots in the absence and presence of 80 nM Cu2+ ions are 1.31 and 4.75, respectively. The C dots allow the detection of Cu2+ ions with linearity over a concentration range of 2-80 nM, with a limit of detection of 1.8 nM at a signal-to-noise ratio of 3. The cell viability values of A549, MCF-10A, and MDA-MB-231 cells treated with 3 μg mL-1 of C dots are all greater than 99%, showing their great biocompatibility. Having great water dispersibility, photostability, chemical stability (against NaCl up to 0.5 M), great selectivity, and biocompatibility, the C dots have been employed for the localization of Cu2+ ions in the cancer cells (A549 cells) treated with 10 μM Cu2+ ions.A simple hydrothermal method was applied to prepare carbon nanodots (C dots) from o-phenylenediamine (OPD). The C dots exhibit photoluminescence at 567 nm when excited at 420 nm. In the presence of Cu2+ ions, the colour of C dots changes from yellow to orange, with an increased PL intensity as a result of the formation of Cu(OPD)2 complexes on the surfaces of C dots. The D-band to G-band ratios of C dots in the absence and presence of 80 nM Cu2+ ions are 1.31 and 4.75, respectively. The C dots allow the detection of Cu2+ ions with linearity over a concentration range of 2-80 nM, with a limit of detection of 1.8 nM at a signal-to-noise ratio of 3. The cell viability values of A549, MCF-10A, and MDA-MB-231 cells treated with 3 μg mL-1 of C dots are all greater than 99%, showing their great biocompatibility. Having great water dispersibility, photostability, chemical stability (against NaCl up to 0.5 M), great selectivity, and biocompatibility, the C dots have been employed for the localization of Cu2+ ions in the cancer cells (A549 cells) treated with 10 μM Cu2+ ions. Electronic supplementary information (ESI) available: XRD, FTIR, absorption, Raman scattering, fluorescence spectra, the effect of pH, photostability and cell viability results. See DOI: 10.1039/c4nr03213f

Distribution of HLA-DQA1 alleles in Arab and Pakistani individuals from Dubai, United Arab Emirates.

PubMed

Tahir, M A; al Khayat, A Q; al Shamali, F; Budowle, B; Novick, G E

1997-03-14

PCR-based typing of the HLA-DQA1 locus, using allele specific oligonucleotide (ASO) probes and reverse dot blot methodology was used to determine allelic distributions and construct a database for Arab and Pakistani individuals living in Dubai. Genotype and allelic frequencies were calculated, and the data were tested for departures from Hardy-Weinberg (HWE) equilibrium. The most frequent HLA-DQA1 alleles among Dubaian Arabs are DQA1 4 and 1.2. Among Pakistanis, the most frequent allele is also DQA1 4. No significant deviations from HWE were detected.

Identifying members of the domain Archaea with rRNA-targeted oligonucleotide probes.

PubMed

Burggraf, S; Mayer, T; Amann, R; Schadhauser, S; Woese, C R; Stetter, K O

1994-09-01

Two 16S rRNA-targeted oligonucleotide probes were designed for the archaeal kingdoms Euryachaeota and Crenarchaeota. Probe specificities were evaluated by nonradioactive dot blot hybridization against selected reference organisms. The successful application of fluorescent-probe derivatives for whole-cell hybridization required organism-specific optimizations of fixation and hybridization conditions to assure probe penetration and morphological integrity of the cells. The probes allowed preliminary grouping of three new hyperthermophilic isolates. Together with other group-specific rRNA-targeted oligonucleotide probes, these probes will facilitate rapid in situ monitoring of the populations present in hydrothermal systems and support cultivation attempts.

In situ growth of ceramic quantum dots in polyaniline host via water vapor flow diffusion as potential electrode materials for energy applications

NASA Astrophysics Data System (ADS)

Mombrú, Dominique; Romero, Mariano; Faccio, Ricardo; Castiglioni, Jorge; Mombrú, Alvaro W.

2017-06-01

In situ preparation of polyaniline-ceramic nanocomposites has recently demonstrated that the electrical properties are highly improved with respect to the typical ex situ preparations. In this report, we present for the first time, to the best of our knowledge, the in situ growth of titanium oxide quantum dots in polyaniline host via water vapor flow diffusion as an easily adaptable route to prepare other ceramic-polymer nanocomposites. The main relevance of this method is the possibility to prepare ceramic quantum dots from alkoxide precursors using water vapor flow into any hydrophobic polymer host and to achieve good homogeneity and size-control. In addition, we perform full characterization by means of high-resolution transmission electron microscopy, X-ray powder diffraction, small angle X-ray scattering, thermogravimetric and calorimetric analyses, confocal Raman microscopy and impedance spectroscopy analyses. The presence of the polymer host and interparticle Coulomb repulsive interactions was evaluated as an influence for the formation of 3-8 nm equally-sized quantum dots independently of the concentration. The polyaniline polaron population showed an increase for the quantum dots diluted regime and the suppression at the concentrated regime, ascribed to the formation of chemical bonds at the interface, which was confirmed by theoretical simulations. In agreement with the previous observation, the in situ growth of ceramic quantum dots in polyaniline host via water vapor flow diffusion could be very useful as a novel approach to prepare electrode materials for energy conversion and storage applications.

Studies of silicon quantum dots prepared at different substrate temperatures

NASA Astrophysics Data System (ADS)

Al-Agel, Faisal A.; Suleiman, Jamal; Khan, Shamshad A.

2017-03-01

In this research work, we have synthesized silicon quantum dots at different substrate temperatures 193, 153 and 123 K at a fixed working pressure 5 Torr. of Argon gas. The structural studies of these silicon quantum dots have been undertaken using X-ray diffraction, Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM). The optical and electrical properties have been studied using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Fluorescence spectroscopy and I-V measurement system. X-ray diffraction pattern of Si quantum dots prepared at different temperatures show the amorphous nature except for the quantum dots synthesized at 193 K which shows polycrystalline nature. FESEM images of samples suggest that the size of quantum dots varies from 2 to 8 nm. On the basis of UV-visible spectroscopy measurements, a direct band gap has been observed for Si quantum dots. FTIR spectra suggest that as-grown Si quantum dots are partially oxidized which is due exposure of as-prepared samples to air after taking out from the chamber. PL spectra of the synthesized silicon quantum dots show an intense peak at 444 nm, which may be attributed to the formation of Si quantum dots. Temperature dependence of dc conductivity suggests that the dc conductivity enhances exponentially by raising the temperature. On the basis above properties i.e. direct band gap, high absorption coefficient and high conductivity, these silicon quantum dots will be useful for the fabrication of solar cells.

Low-density InP-based quantum dots emitting around the 1.5 μm telecom wavelength range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yacob, M.; Reithmaier, J. P.; Benyoucef, M., E-mail: m.benyoucef@physik.uni-kassel.de

The authors report on low-density InAs quantum dots (QDs) grown on AlGaInAs surfaces lattice matched to InP using post-growth annealing by solid-source molecular beam epitaxy. Clearly spatially separated QDs with a dot density of about 5 × 10{sup 8} cm{sup −2} are obtained by using a special capping technique after the dot formation process. High-resolution micro-photoluminescence performed on optimized QD structures grown on distributed Bragg reflector exhibits single QD emissions around 1.5 μm with narrow excitonic linewidth below 50 μeV, which can be used as single photon source in the telecom wavelength range.

Exciton dynamics in GaAs/(Al,Ga)As core-shell nanowires with shell quantum dots

NASA Astrophysics Data System (ADS)

Corfdir, Pierre; Küpers, Hanno; Lewis, Ryan B.; Flissikowski, Timur; Grahn, Holger T.; Geelhaar, Lutz; Brandt, Oliver

2016-10-01

We study the dynamics of excitons in GaAs/(Al,Ga)As core-shell nanowires by continuous-wave and time-resolved photoluminescence and photoluminescence excitation spectroscopy. Strong Al segregation in the shell of the nanowires leads to the formation of Ga-rich inclusions acting as quantum dots. At 10 K, intense light emission associated with these shell quantum dots is observed. The average radiative lifetime of excitons confined in the shell quantum dots is 1.7 ns. We show that excitons may tunnel toward adjacent shell quantum dots and nonradiative point defects. We investigate the changes in the dynamics of charge carriers in the shell with increasing temperature, with particular emphasis on the transfer of carriers from the shell to the core of the nanowires. We finally discuss the implications of carrier localization in the (Al,Ga)As shell for fundamental studies and optoelectronic applications based on core-shell III-As nanowires.

Metal-organic chemical vapor deposition of N-polar InN quantum dots and thin films on vicinal GaN

NASA Astrophysics Data System (ADS)

Lund, Cory; Catalano, Massimo; Wang, Luhua; Wurm, Christian; Mates, Thomas; Kim, Moon; Nakamura, Shuji; DenBaars, Steven P.; Mishra, Umesh K.; Keller, Stacia

2018-02-01

N-polar InN layers were deposited using MOCVD on GaN-on-sapphire templates which were miscut 4° towards the GaN m-direction. For thin layers, quantum dot-like features were spontaneously formed to relieve the strain between the InN and GaN layers. As the thickness was increased, the dots elongated along the step direction before growing outward perpendicular to the step direction and coalescing to form a complete InN layer. XRD reciprocal space maps indicated that the InN films relaxed upon quantum dot formation after nominally 1 nm thick growth, resulting in 5-7 nm tall dots with diameters around 20-50 nm. For thicker layers above 10 nm, high electron mobilities of up to 706 cm2/V s were measured using Hall effect measurements indicating high quality layers.

Studies of mist deposition for the formation of quantum dot CdSe films

NASA Astrophysics Data System (ADS)

Price, S. C.; Shanmugasundaram, K.; Ramani, S.; Zhu, T.; Zhang, F.; Xu, J.; Mohney, S. E.; Zhang, Q.; Kshirsagar, A.; Ruzyllo, J.

2009-10-01

Films of CdSe(ZnS) colloidal nanocrystalline quantum dots (NQDs) were deposited on bare silicon, glass and polymer coated silicon using mist deposition. This effort is a part of an exploratory investigation in which this deposition technique is studied for the first time as a method to form semiconductor NQD films. The process parameters, including deposition time, solution concentration and electric field, were varied to change the thickness of the deposited film. Blanket films and films deposited through a shadow mask were created to investigate the method's ability to pattern films during the deposition process. The differences between these deposition modes in terms of film morphology were observed. Overall, the results show that mist deposition of quantum dots is a viable method for creating thin, patterned quantum dot films using colloidal solution as the precursor. It is concluded that this technique shows very good promise for quantum dot (light emitting diode, LED) fabrication.

Growth and optical characteristics of InAs quantum dot structures with tunnel injection quantum wells for 1.55 μ m high-speed lasers

NASA Astrophysics Data System (ADS)

Bauer, Sven; Sichkovskyi, Vitalii; Reithmaier, Johann Peter

2018-06-01

InP based lattice matched tunnel injection structures consisting of a InGaAs quantum well, InAlGaAs barrier and InAs quantum dots designed to emit at 1.55 μ m were grown by molecular beam epitaxy and investigated by photoluminescence spectroscopy and atomic force microscopy. The strong influence of quantum well and barrier thicknesses on the samples emission properties at low and room temperatures was investigated. The phenomenon of a decreased photoluminescence linewidth of tunnel injection structures compared to a reference InAs quantum dots sample could be explained by the selection of the emitting dots through the tunneling process. Morphological investigations have not revealed any effect of the injector well on the dot formation and their size distribution. The optimum TI structure design could be defined.

Making comparative performance information more comprehensible: an experimental evaluation of the impact of formats on consumer understanding.

PubMed

Damman, Olga C; De Jong, Anco; Hibbard, Judith H; Timmermans, Danielle R M

2016-11-01

We aimed to investigate how different presentation formats influence comprehension and use of comparative performance information (CPI) among consumers. An experimental between-subjects and within-subjects design with manipulations of CPI presentation formats. We enrolled both consumers with lower socioeconomic status (SES)/cognitive skills and consumers with higher SES/cognitive skills, recruited through an online access panel. Respondents received fictitious CPI and completed questions about interpretation and information use. Between subjects, we tested (1) displaying an overall performance score (yes/no); (2) displaying a small number of quality indicators (5 vs 9); and (3) displaying different types of evaluative symbols (star ratings, coloured dots and word icons vs numbers and bar graphs). Within subjects, we tested the effect of a reduced number of healthcare providers (5 vs 20). Data were analysed using descriptive analysis, analyses of variance and paired-sampled t tests. A total of 902 (43%) respondents participated. Displaying an overall performance score and the use of coloured dots and word icons particularly enhanced consumer understanding. Importantly, respondents provided with coloured dots most often correctly selected the top three healthcare providers (84.3%), compared with word icons (76.6% correct), star ratings (70.6% correct), numbers (62.0%) and bars (54.2%) when viewing performance scores of 20 providers. Furthermore, a reduced number of healthcare providers appeared to support consumers, for example, when provided with 20 providers, 69.5% correctly selected the top three, compared with 80.2% with five providers. Particular presentation formats enhanced consumer understanding of CPI, most importantly the use of overall performance scores, word icons and coloured dots, and a reduced number of providers displayed. Public report efforts should use these formats to maximise impact on consumers. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Effect of the deposition of cobalt on the optoelectronic properties of quantum-confined In(Ga)As/GaAs heteronanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volkova, N. S., E-mail: volkovans88@mail.ru; Gorshkov, A. P.; Zdoroveyshchev, A. V.

2015-12-15

The systematic features of the inf luence of defect formation during the deposition of a cobalt contact on the optoelectronic characteristics of structures containing InAs/GaAs quantum dots and In{sub x}Ga{sub 1–x}As/GaAs quantum wells are studied. From analysis of the temperature dependences of the photosensitivity of the InAs/GaAs quantum-dot structures, the values of the resultant recombination lifetime of photoexcited charge carriers in quantum dots at different conditions of Co deposition and at different structural parameters are determined.

Bacteria-Derived Carbon Dots Inhibit Biofilm Formation of Escherichia coli without Affecting Cell Growth

PubMed Central

Lin, Fengming; Li, Chengcheng; Chen, Zhan

2018-01-01

Biofilms are deleterious in many biomedical and industrial applications and prevention of their formation has been a pressing challenge. Here, carbon dots, CDs-LP that were easily synthesized from the biomass of Lactobacillus plantarum by one-step hydrothermal carbonization, were demonstrated to prevent biofilm formation of E. coli. CDs-LP did not thwart the growth of E. coli, indicating the anti-biofilm effect was not due to the bactericidal effect. Moreover, CDs-LP did not affect the growth of the animal cell AT II, showing low cytotoxicity, good safety and excellent biocompatibility. Therefore, CDs-LP could overcome the cytotoxicity issue found in many current antibiofilm agents. CDs-LP represent a new type of anti-biofilm materials, opening up a novel avenue to the development of biofilm treatment. PMID:29503644

Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity

PubMed Central

2012-01-01

Issues of Ge hut cluster array formation and growth at low temperatures on the Ge/Si(001) wetting layer are discussed on the basis of explorations performed by high resolution STM and in-situ RHEED. Dynamics of the RHEED patterns in the process of Ge hut array formation is investigated at low and high temperatures of Ge deposition. Different dynamics of RHEED patterns during the deposition of Ge atoms in different growth modes is observed, which reflects the difference in adatom mobility and their ‘condensation’ fluxes from Ge 2D gas on the surface for different modes, which in turn control the nucleation rates and densities of Ge clusters. Data of HRTEM studies of multilayer Ge/Si heterostructures are presented with the focus on low-temperature formation of perfect films. Heteroepitaxial Si p–i–n-diodes with multilayer stacks of Ge/Si(001) quantum dot dense arrays built in intrinsic domains have been investigated and found to exhibit the photo-emf in a wide spectral range from 0.8 to 5 μm. An effect of wide-band irradiation by infrared light on the photo-emf spectra has been observed. Photo-emf in different spectral ranges has been found to be differently affected by the wide-band irradiation. A significant increase in photo-emf is observed in the fundamental absorption range under the wide-band irradiation. The observed phenomena are explained in terms of positive and neutral charge states of the quantum dot layers and the Coulomb potential of the quantum dot ensemble. A new design of quantum dot infrared photodetectors is proposed. By using a coherent source spectrometer, first measurements of terahertz dynamical conductivity (absorptivity) spectra of Ge/Si(001) heterostructures were performed at frequencies ranged from 0.3 to 1.2 THz in the temperature interval from 300 to 5 K. The effective dynamical conductivity of the heterostructures with Ge quantum dots has been discovered to be significantly higher than that of the structure with the same amount of bulk germanium (not organized in an array of quantum dots). The excess conductivity is not observed in the structures with the Ge coverage less than 8 Å. When a Ge/Si(001) sample is cooled down the conductivity of the heterostructure decreases. PMID:22824144

Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity.

PubMed

Yuryev, Vladimir A; Arapkina, Larisa V; Storozhevykh, Mikhail S; Chapnin, Valery A; Chizh, Kirill V; Uvarov, Oleg V; Kalinushkin, Victor P; Zhukova, Elena S; Prokhorov, Anatoly S; Spektor, Igor E; Gorshunov, Boris P

2012-07-23

: Issues of Ge hut cluster array formation and growth at low temperatures on the Ge/Si(001) wetting layer are discussed on the basis of explorations performed by high resolution STM and in-situ RHEED. Dynamics of the RHEED patterns in the process of Ge hut array formation is investigated at low and high temperatures of Ge deposition. Different dynamics of RHEED patterns during the deposition of Ge atoms in different growth modes is observed, which reflects the difference in adatom mobility and their 'condensation' fluxes from Ge 2D gas on the surface for different modes, which in turn control the nucleation rates and densities of Ge clusters. Data of HRTEM studies of multilayer Ge/Si heterostructures are presented with the focus on low-temperature formation of perfect films.Heteroepitaxial Si p-i-n-diodes with multilayer stacks of Ge/Si(001) quantum dot dense arrays built in intrinsic domains have been investigated and found to exhibit the photo-emf in a wide spectral range from 0.8 to 5 μm. An effect of wide-band irradiation by infrared light on the photo-emf spectra has been observed. Photo-emf in different spectral ranges has been found to be differently affected by the wide-band irradiation. A significant increase in photo-emf is observed in the fundamental absorption range under the wide-band irradiation. The observed phenomena are explained in terms of positive and neutral charge states of the quantum dot layers and the Coulomb potential of the quantum dot ensemble. A new design of quantum dot infrared photodetectors is proposed.By using a coherent source spectrometer, first measurements of terahertz dynamical conductivity (absorptivity) spectra of Ge/Si(001) heterostructures were performed at frequencies ranged from 0.3 to 1.2 THz in the temperature interval from 300 to 5 K. The effective dynamical conductivity of the heterostructures with Ge quantum dots has been discovered to be significantly higher than that of the structure with the same amount of bulk germanium (not organized in an array of quantum dots). The excess conductivity is not observed in the structures with the Ge coverage less than 8 Å. When a Ge/Si(001) sample is cooled down the conductivity of the heterostructure decreases.

Vitronectin (Vn) glycosylation patterned by lectin affinity assays-A potent glycoproteomic tool to discriminate plasma Vn from cancer ascites Vn.

PubMed

Benachour, H; Leroy-Dudal, J; Agniel, R; Wilson, J; Briand, M; Carreiras, F; Gallet, O

2018-05-01

Changes in glycosylation have been associated with human cancer, but their complexity poses an analytical challenge. Ovarian cancer is a major cause of death in women because of an often late diagnosis. At least one-third of patients presents ascites fluid at diagnosis, and almost all have ascites at recurrence. Vitronectin (Vn) is a multifunctional glycoprotein that is suggested to be implicated in ovarian cancer metastasis and is found within ascites. The present study evaluated the potential of using lectin affinity for characterizing the glycosylation pattern of Vn. Human Vn was purified from 1 sample of ovarian cancer ascites or a pool of plasma samples. Consistent findings were observed with both dot blot and lectin array assays. Based on a panel of 40 lectins, the lectin array revealed discriminant patterns of lectin binding to Vn glycans. Interestingly, almost all the highlighted interactions were found to be higher with Vn from ascites relative to the plasma counterpart. Also, the lectin array was able to discriminate profiles of lectin interactions (ConA, SNA-I, PHA-E, PHA-L) between Vn samples that were not evident using dot blot, indicating its high sensitivity. The model of ConA binding during thermal unfolding of Vn confirmed the higher accessibility of mannosylated glycans in Vn from ascites as monitored by turbidimetry. Thus, this study demonstrated the usefulness of lectins and the lectin array as a glycoproteomic tool for high throughput and sensitive analysis of glycosylation patterns. Our data provide novel insights concerning Vn glycosylation patterns in clinical specimens, paving the way for further investigations regarding their functional impact and clinical interest. Copyright © 2017 John Wiley & Sons, Ltd.

Rapid and quantitative detection of zoonotic influenza A virus infection utilizing coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT).

PubMed

Yeo, Seon-Ju; Huong, Dinh Thi; Hong, Nguyen Ngoc; Li, Chun-Ying; Choi, Kyunghan; Yu, Kyoungsik; Choi, Du-Young; Chong, Chom-Kyu; Choi, Hak Soo; Mallik, Shyam Kumar; Kim, Hak Sung; Sung, Haan Woo; Park, Hyun

2014-01-01

Great efforts have been made to develop robust signal-generating fluorescence materials which will help in improving the rapid diagnostic test (RDT) in terms of sensitivity and quantification. In this study, we developed coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT) assay with enhanced sensitivity as a quantitative diagnostic tool in typical RDT environments. The accuracy of the proposed FICT was compared with that of dot blot immunoassay techniques and conventional RDTs. Through conjugation of coumarin-derived dendrimers with latex beads, fluorescent emission covering broad output spectral ranges was obtained which provided a distinct advantage of easy discrimination of the fluorescent emission of the latex beads with a simple insertion of a long-pass optical filter away from the excitation wavelength. The newly developed FICT assay was able to detect 100 ng/10 μL of influenza A nucleoprotein (NP) antigen within 5 minutes, which corresponded to 2.5-fold higher sensitivity than that of the dot blot immunoassay or conventional RDTs. Moreover, the FICT assay was confirmed to detect at least four avian influenza A subtypes (H5N3, H7N1, H7N7, and H9N2). On applying the FICT to the clinical swab samples infected with respiratory viruses, our FICT assay was confirmed to differentiate influenza H1N1 infection from other respiratory viral diseases. These data demonstrate that the proposed FICT assay is able to detect zoonotic influenza A viruses with a high sensitivity, and it enables the quantitation of the infection intensity by providing the numerical diagnostic values; thus demonstrating enhanced detectability of influenza A viruses.

The dynamics of DNA methylation and hydroxymethylation during amelogenesis.

PubMed

Yoshioka, Hirotaka; Minamizaki, Tomoko; Yoshiko, Yuji

2015-11-01

Amelogenesis is a multistep process that relies on specific temporal and spatial signaling networks between the dental epithelium and mesenchymal tissues. Epigenetic modifications of key developmental genes in this process may be closely linked to a network of molecular events. However, the role of epigenetic regulation in amelogenesis remains unclear. Here, we have uncovered the spatial distributions of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) to determine epigenetic events in the mandibular incisors of mice. Immunohistochemistry and dot blotting showed that 5-hmC in ameloblasts increased from the secretory stage to the later maturation stage. We also demonstrated the distribution of 5-mC-positive ameloblasts with punctate nuclear labeling from sometime after the initiation of the secretory stage to the later maturation stage; however, dot blotting failed to detect this change. No obvious alteration of 5-mC/5-hmC staining in odontoblasts and dental pulp cells was observed. Concomitant with quantitative expression data, immunohistochemistry showed that maintenance DNA methyltransferase DNMT1 was highly expressed in immature dental epithelial cells and subsequently decreased at later stages of development. Meanwhile, de novo DNA methyltransferase Dnmt3a and Dnmt3b and DNA demethylase Tet family genes were universally expressed, except Tet1 that was highly expressed in immature dental epithelial cells. Thus, DNMT1 may sustain the undifferentiated status of dental epithelial cells through the maintenance of DNA methylation, while the hydroxylation of 5-mC may occur through the whole differentiation process by TET activity. Taken together, these data indicate that the dynamic changes of 5-mC and 5-hmC may be critical for the regulation of amelogenesis.

Comparison of the performance in detection of HPV infections between the high-risk HPV genotyping real time PCR and the PCR-reverse dot blot assays.

PubMed

Zhang, Lahong; Dai, Yibei; Chen, Jiahuan; Hong, Liquan; Liu, Yuhua; Ke, Qiang; Chen, Yiwen; Cai, Chengsong; Liu, Xia; Chen, Zhaojun

2018-01-01

A new multiplex real-time PCR assay, the high-risk HPV genotyping real time PCR assay (HR HPV RT-PCR), has been developed to detect 15 high-risk HPV types with respective viral loads. In this report, a total of 684 cervical specimens from women diagnosed with vaginitis were assessed by the HR HPV RT-PCR and the PCR reaction and reverse dot blot (PCR-RDB) assays, using a PCR-sequencing method as a reference standard. A total coincidence of 97.7% between the HR HPV RT PCR and the PCR-RDB assays was determined with a Kappa value of 0.953. The HR HPV RT PCR assay had sensitivity, specificity, and concordance rates (accuracy) of 99.7%, 99.7%, and 99.7%, respectively, as confirmed by PCR-sequencing, while the PCR-RDB assay had respective rates of 98.8%, 97.1%, and 98.0%. The overall rate of HPV infection, determined by PCR-sequencing, in women diagnosed with vaginitis was 49.85%, including 36.26% of single infection and 13.6% of multiple infections. The most common infections among the 15 high-risk HPV types in women diagnosed with vaginitis were HPV-52, HPV-16, and HPV-58, with a total detection rate of 10.23%, 7.75%, and 5.85%, respectively. We conclude that the HR HPV RT PCR assay exhibits better clinical performance than the PCR-RDB assay, and is an ideal alternative method for HPV genotyping. In addition, the HR HPV RT PCR assay provides HPV DNA viral loads, and could serve as a quantitative marker in the diagnosis and treatment of single and multiple HPV infections. © 2017 Wiley Periodicals, Inc.

Lipopolysaccharide Specific Immunochromatography Based Lateral Flow Assay for Serogroup Specific Diagnosis of Leptospirosis in India

PubMed Central

Vanithamani, Shanmugam; Shanmughapriya, Santhanam; Narayanan, Ramasamy; Raja, Veerapandian; Kanagavel, Murugesan; Sivasankari, Karikalacholan; Natarajaseenivasan, Kalimuthusamy

2015-01-01

Background Leptospirosis is a re-emerging infectious disease that is under-recognized due to low-sensitivity and cumbersome serological tests. MAT is the gold standard test and it is the only serogroup specific test used till date. Rapid reliable alternative serogroup specific tests are needed for surveillance studies to identify locally circulating serogroups in the study area. Methods/Principal Findings In the present investigation the serological specificity of leptospiral lipopolysaccharides (LPS) was evaluated by enzyme linked immunosorbent assay (ELISA), dot blot assay and rapid immunochromatography based lateral flow assay (ICG-LFA). Sera samples from 120 MAT positive cases, 174 cases with febrile illness other than leptospirosis, and 121 seronegative healthy controls were evaluated for the diagnostic sensitivity and specificity of the developed assays. LPS was extracted from five locally predominant circulating serogroups including: Australis (27.5%), Autumnalis (11.7%), Ballum (25.8%), Grippotyphosa (12.5%), Pomona (10%) and were used as antigens in the diagnostics to detect IgM antibodies in patients’ sera. The sensitivity observed by IgM ELISA and dot blot assay using various leptospiral LPS was >90% for homologous sera. Except for Ballum LPS, no other LPS showed cross-reactivity to heterologous sera. An attempt was made to develop LPS based ICG-LFA for rapid and sensitive serogroup specific diagnostics of leptospirosis. The developed ICG-LFA showed sensitivity in the range between 93 and 100% for homologous sera. The Wilcoxon analysis showed LPS based ICG-LFA did not differ significantly from the gold standard MAT (P>0.05). Conclusion The application of single array of LPS for serogroup specific diagnosis is first of its kind. The developed assay could potentially be evaluated and employed for as MAT alternative. PMID:26340095

The Legionella IcmSW Complex Directly Interacts with DotL to Mediate Translocation of Adaptor-Dependent Substrates

PubMed Central

Sutherland, Molly C.; Nguyen, Thuy Linh; Tseng, Victor; Vogel, Joseph P.

2012-01-01

Legionella pneumophila is a Gram-negative bacterium that replicates within human alveolar macrophages by evasion of the host endocytic pathway through the formation of a replicative vacuole. Generation of this vacuole is dependent upon the secretion of over 275 effector proteins into the host cell via the Dot/Icm type IVB secretion system (T4SS). The type IV coupling protein (T4CP) subcomplex, consisting of DotL, DotM, DotN, IcmS and IcmW, was recently defined. DotL is proposed to be the T4CP of the L. pneumophila T4SS based on its homology to known T4CPs, which function as inner-membrane receptors for substrates. As a result, DotL is hypothesized to play an integral role(s) in the L. pneumophila T4SS for the engagement and translocation of substrates. To elucidate this role, a genetic approach was taken to screen for dotL mutants that were unable to survive inside host cells. One mutant, dotLY725Stop, did not interact with the type IV adaptor proteins IcmS/IcmW (IcmSW) leading to the identification of an IcmSW-binding domain on DotL. Interestingly, the dotLY725Stop mutant was competent for export of one class of secreted effectors, the IcmSW-independent substrates, but exhibited a specific defect in secretion of IcmSW-dependent substrates. This differential secretion illustrates that DotL requires a direct interaction with the type IV adaptor proteins for the secretion of a major class of substrates. Thus, by identifying a new target for IcmSW, we have discovered that the type IV adaptors perform an additional role in the export of substrates by the L. pneumophila Dot/Icm T4SS. PMID:23028312

GaAs/GaP quantum dots: Ensemble of direct and indirect heterostructures with room temperature optical emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dadgostar, S.; Mogilatenko, A.; Masselink, W. T.

2016-03-07

We describe the optical emission and the carrier dynamics of an ensemble of self-assembled GaAs quantum dots embedded in GaP(001). The QD formation is driven by the 3.6% lattice mismatch between GaAs and GaP in the Stranski-Krastanow mode after deposition of more than 1.2 monolayers of GaAs. The quantum dots have an areal density between 6 and 7.6 × 10{sup 10} per cm{sup −2} and multimodal size distribution. The luminescence spectra show two peaks in the range of 1.7 and 2.1 eV. The samples with larger quantum dots have red emission and show less thermal quenching compared with the samples with smaller QDs.more » The large QDs luminescence up to room temperature. We attribute the high energy emission to indirect carrier recombination in the thin quantum wells or small strained quantum dots, whereas the low energy red emission is due to the direct electron-hole recombination in the relaxed quantum dots.« less

Self-organization of colloidal PbS quantum dots into highly ordered superlattices.

PubMed

Baranov, Alexander V; Ushakova, Elena V; Golubkov, Valery V; Litvin, Aleksandr P; Parfenov, Peter S; Fedorov, Anatoly V; Berwick, Kevin

2015-01-13

X-ray structural analysis, together with steady-state and transient optical spectroscopy, is used for studying the morphology and optical properties of quantum dot superlattices (QDSLs) formed on glass substrates by the self-organization of PbS quantum dots with a variety of surface ligands. The diameter of the PbS QDs varies from 2.8 to 8.9 nm. The QDSL's period is proportional to the dot diameter, increasing slightly with dot size due to the increase in ligand layer thickness. Removal of the ligands has a number of effects on the morphology of QDSLs formed from the dots of different sizes: for small QDs the reduction in the amount of ligands obstructs the self-organization process, impairing the ordering of the QDSLs, while for large QDs the ordering of the superlattice structure is improved, with an interdot distance as low as 0.4 nm allowing rapid charge carrier transport through the QDSLs. QDSL formation does not induce significant changes to the absorption and photoluminescence spectra of the QDs. However, the luminescence decay time is reduced dramatically, due to the appearance of nonradiative relaxation channels.

Novel cookie-with-chocolate carbon dots displaying extremely acidophilic high luminescence

NASA Astrophysics Data System (ADS)

Lu, Siyu; Zhao, Xiaohuan; Zhu, Shoujun; Song, Yubin; Yang, Bai

2014-10-01

A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm2) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+.A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm2) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03965c

Microfluidic Technology: Uncovering the Mechanisms of Nanocrystal Nucleation and Growth.

PubMed

Lignos, Ioannis; Maceiczyk, Richard; deMello, Andrew J

2017-05-16

The controlled and reproducible formation of colloidal semiconductor nanocrystals (or quantum dots) is of central importance in nanoscale science and technology. The tunable size- and shape-dependent properties of such materials make them ideal candidates for the development of efficient and low-cost displays, solar cells, light-emitting devices, and catalysts. The formidable difficulties associated with the macroscale preparation of semiconductor nanocrystals (possessing bespoke optical and chemical properties) result from the fact that underlying reaction mechanisms are complex and that the reactive environment is difficult to control. Automated microfluidic reactors coupled with monitoring systems and optimization algorithms aim to elucidate complex reaction mechanisms that govern both nucleation and growth of nanocrystals. Such platforms are ideally suited for the efficient optimization of reaction parameters, assuring the reproducible synthesis of nanocrystals with user-defined properties. This Account aims to inform the nanomaterials community about how microfluidic technologies can supplement flask experimentation for the ensemble investigation of formation mechanisms and design of semiconductor nanocrystals. We present selected studies outlining the preparation of quantum dots using microfluidic systems with integrated analytics. Such microfluidic reaction systems leverage the ability to extract real-time information regarding optical, structural, and compositional characteristics of quantum dots during nucleation and growth stages. The Account further highlights our recent research activities focused on the development and application of droplet-based microfluidics with integrated optical detection systems for the efficient and rapid screening of reaction conditions and a better understanding of the mechanisms of quantum dot synthesis. We describe the features and operation of fully automated microfluidic reactors and their subsequent application to high-throughput parametric screening of metal chalcogenides (CdSe, PbS, PbSe, CdSeTe), ternary and core/shell heavy metal-free quantum dots (CuInS 2 , CuInS 2 /ZnS), and all-inorganic perovskite nanocrystals (CsPbX 3 , X = Cl, Br, I) syntheses. Critically, concurrent absorption and photoluminescence measurements on millisecond to second time scales allow the extraction of basic parameters governing nanocrystal formation. Moreover, experimental data obtained from such microfluidic platforms can be directly supported by theoretical models of nucleation and growth. To this end, we also describe the use of metamodeling algorithms able to accurately predict optimized conditions of CdSe synthesis using a minimal number of sample parameters. Importantly, we discuss future challenges that must be addressed before microfluidic technologies are in a position to be widely adopted for the on-demand formation of nanocrystals. From a technology perspective, these challenges include the development of novel engineering platforms for the formation of complex architectures, the integration of monitoring systems able to harvest photophysical and structural information, the incorporation of continuous purification systems, and the application of optimization algorithms to multicomponent quantum dot systems.

3D superstructures with an orthorhombic lattice assembled by colloidal PbS quantum dots.

PubMed

Ushakova, Elena V; Cherevkov, Sergei A; Litvin, Aleksandr P; Parfenov, Peter S; Kasatkin, Igor A; Fedorov, Anatoly V; Gun'ko, Yurii K; Baranov, Alexander V

2018-05-03

We report a new type of metamaterial comprising a highly ordered 3D network of 3-7 nm lead sulfide quantum dots self-assembled in an organic matrix formed by amphiphilic ligands (oleic acid molecules). The obtained 3D superstructures possess an orthorhombic lattice with the distance between the nanocrystals as large as 10-40 nm. Analysis of self-assembly and destruction of the superstructures in time performed by a SAXS technique shows that their morphology depends on the quantity of amphiphilic ligands and width of the quantum dot size and its distribution. Formation of the superstructures is discussed in terms of a model describing the lyotropic crystal formation by micelles from three-phase mixtures. The results show that the organic molecules possessing surfactant properties and capable of forming micelles with nanoparticles as a micelle core can be utilized as building blocks for the creation of novel metamaterials based on a highly ordered 3D network of semiconductors, metals or magnetic nanoparticles.

Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies

NASA Astrophysics Data System (ADS)

McDonald, M.; Gaspari, M.; McNamara, B. R.; Tremblay, G. R.

2018-05-01

We present a study of 107 galaxies, groups, and clusters spanning ∼3 orders of magnitude in mass, ∼5 orders of magnitude in central galaxy star formation rate (SFR), ∼4 orders of magnitude in the classical cooling rate ({\\dot{M}}cool}\\equiv {M}gas}(r< {r}cool})/{t}cool}) of the intracluster medium (ICM), and ∼5 orders of magnitude in the central black hole accretion rate. For each system in this sample, we measure the ICM cooling rate, {\\dot{M}}cool}, using archival Chandra X-ray data and acquire the SFR and systematic uncertainty in the SFR by combining over 330 estimates from dozens of literature sources. With these data, we estimate the efficiency with which the ICM cools and forms stars, finding {ε }cool}\\equiv {SFR}/{\\dot{M}}cool}=1.4 % +/- 0.4% for systems with {\\dot{M}}cool}> 30 M ⊙ yr‑1. For these systems, we measure a slope in the SFR–{\\dot{M}}cool} relation greater than unity, suggesting that the systems with the strongest cool cores are also cooling more efficiently. We propose that this may be related to, on average, higher black hole accretion rates in the strongest cool cores, which could influence the total amount (saturating near the Eddington rate) and dominant mode (mechanical versus radiative) of feedback. For systems with {\\dot{M}}cool}< 30 M ⊙ yr‑1, we find that the SFR and {\\dot{M}}cool} are uncorrelated and show that this is consistent with star formation being fueled at a low (but dominant) level by recycled ISM gas in these systems. We find an intrinsic log-normal scatter in SFR at a fixed {\\dot{M}}cool} of 0.52 ± 0.06 dex (1σ rms), suggesting that cooling is tightly self-regulated over very long timescales but can vary dramatically on short timescales. There is weak evidence that this scatter may be related to the feedback mechanism, with the scatter being minimized (∼0.4 dex) for systems for which the mechanical feedback power is within a factor of two of the cooling luminosity.

A combined RT-PCR and dot-blot hybridization method reveals the coexistence of SJNNV and RGNNV betanodavirus genotypes in wild meagre (Argyrosomus regius).

PubMed

Lopez-Jimena, B; Cherif, N; Garcia-Rosado, E; Infante, C; Cano, I; Castro, D; Hammami, S; Borrego, J J; Alonso, M C

2010-10-01

To detect the possible coexistence of striped jack nervous necrosis virus (SJNNV) and red-spotted grouper nervous necrosis virus (RGNNV) genotypes in a single fish, a methodology based on the combination of PCR amplification and blot hybridization has been developed and applied in this study. The degenerate primers designed for the PCR procedure target the T4 region within the capsid gene, resulting in the amplification of both genotypes. The subsequent hybridization of these amplification products with two different specific digoxigenin-labelled probes resulted in the identification of both genotypes separately. The application of the RT-PCR protocol to analyse blood samples from asymptomatic wild meagre (Argyrosomus regius) specimens has shown a 46.87% of viral nervous necrosis virus carriers. The combination of RT-PCR and blot hybridization increases the detection rate up to 90.62%, and, in addition, it has shown the coexistence of both genotypes in 18 out of the 32 specimens analysed (56.25%). This study reports the coexistence of betanodaviruses belonging to two different genotypes (SJNNV and RGNNV) in wild fish specimens. This is the first report demonstrating the presence of SJNNV and RGNNV genotypes in the same specimen. This study also demonstrates a carrier state in this fish species for the first time. © 2010 The Authors. Journal compilation © 2010 The Society for Applied Microbiology.

Insect resistance to Nilaparvata lugens and Cnaphalocrocis medinalis in transgenic indica rice and the inheritance of gna+sbti transgenes.

PubMed

Li, Guiying; Xu, Xinping; Xing, Hengtai; Zhu, Huachen; Fan, Qin

2005-04-01

Molecular genetic analysis and insect bioassay of transgenic indica rice 'Zhuxian B' plants carrying snowdrop lectin gene (gna) and soybean trypsin inhibitor gene (sbti) were investigated in detail. PCR, 'dot' blot and PCR-Southern blot analysis showed that both transgenes had been incorporated into the rice genome and transmitted up to R3 progeny in most lines tested. Some transgenic lines exhibited Mendelian segregation, but the other showed either 1:1 (positive: negative for the transgenes) or other aberrant segregation patterns. The segregation patterns of gna gene crossed between R2 and R3 progeny. In half of transgenic R3 lines, gna and sbti transgenes co-segregated. Two independent homozygous lines expressing double transgenes were identified in R3 progeny. Southern blot analysis demonstrated that the copy numbers of integrated gna and sbti transgenes varied from one to ten in different lines. Insect bioassay data showed that most transgenic plants had better resistance to both Nilaparvata lugens (Stahl) and Cnaphalocrocis medinalis (Guenee) than wild-type plants. The insect resistance of transgenic lines increased with the increase in transgene positive ratio in most of the transgenic lines. In all, we obtained nine lines of R3 transgenic plants, including one pure line, which had better resistance to both N lugens and C medinalis than wild-type plants. Copyright 2005 Society of Chemical Industry.

Daunorubicin and gambogic acid coloaded cysteamine-CdTe quantum dots minimizing the multidrug resistance of lymphoma in vitro and in vivo

PubMed Central

Zhou, Yi; Wang, Ruju; Chen, Bing; Sun, Dan; Hu, Yong; Xu, Peipei

2016-01-01

To minimize the side effects and the multidrug resistance (MDR) arising from daunorubicin (DNR) treatment of malignant lymphoma, a chemotherapy formulation of cysteamine-modified cadmium tellurium (Cys-CdTe) quantum dots coloaded with DNR and gambogic acid (GA) nanoparticles (DNR-GA-Cys-CdTe NPs) was developed. The physical property, drug-loading efficiency and drug release behavior of these DNR-GA-Cys-CdTe NPs were evaluated, and their cytotoxicity was explored by 3-[4,5-dimethylthiazol-2-y1]-2,5-diphenyltetrazolium bromide assay. These DNR-GA-Cys-CdTe NPs possessed a pH-responsive behavior, and displayed a dose-dependent antiproliferative activity on multidrug-resistant lymphoma Raji/DNR cells. The accumulation of DNR inside the cells, revealed by flow cytometry assay, and the down-regulated expression of P-glycoprotein inside the Raji/DNR cells measured by Western blotting assay indicated that these DNR-GA-Cys-CdTe NPs could minimize the MDR of Raji/DNR cells. This multidrug delivery system would be a promising strategy for minimizing MDR against the lymphoma. PMID:27799767

IcmS-dependent translocation of SdeA into macrophages by the Legionella pneumophila type IV secretion system.

PubMed

Bardill, J Patrick; Miller, Jennifer L; Vogel, Joseph P

2005-04-01

Legionella pneumophila replicates inside alveolar macrophages and causes an acute, potentially fatal pneumonia called Legionnaires' disease. The ability of this bacterium to grow inside of macrophages is dependent on the presence of a functional dot/icm type IV secretion system (T4SS). Proteins secreted by the Dot/Icm T4SS are presumed to alter the host endocytic pathway, allowing L. pneumophila to establish a replicative niche within the host cell. Here we show that a member of the SidE family of proteins interacts with IcmS and is required for full virulence in the protozoan host Acanthamoeba castellanii. Using immunofluorescence microscopy and adenylate cyclase fusions, we show that SdeA is secreted into host cells by L. pneumophila in an IcmS-dependent manner. The SidE-like proteins are secreted very early during macrophage infection, suggesting that they are important in the initial formation of the replicative phagosome. Secreted SidE family members show a similar localization to other Dot/Icm substrates, specifically, to the poles of the replicative phagosome. This common localization of secreted substrates of the Dot/Icm system may indicate the formation of a multiprotein complex on the cytoplasmic face of the replicative phagosome.

Self-assembly of ordered graphene nanodot arrays

DOE PAGES

Camilli, Luca; Jørgensen, Jakob H.; Tersoff, Jerry; ...

2017-06-29

Our ability to fabricate nanoscale domains of uniform size in two-dimensional materials could potentially enable new applications in nanoelectronics and the development of innovative metamaterials. But, achieving even minimal control over the growth of two-dimensional lateral heterostructures at such extreme dimensions has proven exceptionally challenging. Here we show the spontaneous formation of ordered arrays of graphene nano-domains (dots), epitaxially embedded in a two-dimensional boron–carbon–nitrogen alloy. These dots exhibit a strikingly uniform size of 1.6 ± 0.2 nm and strong ordering, and the array periodicity can be tuned by adjusting the growth conditions. Furthemore, we explain this behaviour with a modelmore » incorporating dot-boundary energy, a moiré-modulated substrate interaction and a long-range repulsion between dots. This new two-dimensional material, which theory predicts to be an ordered composite of uniform-size semiconducting graphene quantum dots laterally integrated within a larger-bandgap matrix, holds promise for novel electronic and optoelectronic properties, with a variety of potential device applications.« less

Design strategy for terahertz quantum dot cascade lasers.

PubMed

Burnett, Benjamin A; Williams, Benjamin S

2016-10-31

The development of quantum dot cascade lasers has been proposed as a path to obtain terahertz semiconductor lasers that operate at room temperature. The expected benefit is due to the suppression of nonradiative electron-phonon scattering and reduced dephasing that accompanies discretization of the electronic energy spectrum. We present numerical modeling which predicts that simple scaling of conventional quantum well based designs to the quantum dot regime will likely fail due to electrical instability associated with high-field domain formation. A design strategy adapted for terahertz quantum dot cascade lasers is presented which avoids these problems. Counterintuitively, this involves the resonant depopulation of the laser's upper state with the LO-phonon energy. The strategy is tested theoretically using a density matrix model of transport and gain, which predicts sufficient gain for lasing at stable operating points. Finally, the effect of quantum dot size inhomogeneity on the optical lineshape is explored, suggesting that the design concept is robust to a moderate amount of statistical variation.

Extracellular biosynthesis of CdTe quantum dots by the fungus Fusarium oxysporum and their anti-bacterial activity

NASA Astrophysics Data System (ADS)

Syed, Asad; Ahmad, Absar

2013-04-01

The growing demand for semiconductor [quantum dots (Q-dots)] nanoparticles has fuelled significant research in developing strategies for their synthesis and characterization. They are extensively investigated by the chemical route; on the other hand, use of microbial sources for biosynthesis witnessed the highly stable, water dispersible nanoparticles formation. Here we report, for the first time, an efficient fungal-mediated synthesis of highly fluorescent CdTe quantum dots at ambient conditions by the fungus Fusarium oxysporum when reacted with a mixture of CdCl2 and TeCl4. Characterization of these biosynthesized nanoparticles was carried out by different techniques such as Ultraviolet-visible (UV-Vis) spectroscopy, Photoluminescence (PL), X-ray Diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transformed Infrared Spectroscopy (FTIR) analysis. CdTe nanoparticles shows antibacterial activity against Gram positive and Gram negative bacteria. The fungal based fabrication provides an economical, green chemistry approach for production of highly fluorescent CdTe quantum dots.

Probable Congenital Transmission of Reticuloendotheliosis Virus Caused by Vaccination with Contaminated Vaccines

PubMed Central

Zhu, Shufen; Guo, Wenlong; Sheng, Pengcheng; Wang, Zunmin; Zhao, Changliang; Zhao, Qingyou; Zhu, Ruiliang

2012-01-01

Contaminated vaccine is one unexpected and potential origin of virus infection. In order to investigate the most likely cause of disease in a broiler breeder company of Shandong Province, all 17 batches of live-virus vaccines used in the affected flocks and 478 tissue samples were tested by dot-blot hybridization, nested PCR, and IFA. The results suggested the outbreak of disease was most probably due to the vaccination of REV-contaminated MD-CVI988/Rispens vaccines and ND-LaSota+IB-H120 vaccines. Furthermore, the REV was probably transmitted to the commercial chickens through congenital transmission. PMID:22912872

Self-assembled InN quantum dots on side facets of GaN nanowires

NASA Astrophysics Data System (ADS)

Bi, Zhaoxia; Ek, Martin; Stankevic, Tomas; Colvin, Jovana; Hjort, Martin; Lindgren, David; Lenrick, Filip; Johansson, Jonas; Wallenberg, L. Reine; Timm, Rainer; Feidenhans'l, Robert; Mikkelsen, Anders; Borgström, Magnus T.; Gustafsson, Anders; Ohlsson, B. Jonas; Monemar, Bo; Samuelson, Lars

2018-04-01

Self-assembled, atomic diffusion controlled growth of InN quantum dots was realized on the side facets of dislocation-free and c-oriented GaN nanowires having a hexagonal cross-section. The nanowires were synthesized by selective area metal organic vapor phase epitaxy. A 3 Å thick InN wetting layer was observed after growth, on top of which the InN quantum dots formed, indicating self-assembly in the Stranski-Krastanow growth mode. We found that the InN quantum dots can be tuned to nucleate either preferentially at the edges between GaN nanowire side facets, or directly on the side facets by tuning the adatom migration by controlling the precursor supersaturation and growth temperature. Structural characterization by transmission electron microscopy and reciprocal space mapping show that the InN quantum dots are close to be fully relaxed (residual strain below 1%) and that the c-planes of the InN quantum dots are tilted with respect to the GaN core. The strain relaxes mainly by the formation of misfit dislocations, observed with a periodicity of 3.2 nm at the InN and GaN hetero-interface. The misfit dislocations introduce I1 type stacking faults (…ABABCBC…) in the InN quantum dots. Photoluminescence investigations of the InN quantum dots show that the emissions shift to higher energy with reduced quantum dot size, which we attribute to increased quantum confinement.

Photoconductive gain and quantum efficiency of remotely doped Ge/Si quantum dot photodetectors

NASA Astrophysics Data System (ADS)

Yakimov, A. I.; Kirienko, V. V.; Armbrister, V. A.; Bloshkin, A. A.; Dvurechenskii, A. V.; Shklyaev, A. A.

2016-10-01

We study the effect of quantum dot charging on the mid-infrared photocurrent, optical gain, hole capture probability, and absorption quantum efficiency in remotely delta-doped Ge/Si quantum dot photodetectors. The dot occupation with holes is controlled by varying dot and doping densities. From our investigations of samples doped to contain from about one to nine holes per dot we observe an over 10 times gain enhancement and similar suppression of the hole capture probability with increased carrier population. The data are explained by quenching the capture process and increasing the photoexcited hole lifetime due to formation of the repulsive Coulomb potential of the extra holes inside the quantum dots. The normal incidence quantum efficiency is found to be strongly asymmetric with respect to applied bias polarity. Based on the polarization-dependent absorption measurements it is concluded that, at a positive voltage, when holes move toward the nearest δ-doping plane, photocurrent is originated from the bound-to-continuum transitions of holes between the ground state confined in Ge dots and the extended states of the Si matrix. At a negative bias polarity, the photoresponse is caused by optical excitation to a quasibound state confined near the valence band edge with subsequent tunneling to the Si valence band. In a latter case, the possibility of hole transfer into continuum states arises from the electric field generated by charge distributed between quantum dots and delta-doping planes.

Self-assembled InAs quantum dot formation on GaAs ring-like nanostructure templates

PubMed Central

Strom, NW; Wang, Zh M; AbuWaar, ZY; Mazur, Yu I; Salamo, GJ

2007-01-01

The evolution of InAs quantum dot (QD) formation is studied on GaAs ring-like nanostructures fabricated by droplet homo-epitaxy. This growth mode, exclusively performed by a hybrid approach of droplet homo-epitaxy and Stransky-Krastanor (S-K) based QD self-assembly, enables one to form new QD morphologies that may find use in optoelectronic applications. Increased deposition of InAs on the GaAs ring first produced a QD in the hole followed by QDs around the GaAs ring and on the GaAs (100) surface. This behavior indicates that the QDs prefer to nucleate at locations of high monolayer (ML) step density.

Different valence Sn doping - A simple way to detect oxygen concentration variation of ZnO quantum dots synthesized under ultrasonic irradiation.

PubMed

Yang, Weimin; Zhang, Bing; Zhang, Qitu; Wang, Lixi; Song, Bo; Wu, Fan; Wong, C P

2017-09-01

An ultrasonic method is employed to synthesize the Sn doped Zn 0.95 Sn 0.05 O quantum dots with green light emission. Sn 2+ and Sn 4+ ions are used to create different optical defects inside Zn 0.95 Sn 0.05 O quantum dots and the changing trend of oxygen concentration under different ultrasonic irradiation power are investigated. The photoluminescence spectra are employed to characterize the optical defects of Zn 0.95 Sn 0.05 O quantum dots. The UV-vis spectra are used to study the band gap of Zn 0.95 Sn 0.05 O quantum dots, which is influenced by their sizes. The results indicate that ultrasonic power would influence the size of Zn 0.95 Sn 0.05 O quantum dots as well as the type and quantity of defects in ZnO quantum dots. Changing trends in size of Sn 2+ and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots are quite similar with each other, while the changing trends in optical defects types and concentration of Sn 2+ and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots are different. The difference of the optical defects concentration changing between Sn 2+ doped Zn 0.95 Sn 0.05 O quantum dots (V O defects) and Sn 4+ doped Zn 0.95 Sn 0.05 O quantum dots (O Zn and O i defects) shows that the formation process of ZnO under ultrasonic irradiation wiped oxygen out. Copyright © 2017 Elsevier B.V. All rights reserved.

Optical and structural properties of carbon dots/TiO2 nanostructures prepared via DC arc discharge in liquid

NASA Astrophysics Data System (ADS)

Biazar, Nooshin; Poursalehi, Reza; Delavari, Hamid

2018-01-01

Synthesis and development of visible active catalysts is an important issue in photocatalytic applications of nanomaterials. TiO2 nanostructures coupled with carbon dots demonstrate a considerable photocatalytic activity in visible wavelengths. Extending optical absorption of a wide band gap semiconductor such as TiO2 with carbon dots is the origin of the visible activity of carbon dots modified semiconductor nanostructures. In addition, carbon dots exhibit high photostability, appropriate electron transport and chemical stability without considerable toxicity or environmental footprints. In this study, optical and structural properties of carbon dots/TiO2 nanostructures prepared via (direct current) DC arc discharge in liquid were investigated. Crystal structure, morphology and optical properties of the samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy respectively. SEM images show formation of spherical nanoparticles with an average size of 27 nm. In comparison with pristine TiO2, optical transmission spectrum of carbon dots/TiO2 nanostructures demonstrates an absorption edge at longer wavelengths as well a high optical absorption in visible wavelengths which is significant for visible activity of nanostructures as a photocatalyst. Finally, these results can provide a flexible and versatile pathway for synthesis of carbon dots/oxide semiconductor nanostructures with an appropriate activity under visible light.

Recombinant expression of Garlic virus C (GARV-C) capsid protein in insect cells and its potential for the production of specific antibodies.

PubMed

Alves-Júnior, Miguel; Menezes Marraccini, Fernanda; Melo Filho, Péricles de Albuquerque; Nepomuceno Dusi, André; Pio-Ribeiro, Gilvan; Morais Ribeiro, Bergmann

2008-01-01

Garlic cultivars in Brazil are infected by a complex of viruses and for some virus species, such as the allexivirus, purification of the virions is sometimes cumbersume. To overcome this problem, recombinant expression of viral proteins in heterologous systems is an alternative method for producing antibodies. The capsid gene from Garlic virus C (GarV-C), an Allexivirus, was inserted into the genome of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) generating the recombinant virus vSynGarV-C. The recombinant protein expression was confirmed by SDS-PAGE and western-blot of extracts from recombinant virus infected insect cells, where a protein band of approximately 32KDa was observed only in extracts from recombinant infected cells. This protein corresponded to the predicted size of the capsid protein of the GarV-C. A rabbit polyclonal antibody was raised against this protein, shown to be specific for the GarV-C protein in western-blot and dot-Elisa, however with a low titer.

Investigation of the internal stresses caused by delayed ettringite formation in concrete.

DOT National Transportation Integrated Search

2008-11-01

Delayed ettringite formation (DEF) in concrete has been identified in recent as a significant cause of deterioration in : some of the reinforced concrete infrastructure in Texas. This report is part of a research project, TxDOT project : 5218, to inv...

Albumin Overload and PINK1/Parkin Signaling-Related Mitophagy in Renal Tubular Epithelial Cells.

PubMed

Tan, Jin; Xie, Qi; Song, Shuling; Miao, Yuyang; Zhang, Qiang

2018-03-01

BACKGROUND Albumin, as a major urinary protein component, is a risk factor for chronic kidney disease progression. Mitochondrial dysfunction is one of the main causes of albumin-induced proximal tubule cells injury. Mitophagy is considered as a pivotal protective mechanism for the elimination of dysfunctional mitochondria. The objective of this research was to determine whether albumin overload-induced mitochondrial dysfunction can activate PINK1/Parkin-mediated mitophagy in renal tubular epithelial cells (TECs). MATERIAL AND METHODS Immunofluorescence assay and Western blot assay were used to detect the effects of albumin overload on autophagy marker protein LC3. Transmission electron microscopy and Western blot assay were used to investigate the role of albumin in mitochondrial injury. Western blot assay and co-localization of acidic lysosomes and mitochondria assay were employed to detect the activation of mitophagy induced by albumin. Finally, we explored the role of PINK1/Parkin signaling in albumin-induced mitophagy by inhibiting mitophagy by knockdown of PARK2 (Parkin) level. RESULTS Immunofluorescence and Western blot results showed that the expression level of LC3-II increased, and the maximum increase point was observed after 8 h of albumin treatment. Transmission electron microscopy results demonstrated that albumin overload-induced mitochondrial injury and quantity of autophagosomes increased. Additionally, expression of PINK1 and cytosolic cytochrome C increased and mitochondria cytochrome C decreased in the albumin group. The co-localization of acidic lysosomes and mitochondria demonstrated that the number of albumin overload-induced mitophagy-positive dots increased. The transient transfection of PARK2 siRNA result showed knockdown of the expression level of PARK2 can inhibit mitophagy induced by albumin. CONCLUSIONS In conclusion, our study suggests that mitochondrial dysfunction activates the PINK1/Parkin signaling and mitophagy in renal tubular epithelial cells under albumin overload condition.

Deciphering RNA-Recognition Patterns of Intrinsically Disordered Proteins.

PubMed

Srivastava, Ambuj; Ahmad, Shandar; Gromiha, M Michael

2018-05-29

Intrinsically disordered regions (IDRs) and protein (IDPs) are highly flexible owing to their lack of well-defined structures. A subset of such proteins interacts with various substrates; including RNA; frequently adopting regular structures in the final complex. In this work; we have analysed a dataset of protein⁻RNA complexes undergoing disorder-to-order transition (DOT) upon binding. We found that DOT regions are generally small in size (less than 3 residues) for RNA binding proteins. Like structured proteins; positively charged residues are found to interact with RNA molecules; indicating the dominance of electrostatic and cation-π interactions. However, a comparison of binding frequency shows that interface hydrophobic and aromatic residues have more interactions in only DOT regions than in a protein. Further; DOT regions have significantly higher exposure to water than their structured counterparts. Interactions of DOT regions with RNA increase the sheet formation with minor changes in helix forming residues. We have computed the interaction energy for amino acids⁻nucleotide pairs; which showed the preference of His⁻G; Asn⁻U and Ser⁻U at for the interface of DOT regions. This study provides insights to understand protein⁻RNA interactions and the results could also be used for developing a tool for identifying DOT regions in RNA binding proteins.

Organic-inorganic nanostructures for luminescent indication in the near-infrared range

NASA Astrophysics Data System (ADS)

Kondratenko, T. S.; Ovchinnikov, O. V.; Grevtseva, I. G.; Smirnov, M. S.

2016-04-01

Amplifying and quenching of IR luminescence of colloidal Ag2S quantum dots were revealed to take place when they couple to organic dye molecules of 3,3'-di-(γ-sulfopropyl)-9-ethyl-4,5,4',5'-dibenzothiacarbocyanine betaine and erytrosine pyridinium salts, respectively. The observed effects are explained as due to the formation of organic-inorganic heterostructures with different mutual arrangement of electronic states of the dyes and the quantum dots.

Distribution of elastic strains appearing in gallium arsenide as a result of doping with isovalent impurities of phosphorus and indium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavlov, D. A.; Bidus, N. V.; Bobrov, A. I., E-mail: bobrov@phys.unn.ru

2015-01-15

The distribution of elastic strains in a system consisting of a quantum-dot layer and a buried GaAs{sub x}P{sub 1−x} layer is studied using geometric phase analysis. A hypothesis is offered concerning the possibility of controlling the process of the formation of InAs quantum dots in a GaAs matrix using a local isovalent phosphorus impurity.

In-situ confined formation of NiFe layered double hydroxide quantum dots in expanded graphite for active electrocatalytic oxygen evolution

NASA Astrophysics Data System (ADS)

Guo, Jinxue; Li, Xiaoyan; Sun, Yanfang; Liu, Qingyun; Quan, Zhenlan; Zhang, Xiao

2018-06-01

Development of noble-metal-free catalysts towards highly efficient electrochemical oxygen evolution reaction (OER) is critical but challenging in the renewable energy area. Herein, we firstly embed NiFe LDHs quantum dots (QDs) into expanded graphite (NiFe LDHs/EG) via in-situ confined formation process. The interlayer spacing of EG layers acts as nanoreactors for spatially confined formation of NiFe LDHs QDs. The QDs supply huge catalytic sites for OER. The in-situ decoration endows the strong affinity between QDs with EG, thus inducing fast charge transfer. Based on the aforementioned benefits, the designed catalyst exhibits outstanding OER properties, in terms of small overpotential (220 mV required to generate 10 mA cm-2), low Tafel slope, and good durable stability, making it a promising candidate for inexpensive OER catalyst.

Interface formation during silica encapsulation of colloidal CdSe/CdS quantum dots observed by in situ Raman spectroscopy

NASA Astrophysics Data System (ADS)

Biermann, Amelie; Aubert, Tangi; Baumeister, Philipp; Drijvers, Emile; Hens, Zeger; Maultzsch, Janina

2017-04-01

We investigate the encapsulation of CdSe/CdS quantum dots (QDs) in a silica shell by in situ Raman spectroscopy and find a distinct shift of the CdS Raman signal during the first hours of the synthesis. This shift does not depend on the final silica shell thickness but on the properties of the initial core-shell QD. We find a correlation between the Raman shift rate and the speed of the silica formation and attribute this to the changing configuration of the outermost layers of the QD shell, where an interface to the newly formed silica is created. This dependence of Raman shift rate on the speed of silica formation process will give rise to many possible studies concerning the growth mechanism in the water-in-oil microemulsion, rendering in situ Raman a valuable instrument in monitoring this type of reaction.

Strategy for synthesizing quantum dot-layered double hydroxide nanocomposites and their enhanced photoluminescence and photostability.

PubMed

Cho, Seungho; Jung, Sungwook; Jeong, Sanghwa; Bang, Jiwon; Park, Joonhyuck; Park, Youngrong; Kim, Sungjee

2013-01-08

Layered double hydroxide-quantum dot (LDH-QD) composites are synthesized via a room temperature LDH formation reaction in the presence of QDs. InP/ZnS (core/shell) QD, a heavy metal free QD, is used as a model constituent. Interactions between QDs (with negative zeta potentials), decorated with dihydrolipoic acids, and inherently positively charged metal hydroxide layers of LDH during the LDH formations are induced to form the LDH-QD composites. The formation of the LDH-QD composites affords significantly enhanced photoluminescence quantum yields and thermal- and photostabilities compared to their QD counterparts. In addition, the fluorescence from the solid LDH-QD composite preserved the initial optical properties of the QD colloid solution without noticeable deteriorations such as red-shift or deep trap emission. Based on their advantageous optical properties, we also demonstrate the pseudo white light emitting diode, down-converted by the LDH-QD composites.

A Quick and Parallel Analytical Method Based on Quantum Dots Labeling for ToRCH-Related Antibodies

NASA Astrophysics Data System (ADS)

Yang, Hao; Guo, Qing; He, Rong; Li, Ding; Zhang, Xueqing; Bao, Chenchen; Hu, Hengyao; Cui, Daxiang

2009-12-01

Quantum dot is a special kind of nanomaterial composed of periodic groups of II-VI, III-V or IV-VI materials. Their high quantum yield, broad absorption with narrow photoluminescence spectra and high resistance to photobleaching, make them become a promising labeling substance in biological analysis. Here, we report a quick and parallel analytical method based on quantum dots for ToRCH-related antibodies including Toxoplasma gondii, Rubella virus, Cytomegalovirus and Herpes simplex virus type 1 (HSV1) and 2 (HSV2). Firstly, we fabricated the microarrays with the five kinds of ToRCH-related antigens and used CdTe quantum dots to label secondary antibody and then analyzed 100 specimens of randomly selected clinical sera from obstetric outpatients. The currently prevalent enzyme-linked immunosorbent assay (ELISA) kits were considered as “golden standard” for comparison. The results show that the quantum dots labeling-based ToRCH microarrays have comparable sensitivity and specificity with ELISA. Besides, the microarrays hold distinct advantages over ELISA test format in detection time, cost, operation and signal stability. Validated by the clinical assay, our quantum dots-based ToRCH microarrays have great potential in the detection of ToRCH-related pathogens.

Real-time spectro-ellipsometric approach to distinguish between two-dimensional Ge layer growth and Ge dot formation on SiO2 substrates

NASA Astrophysics Data System (ADS)

Akazawa, Housei

2018-04-01

Morphological evolution of Ge layers on SiO2 substrates grown by photo-excited chemical vapor deposition from GeH4 was monitored in real time by recording (Ψ, Δ) angles of spectroscopic ellipsometry and ex-situ analyzed by atomic force microscopy (AFM). Distinct Ψ-Δ trajectory shapes were demonstrated to discriminate the two-dimensional (2D) and three-dimensional (3D) growth modes. While the trajectory of 2D growth is characterized by a one-turn spiral, that of 3D growth consisted of three sections corresponding to initial wetting of the SiO2 surface, creation of nucleation centers, and dot growth. The critical point where the system turns into 2D or 3D growth can be in situ identified in terms of the directions of the Ψ-Δ trajectories. AFM images revealed characteristic changes in the microstructure, including self-assembling dots and dots merging with one another. While the root-mean-square surface roughness increased linearly against film thickness, the maximum peak-to-valley height deviated once from linear dependence and later returned back to it, which reflected coarsening of dots and embedding of valleys between dots.

Near-identical star formation rate densities from Hα and FUV at redshift zero

NASA Astrophysics Data System (ADS)

Audcent-Ross, Fiona M.; Meurer, Gerhardt R.; Wong, O. I.; Zheng, Z.; Hanish, D.; Zwaan, M. A.; Bland-Hawthorn, J.; Elagali, A.; Meyer, M.; Putman, M. E.; Ryan-Weber, E. V.; Sweet, S. M.; Thilker, D. A.; Seibert, M.; Allen, R.; Dopita, M. A.; Doyle-Pegg, M. T.; Drinkwater, M.; Ferguson, H. C.; Freeman, K. C.; Heckman, T. M.; Kennicutt, R. C.; Kilborn, V. A.; Kim, J. H.; Knezek, P. M.; Koribalski, B.; Smith, R. C.; Staveley-Smith, L.; Webster, R. L.; Werk, J. K.

2018-06-01

For the first time both Hα and far-ultraviolet (FUV) observations from an H I-selected sample are used to determine the dust-corrected star formation rate density (SFRD: \\dot{ρ }) in the local Universe. Applying the two star formation rate indicators on 294 local galaxies we determine log(\\dot{ρ } _{Hα }) = -1.68 ^{+0.13}_{-0.05} [M⊙ yr-1 Mpc-3] and log(\\dot{ρ }_{FUV}) = -1.71 ^{+0.12}_{-0.13} [M⊙ yr-1 Mpc-3]. These values are derived from scaling Hα and FUV observations to the H I mass function. Galaxies were selected to uniformly sample the full H I mass (M_{H I}) range of the H I Parkes All-Sky Survey (M_{H I} ˜ 107 to ˜1010.7 M⊙). The approach leads to relatively larger sampling of dwarf galaxies compared to optically-selected surveys. The low H I mass, low luminosity and low surface brightness galaxy populations have, on average, lower Hα/FUV flux ratios than the remaining galaxy populations, consistent with the earlier results of Meurer. The near-identical Hα- and FUV-derived SFRD values arise with the low Hα/FUV flux ratios of some galaxies being offset by enhanced Hα from the brightest and high mass galaxy populations. Our findings confirm the necessity to fully sample the H I mass range for a complete census of local star formation to include lower stellar mass galaxies which dominate the local Universe.

AgCl-doped CdSe quantum dots with near-IR photoluminescence.

PubMed

Kotin, Pavel Aleksandrovich; Bubenov, Sergey Sergeevich; Mordvinova, Natalia Evgenievna; Dorofeev, Sergey Gennadievich

2017-01-01

We report the synthesis of colloidal CdSe quantum dots doped with a novel Ag precursor: AgCl. The addition of AgCl causes dramatic changes in the morphology of synthesized nanocrystals from spherical nanoparticles to tetrapods and finally to large ellipsoidal nanoparticles. Ellipsoidal nanoparticles possess an intensive near-IR photoluminescence ranging up to 0.9 eV (ca. 1400 nm). In this article, we explain the reasons for the formation of the ellipsoidal nanoparticles as well as the peculiarities of the process. The structure, Ag content, and optical properties of quantum dots are also investigated. The optimal conditions for maximizing both the reaction yield and IR photoluminescence quantum yield are found.

Pattern transfer with stabilized nanoparticle etch masks

NASA Astrophysics Data System (ADS)

Hogg, Charles R.; Picard, Yoosuf N.; Narasimhan, Amrit; Bain, James A.; Majetich, Sara A.

2013-03-01

Self-assembled nanoparticle monolayer arrays are used as an etch mask for pattern transfer into Si and SiOx substrates. Crack formation within the array is prevented by electron beam curing to fix the nanoparticles to the substrate, followed by a brief oxygen plasma to remove excess carbon. This leaves a dot array of nanoparticle cores with a minimum gap of 2 nm. Deposition and liftoff can transform the dot array mask into an antidot mask, where the gap is determined by the nanoparticle core diameter. Reactive ion etching is used to transfer the dot and antidot patterns into the substrate. The effect of the gap size on the etching rate is modeled and compared with the experimental results.

Influence of pH on the quantum-size-controlled photoelectrochemical etching of epitaxial InGaN quantum dots

DOE PAGES

Xiao, Xiaoyin; Lu, Ping; Fischer, Arthur J.; ...

2015-11-18

Illumination by a narrow-band laser has been shown to enable photoelectrochemical (PEC) etching of InGaN thin films into quantum dots with sizes controlled by the laser wavelength. Here, we investigate and elucidate the influence of solution pH on such quantum-size-controlled PEC etch process. We find that although a pH above 5 is often used for PEC etching of GaN-based materials, oxides (In 2O 3 and/or Ga 2O 3) form which interfere with quantum dot formation. Furthermore, at pH below 3, however, oxide-free QDs with self-terminated sizes can be successfully realized.

PRISM3 DOT1 Atlantic Basin Reconstruction

USGS Publications Warehouse

Dowsett, Harry; Robinson, Marci; Dwyer, Gary S.; Chandler, Mark; Cronin, Thomas

2006-01-01

PRISM3 DOT1 (Pliocene Research, Interpretation and Synoptic Mapping 3, Deep Ocean Temperature 1) provides a three-dimensional temperature reconstruction for the mid-Pliocene Atlantic basin, the first of several regional data sets that will comprise a global mid-Pliocene reconstruction. DOT1 is an alteration of modern temperature values for the Atlantic Ocean in 4 degree x 5 degree cells in 13 depth layers for December 1 based on Mg/Ca-derived BWT estimates from seventeen DSDP and ODP Sites and SST estimates from the PRISM2 reconstruction (Dowsett et al., 1999). DOT1 reflects a vaguely modern circulation system, assuming similar processes of deep-water formation; however, North Atlantic Deep Water (NADW) production is increased, and Antarctic Bottom Water (AABW) production is decreased. Pliocene NADW was approximately 2 degreesC warmer than modern temperatures, and Pliocene AABW was approximately 0.3 degreesC warmer than modern temperatures.

Growing High-Quality InAs Quantum Dots for Infrared Lasers

NASA Technical Reports Server (NTRS)

Qiu, Yueming; Uhl, David

2004-01-01

An improved method of growing high-quality InAs quantum dots embedded in lattice-matched InGaAs quantum wells on InP substrates has been developed. InAs/InGaAs/InP quantum dot semiconductor lasers fabricated by this method are capable of operating at room temperature at wavelengths greater than or equal to 1.8 mm. Previously, InAs quantum dot lasers based on InP substrates have been reported only at low temperature of 77 K at a wavelength of 1.9 micrometers. In the present method, as in the prior method, one utilizes metalorganic vapor phase epitaxy to grow the aforementioned semiconductor structures. The development of the present method was prompted in part by the observation that when InAs quantum dots are deposited on an InGaAs layer, some of the InAs in the InGaAs layer becomes segregated from the layer and contributes to the formation of the InAs quantum dots. As a result, the quantum dots become highly nonuniform; some even exceed a critical thickness, beyond which they relax. In the present method, one covers the InGaAs layer with a thin layer of GaAs before depositing the InAs quantum dots. The purpose and effect of this thin GaAs layer is to suppress the segregation of InAs from the InGaAs layer, thereby enabling the InAs quantum dots to become nearly uniform (see figure). Devices fabricated by this method have shown near-room-temperature performance.

SHORT-LIVED STAR-FORMING GIANT CLUMPS IN COSMOLOGICAL SIMULATIONS OF z Almost-Equal-To 2 DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genel, Shy; Genzel, Reinhard; Foerster Schreiber, Natascha M.

Many observed massive star-forming z Almost-Equal-To 2 galaxies are large disks that exhibit irregular morphologies, with Almost-Equal-To 1 kpc, Almost-Equal-To 10{sup 8}-10{sup 10}M{sub o-dot} clumps. We present the largest sample to date of high-resolution cosmological smoothed particle hydrodynamics simulations that zoom-in on the formation of individual M{sub *} Almost-Equal-To 10{sup 10.5}M{sub o-dot} galaxies in Almost-Equal-To 10{sup 12}M{sub o-dot} halos at z Almost-Equal-To 2. Our code includes strong stellar feedback parameterized as momentum-driven galactic winds. This model reproduces many characteristic features of this observed class of galaxies, such as their clumpy morphologies, smooth and monotonic velocity gradients, high gas fractions (f{submore » g} Almost-Equal-To 50%), and high specific star formation rates ({approx}>1 Gyr{sup -1}). In accord with recent models, giant clumps (M{sub clump} Almost-Equal-To (5 Multiplication-Sign 10{sup 8}-10{sup 9})M{sub o-dot}) form in situ via gravitational instabilities. However, the galactic winds are critical for their subsequent evolution. The giant clumps we obtain are short-lived and are disrupted by wind-driven mass loss. They do not virialize or migrate to the galaxy centers as suggested in recent work neglecting strong winds. By phenomenologically implementing the winds that are observed from high-redshift galaxies and in particular from individual clumps, our simulations reproduce well new observational constraints on clump kinematics and clump ages. In particular, the observation that older clumps appear closer to their galaxy centers is reproduced in our simulations, as a result of inside-out formation of the disks rather than inward clump migration.« less

The impact of numeracy on reactions to different graphic risk presentation formats: An experimental analogue study.

PubMed

Wright, Alison J; Whitwell, Sophia C L; Takeichi, Chika; Hankins, Matthew; Marteau, Theresa M

2009-02-01

Numeracy, the ability to process basic mathematical concepts, may affect responses to graphical displays of health risk information. Displays of probabilistic risk information using grouped dots are easier to understand than displays using dispersed dots. However, dispersed dots may better convey the randomness with which health threats occur, so increasing perceived susceptibility. We hypothesized that low numeracy participants would better understand risks presented using grouped dot displays, while high numeracy participants would have good understanding, regardless of display type. Moreover, we predicted that dispersed dot displays, in contrast to grouped dot displays, would increase risk perceptions and worry only for highly numerate individuals. One hundred and forty smokers read vignettes asking them to imagine being at risk of Crohn's disease, in a 2(display type: dispersed/grouped dots) x 3(risk magnitude: 3%/6%/50%) x 2(numeracy: high/low) design. They completed measures of risk comprehension, perceived susceptibility and worry. More numerate participants had better objective risk comprehension, but this effect was not moderated by display type. There was marginally significant support for the predicted numeracy x display type interaction for worry about Crohn's disease, but not for perceived susceptibility to the condition. Dispersed dot displays somewhat increase worry in highly numerate individuals, but only numeracy influenced objective risk comprehension. The most effective display type for communicating risk information will depend on the numeracy of the population and the goal(s) of the communication.

InAs wetting layer and quantum dots on GaAs(001) surface studied by in situ STM placed inside MBE growth chamber and kMC simulations based on first-principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsukamoto, S.; Arakawa, Y.; Bell, G. R.

2007-04-10

Dynamic images of InAs quantum dots (QDs) formation are obtained using a unique scanning tunneling microscope (STM) placed within the growth chamber. These images are interpreted with the aid of kinetic Monte Carlo (kMC) simulations of the QD nucleation process. Alloy fluctuations in the InGaAs wetting layer prior to QD formation assist in the nucleation of stable InAs islands containing tens of atoms which grow extremely rapidly to form QDs. Furthermore, not all deposited In is initially incorporated into the lattice, providing a large supply of material to rapidly form QDs at the critical thickness.

Forming the First Stars in the Universe: The Fragmentation of Primordial Gas.

PubMed

Bromm; Coppi; Larson

1999-12-10

In order to constrain the initial mass function of the first generation of stars (Population III), we investigate the fragmentation properties of metal-free gas in the context of a hierarchical model of structure formation. We investigate the evolution of an isolated 3 sigma peak of mass 2x106 M middle dot in circle that collapses at zcoll approximately 30 using smoothed particle hydrodynamics. We find that the gas dissipatively settles into a rotationally supported disk that has a very filamentary morphology. The gas in these filaments is Jeans unstable with MJ approximately 103 M middle dot in circle. Fragmentation leads to the formation of high-density (n>108 cm-3) clumps that subsequently grow in mass by accreting the surrounding gas and by merging with other clumps up to masses of approximately 104 M middle dot in circle. This suggests that the very first stars were rather massive. We explore the complex dynamics of the merging and tidal disruption of these clumps by following their evolution over a few dynamical times.

Nano-Bio Engineered Carbon Dot-Peptide Functionalized Water Dispersible Hyperbranched Polyurethane for Bone Tissue Regeneration.

PubMed

Gogoi, Satyabrat; Maji, Somnath; Mishra, Debasish; Devi, K Sanjana P; Maiti, Tapas Kumar; Karak, Niranjan

2017-03-01

The present study delves into a combined bio-nano-macromolecular approach for bone tissue engineering. This approach relies on the properties of an ideal scaffold material imbued with all the chemical premises required for fostering cellular growth and differentiation. A tannic acid based water dispersible hyperbranched polyurethane is fabricated with bio-nanohybrids of carbon dot and four different peptides (viz. SVVYGLR, PRGDSGYRGDS, IPP, and CGGKVGKACCVPTKLSPISVLYK) to impart target specific in vivo bone healing ability. This polymeric bio-nanocomposite is blended with 10 wt% of gelatin and examined as a non-invasive delivery vehicle. In vitro assessment of the developed polymeric system reveals good osteoblast adhesion, proliferation, and differentiation. Aided by this panel of peptides, the polymeric bio-nanocomposite exhibits in vivo ectopic bone formation ability. The study on in vivo mineralization and vascularization reveals the occurrence of calcification and blood vessel formation. Thus, the study demonstrates carbon dot/peptide functionalized hyperbranched polyurethane gel for bone tissue engineering application. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultra-broad band, low power, highly efficient coherent wavelength conversion in quantum dot SOA.

PubMed

Contestabile, G; Yoshida, Y; Maruta, A; Kitayama, K

2012-12-03

We report broadband, all-optical wavelength conversion over 100 nm span, in full S- and C-band, with positive conversion efficiency with low optical input power exploiting dual pump Four-Wave-Mixing in a Quantum Dot Semiconductor Optical Amplifier (QD-SOA). We also demonstrate by Error Vector Magnitude analysis the full transparency of the conversion scheme for coherent modulation formats (QPSK, 8-PSK, 16-QAM, OFDM-16QAM) in the whole C-band.

Microwave formation and photoluminescence mechanisms of multi-states nitrogen doped carbon dots

NASA Astrophysics Data System (ADS)

He, Guili; Shu, Mengjun; Yang, Zhi; Ma, Yujie; Huang, Da; Xu, Shusheng; Wang, Yanfang; Hu, Nantao; Zhang, Yafei; Xu, Lin

2017-11-01

In recent years, carbon dots (CDs) have attracted much attention in the material field because of their remarkable performance in various aspects. Therefore, the exploration of complex and variable photoluminescence mechanisms shows great significance. Herein, we present a systematic study on the correlation between the formation process and photoluminescence mechanisms through the characterization and analysis of three states of nitrogen doped carbon dots (N-CDs) obtained by microwave irradiation. At low temperature of 160 °C, the small organic molecule polymer nanodots whose photoluminescence center is molecule state are obtained with superior quantum yield of about 51.61%. Increasing the reaction temperature up to 200 °C, the intermediate transition products named carbon nanodots begin to appear. Prolonging the holding time, the typical carbon quantum dots with a special stable optical properties are finally generated, and their most photoluminescence arises from the carbon cores which are gained through the polymerization, dehydration, carbonation of organic fluorescent molecules. Furthermore, N-CDs have been applied in metal ions detection as well as animal and plant cell fluorescence imaging owing to their excellent water solubility and low cytotoxicity. Our exploration provides the theoretical basis for synthesis of CDs with different properties and purposes. In the near future, more high-quality CDs will be developed in order to better benefit the various fields of mankind.

Patterned growth of individual and multiple vertically aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Merkulov, V. I.; Lowndes, D. H.; Wei, Y. Y.; Eres, G.; Voelkl, E.

2000-06-01

The results of studies of patterned growth of vertically aligned carbon nanofibers (VACNFs) prepared by plasma-enhanced chemical vapor deposition are reported. Nickel (Ni) dots of various diameters and Ni lines with variable widths and shapes were fabricated using electron beam lithography and evaporation, and served for catalytic growth of VACNFs whose structure was determined by high resolution transmission electron microscopy. It is found that upon plasma pre-etching and heating up to 600-700 °C, thin films of Ni break into droplets which initiate the growth of VACNFs. Above a critical dot size multiple droplets are formed, and consequently multiple VACNFs grow from a single evaporated dot. For dot sizes smaller than the critical size only one droplet is formed, resulting in a single VACNF. In the case of a patterned line, the growth mechanism is similar to that from a dot. VACNFs grow along the line, and above a critical linewidth multiple VACNFs are produced across the line. The mechanism of the formation of single and multiple catalyst droplets and subsequently of VACNFs is discussed.

Loss of adiabaticity with increasing tunneling gap in nonintegrable multistate Landau-Zener models

NASA Astrophysics Data System (ADS)

Malla, Rajesh K.; Raikh, M. E.

2017-09-01

We consider the simplest nonintegrable model of the multistate Landau-Zener transition. In this model, two pairs of levels in two tunnel-coupled quantum dots are swept past each other by the gate voltage. Although this 2 ×2 model is nonintegrable, it can be solved analytically in the limit when the interlevel energy distance is much smaller than their tunnel splitting. The result is contrasted to the similar 2 ×1 model, in which one of the dots contains only one level. The latter model does not allow interference of the virtual transition amplitudes, and it is exactly solvable. In the 2 ×1 model, the probability for a particle, residing at time t →-∞ in one dot, to remain in the same dot at t →∞ , falls off exponentially with tunnel coupling. By contrast, in the 2 ×2 model, this probability grows rapidly with tunnel coupling. The physical origin of this growth is the formation of the tunneling-induced collective states in the system of two dots. This can be viewed as a manifestation of the Dicke effect.

Cathodic Corrosion at the Bismuth-Ionic Liquid Electrolyte Interface under Conditions for CO 2 Reduction

DOE PAGES

Medina Ramos, Jonnathan; Zhang, Weiwei; Yoon, Kichul; ...

2018-03-08

Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im])(+))-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi 2O 3 layer. This oxide layer gets reduced to Bi(0)during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM](+)) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between -1.5 and -1.9 V vs Ag/AgCI due to a similar to 4-10% thinning and a similar to 40% decrease in lateral sizemore » of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density functional theory (DFT) calculations. Both approaches indicate that [Im] + cations bind to the metal surface more strongly than tetrabutylammonium (TBA +) as the potential and the charge on the Bi surface become more negative. ReaxFF simulations predict a higher degree of disorder for a negatively charged Bi (001) slab in the presence of the [Im](+)cations and substantial migration of Bi atoms from the surface. DFT simulations show the formation of Bi center dot center dot center dot[Im] + complexes that lead to the dissolution of Bi atoms from step edges on the Bi (001) surface at potentials between -1.65 and -1.95 V. Bi desorption from a flat terrace requires a potential of approximately -2.25 V. Together, these results suggest the formation of a Bi center dot center dot center dot[Im] + complex through partial cathodic corrosion of the Bi film under conditions (potential and electrolyte composition) that favor the catalytic reduction of CO 2 .« less

Cathodic Corrosion at the Bismuth-Ionic Liquid Electrolyte Interface under Conditions for CO 2 Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medina Ramos, Jonnathan; Zhang, Weiwei; Yoon, Kichul

Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im])(+))-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi 2O 3 layer. This oxide layer gets reduced to Bi(0)during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM](+)) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between -1.5 and -1.9 V vs Ag/AgCI due to a similar to 4-10% thinning and a similar to 40% decrease in lateral sizemore » of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density functional theory (DFT) calculations. Both approaches indicate that [Im] + cations bind to the metal surface more strongly than tetrabutylammonium (TBA +) as the potential and the charge on the Bi surface become more negative. ReaxFF simulations predict a higher degree of disorder for a negatively charged Bi (001) slab in the presence of the [Im](+)cations and substantial migration of Bi atoms from the surface. DFT simulations show the formation of Bi center dot center dot center dot[Im] + complexes that lead to the dissolution of Bi atoms from step edges on the Bi (001) surface at potentials between -1.65 and -1.95 V. Bi desorption from a flat terrace requires a potential of approximately -2.25 V. Together, these results suggest the formation of a Bi center dot center dot center dot[Im] + complex through partial cathodic corrosion of the Bi film under conditions (potential and electrolyte composition) that favor the catalytic reduction of CO 2 .« less

Spectroscopic manifestations of hybrid association of CdS colloidal quantum dots with J-aggregates of a thiatrimethine cyanine dye

NASA Astrophysics Data System (ADS)

Ovchinnikov, O. V.; Smirnov, M. S.; Shapiro, B. I.; Dedikova, A. O.; Shatskikh, T. S.

2015-11-01

We have found spectroscopic manifestations of hybrid association in mixtures of CdS colloidal quantum dots with an average size of 2.5-4.2 nm with J-aggregates of pyridinium salt of the 3,3'-di-(γ- sulfopropyl)-9-ethyl-4,5,4',5'-dibenzo-thiacarbocyanine betaine dye that were prepared by the sol-gel method in gelatin. Observed changes of the spectral properties of J-aggregates of dye molecules due to their hybrid association with CdS quantum dots are ensured by steric transformations of dye molecules, which lead to the formation of luminescent trans-J-aggregates. The hybrid association is accompanied by the quenching of the recombination luminescence band of CdS quantum dots (540-640 nm) and by an increase in the luminescence intensity of J-aggregates of dye molecules (670-680 nm). This regularity becomes enhanced with an increase in the ratio of the number of dye molecules to the number of quantum dots [ n dye]: [ n QD] and in the degree of overlap between the luminescence spectrum of quantum dots and the absorption spectrum of J-aggregates, which indicates that there is a resonant nonradiative transfer of the electronic excitation energy from recombination luminescence centers in CdS quantum dots to trans-J-aggregates of dye molecules conjugated to them.

Multiplex autoantibody detection for autoimmune liver diseases and autoimmune gastritis.

PubMed

Vanderlocht, Joris; van der Cruys, Mart; Stals, Frans; Bakker-Jonges, Liesbeth; Damoiseaux, Jan

2017-09-01

Autoantibody detection for autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC) and autoimmune gastritis (AIG) is traditionally performed by IIF on a combination of tissues. Multiplex line/dot blots (LIA/DIA) offer multiple advantages, i.e. automation, objective reading, no interfering reactivities, no coincidental findings. In the current study we evaluated automated DIA (D-Tek) for detecting autoantibodies related to autoimmune diseases of the gastrointestinal tract. We tested samples of the Dutch EQC program and compared the results with the consensus of the participating labs. For the autoimmune liver diseases and AIG, respectively, 64 and 36 samples were tested. For anti-mitochondrial and anti-smooth muscle antibodies a concordance rate of 97% and 88% was observed, respectively. The concordance rate for anti-parietal cell antibodies was 92% when samples without EQC consensus (n=15) were excluded. For antibodies against intrinsic factor a concordance of 96% was observed. For all these antibodies discrepancies were identified that relate to the different test characteristics and the preponderance of IIF utilizing labs in the EQC program. In conclusion, we observed good agreement of the tested DIA blots with the consensus results of the Dutch EQC program. Taken together with the logistic advantages these blots are a good alternative for autoantibody detection in the respective diseases. A large prospective multicenter study is warranted to position these novel tests further in the whole spectrum of assays for the detection of these antibodies in a routine autoimmune laboratory. Copyright © 2017 Elsevier B.V. All rights reserved.

Streptococcus pneumoniae PstS production is phosphate responsive and enhanced during growth in the murine peritoneal cavity

NASA Technical Reports Server (NTRS)

Orihuela, C. J.; Mills, J.; Robb, C. W.; Wilson, C. J.; Watson, D. A.; Niesel, D. W.

2001-01-01

Differential display-PCR (DDPCR) was used to identify a Streptococcus pneumoniae gene with enhanced transcription during growth in the murine peritoneal cavity. Northern dot blot analysis and comparative densitometry confirmed a 1.8-fold increase in expression of the encoded sequence following murine peritoneal culture (MPC) versus laboratory culture or control culture (CC). Sequencing and basic local alignment search tool analysis identified the DDPCR fragment as pstS, the phosphate-binding protein of a high-affinity phosphate uptake system. PCR amplification of the complete pstS gene followed by restriction analysis and sequencing suggests a high level of conservation between strains and serotypes. Quantitative immunodot blotting using antiserum to recombinant PstS (rPstS) demonstrated an approximately twofold increase in PstS production during MPC from that during CCs, a finding consistent with the low levels of phosphate observed in the peritoneum. Moreover, immunodot blot and Northern analysis demonstrated phosphate-dependent production of PstS in six of seven strains examined. These results identify pstS expression as responsive to the MPC environment and extracellular phosphate concentrations. Presently, it remains unclear if phosphate concentrations in vivo contribute to the regulation of pstS. Finally, polyclonal antiserum to rPstS did not inhibit growth of the pneumococcus in vitro, suggesting that antibodies do not block phosphate uptake; moreover, vaccination of mice with rPstS did not protect against intraperitoneal challenge as assessed by the 50% lethal dose.

Production and characterization of monoclonal antibodies to budgerigar fledgling disease virus major capsid protein VP

NASA Technical Reports Server (NTRS)

Fattaey, A.; Lenz, L.; Consigli, R. A.; Spooner, B. S. (Principal Investigator)

1992-01-01

Eleven hybridoma cell lines producing monoclonal antibodies (MAbs) against intact budgerigar fledgling disease (BFD) virions were produced and characterized. These antibodies were selected for their ability to react with BFD virions in an enzyme-linked immunosorbent assay. Each of these antibodies was reactive in the immunofluorescent detection of BFD virus-infected cells. These antibodies immunoprecipitated intact virions and specifically recognized the major capsid protein, VP1, of the dissociated virion. The MAbs were found to preferentially recognize native BFD virus capsid protein when compared with denatured virus protein. These MAbs were capable of detecting BFD virus protein in chicken embryonated cell-culture lysates by dot-blot analysis.

Avian pathogenic Escherichia coli bind fibronectin and laminin.

PubMed

Ramírez, Rosa María; Almanza, Yolanda; González, Rafael; García, Santos; Heredia, Norma

2009-04-01

Avian colisepticemia frequently occurs after respiratory tract damage, the primary site for infection allows bacteria to encounter an exposed basement membrane, where laminin and fibronectin are important components. We investigated the ability of an isolate of avian pathogenic Escherichia coli to bind fibronectin and laminin. Using Far-western dot blot analysis, we demonstrated the ability of this microorganism to bind basement membrane proteins fibronectin and laminin. Results from an ELISA-based approach indicate that the binding to these membrane proteins was bacterial-dose dependent. Furthermore, two specific E. coli polypeptides, of 32 kDa and 130 kDa, reacted with laminin and fibronectin, respectively. Further evaluation of these potential bacterial adhesins may provide insights into the pathogenesis of colibacillosis.

De Novo Centromere Formation and Centromeric Sequence Expansion in Wheat and its Wide Hybrids.

PubMed

Guo, Xiang; Su, Handong; Shi, Qinghua; Fu, Shulan; Wang, Jing; Zhang, Xiangqi; Hu, Zanmin; Han, Fangpu

2016-04-01

Centromeres typically contain tandem repeat sequences, but centromere function does not necessarily depend on these sequences. We identified functional centromeres with significant quantitative changes in the centromeric retrotransposons of wheat (CRW) contents in wheat aneuploids (Triticum aestivum) and the offspring of wheat wide hybrids. The CRW signals were strongly reduced or essentially lost in some wheat ditelosomic lines and in the addition lines from the wide hybrids. The total loss of the CRW sequences but the presence of CENH3 in these lines suggests that the centromeres were formed de novo. In wheat and its wide hybrids, which carry large complex genomes or no sequenced genome, we performed CENH3-ChIP-dot-blot methods alone or in combination with CENH3-ChIP-seq and identified the ectopic genomic sequences present at the new centromeres. In adcdition, the transcription of the identified DNA sequences was remarkably increased at the new centromere, suggesting that the transcription of the corresponding sequences may be associated with de novo centromere formation. Stable alien chromosomes with two and three regions containing CRW sequences induced by centromere breakage were observed in the wheat-Th. elongatum hybrid derivatives, but only one was a functional centromere. In wheat-rye (Secale cereale) hybrids, the rye centromere-specific sequences spread along the chromosome arms and may have caused centromere expansion. Frequent and significant quantitative alterations in the centromere sequence via chromosomal rearrangement have been systematically described in wheat wide hybridizations, which may affect the retention or loss of the alien chromosomes in the hybrids. Thus, the centromere behavior in wide crosses likely has an important impact on the generation of biodiversity, which ultimately has implications for speciation.

De Novo Centromere Formation and Centromeric Sequence Expansion in Wheat and its Wide Hybrids

PubMed Central

Fu, Shulan; Wang, Jing; Zhang, Xiangqi; Hu, Zanmin; Han, Fangpu

2016-01-01

Centromeres typically contain tandem repeat sequences, but centromere function does not necessarily depend on these sequences. We identified functional centromeres with significant quantitative changes in the centromeric retrotransposons of wheat (CRW) contents in wheat aneuploids (Triticum aestivum) and the offspring of wheat wide hybrids. The CRW signals were strongly reduced or essentially lost in some wheat ditelosomic lines and in the addition lines from the wide hybrids. The total loss of the CRW sequences but the presence of CENH3 in these lines suggests that the centromeres were formed de novo. In wheat and its wide hybrids, which carry large complex genomes or no sequenced genome, we performed CENH3-ChIP-dot-blot methods alone or in combination with CENH3-ChIP-seq and identified the ectopic genomic sequences present at the new centromeres. In adcdition, the transcription of the identified DNA sequences was remarkably increased at the new centromere, suggesting that the transcription of the corresponding sequences may be associated with de novo centromere formation. Stable alien chromosomes with two and three regions containing CRW sequences induced by centromere breakage were observed in the wheat-Th. elongatum hybrid derivatives, but only one was a functional centromere. In wheat-rye (Secale cereale) hybrids, the rye centromere-specific sequences spread along the chromosome arms and may have caused centromere expansion. Frequent and significant quantitative alterations in the centromere sequence via chromosomal rearrangement have been systematically described in wheat wide hybridizations, which may affect the retention or loss of the alien chromosomes in the hybrids. Thus, the centromere behavior in wide crosses likely has an important impact on the generation of biodiversity, which ultimately has implications for speciation. PMID:27110907

Modeling elastic anisotropy in strained heteroepitaxy

NASA Astrophysics Data System (ADS)

Krishna Dixit, Gopal; Ranganathan, Madhav

2017-09-01

Using a continuum evolution equation, we model the growth and evolution of quantum dots in the heteroepitaxial Ge on Si(0 0 1) system in a molecular beam epitaxy unit. We formulate our model in terms of evolution due to deposition, and due to surface diffusion which is governed by a free energy. This free energy has contributions from surface energy, curvature, wetting effects and elastic energy due to lattice mismatch between the film and the substrate. In addition to anisotropy due to surface energy which favors facet formation, we also incorporate elastic anisotropy due to an underlying crystal lattice. The complicated elastic problem of the film-substrate system subjected to boundary conditions at the free surface, interface and the bulk substrate is solved by perturbation analysis using a small slope approximation. This permits an analysis of effects at different orders in the slope and sheds new light on the observed behavior. Linear stability analysis shows the early evolution of the instability towards dot formation. The elastic anisotropy causes a change in the alignment of dots in the linear regime, whereas the surface energy anisotropy changes the dot shapes at the nonlinear regime. Numerical simulation of the full nonlinear equations shows the evolution of the surface morphology. In particular, we show, for parameters of the Ge0.25 Si0.75 on Si(0 0 1), the surface energy anisotropy dominates the shapes of the quantum dots, whereas their alignment is influenced by the elastic energy anisotropy. The anisotropy in elasticity causes a further elongation of the islands whose coarsening is interrupted due to < 1 0 5 > facets on the surface.

Modeling elastic anisotropy in strained heteroepitaxy.

PubMed

Dixit, Gopal Krishna; Ranganathan, Madhav

2017-09-20

Using a continuum evolution equation, we model the growth and evolution of quantum dots in the heteroepitaxial Ge on Si(0 0 1) system in a molecular beam epitaxy unit. We formulate our model in terms of evolution due to deposition, and due to surface diffusion which is governed by a free energy. This free energy has contributions from surface energy, curvature, wetting effects and elastic energy due to lattice mismatch between the film and the substrate. In addition to anisotropy due to surface energy which favors facet formation, we also incorporate elastic anisotropy due to an underlying crystal lattice. The complicated elastic problem of the film-substrate system subjected to boundary conditions at the free surface, interface and the bulk substrate is solved by perturbation analysis using a small slope approximation. This permits an analysis of effects at different orders in the slope and sheds new light on the observed behavior. Linear stability analysis shows the early evolution of the instability towards dot formation. The elastic anisotropy causes a change in the alignment of dots in the linear regime, whereas the surface energy anisotropy changes the dot shapes at the nonlinear regime. Numerical simulation of the full nonlinear equations shows the evolution of the surface morphology. In particular, we show, for parameters of the [Formula: see text] [Formula: see text] on Si(0 0 1), the surface energy anisotropy dominates the shapes of the quantum dots, whereas their alignment is influenced by the elastic energy anisotropy. The anisotropy in elasticity causes a further elongation of the islands whose coarsening is interrupted due to [Formula: see text] facets on the surface.

Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si(001) surface: nucleation, morphology, and CMOS compatibility.

PubMed

Yuryev, Vladimir A; Arapkina, Larisa V

2011-09-05

Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (≲600°C) and high (≳600°C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.

Optical pumping and negative luminescence polarization in charged GaAs quantum dots

NASA Astrophysics Data System (ADS)

Shabaev, Andrew; Stinaff, Eric A.; Bracker, Allan S.; Gammon, Daniel; Efros, Alexander L.; Korenev, Vladimir L.; Merkulov, Igor

2009-01-01

Optical pumping of electron spins and negative photoluminescence polarization are observed when interface quantum dots in a GaAs quantum well are excited nonresonantly by circularly polarized light. Both observations can be explained by the formation of long-lived dark excitons through hole spin relaxation in the GaAs quantum well prior to exciton capture. In this model, optical pumping of resident electron spins is caused by capture of dark excitons and recombination in charged quantum dots. Negative polarization results from accumulation of dark excitons in the quantum well and is enhanced by optical pumping. The dark exciton model describes the experimental results very well, including intensity and bias dependence of the photoluminescence polarization and the Hanle effect.

Dynamics of plasmonic field polarization induced by quantum coherence in quantum dot-metallic nanoshell structures.

PubMed

Sadeghi, S M

2014-09-01

When a hybrid system consisting of a semiconductor quantum dot and a metallic nanoparticle interacts with a laser field, the plasmonic field of the metallic nanoparticle can be normalized by the quantum coherence generated in the quantum dot. In this Letter, we study the states of polarization of such a coherent-plasmonic field and demonstrate how these states can reveal unique aspects of the collective molecular properties of the hybrid system formed via coherent exciton-plasmon coupling. We show that transition between the molecular states of this system can lead to ultrafast polarization dynamics, including sudden reversal of the sense of variations of the plasmonic field and formation of circular and elliptical polarization.

α-Synuclein Fibrils Exhibit Gain of Toxic Function, Promoting Tau Aggregation and Inhibiting Microtubule Assembly*

PubMed Central

Oikawa, Takayuki; Nonaka, Takashi; Terada, Makoto; Tamaoka, Akira; Hisanaga, Shin-ichi; Hasegawa, Masato

2016-01-01

α-Synuclein is the major component of Lewy bodies and Lewy neurites in Parkinson disease and dementia with Lewy bodies and of glial cytoplasmic inclusions in multiple system atrophy. It has been suggested that α-synuclein fibrils or intermediate protofibrils in the process of fibril formation may have a toxic effect on neuronal cells. In this study, we investigated the ability of soluble monomeric α-synuclein to promote microtubule assembly and the effects of conformational changes of α-synuclein on Tau-promoted microtubule assembly. In marked contrast to previous findings, monomeric α-synuclein had no effect on microtubule polymerization. However, both α-synuclein fibrils and protofibrils inhibited Tau-promoted microtubule assembly. The inhibitory effect of α-synuclein fibrils was greater than that of the protofibrils. Dot blot overlay assay and spin-down techniques revealed that α-synuclein fibrils bind to Tau and inhibit microtubule assembly by depleting the Tau available for microtubule polymerization. Using various deletion mutants of α-synuclein and Tau, the acidic C-terminal region of α-synuclein and the basic central region of Tau were identified as regions involved in the binding. Furthermore, introduction of α-synuclein fibrils into cultured cells overexpressing Tau protein induced Tau aggregation. These results raise the possibility that α-synuclein fibrils interact with Tau, inhibit its function to stabilize microtubules, and also promote Tau aggregation, leading to dysfunction of neuronal cells. PMID:27226637

Protection against β-amyloid-induced synaptic and memory impairments via altering β-amyloid assembly by bis(heptyl)-cognitin

PubMed Central

Chang, Lan; Cui, Wei; Yang, Yong; Xu, Shujun; Zhou, Wenhua; Fu, Hongjun; Hu, Shengquan; Mak, Shinghung; Hu, Juwei; Wang, Qin; Pui-Yan Ma, Victor; Chung-lit Choi, Tony; Dik-lung Ma, Edmond; Tao, Liang; Pang, Yuanping; Rowan, Michael J.; Anwyl, Roger; Han, Yifan; Wang, Qinwen

2015-01-01

β-amyloid (Aβ) oligomers have been closely implicated in the pathogenesis of Alzheimer’s disease (AD). We found, for the first time, that bis(heptyl)-cognitin, a novel dimeric acetylcholinesterase (AChE) inhibitor derived from tacrine, prevented Aβ oligomers-induced inhibition of long-term potentiation (LTP) at concentrations that did not interfere with normal LTP. Bis(heptyl)-cognitin also prevented Aβ oligomers-induced synaptotoxicity in primary hippocampal neurons. In contrast, tacrine and donepezil, typical AChE inhibitors, could not prevent synaptic impairments in these models, indicating that the modification of Aβ oligomers toxicity by bis(heptyl)-cognitin might be attributed to a mechanism other than AChE inhibition. Studies by using dot blotting, immunoblotting, circular dichroism spectroscopy, and transmission electron microscopy have shown that bis(heptyl)-cognitin altered Aβ assembly via directly inhibiting Aβ oligomers formation and reducing the amount of preformed Aβ oligomers. Molecular docking analysis further suggested that bis(heptyl)-cognitin presumably interacted with the hydrophobic pockets of Aβ, which confers stabilizing powers and assembly alteration effects on Aβ. Most importantly, bis(heptyl)-cognitin significantly reduced cognitive impairments induced by intra-hippocampal infusion of Aβ oligomers in mice. These results clearly demonstrated how dimeric agents prevent Aβ oligomers-induced synaptic and memory impairments, and offered a strong support for the beneficial therapeutic effects of bis(heptyl)-cognitin in the treatment of AD. PMID:26194093

Inhibition of tumor angiogenesis in lung cancer by T4 phage surface displaying mVEGFR2 vaccine.

PubMed

Ren, Shunxiang; Fengyu; Zuo, Shuguang; Zhao, Minyi; Wang, Xiaobin; Wang, Xicai; Chen, Yan; Wu, Zhiping; Ren, Zhaojun

2011-08-05

Vascular endothelial growth factor (VEGF) has been known as a potential vasculogenic and angiogenic factor and its receptor (VEGFR2) is a major receptor to response to the angiogenic activity of VEGF. The technique that to break the immune tolerance of "self-antigens" associated with angiogenesis is an attractive approach for cancer therapy with T4 phage display system. In this experiment, mouse VEGFR2 was constructed on T4 phage nanometer-particle surface as a recombinant vaccine. T4-mVEGFR2 recombinant vaccine was identified by PCR and western blot assay. Immunotherapy with T4-mVEGFR2 was confirmed by protective immunity against Lewis lung carcinoma (LLC) in mice. The antibody against mVEGFR2 was detected by ELISPOT, ELISA and Dot ELISA. The inhibitive effects against angiogenesis were studied using CD31 and CD105 via histological analysis. VEGF-mediated endothelial cells proliferation and tube formation were inhibited in vitro by immunoglobulin induced by T4-mVEGFR2. The antitumor activity was substantiated from the adoptive transfer of the purified immunoglobulin. Antitumor activity and autoantibody production of mVEGFR2 could be neutralized by the depletion of CD4+T lymphocytes. These studies strongly suggest that T4-mVEGFR2 recombinant vaccine might be a promising antitumor approach. Copyright © 2011 Elsevier Ltd. All rights reserved.

Detection of Hepatitis A Virus by the Nucleic Acid Sequence-Based Amplification Technique and Comparison with Reverse Transcription-PCR

PubMed Central

Jean, Julie; Blais, Burton; Darveau, André; Fliss, Ismaïl

2001-01-01

A nucleic acid sequence-based amplification (NASBA) technique for the detection of hepatitis A virus (HAV) in foods was developed and compared to the traditional reverse transcription (RT)-PCR technique. Oligonucleotide primers targeting the VP1 and VP2 genes encoding the major HAV capsid proteins were used for the amplification of viral RNA in an isothermal process resulting in the accumulation of RNA amplicons. Amplicons were detected by hybridization with a digoxigenin-labeled oligonucleotide probe in a dot blot assay format. Using the NASBA, as little as 0.4 ng of target RNA/ml was detected per comparison to 4 ng/ml for RT-PCR. When crude HAV viral lysate was used, a detection limit of 2 PFU (4 × 102 PFU/ml) was obtained with NASBA, compared to 50 PFU (1 × 104 PFU/ml) obtained with RT-PCR. No interference was encountered in the amplification of HAV RNA in the presence of excess nontarget RNA or DNA. The NASBA system successfully detected HAV recovered from experimentally inoculated samples of waste water, lettuce, and blueberries. Compared to RT-PCR and other amplification techniques, the NASBA system offers several advantages in terms of sensitivity, rapidity, and simplicity. This technique should be readily adaptable for detection of other RNA viruses in both foods and clinical samples. PMID:11722911

Detection of hepatitis A virus by the nucleic acid sequence-based amplification technique and comparison with reverse transcription-PCR.

PubMed

Jean, J; Blais, B; Darveau, A; Fliss, I

2001-12-01

A nucleic acid sequence-based amplification (NASBA) technique for the detection of hepatitis A virus (HAV) in foods was developed and compared to the traditional reverse transcription (RT)-PCR technique. Oligonucleotide primers targeting the VP1 and VP2 genes encoding the major HAV capsid proteins were used for the amplification of viral RNA in an isothermal process resulting in the accumulation of RNA amplicons. Amplicons were detected by hybridization with a digoxigenin-labeled oligonucleotide probe in a dot blot assay format. Using the NASBA, as little as 0.4 ng of target RNA/ml was detected per comparison to 4 ng/ml for RT-PCR. When crude HAV viral lysate was used, a detection limit of 2 PFU (4 x 10(2) PFU/ml) was obtained with NASBA, compared to 50 PFU (1 x 10(4) PFU/ml) obtained with RT-PCR. No interference was encountered in the amplification of HAV RNA in the presence of excess nontarget RNA or DNA. The NASBA system successfully detected HAV recovered from experimentally inoculated samples of waste water, lettuce, and blueberries. Compared to RT-PCR and other amplification techniques, the NASBA system offers several advantages in terms of sensitivity, rapidity, and simplicity. This technique should be readily adaptable for detection of other RNA viruses in both foods and clinical samples.

Microwave detector

DOEpatents

Meldner, H.W.; Cusson, R.Y.; Johnson, R.M.

1985-02-08

A microwave detector is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite produces a magnetization field flux that links a B-dot loop. The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

NASA Astrophysics Data System (ADS)

Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

We report the characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. Previously, all heterostructures used to form quantum dots were created using the strain-grading method of strain relaxation, a method that necessarily introduces misfit dislocations into a heterostructure and thereby degrades the reproducibility of quantum devices. Using a SiGe nanomembrane as a virtual substrate eliminates the need for misfit dislocations but requires a wet-transfer process that results in a non-epitaxial interface in close proximity to the quantum dots. We show that this interface does not prevent the formation of quantum dots, and is compatible with a tunable inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of the applied magnetic field. This work was supported in part by ARO (W911NF-12-0607), NSF (DMR-1206915, PHY-1104660), and the United States Department of Defense. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressly or implied, of the US Government. T.J. Knapp et al. (2015). arXiv:1510.08888 [cond-mat.mes-hall].

Specialization in the Human Brain: The Case of Numbers

PubMed Central

Kadosh, Roi Cohen; Bahrami, Bahador; Walsh, Vincent; Butterworth, Brian; Popescu, Tudor; Price, Cathy J.

2011-01-01

How numerical representation is encoded in the adult human brain is important for a basic understanding of human brain organization, its typical and atypical development, its evolutionary precursors, cognitive architectures, education, and rehabilitation. Previous studies have shown that numerical processing activates the same intraparietal regions irrespective of the presentation format (e.g., symbolic digits or non-symbolic dot arrays). This has led to claims that there is a single format-independent, numerical representation. In the current study we used a functional magnetic resonance adaptation paradigm, and effective connectivity analysis to re-examine whether numerical processing in the intraparietal sulci is dependent or independent on the format of the stimuli. We obtained two novel results. First, the whole brain analysis revealed that format change (e.g., from dots to digits), in the absence of a change in magnitude, activated the same intraparietal regions as magnitude change, but to a greater degree. Second, using dynamic causal modeling as a tool to disentangle neuronal specialization across regions that are commonly activated, we found that the connectivity between the left and right intraparietal sulci is format-dependent. Together, this line of results supports the idea that numerical representation is subserved by multiple mechanisms within the same parietal regions. PMID:21808615

The fraction of quiescent massive galaxies in the early Universe

NASA Astrophysics Data System (ADS)

Fontana, A.; Santini, P.; Grazian, A.; Pentericci, L.; Fiore, F.; Castellano, M.; Giallongo, E.; Menci, N.; Salimbeni, S.; Cristiani, S.; Nonino, M.; Vanzella, E.

2009-07-01

Aims: We attempt to compile a complete, mass-selected sample of galaxies with low specific star-formation rates, and compare their properties with theoretical model predictions. Methods: We use the f(24 μ m})/f(K) flux ratio and the SED fitting to the 0.35-8.0 μm spectral distribution, to select quiescent galaxies from z≃ 0.4 to z≃ 4 in the GOODS-MUSIC sample. Our observational selection can be translated into thresholds in specific star-formation rate dot{M}/M_*, which can be compared with theoretical predictions. Results: In the framework of the well-known global decline in quiescent galaxy fraction with redshift, we find that a non-negligible fraction {≃ 15-20% of massive galaxies with low specific star-formation rate exists up to z≃ 4, including a tail of “red and dead” galaxies with dot{M}/M_*<10-11 yr-1. Theoretical models vary to a large extent in their predictions for the fraction of galaxies with low specific star-formation rates, but are unable to provide a global match to our data.

Emission spectra of a laser based on an In(Ga)As/GaAs quantum-dot superlattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolev, M. M., E-mail: m.sobolev@mail.ioffe.ru; Buyalo, M. S.; Nevedomskiy, V. N.

2015-10-15

The spectral characteristics of a laser with an active region based on a ten-layer system of In(Ga)As/GaAs vertically correlated quantum dots with 4.5-nm GaAs spacer layers between InAs quantum dots are studied under the conditions of spontaneous and stimulated emission, depending on the current and the duration of pump pulses. Data obtained by transmission electron microscopy and electroluminescence and absorption polarization anisotropy measurements make it possible to demonstrate that the investigated system of tunnel-coupled InAs quantum dots separated by thin GaAs barriers represents a quantum-dot superlattice. With an increase in the laser pump current, the electroluminescence intensity increases linearly andmore » the spectral position of the electroluminescence maximum shifts to higher energies, which is caused by the dependence of the miniband density-of-states distribution on the pump current. Upon exceeding the threshold current, multimode lasing via the miniband ground state is observed. One of the lasing modes can be attributed to the zero-phonon line, and the other is determined by the longitudinal-optical phonon replica of quantum-dot emission. The results obtained give evidence that, under conditions of the laser pumping of an In(Ga)As/GaAs quantum-dot superlattice, strong coupling between the discrete electron states in the miniband and optical phonons takes place. This leads to the formation of quantum-dot polarons, resulting from the resonant mixing of electronic states whose energy separation is comparable to the optical-phonon energy.« less

Southern blotting.

PubMed

Brown, T

2001-05-01

Southern blotting is the transfer of DNA fragments from an electrophoresis gel to a membrane support (the properties and advantages of the different types of membrane, transfer buffer, and transfer method are discussed in detail), resulting in immobilization of the DNA fragments, so the membrane carries a semipermanent reproduction of the banding pattern of the gel. After immobilization, the DNA can be subjected to hybridization analysis, enabling bands with sequence similarity to a labeled probe to be identified. This appendix describes Southern blotting via upward capillary transfer of DNA from an agarose gel onto a nylon or nitrocellulose membrane, using a high-salt transfer buffer to promote binding of DNA to the membrane. With the high-salt buffer, the DNA becomes bound to the membrane during transfer but not permanently immobilized. Immobilization is achieved by UV irradiation (for nylon) or baking (for nitrocellulose). A Support Protocol describes how to calibrate a UV transilluminator for optimal UV irradiation of a nylon membrane. An alternate protocol details transfer using nylon membranes and an alkaline buffer, and is primarily used with positively charged nylon membranes. The advantage of this combination is that no post-transfer immobilization step is required, as the positively charged membrane binds DNA irreversibly under alkaline transfer conditions. The method can also be used with neutral nylon membranes but less DNA will be retained. A second alternate protocol describes a transfer method based on a different transfer-stack setup. The traditional method of upward capillary transfer of DNA from gel to membrane described in the first basic and alternate protocols has certain disadvantages, notably the fact that the gel can become crushed by the weighted filter papers and paper towels that are laid on top of it. This slows down the blotting process and may reduce the amount of DNA that can be transferred. The downward capillary method described in the second alternate protocol is therefore more rapid than the basic protocol and can result in more complete transfer. Although the ease and reliability of capillary transfer methods makes this far and away the most popular system for Southern blotting with agarose gels, it unfortunately does not work with polyacrylamide gels, whose smaller pore size impedes the transverse movement of the DNA molecules. The third alternate protocol describes an electroblotting procedure that is currently the most reliable method for transfer of DNA from a polyacrylamide gel. Dot and slot blotting are also described.

Estimating the number of double-strand breaks formed during meiosis from partial observation.

PubMed

Toyoizumi, Hiroshi; Tsubouchi, Hideo

2012-12-01

Analyzing the basic mechanism of DNA double-strand breaks (DSB) formation during meiosis is important for understanding sexual reproduction and genetic diversity. The location and amount of meiotic DSBs can be examined by using a common molecular biological technique called Southern blotting, but only a subset of the total DSBs can be observed; only DSB fragments still carrying the region recognized by a Southern blot probe are detected. With the assumption that DSB formation follows a nonhomogeneous Poisson process, we propose two estimators of the total number of DSBs on a chromosome: (1) an estimator based on the Nelson-Aalen estimator, and (2) an estimator based on a record value process. Further, we compared their asymptotic accuracy.

Pneumococcal LytR Protein Is Required for the Surface Attachment of Both Capsular Polysaccharide and Teichoic Acids: Essential for Pneumococcal Virulence.

PubMed

Ye, Weijie; Zhang, Jinghui; Shu, Zhaoche; Yin, Yibing; Zhang, Xuemei; Wu, Kaifeng

2018-01-01

The LytR-Cps-Psr family proteins are commonly present in Gram-positive bacteria, which have been shown to implicate in anchoring cell wall-related glycopolymers to the peptidoglycan. Here, we report the cellular function of SPD_1741 (LytR) in Streptococcus pneumoniae and its role in virulence of pneumococci. Pneumococcal Δ lytR mutants have been successfully constructed by replacing the lytR gene with erm cassette. The role of LytR in pneumococcal growth was determined by growth experiments, and surface accessibility of the LytR protein was analyzed using flow cytometry. Transmission electron microscopy (TEM) and immunoblotting were used to reveal the changes in capsular polysaccharide (CPS). Dot blot and ELISA were used to quantify the amount of teichoic acids (TAs). The contribution of LytR on bacterial virulence was assessed using in vitro phagocytosis assays and infection experiments. Compared to the wild-type strain, the Δ lytR mutant showed a defect in growth which merely grew to a maximal OD 620 of 0.2 in the liquid medium. The growth of the Δ lytR mutant could be restored by addition of recombinant ΔTM-LytR protein in culture medium in a dose-dependent manner. TEM results showed that the D39Δ lytR mutant was impaired in the surface attachment of CPS. Deletion of lytR gene also impaired the retention of TAs on the surface of pneumococci. The reduction of CPS and TAs on the pneumocccal cells were confirmed using Dot blot and ELISA assays. Compared to wild-type D39, the Δ lytR mutant was more susceptible to the phagocytosis. Animal studies showed that the ability to colonize the nasophaynx and virulence of pneumococci were affected by impairment of the lytR gene. Collectively, these results suggest that pneumococcal LytR is involved in anchoring both the CPS and TAs to cell wall, which is important for virulence of pneumococci.

Expression of the protein serum amyloid A in response to Aspergillus fumigatus in murine models of allergic airway inflammation.

PubMed

Moran, Gabriel; Carcamo, Carolina; Concha, Margarita; Folch, Hugo

2015-01-01

Serum amyloid A (SAA) is an acute phase protein that is elevated in blood during inflammation. The role of this protein in allergic diseases of airways remains unclear. The objective of this study was to evaluate the SAA in blood, lung and bronchial cells in a murine model of bronchial hypersensitivity to Aspergillus fumigatus. To achieve this purpose, different groups of 5-month-old mice were housed in cages containing hay bedding that was contaminated with A. fumigatus and were kept in an isolation room for 16 days to allow for the induction of allergic airway inflammation. Subsequently, the mice were then exposed once again to Aspergillus spores at 0, 2, 8, 24 and 72 h, and they were bled to acquire serum and sacrificed to obtain bronchoalveolar lavage fluid (BALF) or lung tissues for analysis. SAA levels were measured in lung, serum and BALF by dot blot assay and RT-PCR (reverse transcription polymerase chain reaction). The results indicated that SAA protein levels increased in both serum and lung within 2-24h after mice were exposed to Aspergillus spores. Moreover, the SAA mRNA expression levels in the lungs and BALF cells demonstrated the same trend that was observed for the protein levels through the dot blot assay; in particular, SAA mRNA levels increased within the first hour after mice were exposed to A. fumigatus. In this allergic airway model, we conclude that A. fumigatus can induce an acute inflammatory response in the airways through the stimulation of the SAA protein, increasing its levels in serum, lung tissue and BALF samples during the early hours of exposure of mice that have been sensitised for this fungus. Copyright © 2012 Revista Iberoamericana de Micología. Published by Elsevier Espana. All rights reserved.

Development of an Enzyme-Linked Immunosorbent Assay Using a Recombinant LigA Fragment Comprising Repeat Domains 4 to 7.5 as an Antigen for Diagnosis of Equine Leptospirosis

PubMed Central

Yan, Weiwei; Saleem, Muhammad Hassan; McDonough, Patrick; McDonough, Sean P.; Divers, Thomas J.

2013-01-01

Leptospira immunoglobulin (Ig)-like (Lig) proteins are a novel family of surface-associated proteins in which the N-terminal 630 amino acids are conserved. In this study, we truncated the LigA conserved region into 7 fragments comprising the 1st to 3rd (LigACon1-3), 4th to 7.5th (LigACon4-7.5), 4th (LigACon4), 4.5th to 5.5th (LigACon4.5–5.5), 5.5th to 6.5th (LigACon5.5–6.5), 4th to 5th (LigACon4-5), and 6th to 7.5th (LigACon6-7.5) repeat domains. All 7 recombinant Lig proteins were screened using a slot-shaped dot blot assay for the diagnosis of equine leptospirosis. Our results showed that LigACon4-7.5 is the best candidate diagnostic antigen in a slot-shaped dot blot assay. LigACon4-7.5 was further evaluated as an indirect enzyme-linked immunosorbent assay (ELISA) antigen for the detection of Leptospira antibodies in equine sera. This assay was evaluated with equine sera (n = 60) that were microscopic agglutination test (MAT) negative and sera (n = 220) that were MAT positive to the 5 serovars that most commonly cause equine leptospirosis. The indirect ELISA results showed that at a single serum dilution of 1:250, the sensitivity and specificity of ELISA were 80.0% and 87.2%, respectively, compared to those of MAT. In conclusion, an indirect ELISA was developed utilizing a recombinant LigA fragment comprising the 4th to 7.5th repeat domain (LigACon4-7.5) as a diagnostic antigen for equine leptospirosis. This ELISA was found to be sensitive and specific, and it yielded results that concurred with those of the standard MAT. PMID:23720368

Mycothiol acetyltransferase (Rv0819) of Mycobacterium tuberculosis is a potential biomarker for direct diagnosis of tuberculosis using patient serum specimens.

PubMed

Zeitoun, H; Bahey-El-Din, M; Kassem, M A; Aboushleib, H M

2017-12-01

Mycobacterium tuberculosis infection constitutes a global threat that results in significant morbidity and mortality worldwide. Efficient and early diagnosis of tuberculosis (TB) is of paramount importance for successful treatment. The aim of the current study is to investigate the mycobacterial mycothiol acetyltransferase Rv0819 as a potential novel biomarker for the diagnosis of active TB infection. The gene encoding Rv0819 was cloned and successfully expressed in Escherichia coli. The recombinant Rv0819 was purified using metal affinity chromatography and was used to raise murine polyclonal antibodies against Rv0819. The raised antibodies were employed for direct detection of Rv0819 in patient serum samples using dot blot assay and competitive enzyme-linked immunosorbent assay (ELISA). Serum samples were obtained from 68 confirmed new TB patients and 35 healthy volunteers as negative controls. The dot blot assay showed sensitivity of 64·7% and specificity of 100%, whereas the competitive ELISA assay showed lower sensitivity (54·4%) and specificity (88·57%). The overall sensitivity of the combined results of the two tests was found to be 89·7%. Overall, the mycobacterial Rv0819 is a potential TB serum biomarker that can be exploited, in combination with other TB biomarkers, for efficient and reliable diagnosis of active TB infection. The early and accurate diagnosis of tuberculosis infection is of paramount importance for initiating treatment and avoiding clinical complications. Most current diagnostic tests have poor sensitivity and/or specificity and in many cases they are too expensive for routine diagnostic testing in resource-limited settings. In the current study, we examined a novel mycobacterial serum biomarker, namely mycothiol acetyltransferase Rv0819. The antigen was detectable in serum specimens of a significant number of tuberculosis patients. This article proves the importance of Rv0819 and paves the way towards its future use as a useful diagnostic marker for tuberculosis infection. © 2017 The Society for Applied Microbiology.

Significant association of the dupA gene of Helicobacter pylori with duodenal ulcer development in a South-east Indian population.

PubMed

Alam, Jawed; Maiti, Sankar; Ghosh, Prachetash; De, Ronita; Chowdhury, Abhijit; Das, Suryasnata; Macaden, Ragini; Devarbhavi, Harshad; Ramamurthy, T; Mukhopadhyay, Asish K

2012-09-01

A novel virulence factor, duodenal ulcer-promoting gene A (dupA), in Helicobacter pylori has been found to be associated with disease in certain populations but not in others. This study analysed a South-east Indian population as part of the debate about the relevance of dupA for the prediction of clinical outcomes. A total of 140 H. pylori strains isolated from duodenal ulcer (DU) (n = 83) and non-ulcer dyspepsia (NUD) patients (n = 57) were screened by PCR and dot-blot hybridization to determine the presence of the ORFs jhp0917 and jhp0918. Part of jhp0917-jhp0918 was sequenced to search for the C/T insertion that characterizes dupA and the levels of dupA transcripts were also assessed. The PCR and dot-blot results indicated the presence of jhp0917 and jhp0918 in 37.3 % (31/83) and 12.2 % (7/57) of H. pylori strains isolated from DU and NUD patients, respectively. Sequencing analysis showed insertion of a C at nt 1386 in the 3' region of jhp0917, forming the dupA gene in 35 strains. RT-PCR analysis detected the dupA transcript in 28 of these 35 strains. The expression level of the dupA transcript varied from strain to strain, as shown by real-time PCR. The results demonstrated that analysis based on PCR only for dupA may produce an erroneous interpretation. The prevalence of dupA was significantly greater among strains isolated from patients with DU than from patients with NUD in this population (P = 0.001, odds ratio = 4.26, confidence interval = 1.60-11.74). Based on these findings, dupA can be considered a biomarker for DU patients in India. The reported discrepancies for this putative virulence marker in different populations may be due to the genome plasticity of H. pylori.

Not All Lacrimal Epithelial Cells are Created Equal—Heterogeneity of the Rabbit Lacrimal Gland and Differential Secretion

PubMed Central

Ding, Chuanqing; Huang, Jianyan; MacVeigh-Aloni, Michelle; Lu, Michael

2013-01-01

Aims To test the hypotheses that some epithelial cells in the rabbit lacrimal gland (LG) are mucin-secreting cells that are also particularly rich in aquaporin 5 (AQP5) and sodium potassium ATPase β1 subunit (NKAβ1), LG-secreted mucins contribute to the total mucin pool in tear film, and that the rabbit LG is a heterogenic gland where proteins secreted in response to different agonists are varied. Materials and methods LGs were obtained from adult female rabbits and processed for paraffin sections for hematoxylin and eosin (HE) staining, periodic acid-Schiff (PAS), mucicarmine, and Alcian blue (pH 0.4, 1.0, and 2.5) for the detection of mucins. Serial sections were used for immunohistochemistry (IHC) and PAS. LG lysates and fluids were assayed by dot blot for detection of mucins, and by SDS-PAGE to detect differences in protein profiles of LG fluids stimulated by different agonists. Results HE staining demonstrated that the LG is a heterogeneous gland where most epithelial cells are serous, while all duct cells are mucous cells. Some acini and individual acinar cells within serous acini are also mucous or seromucous cells and these cells are particularly rich in AQP5 and NKAβ1. Dot blot assay showed the presence of mucins in the LG fluids. The protein profiles of LG fluids from pilocarpine, phenylephrine, and isoproterenol varied significantly, particularly in the mid range. Conclusions Our data indicated that the rabbit LG is a heterogeneous gland that is composed of both serous and mucin-secreting cells, and mucins produced by the LG contribute to the mucin pool in the tear film. The heterogeneity of the rabbit LG supports the notion of differential secretion, i.e. the volume and composition of the LG fluids vary depending on various circumstances in the ocular surface and the body’s needs. PMID:21999223

Anti-myeloperoxidase autoantibodies react with native but not denatured myeloperoxidase.

PubMed Central

Falk, R J; Becker, M; Terrell, R; Jennette, J C

1992-01-01

We wondered whether anti-myeloperoxidase (MPO) autoantibodies (MPO-ANCA) found in patients with systemic vasculitis react with a conformational epitope or epitopes on the MPO molecule. Sera from 15 human MPO-ANCA, and a polyclonal and a monoclonal anti-MPO antibodies were reacted with MPO in native and denatured states. Human MPO-ANCA and mouse monoclonal anti-MPO reacted with native MPO, and a 120-kD band representing the MPO hologenzyme, but not with denatured MPO fragments; however, MPO-ANCA and mouse anti-MPO did not demonstrate competitive inhibition of binding to MPO. Polyclonal rabbit anti-MPO reacted with both native and denatured MPO. All MPO-ANCA tested showed the same patterns of reactivity with native and denatured MPO in dot blot and Western blot analyses. Both polyclonal and monoclonal anti-MPO antibodies inhibited MPO's protein iodination by over 90%, whereas MPO-ANCA IgGs, normal IgGs and disease control IgGs did not. These data suggest that (i) MPO-ANCA interact with a conformational epitope on the MPO molecule; and (ii) MPO-ANCA from different patients have similar reactivity with native versus denatured MPO. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:1379133

Identification of IgE- binding pollen protein from Cannabis sativa in pollen-hypersensitive patients from north Pakistan.

PubMed

Choudhary, Shazia; Murad, Sheeba; Hayat, Muhammad Qasim; Shakoor, Zahid; Arshad, Muhammad

2017-01-01

Cannabis sativa (C.sativa) is well-known for its medicinal, industrial and recreational use. However, allergies in relation to Cannabis sativa (C.sativa) are rarely reported. C. sativa is one of the common weeds found in Pakistan and its pollen grains are common in spring and fall season. Although categorized as an aeroallergen, there are limited number of reports regarding allergenic potential in C. sativa. Therefore, the current study is aimed at exploring the IgE- binding potential among the C. sativa pollen in local pollen allergic patients. Initial screening of C. sativa sensitized individuals was carried out by dot blot from the sera of pollen allergic patients. Proteins from the pollen grains were extracted and resolved on 10% gel. Eight bands were visible on gel however only one protein fragment i.e. of 14KDa size was found to bind to IgE as analyzed through protein gel blot analysis. Strong IgE affinity of a 14 kDa protein fragment from C. sativa pollen extract suggests its allergenic potential. Further study is required to find the exact nature of this protein fragment.

Development of transgenic wheat (Triticum aestivum L.) expressing avidin gene conferring resistance to stored product insects.

PubMed

Abouseadaa, Heba H; Osman, Gamal H; Ramadan, Ahmed M; Hassanein, Sameh E; Abdelsattar, Mohamed T; Morsy, Yasser B; Alameldin, Hussien F; El-Ghareeb, Doaa K; Nour-Eldin, Hanan A; Salem, Reda; Gad, Adel A; Elkhodary, Soheir E; Shehata, Maher M; Mahfouz, Hala M; Eissa, Hala F; Bahieldin, Ahmed

2015-07-22

Wheat is considered the most important cereal crop all over the world. The wheat weevil Sitophilus granarius is a serious insect pests in much of the wheat growing area worldwide and is responsible for significant loss of yield. Avidin proteins has been proposed to function as plant defense agents against insect pests. A synthetic avidin gene was introduced into spring wheat (Triticum aestivum L.) cv. Giza 168 using a biolistic bombardment protocol. The presence and expression of the transgene in six selected T0 transgenic wheat lines were confirmed at the molecular level. Accumulation of avidin protein was detected in transgenic plants compared to non-transgenic plants. Avidin transgene was stably integrated, transcribed and translated as indicated by Southern blot, ELISA, and dot blot analyses, with a high level of expression in transgenic wheat seeds. However, no expression was detected in untransformed wheat seeds. Functional integrity of avidin was confirmed by insect bioassay. The results of bioassay using transgenic wheat plants challenged with wheat weevil revealed 100 % mortality of the insects reared on transgenic plants after 21 days. Transgenic wheat plants had improved resistance to Sitophilus granarius.

Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomizawa, H.; Department of Applied Physics, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585; Yamaguchi, T., E-mail: tyamag@riken.jp

We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots withmore » serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.« less

Highly sensitive humidity sensing properties of carbon quantum dots films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xing; Ming, Hai; Liu, Ruihua

2013-02-15

Graphical abstract: Display Omitted Highlights: ► A humidity sensing device was fabricated based on carbon quantum dots (CQDs) films. ► The conductivity of the CQDs films shows a linear and rapid response to atmosphere humidity. ► The humidity sensing property was due to the hydrogen bonds between the functional groups on CQDs. -- Abstract: We reported the fabrication of a humidity sensing device based on carbon quantum dots (CQDs) film. The conductivity of the CQDs film has a linear and rapid response to relative humidity, providing the opportunity for the fabrication of humidity sensing devices. The mechanism of our humiditymore » sensor was proposed to be the formation of hydrogen bonds between carbon quantum dots and water molecules in the humidity environment, which significantly promote the electrons migration. In a control experiment, this hypothesis was confirmed by comparing the humidity sensitivity of candle soot (i.e. carbon nanoparticles) with and without oxygen containing groups on the surfaces.« less

Performance improvement of the one-dot lateral flow immunoassay for aflatoxin B1 by using a smartphone-based reading system.

PubMed

Lee, Sangdae; Kim, Giyoung; Moon, Jihea

2013-04-18

This study was conducted to develop a simple, rapid, and accurate lateral flow immunoassay (LFIA) detection method for point-of-care diagnosis. The one-dot LFIA for aflatoxin B1 (AFB1) was based on the modified competitive binding format using competition between AFB1 and colloidal gold-AFB1-BSA conjugate for antibody binding sites in the test zone. A Smartphone-based reading system consisting of a Samsung Galaxy S2 Smartphone, a LFIA reader, and a Smartphone application for the image acquisition and data analysis. The detection limit of one-dot LFIA for AFB1 is 5 μg/kg. This method provided semi-quantitative analysis of AFB1 samples in the range of 5 to 1,000 μg/kg. Using combination of the one-dot LFIA and the Smartphone-based reading system, it is possible to conduct a more fast and accurate point-of-care diagnosis.

Performance Improvement of the One-Dot Lateral Flow Immunoassay for Aflatoxin B1 by Using a Smartphone-Based Reading System

PubMed Central

Lee, Sangdae; Kim, Giyoung; Moon, Jihea

2013-01-01

This study was conducted to develop a simple, rapid, and accurate lateral flow immunoassay (LFIA) detection method for point-of-care diagnosis. The one-dot LFIA for aflatoxin B1 (AFB1) was based on the modified competitive binding format using competition between AFB1 and colloidal gold-AFB1-BSA conjugate for antibody binding sites in the test zone. A Smartphone-based reading system consisting of a Samsung Galaxy S2 Smartphone, a LFIA reader, and a Smartphone application for the image acquisition and data analysis. The detection limit of one-dot LFIA for AFB1 is 5 μg/kg. This method provided semi-quantitative analysis of AFB1 samples in the range of 5 to 1,000 μg/kg. Using combination of the one-dot LFIA and the Smartphone-based reading system, it is possible to conduct a more fast and accurate point-of-care diagnosis. PMID:23598499

Paralinear Oxidation of CVD SiC in Simulated Fuel-Rich Combustion

NASA Technical Reports Server (NTRS)

Fox, Dennis S.; Opila, Elizabeth J.; Hann, Raiford E.

2000-01-01

The oxidation kinetics of CVD SiC were measured by thermogravimetric analysis (TGA) in a 4H2 (central dot) 12H2O (central dot) 10CO (central dot) 7CO2 (central dot) 67N2 gas mixture flowing at 0.44 cm/s at temperatures between 1300 and 1450 C in fused quartz furnace tubes at I atm total pressure. The SiC was oxidized to form solid SiO2. At less than or = 1350 C, the SiO2 was in turn volatilized. Volatilization kinetics were consistent with the thermodynamic predictions based on SiO formation. These two simultaneous reactions resulted in overall paralinear kinetics. A curve fitting technique was used to determine the linear and parabolic rate constants from the paralinear kinetic data. Volatilization of the protective SiO2 scale resulted in accelerated consumption of SiC. Recession rates under conditions more representative of actual combustors were estimated from the furnace data.

76 FR 5431 - Released Rates of Motor Common Carriers of Household Goods

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-31

... may be submitted either via the Board's e-filing format or in traditional paper format. Any person using e-filing should attach a document and otherwise comply with the instructions at the E- FILING link on the Board's website at http://www.stb.dot.gov . Any person submitting a filing in the traditional...

75 FR 52054 - Assessment of Mediation and Arbitration Procedures

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-24

...: Comments may be submitted either via the Board's e-filing format or in the traditional paper format. Any person using e-filing should attach a document and otherwise comply with the instructions at the E-FILING link on the Board's Web site, at http://www.stb.dot.gov . Any person submitting a filing in the...

Prospects for star formation studies with infrared instruments (TIRCAM2 and TANSPEC) on the 3.6-m Devasthal Optical Telescope

NASA Astrophysics Data System (ADS)

Ojha, Devendra; Ghosh, Swarna Kanti; Sharma, Saurabh; Pandey, Anil Kumar; Baug, Tapas; Ninan, Joe Philip; Kumar, Brijesh; Puravankara, Manoj; D'Costa, Savio; Naik, Milind; Poojari, Satheesha; Bhagat, Shailesh; Jadhav, Rajesh; Meshram, Ganesh; Sandimani, Pradeep; Gharat, Sanjay; Bakalkar, Chandrakant

2018-04-01

We present a brief description of the activities of the infrared astronomy group of Tata Institute of Fundamental Research with special emphasis on the ground-based near infrared instrumentation for star formation studies. We describe the unique capability of TIRCAM2 for observations in the polycyclic aromatic hydrocarbon (λcen˜3.3 μm) and narrow-band L (λcen˜3.59 μm) bands, currently being used by the astronomy community, and of the upcoming TANSPEC, which is being built for India's largest telescope, i.e. the 3.6-m Devasthal Optical Telescope (DOT). The TIRCAM2 on the 3.6-m DOT was successfully commissioned in June 2016, and the subsequent characterization and astronomical observations are presented here. Based on the successful engineering runs on the 3.6-m DOT, TIRCAM2 has been made available to the Indian and Belgian astronomical community for science observations since Early Science Cycle 2017A (May 2017) onwards. The fabrication of TANSPEC is in an advanced stage and the spectrometer is expected to be commissioned by the end of January 2018.

Millisecond-Timescale Monitoring of PbS Nanoparticle Nucleation and Growth Using Droplet-Based Microfluidics.

PubMed

Lignos, Ioannis; Stavrakis, Stavros; Kilaj, Ardita; deMello, Andrew J

2015-08-26

The early-time kinetics (<1 s) of lead sulfide (PbS) quantum dot formation are probed using a novel droplet-based microfluidic platform, which allows for high-throughput and real-time optical analysis of the reactive process with millisecond time resolution. The reaction platform enables the concurrent investigation of the emission characteristics of PbS quantum dots and a real-time estimation of their size and concentration during nucleation and growth. These investigations reveal a two-stage mechanism for PbS nanoparticle formation. The first stage corresponds to the fast conversion of precursor species to PbS crystals, followed by the growth of the formed particles. The growth kinetics of the PbS nanoparticles follow the Lifshitz-Slyozov-Wagner model for Ostwald ripening, allowing direct estimation of the rate constants for the process. In addition, the extraction of absorption spectra of ultrasmall quantum dots is demonstrated for first time in an online manner. The droplet-based microfluidic platform integrated with online spectroscopic analysis provides a new tool for the quantitative extraction of high temperature kinetics for systems with rapid nucleation and growth stages. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

640 x 512 Pixels Long-Wavelength Infrared (LWIR) Quantum-Dot Infrared Photodetector (QDIP) Imaging Focal Plane Array

NASA Technical Reports Server (NTRS)

Gunapala, Sarath D.; Bandara, Sumith V.; Hill, Cory J.; Ting, David Z.; Liu, John K.; Rafol, Sir B.; Blazejewski, Edward R.; Mumolo, Jason M.; Keo, Sam A.; Krishna, Sanjay;

Silver electrodeposition on nanostructured gold: from nanodots to nanoripples.

PubMed

Dos Santos Claro, P C; Fonticelli, M; Benítez, G; Azzaroni, O; Schilardi, P L; Luque, N B; Leiva, E; Salvarezza, R C

2006-07-28

Silver nanodots and nanoripples have been grown on nanocavity-patterned polycrystalline Au templates by controlled electrodeposition. The initial step is the growth of a first continuous Ag monolayer followed by preferential deposition at nanocavities. The Ag-coated nanocavities act as preferred sites for instantaneous nucleation and growth of the three-dimensional metallic centres. By controlling the amount of deposited Ag, dots of approximately 50 nm average size and approximately 4 nm average height can be grown with spatial and size distributions dictated by the template. The dots are in a metastable state. Further Ag deposition drives the dot surface structure to nanoripple formation. Results show that electrodeposition on nanopatterned electrodes can be used to prepare a high density of nanostructures with a narrow size distribution and spatial order.

The new high-pressure borate Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O-Formation of edge-sharing BO{sub 4} tetrahedra in a hydrated borate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neumair, Stephanie C.; Kaindl, Reinhard; Huppertz, Hubert, E-mail: hubert.huppertz@uibk.ac.at

2012-01-15

The new borate hydrate Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O was synthesized under high-pressure/high-temperature conditions of 6 GPa and 880 Degree-Sign C in a Walker-type multianvil apparatus. The compound crystallizes in the orthorhombic space group Pbam (Z=2) with the lattice parameters a=819.0(2), b=2016.9(4), c=769.9(2) pm, V=1.2717(4) nm{sup 3}, R{sub 1}=0.0758, wR{sub 2}=0.0836 (all data). The new structure type of Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O is built up from corner-sharing BO{sub 4} tetrahedra forming corrugated layers, that are interconnected among each other by two edge-sharing BO{sub 4} tetrahedra (B{sub 2}O{sub 6} units) forming Z-shaped channels. Interestingly, the heremore » presented structure of Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O is closely related to the structures of M{sub 6}B{sub 22}O{sub 39}{center_dot}H{sub 2}O (M=Fe, Co), which exhibit BO{sub 4} tetrahedra in an intermediate state on the way to edge-sharing BO{sub 4} tetrahedra. - Graphical Abstract: The new high-pressure borate hydrate Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O is built up from corner-sharing BO{sub 4} tetrahedra forming corrugated layers, that are interconnected among each other by two edge-sharing BO{sub 4} tetrahedra (B{sub 2}O{sub 6} units). In this paper we report on synthesis, structural details, and properties of the new compound Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O. Highlights: Black-Right-Pointing-Pointer High-pressure/high-temperature synthesis of the new borate hydrate Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O. Black-Right-Pointing-Pointer In the structure of Co{sub 7}B{sub 24}O{sub 42}(OH){sub 2}{center_dot}2 H{sub 2}O, two B{sub 2}O{sub 6} units are connected to 'vierer' rings. Black-Right-Pointing-Pointer Pressure favours the formation of edge-sharing BO{sub 4} tetrahedra in the chemistry of borates.« less

Centrifugally driven winds from protostellar accretion discs - I. Formulation and initial results

NASA Astrophysics Data System (ADS)

Nolan, C. A.; Salmeron, R.; Federrath, C.; Bicknell, G. V.; Sutherland, R. S.

2017-10-01

Protostellar discs play an important role in star formation, acting as the primary mass reservoir for accretion on to young stars and regulating the extent to which angular momentum and gas is released back into stellar nurseries through the launching of powerful disc winds. In this study, we explore how disc structure relates to the properties of the wind-launching region, mapping out the regions of protostellar discs where wind launching could be viable. We combine a series of 1.5D semi-analytic, steady-state, vertical disc-wind solutions into a radially extended 1+1.5D model, incorporating all three diffusion mechanisms (Ohm, Hall and ambipolar). We observe that the majority of mass outflow via disc winds occurs over a radial width of a fraction of an astronomical unit, with outflow rates attenuating rapidly on either side. We also find that the mass accretion rate, magnetic field strength and surface density profile each have significant effects on both the location of the wind-launching region and the ejection/accretion ratio \\dot{M}_out/\\dot{M}_in. Increasing either the accretion rate or the magnetic field strength corresponds to a shift of the wind-launching region to smaller radii and a decrease in \\dot{M}_out/\\dot{M}_in, while increasing the surface density corresponds to launching regions at larger radii with increased \\dot{M}_out/\\dot{M}_in. Finally, we discover a class of disc winds containing an ineffective launching configuration at intermediate radii, leading to two radially separated regions of wind launching and diminished \\dot{M}_out/\\dot{M}_in. We find that the wind locations and ejection/accretion ratio are consistent with current observational and theoretical estimates.

Fluorophotometric determination of critical micelle concentration (CMC) of ionic and non-ionic surfactants with carbon dots via Stokes shift.

PubMed

Lavkush Bhaisare, Mukesh; Pandey, Sunil; Shahnawaz Khan, M; Talib, Abou; Wu, Hui-Fen

2015-01-01

A new and facile method for the determination of critical micelle concentration (CMC) of ionic and non-ionic surfactants is proposed in this article. Carbon dots exhibited substantial fluorescence and therefore enhanced the sensitivity of this evaluation. Understanding the formation of surfactant micelles is vital for the applications of biomedicine such as drug fabrication and smart molecular vehicles in delivering therapeutic dosage to various molecular sites. The fluorescence property of carbon dots was utilized for the first time to estimate the critical micelle concentration of surfactants. The central concept of the approach is based on the Stokes shift determination of a system composed of constant amount of carbon dots with varying concentrations of ionic and non-ionic surfactants. The synthesized carbon dots were characterized by FTIR, TEM, XRD, Raman, UV, and fluorescence spectroscope. The carbon dots were excited at 280 nm so as to obtain maximum emission for the Stokes shift measurement. The CMC value of cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), Triton X-100, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide (SB-12) evaluated by this approach was found to be 0.98, 7.3, 0.19, and 3.5mM, respectively. The signals of spectra were assigned and explained in terms of both electron transitions between specific molecular orbital and the interaction with solvent. Copyright © 2014 Elsevier B.V. All rights reserved.

Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si(001) surface: nucleation, morphology, and CMOS compatibility

PubMed Central

2011-01-01

Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (≲600°C) and high (≳600°C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature. PMID:21892938

Tailoring of quantum dot emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings.

PubMed

Margapoti, Emanuela; Gentili, Denis; Amelia, Matteo; Credi, Alberto; Morandi, Vittorio; Cavallini, Massimiliano

2014-01-21

We report on the tailoring of quantum dot (QD) emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings. Ag nanoparticles (NPs) with CdSe QDs embedded in a polymeric matrix are spatially organised in mesoscopic rings and coupled in a tuneable fashion by breath figure formation. The mean distance between NPs and QDs and consequently the intensity of QD photoluminescence, which is enhanced by the coupling of surface plasmons and excitons, are tuned by acting on the NP concentration.

Self-organized formation of GaSb/GaAs quantum rings.

PubMed

Timm, R; Eisele, H; Lenz, A; Ivanova, L; Balakrishnan, G; Huffaker, D L; Dähne, M

2008-12-19

Ring-shaped GaSb/GaAs quantum dots, grown by molecular beam epitaxy, were studied using cross-sectional scanning tunneling microscopy. These quantum rings have an outer shape of a truncated pyramid with baselengths around 15 nm and heights of about 2 nm but are characterized by a clear central opening extending over about 40% of the outer baselength. They form spontaneously during the growth and subsequent continuous capping of GaSb/GaAs quantum dots due to the large strain and substantial As-for-Sb exchange reactions leading to strong Sb segregation.

Theory of confined states of positronium in spherical and circular quantum dots with Kane’s dispersion law

PubMed Central

2013-01-01

Confined states of a positronium (Ps) in the spherical and circular quantum dots (QDs) are theoretically investigated in two size quantization regimes: strong and weak. Two-band approximation of Kane’s dispersion law and parabolic dispersion law of charge carriers are considered. It is shown that electron-positron pair instability is a consequence of dimensionality reduction, not of the size quantization. The binding energies for the Ps in circular and spherical QDs are calculated. The Ps formation dependence on the QD radius is studied. PMID:23826867

Highly efficient organic light-emitting diodes with a quantum dot interfacial layer.

PubMed

Ryu, Seung Yoon; Hwang, Byoung Har; Park, Ki Wan; Hwang, Hyeon Seok; Sung, Jin Woo; Baik, Hong Koo; Lee, Chang Ho; Song, Seung Yong; Lee, Jun Yeob

2009-02-11

Advanced organic light-emitting diodes (OLEDs), based on a multiple structure, were achieved in combination with a quantum dot (QD) interfacial layer. The authors used core/shell CdSe/ZnS QDs passivated with trioctylphosphine oxide (TOPO) and TOPO-free QDs as interlayers. Multiple-structure OLEDs (MOLEDs) with TOPO-free QDs showed higher device efficiency because of a well-defined interfacial monolayer formation. Additionally, the three-unit MOLED showed high performance for device efficiency with double-structured QD interfacial layers due to the enhanced charge balance and recombination probability.

Microwave detector

DOEpatents

Meldner, Heiner W.; Cusson, Ronald Y.; Johnson, Ray M.

1986-01-01

A microwave detector (10) is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite (26, 28) produces a magnetization field flux that links a B-dot loop (16, 20). The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means (18, 22) are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

Composition and immunoreactivity of the A60 complex and other cell fractions from Mycobacterium bovis BCG.

PubMed

Cocito, C; Vanlinden, F

1995-02-01

Surface static cultures of Mycobacterium bovis BCG contained cells embedded in an extracellular matrix, whose mechanical removal yielded free cells that were pressure disrupted and fractionated into cytoplasm and walls. Cell envelopes were either mechanically disrupted or extracted with detergents. Intracellular and extracellular fractions were analysed for proteins, polysaccharides, and antigen 6O (A60), a major complex immunodominant in tuberculosis. A60 was present in extracellular matrix, cytoplasm and walls: it represented a substantial portion of the proteins and polysaccharides of these fractions. While the protein/polysaccharide ratio varied according to the origin of A60 preparations, the electrophoretic patterns of A60 proteins (which accounted for the immunogenicity of the complex) remained unchanged. Western blots pointed to the proteins present within the 29-45 kDa range as the A60 components endowed with the highest immunogenicity level. Since the most heavily stained protein bands in SDS-PAGE patterns were located outside the region best recognized by antisera, a striking discordance was found between concentration and immunogenicity patterns of A60 proteins. The electrophoretic patterns of A60- and non-A60-proteins from cytoplasm were also different. A60 complexes in dot blots and some electrophoresed A60 proteins reacted with monoclonal antibodies directed against lipoarabinomannan (LAM), a highly immunogenic polymer of cell envelope. This contaminating compound was removed from A60 with organic solvents and detergents. SDS-PAGE and Western blot patterns of proteins from delipidated A60 were similar to those of native A60 proteins.

Upregulated Genes In Sporadic, Idiopathic Pulmonary Arterial Hypertension

PubMed Central

Edgar, Alasdair J; Chacón, Matilde R; Bishop, Anne E; Yacoub, Magdi H; Polak, Julia M

2006-01-01

Background To elucidate further the pathogenesis of sporadic, idiopathic pulmonary arterial hypertension (IPAH) and identify potential therapeutic avenues, differential gene expression in IPAH was examined by suppression subtractive hybridisation (SSH). Methods Peripheral lung samples were obtained immediately after removal from patients undergoing lung transplant for IPAH without familial disease, and control tissues consisted of similarly sampled pieces of donor lungs not utilised during transplantation. Pools of lung mRNA from IPAH cases containing plexiform lesions and normal donor lungs were used to generate the tester and driver cDNA libraries, respectively. A subtracted IPAH cDNA library was made by SSH. Clones isolated from this subtracted library were examined for up regulated expression in IPAH using dot blot arrays of positive colony PCR products using both pooled cDNA libraries as probes. Clones verified as being upregulated were sequenced. For two genes the increase in expression was verified by northern blotting and data analysed using Student's unpaired two-tailed t-test. Results We present preliminary findings concerning candidate genes upregulated in IPAH. Twenty-seven upregulated genes were identified out of 192 clones examined. Upregulation in individual cases of IPAH was shown by northern blot for tissue inhibitor of metalloproteinase-3 and decorin (P < 0.01) compared with the housekeeping gene glyceraldehydes-3-phosphate dehydrogenase. Conclusion Four of the up regulated genes, magic roundabout, hevin, thrombomodulin and sucrose non-fermenting protein-related kinase-1 are expressed specifically by endothelial cells and one, muscleblind-1, by muscle cells, suggesting that they may be associated with plexiform lesions and hypertrophic arterial wall remodelling, respectively. PMID:16390543

Advanced glycation end product (AGE) modified proteins in tears of diabetic patients.

PubMed

Zhao, Zhenjun; Liu, Jingfang; Shi, Bingyin; He, Shuixiang; Yao, Xiaoli; Willcox, Mark D P

2010-08-11

High glucose level in diabetic patients may lead to advanced glycation end product (AGE) modified proteins. This study investigated AGE modified proteins in tears and compared their levels in diabetic patients (DM) with non-diabetic controls (CTL). Basal tears were collected from DM with (DR) or without (DNR) retinopathy and CTL. Total AGE modified proteins were detected quantitatively by a dot immunobinding assay. The AGE modified proteins were separated in 1D- and 2D-SDS gels and detected by western-blotting. The individual AGE modified proteins were also compared between groups using densitometry. Compared with the CTL group, tear concentrations of AGE modified proteins were significantly elevated in DR and DNR groups. The concentration of AGE modified proteins in diabetic tears were positively correlated with AGE modified hemoglobin (HbA1c) and postprandial blood glucose level (PBG). Western blotting of AGE modified proteins from 1D-SDS gels showed several bands, the major one at around 60 kDa. The intensities of AGE modified protein bands were higher in DM tears than in CTL tears. Western blotting from 2D-SDS gels showed a strongly stained horizontal strip, which corresponded to the major band in 1D-SDS gels. Most of the other AGE modified protein species were within molecular weight of 30-60 kDa, PI 5.2-7.0. Densitometry analysis demonstrated several AGE modified proteins were elevated in DR or DNR tears. Total and some individual AGE modified proteins were elevated in DM tears. AGE modified proteins in tears may be used as biomarkers to diagnose diabetes and/or diabetic retinopathy.

Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots

PubMed Central

Qu, Dan; Zheng, Min; Zhang, Ligong; Zhao, Haifeng; Xie, Zhigang; Jing, Xiabin; Haddad, Raid E.; Fan, Hongyou; Sun, Zaicheng

2014-01-01

Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction. N-doped GQDs were prepared using a series of N-containing bases such as urea. Detailed structural and property studies demonstrated the formation mechanism of N-doped GQDs for tunable optical emissions. Hydrothermal conditions promote formation of amide between –NH2 and –COOH with the presence of amine in the reaction. The intramoleculur dehydrolysis between neighbour amide and COOH groups led to formation of pyrrolic N in the graphene framework. Further, the pyrrolic N transformed to graphite N under hydrothermal conditions. N-doping results in a great improvement of PL quantum yield (QY) of GQDs. By optimized reaction conditions, the highest PL QY (94%) of N-doped GQDs was obtained using CA as a carbon source and ethylene diamine as a N source. The obtained N-doped GQDs exhibit an excitation-independent blue emission with single exponential lifetime decay. PMID:24938871

Massive star formation in 100,000 years from turbulent and pressurized molecular clouds.

PubMed

McKee, Christopher F; Tan, Jonathan C

2002-03-07

Massive stars (with mass m* > 8 solar masses Mmiddle dot in circle) are fundamental to the evolution of galaxies, because they produce heavy elements, inject energy into the interstellar medium, and possibly regulate the star formation rate. The individual star formation time, t*f, determines the accretion rate of the star; the value of the former quantity is currently uncertain by many orders of magnitude, leading to other astrophysical questions. For example, the variation of t*f with stellar mass dictates whether massive stars can form simultaneously with low-mass stars in clusters. Here we show that t*f is determined by the conditions in the star's natal cloud, and is typically about 105yr. The corresponding mass accretion rate depends on the pressure within the cloud--which we relate to the gas surface density--and on both the instantaneous and final stellar masses. Characteristic accretion rates are sufficient to overcome radiation pressure from about 100M middle dot in circle protostars, while simultaneously driving intense bipolar gas outflows. The weak dependence of t*f on the final mass of the star allows high- and low-mass star formation to occur nearly simultaneously in clusters.

Development of a Quantum Dot, 0.6 eV InGaAs Thermophotovoltaic (TPV) Converter

NASA Technical Reports Server (NTRS)

Forbes, David; Sinharoy, Samar; Raffalle, Ryne; Weizer, Victor; Homann, Natalie; Valko, Thomas; Bartos,Nichole; Scheiman, David; Bailey, Sheila

2007-01-01

Thermophotovoltaic (TPV) power conversion has to date demonstrated conversion efficiencies exceeding 20% when coupled to a heat source. Current III-V semiconductor TPV technology makes use of planar devices with bandgaps tailored to the heat source. The efficiency can be improved further by increasing the collection efficiency through the incorporation of InAs quantum dots. The use of these dots can provide sub-gap absorption and thus improve the cell short circuit current without the normal increase in dark current associated with lowering the bandgap. We have developed self-assembled InAs quantum dots using the Stranski-Krastanov growth mode on 0.74 eV In0.53GaAs lattice-matched to InP and also on lattice-mismatched 0.6 eV In0.69GaAs grown on InP through the use of a compositionally graded InPAsx buffer structure, by metalorganic vapor phase epitaxy (MOVPE). Atomic force microscopy (AFM) measurements showed that the most reproducible dot pattern was obtained with 5 monolayers of InAs grown at 450 C. The lattice mismatch between InAs and In0.69GaAs is only 2.1%, compared to 3.2% between InAs and In0.53GaAs. The smaller mismatch results in lower strain, making dot formation somewhat more complicated, resulting in quantum dashes, rather than well defined quantum dots in the lattice-mismatched case. We have fabricated 0.6 eV InGaAs planer TPV cells with and without the quantum dashes

Pedestrian accessibility at signalized intersections.

DOT National Transportation Integrated Search

2009-09-01

This product is formatted as a chapter to be included in a current or future TxDOT manual. The chapter : presents guidance on the use and placement of selected treatments to accommodate pedestrian accessibility at : signalized intersections. Specific...

Suppression of quantum decoherence via infrared-driven coherent exciton-plasmon coupling: Undamped field and Rabi oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadeghi, S. M., E-mail: seyed.sadeghi@uah.edu; Nano and Micro Device Center, University of Alabama in Huntsville, Huntsville, Alabama 35899; Patty, K. D.

2014-02-24

We show that when a semiconductor quantum dot is in the vicinity of a metallic nanoparticle and driven by a mid-infrared laser field, its coherent dynamics caused by interaction with a visible laser field can become free of quantum decoherence. We demonstrate that this process, which can offer undamped Rabi and field oscillations, is the result of coherent normalization of the “effective” polarization dephasing time of the quantum dot (T{sub 2}{sup *}). This process indicates formation of infrared-induced coherently forced oscillations, which allows us to control the value of T{sub 2}{sup *} using the infrared laser. The results offer decay-freemore » ultrafast modulation of the effective field experienced by the quantum dot when neither the visible laser field nor the infrared laser changes with time.« less

Role of water and carbonates in photocatalytic transformation of CO{sub 2} to CH{sub 4} on titania.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimitrijevic, N. M.; Vijayan, B. K.; Poluektov, O. G.

Using the electron paramagnetic resonance technique, we have elucidated the multiple roles of water and carbonates in the overall photocatalytic reduction of carbon dioxide to methane over titania nanoparticles. The formation of H atoms (reduction product) and {center_dot}OH radicals (oxidation product) from water, and CO{sub 3}{sup -} radical anions (oxidation product) from carbonates, was detected in CO{sub 2}-saturated titania aqueous dispersion under UV illumination. Additionally, methoxyl, {center_dot}OCH{sub 3}, and methyl, {center_dot}CH{sub 3}, radicals were identified as reaction intermediates. The two-electron, one-proton reaction proposed as an initial step in the reduction of CO{sub 2} on the surface of TiO{sub 2} ismore » supported by the results of first-principles calculations.« less

Nano-scale engineering using lead chalcogenide nanocrystals for opto-electronic applications

NASA Astrophysics Data System (ADS)

Xu, Fan

Colloidal quantum dots (QDs) or nanocrystals of inorganic semiconductors exhibit exceptional optoelectronic properties such as tunable band-gap, high absorption cross-section and narrow emission spectra. This thesis discusses the characterizations and physical properties of lead-chalcogenide nanocrystals, their assembly into more complex nanostructures and applications in solar cells and near-infrared light-emitting devices. In the first part of this work, we demonstrate that the band edge emission of PbS quantum dots can be tuned from the visible to the mid-infrared region through size control, while the self-attachment of PbS nanocrystals can lead to the formation of 1-D nanowires, 2-D quantum dot monolayers and 3-D quantum dot solids. In particular, the assembly of closely-packed quantum dot solids has attracted enormous attention. A series of distinctive optoelectronic properties has been observed, such as superb multiple exciton generation efficiencies, efficient hot-electron transfer and cold-exciton recycling. Since the surfactant determines the quantum dot surface passivation and inter dot electronic coupling, we examine the influence of different cross-linking surfactants on the optoelectronic properties of the quantum dot solids. Then, we discuss the ability to tune the quantum dot band-gap combined with the controllable assembly of lead-chalcogenide quantum dots, which opens new possibilities to engineer the properties of quantum dot solids. The PbS and PbSe quantum dot cascade structures and PbS/PbSe quantum dot heterojunctions are assembled using the layer-by-layer deposition method. We show that exciton funnelling and trap state-bound exciton recycling in the quantum dot cascade structure dramatically enhances the quantum dots photoluminescence. Moreover, we show that both type-I and type-II PbS/PbSe quantum dot heterojunctions can be assembled by carefully choosing the quantum dot sizes. In type-I heterojunctions, the excited electron-hole pairs tend to localize in narrower band-gap quantum dots, leading to significant photoluminescence enhancement. In contrast, the staggered energy bands in type-II heterojunctions lead to rapid exciton separation at the junctions that considerably quenches the photoluminescence. As such, this strategy can be fruitfully employed to enhance performances in nanocrystal-based photovoltaic devices. Using this approach, we achieve efficient PbS nanocrystal-based solar cells using an ITO/ TiO2/ PbS QDs/Au architecture, where a porous TiO2 nanowire network is employed as electron transporting layer. Our best heterojunction solar cells exhibit a decent short circuit current of 2.5 mA/cm2, a large open circuit voltage of 0.6 V and a power converting efficiency of 5.4 % under 8.5 mW/cm2 low-light illumination. On the other hand, nanocrystal-based near infrared LED devices are fabricated using a simple ITO-PbS QDs-Al device structure. There, the active quantum dot layer serves as both the electron- and hole-transporting layer. With appropriate surface chemistry treatment on quantum dots, a high-brightness near-infrared LED device is achieved.

Measurement of the spin temperature of optically cooled nuclei and GaAs hyperfine constants in GaAs/AlGaAs quantum dots

NASA Astrophysics Data System (ADS)

Chekhovich, E. A.; Ulhaq, A.; Zallo, E.; Ding, F.; Schmidt, O. G.; Skolnick, M. S.

2017-10-01

Deep cooling of electron and nuclear spins is equivalent to achieving polarization degrees close to 100% and is a key requirement in solid-state quantum information technologies. While polarization of individual nuclear spins in diamond and SiC (ref. ) reaches 99% and beyond, it has been limited to 50-65% for the nuclei in quantum dots. Theoretical models have attributed this limit to formation of coherent `dark' nuclear spin states but experimental verification is lacking, especially due to the poor accuracy of polarization degree measurements. Here we measure the nuclear polarization in GaAs/AlGaAs quantum dots with high accuracy using a new approach enabled by manipulation of the nuclear spin states with radiofrequency pulses. Polarizations up to 80% are observed--the highest reported so far for optical cooling in quantum dots. This value is still not limited by nuclear coherence effects. Instead we find that optically cooled nuclei are well described within a classical spin temperature framework. Our findings unlock a route for further progress towards quantum dot electron spin qubits where deep cooling of the mesoscopic nuclear spin ensemble is used to achieve long qubit coherence. Moreover, GaAs hyperfine material constants are measured here experimentally for the first time.

Manipulating spins of magnetic molecules: Hysteretic behavior with respect to bias voltage

NASA Astrophysics Data System (ADS)

Płomińska, Anna; Misiorny, Maciej; Weymann, Ireneusz

2018-02-01

Formation of a magnetic hysteresis loop with respect to a bias voltage is investigated theoretically in a spin-valve device based on a single magnetic molecule. We consider a device consisting of two ferromagnetic electrodes bridged by a carbon nanotube, acting as a quantum dot, to which a spin-anisotropic molecule is exchange-coupled. Such a coupling allows for transfer of angular momentum between the molecule and a spin current flowing through the dot, and thus, for switching orientation of the molecular spin. We demonstrate that this current-induced switching process exhibits a hysteretic behavior with respect to a bias voltage applied to the device. The analysis is carried out with the use of the real-time diagrammatic technique in the lowest-order expansion of the tunnel coupling of the dot to electrodes. The influence of both the intrinsic properties of the spin-valve device (the spin polarization of electrodes and the coupling strength of the molecule to the dot) and those of the molecule itself (magnetic anisotropy and spin relaxation) on the size of the magnetic hysteresis loop is discussed.

49 CFR 195.59 - Abandonment or deactivation of facilities.

Code of Federal Regulations, 2010 CFR

2010-10-01

....phmsa.dot.gov or contact the NPMS National Repository at 703-317-3073. A digital data format is preferred, but hard copy submissions are acceptable if they comply with the NPMS Standards. In addition to...

Real time analysis of self-assembled InAs/GaAs quantum dot growth by probing reflection high-energy electron diffraction chevron image

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kudo, Takuya; Inoue, Tomoya; Kita, Takashi

2008-10-01

Self-assembling process of InAs/GaAs quantum dots has been investigated by analyzing reflection high-energy electron diffraction chevron images reflecting the crystal facet structure surrounding the island. The chevron image shows dramatic changes during the island formation. From the temporal evolution of the chevron tail structure, the self-assembling process has been found to consist of four steps. The initial islands do not show distinct facet structures. Then, the island surface is covered by high-index facets, and this is followed by the formation of stable low-index facets. Finally, the flow of In atoms from the islands occurs, which contributes to flatten the wettingmore » layer. Furthermore, we have investigated the island shape evolution during the GaAs capping layer growth by using the same real-time analysis technique.« less

Self-organized microstructures induced by MeV ion beam on silicon surface

NASA Astrophysics Data System (ADS)

Ahmad, Muthanna

2017-02-01

Micro patterning of self organized structure on silicon surface is induced by ion implantation of energetic (MeV) copper ions. This work reports for the first time the ability of using energetic ions for producing highly ordered ripples and dots of micro sizes. The experiments are realized at the Tandem ion beam accelerator (3 MV) at the IBA laboratory of the Atomic Energy Commission of Syria. Similarly to nano patterning formed by slow ions, the formation of micro patterned structures dots and ripples is observed to be depending on the angle of ion beam incidence, energy and ion fluence. The observation of such microstructures formation is limited to a range of ion energies (few MeV) at fluence higher than 1.75 × 1017 ion cm-2. The patterned surface layer is completely amorphousized by the ion implantation. Shadowing effect is observed in the formation of microripples and superstructures in the top of ripples. The superstructure develops new morphology that is not observed before. This morphology has butterfly shape with symmetry in its structure.

New algorithms to represent complex pseudoknotted RNA structures in dot-bracket notation.

PubMed

Antczak, Maciej; Popenda, Mariusz; Zok, Tomasz; Zurkowski, Michal; Adamiak, Ryszard W; Szachniuk, Marta

2018-04-15

Understanding the formation, architecture and roles of pseudoknots in RNA structures are one of the most difficult challenges in RNA computational biology and structural bioinformatics. Methods predicting pseudoknots typically perform this with poor accuracy, often despite experimental data incorporation. Existing bioinformatic approaches differ in terms of pseudoknots' recognition and revealing their nature. A few ways of pseudoknot classification exist, most common ones refer to a genus or order. Following the latter one, we propose new algorithms that identify pseudoknots in RNA structure provided in BPSEQ format, determine their order and encode in dot-bracket-letter notation. The proposed encoding aims to illustrate the hierarchy of RNA folding. New algorithms are based on dynamic programming and hybrid (combining exhaustive search and random walk) approaches. They evolved from elementary algorithm implemented within the workflow of RNA FRABASE 1.0, our database of RNA structure fragments. They use different scoring functions to rank dissimilar dot-bracket representations of RNA structure. Computational experiments show an advantage of new methods over the others, especially for large RNA structures. Presented algorithms have been implemented as new functionality of RNApdbee webserver and are ready to use at http://rnapdbee.cs.put.poznan.pl. mszachniuk@cs.put.poznan.pl. Supplementary data are available at Bioinformatics online.

Investigation of magnetization dynamics in 2D Ni80Fe20 diatomic nanodot arrays

NASA Astrophysics Data System (ADS)

De, Anulekha; Mondal, Sucheta; Banerjee, Chandrima; Chaurasiya, Avinash K.; Mandal, Ruma; Otani, Yoshichika; Mitra, Rajib K.; Barman, Anjan

2017-09-01

Magnetization dynamics in Ni80Fe20 (Py) diatomic nanodots (nanodots of the same thickness but with large and small diameters that are closely placed to each other so as to act as a diatomic basis structure) embedded in 2D arrays have been investigated by the Brillouin light scattering technique. A distinct variation of resonant mode characteristics for different in-plane bias magnetic field applied along two different orientations of the lattice has been observed. Micromagnetic simulations reproduced the observed dynamical behaviour and revealed the variation of spatial distribution of collective modes of constituent single nanodots with different diameter and a diatomic unit forming the large array to understand the evolution of the magnetization dynamics from a single dot to the large array via a diatomic unit. The changes in mode frequency, spatial profiles of the modes, and appearance of new modes in a diatomic unit and its array from that of the constituent single dots indicate the strong magnetostatic interaction among the dots within the diatomic unit. Also, the occurrence of the new interacting mode at different frequencies for different orientations of the bias field indicates the change in the nature of interaction among the dots within the diatomic unit with bias magnetic field. The mode profiles also show distinct behaviour for smooth and rough-edged dots. This work motivates the study of magnonic band structure formation of such a dipolarly coupled nanodot array containing a complex double-dot unit cell.

Expression of the serine/threonine kinase hSGK1 in chronic viral hepatitis.

PubMed

Fillon, Sophie; Klingel, Karin; Wärntges, Simone; Sauter, Martina; Gabrysch, Sabine; Pestel, Sabine; Tanneur, Valerie; Waldegger, Siegfried; Zipfel, Annette; Viebahn, Richard; Häussinger, Dieter; Bröer, Stefan; Kandolf, Reinhard; Lang, Florian

2002-01-01

The human serine/threonine kinase hSGK1 is expressed ubiquitously with highest transcript levels in pancreas and liver. This study has been performed to determine the hSGK1 distribution in normal liver and its putative role in fibrosing liver disease. HSGK1-localization was determined by in situ hybridization, regulation of hSGK1-transcription by Northern blotting, fibronectin synthesis and hSGK1 phosphorylation by Western blotting. In normal liver hSGK1 was mainly transcribed by Kupffer cells. In liver tissue from patients with chronic viral hepatitis, hSGK1 transcript levels were excessively high in numerous activated Kupffer cells and inflammatory cells localized within fibrous septum formations. HSGK1 transcripts were also detected in activated hepatic stellate cells. Accordingly, Western blotting revealed that tissue from fibrotic liver expresses excessive hSGK1 protein as compared to normal liver. TGF-beta1 (2 ng/ml) increases hSGK1 transcription in both human U937 macro-phages and HepG2 hepatoma cells. H(2)O(2) (0.3 mM) activated hSGK1 and increased fibronectin formation in HepG2 cells overexpressing hSGK1 but not in HepG2 cells expressing the inactive mutant hSGK1(K127R). In conclusion hSGK1 is upregulated by TGF-beta1 during hepatitis and may contribute to enhanced matrix formation during fibrosing liver disease. Copyright 2002 S. Karger AG, Basel

Multifunctional QD-based co-delivery of siRNA and doxorubicin to HeLa cells for reversal of multidrug resistance and real-time tracking.

PubMed

Li, Jin-Ming; Wang, Yuan-Yuan; Zhao, Mei-Xia; Tan, Cai-Ping; Li, Yi-Qun; Le, Xue-Yi; Ji, Liang-Nian; Mao, Zong-Wan

2012-03-01

Co-delivery of siRNA and chemotherapeutic agents has been developed to combat multidrug resistance in cancer therapy. Recently, we developed a series of quantum dots (QDs) functionalized by β-cyclodextrin (β-CD) coupled to amino acids, some of which can be used to facilitate the delivery of siRNA. In this study, two CdSe/ZnSe QDs modified with β-CD coupled to L-Arg or L-His were used to simultaneously deliver doxorubicin (Dox) and siRNA targeting the MDR1 gene to reverse the multidrug resistance of HeLa cells. In this co-delivery system, Dox was firstly encapsulated into the hydrophobic cavities of β-CD, resulting in bypass of P-glycoprotein (P-gp)-mediated drug efflux. After complex formation of the mdr1 siRNA with Dox-loaded QDs via electrostatic interaction, significant down-regulation of mdr1 mRNA levels and P-gp expression was achieved as shown by RT-PCR and Western blotting experiments, respectively. The number of apoptotic HeLa cells after treatment with the complexes substantially exceeded the number of apoptotic cells induced by free Dox only. The intrinsic fluorescence of the QDs provided an approach to track the system by laser confocal microscopy. These multifunctional QDs are promising vehicles for the co-delivery of nucleic acids and chemotherapeutics and for real-time tracking of treatment. Copyright © 2011 Elsevier Ltd. All rights reserved.

First evidence of DNA methylation in insect Tribolium castaneum: environmental regulation of DNA methylation within heterochromatin.

PubMed

Feliciello, Isidoro; Parazajder, Josip; Akrap, Ivana; Ugarković, Durđica

2013-05-01

DNA methylation has been studied in many eukaryotic organisms, in particular vertebrates, and was implicated in developmental and phenotypic variations. Little is known about the role of DNA methylation in invertebrates, although insects are considered as excellent models for studying the evolution of DNA methylation. In the red flour beetle, Tribolium castaneum (Tenebrionidae, Coleoptera), no evidence of DNA methylation has been found till now. In this paper, a cytosine methylation in Tribolium castaneum embryos was detected by methylation sensitive restriction endonucleases and immuno-dot blot assay. DNA methylation in embryos is followed by a global demethylation in larvae, pupae and adults. DNA demethylation seems to proceed actively through 5-hydroxymethylcytosine, most probably by the action of TET enzyme. Bisulfite sequencing of a highly abundant satellite DNA located in pericentromeric heterochromatin revealed similar profile of cytosine methylation in adults and embryos. Cytosine methylation was not only restricted to CpG sites but was found at CpA, CpT and CpC sites. In addition, complete cytosine demethylation of heterochromatic satellite DNA was induced by heat stress. The results reveal existence of DNA methylation cycling in T. castaneum ranging from strong overall cytosine methylation in embryos to a weak DNA methylation in other developmental stages. Nevertheless, DNA methylation is preserved within heterochromatin during development, indicating its role in heterochromatin formation and maintenance. It is, however, strongly affected by heat stress, suggesting a role for DNA methylation in heterochromatin structure modulation during heat stress response.

Humic acid inhibits HBV-induced autophagosome formation and induces apoptosis in HBV-transfected Hep G2 cells

PubMed Central

Pant, Kishor; Yadav, Ajay K.; Gupta, Parul; Rathore, Abhishek Singh; Nayak, Baibaswata; Venugopal, Senthil K.

2016-01-01

Hepatitis B Virus (HBV) utilizes several mechanisms to survive in the host cells and one of the main pathways being autophagosome formation. Humic acid (HA), one of the major components of Mineral pitch, is an Ayurvedic medicinal food, commonly used by the people of the Himalayan regions of Nepal and India for various body ailments. We hypothesized that HA could induce cell death and inhibit HBV-induced autophagy in hepatic cells. Incubation of Hep G2.2.1.5 cells (HepG2 cells stably expressing HBV) with HA (100 μM) inhibited both cell proliferation and autophagosome formation significantly, while apoptosis induction was enhanced. Western blot results showed that HA incubation resulted in decreased levels of beclin-1, SIRT-1 and c-myc, while caspase-3 and β-catenin expression were up-regulated. Western blot results showed that HA significantly inhibited the expression of HBx (3-fold with 50 μM and 5-fold with 100 μM) compared to control cells. When HA was incubated with HBx-transfected Hep G2 cells, HBx-induced autophagosome formation and beclin-1 levels were decreased. These data showed that HA induced apoptosis and inhibited HBV-induced autophagosome formation and proliferation in hepatoma cells. PMID:27708347

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Xiaoyin; Lu, Ping; Fischer, Arthur J.

Illumination by a narrow-band laser has been shown to enable photoelectrochemical (PEC) etching of InGaN thin films into quantum dots with sizes controlled by the laser wavelength. Here, we investigate and elucidate the influence of solution pH on such quantum-size-controlled PEC etch process. We find that although a pH above 5 is often used for PEC etching of GaN-based materials, oxides (In 2O 3 and/or Ga 2O 3) form which interfere with quantum dot formation. Furthermore, at pH below 3, however, oxide-free QDs with self-terminated sizes can be successfully realized.

A Bridging Water Anchors the Tethered 5-(3-Aminopropyl)-2′-deoxyuridine Amine in the DNA Major Groove Proximate to the N+2 C·G Base Pair: Implications for Formation of Interstrand 5′-GNC-3′ Cross-Links by Nitrogen Mustards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Feng; Li, Feng; Ganguly, Manjori

2008-11-14

Site-specific insertion of t-(3-aminopropyl)-2'-deoxyuridine (Z3dU) and 7-deaza-dG into the Dickerson-Drew dodecamers 5'-d(C{sup 1}G{sup 2}C{sup 3}G{sup 4}A{sup 5}A{sup 6}T{sup 7}T{sup 8}C{sup 9}{und Z}{sup 10}C{sup 11}G{sup 12})-3'{center_dot}5'-d (C{sup 13}G{sup 14}C{sup 15}G{sup 16}A{sup 17}A{sup 18}T{sup 19}T{sup 20}C{sup 21}{und Z}{sup 22}C{sup 23}G{sup 24})-3' (named DDD{sup Z10}) and 5'-d(C{sup 1}G{sup 2}C{sup 3}G{sup 4}A{sup 5}A{sup 6}T{sup 7}{und X}{sup 20}C{sup 21}{und Z}{sup 22}C{sup 23}G{sup 24})-3' (named DDD{sup 2+Z10}) (X = 73dU; Z = 7-deaza-dG) suggests a mechanism underlying the formation of interstrand N+2 DNA cross-links by nitrogen mustards, e.g., melphalan and mechlorethamine. Analysis of the DDD{sup 2+Z10} duplex reveals that the tethered cations at base pairs A{supmore » 5}{center_dot}X{sup 20} and X{sup 8}{center_dot}A{sup 17} extend within the major groove in the 3'-direction, toward conserved Mg{sup 2+} binding sites located adjacent to N+2 base pairs C{sup 3}{center_dot}Z{sup 22} and Z{sup 10}{center_dot}C{sup 15}. Bridging waters located between the tethered amines and either Z{sup 10} or Z{sup 22} O{sup 6} stabilize the tethered cations and allow interactions with the N + 2 base pairs without DNA bending. Incorporation of 7-deaza-dG into the DDD{sup 2+Z10} duplex weakens but does not eliminate electrostatic interactions between tethered amines and Z{sup 10} O{sup 6} and Z{sup 22} O{sup 6}. The results suggest a mechanism by which tethered N7-dG aziridinium ions, the active species involved in formation of interstrand 5'-GNC-3' cross-links by nitrogen mustards, modify the electrostatics of the major groove and position the aziridinium ions proximate to the major groove edge of the N+2 C{center_dot}G base pair, facilitating interstrand cross-linking.« less

Perturbation effect of reduced graphene oxide quantum dots (rGOQDs) on aryl hydrocarbon receptor (AhR) pathway in zebrafish.

PubMed

Zhang, Jing-Hui; Sun, Tai; Niu, Aping; Tang, Yu-Mei; Deng, Shun; Luo, Wei; Xu, Qun; Wei, Dapeng; Pei, De-Sheng

2017-07-01

Graphene quantum dots (GQDs) has been widely used in enormous fields, however, the inherent molecular mechanism of GQDs for potential risks in biological system is still elusive to date. In this study, the outstanding reduced graphene quantum dots (rGOQDs) with the QY as high as 24.62% were successfully synthesized by the improved Hummers method and DMF hydrothermal treatment approach. The rGOQDs were N-doped photoluminescent nanomaterials with functional groups on the surface. The fluorescent bio-imaging was performed by exposing zebrafish in different concentrations of the as-prepared rGOQDs, and the distribution of rGOQDs was successfully observed. Moreover, the developmental toxicity and genotoxicity were evaluated to further investigate the potential hazard of rGOQDs. The result indicated that rGOQDs were responsible for the dose-dependent abnormalities on the development of zebrafish. Since the real-time polymerase chain reaction (RT-PCR) results showed that the expression of cyp1a was the highest expression in the selected genes and significantly up-regulated 8.49 fold in zebrafish, the perturbation of rGOQDs on aryl hydrocarbon receptor (AhR) pathway was investigated by using the Tg(cyp1a:gfp) zebrafish for the first time. The results demonstrated that rGOQDs significantly increased the green fluorescent protein (GFP) expression promoted by cyp1a in a dose-dependent manner, which was also further confirmed by the western blotting. This study offered an opportunity to reveal the potential hazards of in vivo bio-probes, which provided a valuable reference for investigating the graphene-based materials on the disturbance of AhR pathway in biological organisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

SPT-CL J2040–4451: An SZ-selected galaxy cluster at x=1.478 with significant ongoing star formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayliss, M. B.; Ashby, M. L. N.; Ruel, J.

2014-09-18

SPT-CL J2040-4451-spectroscopically confirmed at z = 1.478-is the highest-redshift galaxy cluster yet discovered via the Sunyaev-Zel'dovich effect. SPT-CL J2040-4451 was a candidate galaxy cluster identified in the first 720 deg(2) of the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey, and has been confirmed in follow-up imaging and spectroscopy. From multi-object spectroscopy with Magellan-I/Baade+ IMACS we measure spectroscopic redshifts for 15 cluster member galaxies, all of which have strong [O Pi]lambda lambda 3727 emission. SPT-CL J2040-4451 has an SZ-measured mass of M-500,(SZ) = 3.2 ± 0.8 x 10 14M(circle dot) h(-1) 70, corresponding to M-200,M- (SZ) = 5.8 ± 1.4 x 10more » 14M(circle dot) h(70-)(1.) The velocity dispersion measured entirely from blue star-forming members is sv = 1500 ± 520 km s -1. The prevalence of star-forming cluster members (galaxies with > 1.5M(circle dot) yr -1 implies that this massive, high-redshift cluster is experiencing a phase of active star formation, and supports recent results showing a marked increase in star formation occurring in galaxy clusters at z greater than or similar to 1.4. We also compute the probability of finding a cluster as rare as this in the SPT-SZ survey to be > 99%, indicating that its discovery is not in tension with the concordance Lambda CDM cosmological model.« less

Highly sensitive strategy for Hg2+ detection in environmental water samples using long lifetime fluorescence quantum dots and gold nanoparticles.

PubMed

Huang, Dawei; Niu, Chenggang; Ruan, Min; Wang, Xiaoyu; Zeng, Guangming; Deng, Canhui

2013-05-07

The authors herein described a time-gated fluorescence resonance energy transfer (TGFRET) sensing strategy employing water-soluble long lifetime fluorescence quantum dots and gold nanoparticles to detect trace Hg(2+) ions in aqueous solution. The water-soluble long lifetime fluorescence quantum dots and gold nanoparticles were functionalized by two complementary ssDNA, except for four deliberately designed T-T mismatches. The quantum dot acted as the energy-transfer donor, and the gold nanoparticle acted as the energy-transfer acceptor. When Hg(2+) ions were present in the aqueous solution, DNA hybridization will occur because of the formation of T-Hg(2+)-T complexes. As a result, the quantum dots and gold nanoparticles are brought into close proximity, which made the energy transfer occur from quantum dots to gold nanoparticles, leading to the fluorescence intensity of quantum dots to decrease obviously. The decrement fluorescence intensity is proportional to the concentration of Hg(2+) ions. Under the optimum conditions, the sensing system exhibits the same liner range from 1 × 10(-9) to 1 × 10(-8) M for Hg(2+) ions, with the detection limits of 0.49 nM in buffer and 0.87 nM in tap water samples. This sensor was also used to detect Hg(2+) ions from samples of tap water, river water, and lake water spiked with Hg(2+) ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. In comparison to some reported colorimetric and fluorescent sensors, the proposed method displays the advantage of higher sensitivity. The TGFRET sensor also exhibits excellent selectivity and can provide promising potential for Hg(2+) ion detection.

Peanut digestome: Identification of digestion resistant IgE binding peptides.

PubMed

Di Stasio, Luigia; Picariello, Gianluca; Mongiello, Mariantonietta; Nocerino, Rita; Berni Canani, Roberto; Bavaro, Simona; Monaci, Linda; Ferranti, Pasquale; Mamone, Gianfranco

2017-09-01

Stability to proteolytic degradation in the digestive tract is considered a general feature shared by most food allergens. Current digestibility models exclusively utilize purified allergen proteins, neglecting the relevant effects of matrix that occur for foodstuff systems. In the present study, we investigated digestion stability of the major peanut allergens directly in the natural matrix using an in vitro static model that simulates the gastrointestinal digestion including the oral, gastric, duodenal and intestinal (brush border membrane enzymes) phases. Immunogenicity was evaluated by Western Blot using N=8 pooled sera of peanut allergic pediatric subjects. Immunoreactive, large-sized and fragments of Ara h 2, Ara h 6 and Ara h 3 survived hydrolysis as assessed by SDS-PAGE. Smaller resistant peptides mainly arising from Ara h 3 and also Ara h 1 were detected and further identified by LC-high resolution-MS/MS. RP-HPLC purification followed by dot-blot analysis and MS/MS-based identification demonstrated that stable IgE-binding peptides derived from Ara h 3. These results provide a more realistic picture of the potentially allergenic determinants of peanuts that survived the human digestion, taking into account the role of the food matrix, which may significantly affect gastrointestinal breakdown of peanut allergens. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of emodin on the demethylation of tumor-suppressor genes in pancreatic cancer PANC-1 cells.

PubMed

Zhang, Hao; Chen, Liang; Bu, He-Qi; Yu, Qing-Jiang; Jiang, Dan-Dan; Pan, Feng-Ping; Wang, Yu; Liu, Dian-Lei; Lin, Sheng-Zhang

2015-06-01

Emodin, a natural anthraquinone derivative isolated from Rheum palmatum, has been reported to inhibit the growth of pancreatic cancer cells through different modes of action; yet, the detailed mechanism remains unclear. In the present study, we hypothesized that emodin exerts its antitumor effect by participating in the regulation of the DNA methylation level. Our research showed that emodin inhibited the growth of pancreatic cancer PANC-1 cells in a dose- and time-dependent manner. Dot-blot results showed that 40 µM emodin significantly inhibited genomic 5 mC expression in the PANC-1 cells, and mRNA-Seq showed that different concentrations of emodin could alter the gene expression profile in the PANC-1 cells. BSP confirmed that the methylation levels of P16, RASSF1A and ppENK were decreased, while concomitantly the unmethylated status was increased. RT-PCR and western blotting results confirmed that the low expression or absence of expression of mRNA and protein in the PANC-1 cells was re-expressed following treatment with emodin. In conclusion, our study for the first time suggests that emodin inhibits pancreatic cancer cell growth, which may be related to the demethylation of tumor-suppressor genes. The related mechanism may be through the inhibition of methyltransferase expression.

Improved soluble expression and characterization of the Hc domain of Clostridium botulinum neurotoxin serotype A in Escherichia coli by using a PCR-synthesized gene and a Trx co-expression strain.

PubMed

Chen, Rongchang; Shi, Jing; Cai, Kun; Tu, Wei; Hou, Xiaojun; Liu, Hao; Xiao, Le; Wang, Qin; Tang, Yunming; Wang, Hui

2010-05-01

Botulinum neurotoxin serotype A (BoNT/A) is an extremely potent bacterial protein toxin. The Hc fragment of BoNT/A (AHc) was shown to be non-toxic, antigenic, and capable of eliciting a protective immunity in animals challenged with homologous BoNT. In this study, we synthesized AHc gene by using T4 DNA ligase and PCR. The AHc was expressed at a high level in Escherichia coli successfully. Because of using the Trx co-expression strain, the expressed AHc is in a soluble and active form. The yield of the purified AHc was about 70mg/L, and its purity was up to 90% through one-step affinity chromatography. The AHc was positively identified by the antibodies raised against BoNT/A using immunological-dot-blot and Western blot assays. AHc was shown to bind with gangliosides and elicit immunity against BoNT/A, indicating that the expressed and purified AHc protein retains a functionally active conformation. Furthermore, the purified AHc has a strong immunogenicity and can be used as a potential subunit candidate vaccine for botulinum toxin serotype A. Copyright (c) 2009 Elsevier Inc. All rights reserved.

Silver enhancement of nanogold and undecagold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hainfield, J.F.; Furuya, F.R.

1995-07-01

A recent advance in immunogold technology has been the use of molecular gold instead of colloidal gold. A number of advantages are realized by this approach, such as stable covalent, site-specific attachment, small probe size and absence of aggregates for improved penetration. Silver enhancement has led to improved and unique results for electron and light microscopy, as well as their use with blots and gels. Most previous work with immunogold silver staining has been done with colloidal gold particles. More recently, large gold compounds (``clusters``) having a definite number of gold atoms and defined organic shell, have been used, frequentlymore » with improved results. These gold dusters, large compared to simple compounds, are, however, at the small end of the colloidal gold scale in size; undecagold is 0.8 nm and Nanogold is 1.4 nm. They may be used in practically all applications where colloidal gold is used (Light and electron microscopy, dot blots, etc.) and in some unique applications, where at least the larger colloidal golds don`t work, such as running gold labeled proteins on gels (which are later detected by silver enhancement). The main differences between gold clusters and colloidal golds are the small size of the dusters and their covalent attachment to antibodies or other molecules.« less

Subcellular Localization and Rolling Circle Replication of Peach Latent Mosaic Viroid: Hallmarks of Group A Viroids

PubMed Central

Bussière, F.; Lehoux, J.; Thompson, D. A.; Skrzeczkowski, L. J.; Perreault, J.-P.

1999-01-01

We characterized the peach latent mosaic viroid (PLMVd) replication intermediates that accumulate in infected peach leaves and determined the tissue and subcellular localization of the RNA species. Using in situ hybridization, we showed that PLMVd strands of both plus and minus polarities concentrate in the cells forming the palisade parenchyma. At the cellular level, PLMVd was found to accumulate predominantly in chloroplasts. Northern blot analyses demonstrated that PLMVd replicates via a symmetric mode involving the accumulation of both circular and linear monomeric strands of both polarities. No multimeric conformer was detected, indicating that both strands self-cleave efficiently via their hammerhead sequences. Dot blot hybridizations revealed that PLMVd strands of both polarities accumulate equally but that the relative concentrations vary by more than 50-fold between peach cultivars. Taken together these results establish two hallmarks for the classification of viroids. Group A viroids (e.g., PLMVd), which possess hammerhead structures, replicate in the chloroplasts via the symmetric mode. By contrast, group B viroids, which share a conserved central region, replicate in the nucleus via an asymmetric mechanism. This is an important difference between self-cleaving and non-self-cleaving viroids, and the implications for the evolutionary origin and replication are discussed. PMID:10400727

Genes up-regulated during red coloration in UV-B irradiated lettuce leaves.

PubMed

Park, Jong-Sug; Choung, Myoung-Gun; Kim, Jung-Bong; Hahn, Bum-Soo; Kim, Jong-Bum; Bae, Shin-Chul; Roh, Kyung-Hee; Kim, Yong-Hwan; Cheon, Choong-Ill; Sung, Mi-Kyung; Cho, Kang-Jin

2007-04-01

Molecular analysis of gene expression differences between green and red lettuce leaves was performed using the SSH method. BlastX comparisons of subtractive expressed sequence tags (ESTs) indicated that 7.6% of clones encoded enzymes involved in secondary metabolism. Such clones had a particularly high abundance of flavonoid-metabolism proteins (6.5%). Following SSH, 566 clones were rescreened for differential gene expression using dot-blot hybridization. Of these, 53 were found to overexpressed during red coloration. The up-regulated expression of six genes was confirmed by Northern blot analyses. The expression of chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and dihydroflavonol 4-reductase (DFR) genes showed a positive correlation with anthocyanin accumulation in UV-B-irradiated lettuce leaves; flavonoid 3',5'-hydroxylase (F3',5'H) and anthocyanidin synthase (ANS) were expressed continuously in both samples. These results indicated that the genes CHS, F3H, and DFR coincided with increases in anthocyanin accumulation during the red coloration of lettuce leaves. This study show a relationship between red coloration and the expression of up-regulated genes in lettuce. The subtractive cDNA library and EST database described in this study represent a valuable resource for further research for secondary metabolism in the vegetable crops.

GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis.

PubMed

Gallardo, W G; Hagiwara, A; Hara, K; Soyano, K; Snell, T W

2000-11-01

gamma-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids.

Study of light signal receptor of Stephanopyxis palmeriana during sexual reproduction

NASA Astrophysics Data System (ADS)

Hu, Ren; Lin, Junmin; Lin, Qiuqi; Han, Boping

2005-09-01

We collected centric diatom Stephanopyxis palmeriana samples in coastal waters of Xiamen for characteristic red light/far red light (R/FR) phytochrome reactions to identify its photoreceptor in the course of sexual reproduction. The result showed that pre-illumination of 2 3h red light before darkness could induce sexualization of S. palmeriana, while the follow-up illumination of far red light could reverse the effect of red light, which is a featured reaction of phytochrome. The Southern Dot Blot was carried out to identify the type of phytochrome that induces the sexualization. The result also showed high homogeneity of DNA fragment of S. palmeriana with phyB, but phyA. This means the photoreceptor in the process of sexual reproduction of S. palmeriana is phytochrome B (phyB).

A gold nanoparticles-based colorimetric test to detect single nucleotide polymorphisms for improvement of personalized therapy of psoriasis

NASA Astrophysics Data System (ADS)

Marsella, Alessandra; Valentini, Paola; Tarantino, Paolo; Congedo, Maurizio; Pompa, Pier Paolo

2016-04-01

We report a simple, rapid and low-cost test, based on gold nanoparticles, for the naked-eye colorimetric detection of a signature of single nucleotide polymorphisms (SNPs) relevant for the personalized medicine of psoriasis patients. We validated the colorimetric assay on real-world DNA samples from a cohort of 30 psoriasis patients and we compared the results, in double-blind, with those obtained with two state-of-the-art instrumental techniques, namely reverse dot blotting and direct sequencing, finding 100% agreement. We demonstrated high accuracy, sensitivity and specificity of the colorimetric test that can be easily adapted for the genotypization of different SNPs, important for the pharmacogenomics of various diseases, and in other fields, such as food traceability and population structure analysis.

Electron Spin Optical Orientation in Charged Quantum Dots

NASA Astrophysics Data System (ADS)

Shabaev, A.; Gershoni, D.; Korenev, V. L.

2005-03-01

We present a theory of nonresonant optical orientation of electron spins localized in quantum dots. This theory explains the negative circularly polarized photoluminescence of singlet trions localized in quantum dots previously observed in experiments where trion polarization changed to negative with time and where the degree of the negative polarization increased with intensity of pumping light. We have shown that this effect can be explained by the accumulation of dark excitons that occurs due to the spin blocking of the singlet trion formation - the major mechanism of dark exciton recombination. The accumulation of dark excitons results from a lack of electrons with a spin matching the exciton polarization. The electron spin lifetime is shortened by a transverse magnetic field or a temperature increase. This takes the block off the dark exciton recombination and restores the positive degree of trion polarization. The presented theory gives good agreement with experimental data.

Time-resolved energy transduction in a quantum capacitor

PubMed Central

Jung, Woojin; Cho, Doohee; Kim, Min-Kook; Choi, Hyoung Joon; Lyo, In-Whan

2011-01-01

The capability to deposit charge and energy quantum-by-quantum into a specific atomic site could lead to many previously unidentified applications. Here we report on the quantum capacitor formed by a strongly localized field possessing such capability. We investigated the charging dynamics of such a capacitor by using the unique scanning tunneling microscopy that combines nanosecond temporal and subangstrom spatial resolutions, and by using Si(001) as the electrode as well as the detector for excitations produced by the charging transitions. We show that sudden switching of a localized field induces a transiently empty quantum dot at the surface and that the dot acts as a tunable excitation source with subangstrom site selectivity. The timescale in the deexcitation of the dot suggests the formation of long-lived, excited states. Our study illustrates that a quantum capacitor has serious implications not only for the bottom-up nanotechnology but also for future switching devices. PMID:21817067

Final Report: Mechanisms of sputter ripple formation: coupling among energetic ions, surface kinetics, stress and composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chason, Eric; Shenoy, Vivek

Self-organized pattern formation enables the creation of nanoscale surface structures over large areas based on fundamental physical processes rather than an applied template. Low energy ion bombardment is one such method that induces the spontaneous formation of a wide variety of interesting morphological features (e.g., sputter ripples and/or quantum dots). This program focused on the processes controlling sputter ripple formation and the kinetics controlling the evolution of surfaces and nanostructures in high flux environments. This was done by using systematic, quantitative experiments to measure ripple formation under a variety of processing conditions coupled with modeling to interpret the results.

Rapid diagnosis of soybean mosaic virus N soybean by tissue-print immunoassay and DIBA in comparison to other serological methods.

PubMed

Ahangaran, A; Mohammadi, Gh Mosahebi; Habibi, M Koohi; Shahraeen, N; Khezri, S

2006-01-01

Soybean mosaic virus (SMV) is an important disease in soybean and is widely distributed in northern of Iran. SMV transmitted by soybean seed and detection of it is very important for disease management. In this study, several detection methods including DAS-ELISA, indirect-ELISA, tissue-print immunoassay (TPIA) and Dot immunobinding assay (DIBA) were optimized and compared with each other to identify the virus, using polyclonal antibody. For TPIA, nitrocellulose membrane was used to imprint fresh sections of healthy and infected plant materials, and for DIBA 10 microl of extracts was doted onto nitrocellulose membranes. Both membranes were incubated 1 hour in blocking buffer, and then incubated 2 h in 1:1000 dilution of IgG-conjugate. After incubation the membranes were washed three times with PBS-T buffer for 15 min. Then the membranes were incubated in substrate solution containing NBT/BCIP. After some minutes prints or blots of infected tissues turned dark violet, whereas prints or blots of healthy ones did not show any color changes. In some cases, substrate solution was Fast red, containing 0.2M Tris-HCl buffer and 2mM MgCl2, pH = 7.8, producing red color in infected prints or blots. Both methods are simple and TPIA is rapidly and easily applicable in the field. However, TPIA had some advantages over the others. TPIA is time-saving as there is no need for conventional sap extraction and also nitrocellulose membranes used for printing can be used in the field and stored for a long time or transported to another laboratory for process. These two methods can be used routinely for detection of SMV in many samples.

Review of Current Geographic Information Systems Technology for TxDOT Pavement Management Information System

DOT National Transportation Integrated Search

1998-05-01

A geographic information system (GIS) is a tool for effectively managing and analyzing tremendous amounts of geographic information. It employs the essential principle of geography to organize in formation and express relationships between real-world...

Abstract number and arithmetic in preschool children.

PubMed

Barth, Hilary; La Mont, Kristen; Lipton, Jennifer; Spelke, Elizabeth S

2005-09-27

Educated humans use language to express abstract number, applying the same number words to seven apples, whistles, or sins. Is language or education the source of numerical abstraction? Claims to the contrary must present evidence for numerical knowledge that applies to disparate entities, in people who have received no formal mathematics instruction and cannot express such knowledge in words. Here we show that preschool children can compare and add large sets of elements without counting, both within a single visual-spatial modality (arrays of dots) and across two modalities and formats (dot arrays and tone sequences). In two experiments, children viewed animations and either compared one visible array of dots to a second array or added two successive dot arrays and compared the sum to a third array. In further experiments, a dot array was replaced by a sequence of sounds, so that participants had to integrate quantity information presented aurally and visually. Children performed all tasks successfully, without resorting to guessing strategies or responding to continuous variables. Their accuracy varied with the ratio of the two quantities: a signature of large, approximate number representations in adult humans and animals. Addition was as accurate as comparison, even though children showed no relevant knowledge when presented with symbolic versions of the addition tasks. Abstract knowledge of number and addition therefore precedes, and may guide, language-based instruction in mathematics.

Structural and optoelectronic studies on Ag-CdS quantum dots

NASA Astrophysics Data System (ADS)

Ibrahim Mohammed S., M.; Gubari, Ghamdan M. M.; Huse, Nanasaheb P.; Dive, Avinash S.; Sharma, Ramphal

2018-05-01

In the present study, we have successfully deposited CdS quantum dot thin films and Ag doped CdS on a glass slide by simple and economical chemical bath deposition at room temperature. The X-ray diffraction method analysis reveals that CdS thin films exhibit hexagonal structure when compared with standard JCPDS data. The estimated average crystallite size of the quantum dots and resulted in the least crystallite size of ˜9 nm. a comparison between the optical and electrical properties of the films before and after doping Ag was made through measuring and analyzing the curves for UV and I-V. From UV absorption spectra we observed that the samples exhibited a band edge near ˜400 nm with a slight deviation with the presence of excitonic peak for both CdS and Ag doped CdS. The presence of excitonic peak may be referred to the formation of quantum dots. The calculated band gap energy of thin films was found to be 3.45 eV and 3.15 eV for both CdS and Ag doped CdS thin films respectively, where the optical absorption spectra of Ag doped CdS nanoparticles also exhibit shift with respect to that of CdS quantum dots thin films. The photosensitive of CdS thin films show an increase in photocurrent when Ag doped CdS.

FORMING HABITABLE PLANETS AROUND DWARF STARS: APPLICATION TO OGLE-06-109L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Su; Zhou Jilin, E-mail: suwang@nju.edu.cn, E-mail: zhoujl@nju.edu.cn

2011-02-01

Dwarf stars are believed to have a small protostar disk where planets may grow up. During the planet formation stage, embryos undergoing type I migration are expected to be stalled at an inner edge of the magnetically inactive disk (a{sub crit} {approx} 0.2-0.3 AU). This mechanism makes the location around a{sub crit} a 'sweet spot' for forming planets. In dwarf stars with masses {approx}0.5 M{sub sun}, a{sub crit} is roughly inside the habitable zone of the system. In this paper, we study the formation of habitable planets due to this mechanism using model system OGLE-06-109L, which has a 0.51 M{submore » sun} dwarf star with two giant planets in 2.3 and 4.6 AU observed by microlensing. We model the embryos undergoing type I migration in the gas disk with a constant disk-accretion rate ( M-dot ). Giant planets in outside orbits affect the formation of habitable planets through secular perturbations at the early stage and secular resonance at the late stage. We find that the existence and the masses of the habitable planets in the OGLE-06-109L system depend on both M-dot and the speed of type I migration. If planets are formed earlier, so that M-dot is larger ({approx}10{sup -7} M{sub sun} yr{sup -1}), terrestrial planets cannot survive unless the type I migration rate is an order of magnitude less. If planets are formed later, so that M-dot is smaller ({approx}10{sup -8} M{sub sun} yr{sup -1}), single and high-mass terrestrial planets with high water contents ({approx}5%) will be formed by inward migration of outer planet cores. A slower-speed migration will result in several planets via collisions of embryos, and thus their water contents will be low ({approx}2%). Mean motion resonances or apsidal resonances among planets may be observed if multiple planets survive in the inner system.« less

The influence of graphic display format on the interpretations of quantitative risk information among adults with lower education and literacy: a randomized experimental study.

PubMed

McCaffery, Kirsten J; Dixon, Ann; Hayen, Andrew; Jansen, Jesse; Smith, Sian; Simpson, Judy M

2012-01-01

To test optimal graphic risk communication formats for presenting small probabilities using graphics with a denominator of 1000 to adults with lower education and literacy. A randomized experimental study, which took place in adult basic education classes in Sydney, Australia. The participants were 120 adults with lower education and literacy. An experimental computer-based manipulation compared 1) pictographs in 2 forms, shaded "blocks" and unshaded "dots"; and 2) bar charts across different orientations (horizontal/vertical) and numerator size (small <100, medium 100-499, large 500-999). Accuracy (size of error) and ease of processing (reaction time) were assessed on a gist task (estimating the larger chance of survival) and a verbatim task (estimating the size of difference). Preferences for different graph types were also assessed. Accuracy on the gist task was very high across all conditions (>95%) and not tested further. For the verbatim task, optimal graph type depended on the numerator size. For small numerators, pictographs resulted in fewer errors than bar charts (blocks: odds ratio [OR] = 0.047, 95% confidence interval [CI] = 0.023-0.098; dots: OR = 0.049, 95% CI = 0.024-0.099). For medium and large numerators, bar charts were more accurate (e.g., medium dots: OR = 4.29, 95% CI = 2.9-6.35). Pictographs were generally processed faster for small numerators (e.g., blocks: 14.9 seconds v. bars: 16.2 seconds) and bar charts for medium or large numerators (e.g., large blocks: 41.6 seconds v. 26.7 seconds). Vertical formats were processed slightly faster than horizontal graphs with no difference in accuracy. Most participants preferred bar charts (64%); however, there was no relationship with performance. For adults with low education and literacy, pictographs are likely to be the best format to use when displaying small numerators (<100/1000) and bar charts for larger numerators (>100/1000).

Effects of bending and heat on the ductility and fracture toughness of flange plate.

DOT National Transportation Integrated Search

2012-05-01

Bridge fabricators for the Texas Department of Transportation (TxDOT) have occasionally experienced the : formation of cracks in flange plate during bending operations, particularly when heat is applied. Bending the : flange plate is necessary for ce...

United States Department of Transportation report to Congress on public-private partnerships, December 2004.

DOT National Transportation Integrated Search

2004-12-01

House Report 108-243 (2003) accompanying the FY 2004 Department of Transportation : Appropriations Act requested the U.S. Department of Transportation (DOT) to prepare a : report identifying the impediments to the formation of large, capital-intensiv...

How supernovae launch galactic winds?

NASA Astrophysics Data System (ADS)

Fielding, Drummond; Quataert, Eliot; Martizzi, Davide; Faucher-Giguère, Claude-André

2017-09-01

We use idealized three-dimensional hydrodynamic simulations of global galactic discs to study the launching of galactic winds by supernovae (SNe). The simulations resolve the cooling radii of the majority of supernova remnants (SNRs) and thus self-consistently capture how SNe drive galactic winds. We find that SNe launch highly supersonic winds with properties that agree reasonably well with expectations from analytic models. The energy loading (η _E= \\dot{E}_wind/ \\dot{E}_SN) of the winds in our simulations are well converged with spatial resolution while the wind mass loading (η _M= \\dot{M}_wind/\\dot{M}_\\star) decreases with resolution at the resolutions we achieve. We present a simple analytic model based on the concept that SNRs with cooling radii greater than the local scaleheight break out of the disc and power the wind. This model successfully explains the dependence (or lack thereof) of ηE (and by extension ηM) on the gas surface density, star formation efficiency, disc radius and the clustering of SNe. The winds our simulations are weaker than expected in reality, likely due to the fact that we seed SNe preferentially at density peaks. Clustering SNe in time and space substantially increases the wind power.

Sensitivity to Heavy-Metal Ions of Unfolded Fullerene Quantum Dots

PubMed Central

Ciotta, Erica; Paoloni, Stefano; Richetta, Maria; Tagliatesta, Pietro; Lorecchio, Chiara; Casciardi, Stefano

2017-01-01

A novel type of graphene-like quantum dots, synthesized by oxidation and cage-opening of C60 buckminsterfullerene, has been studied as a fluorescent and absorptive probe for heavy-metal ions. The lattice structure of such unfolded fullerene quantum dots (UFQDs) is distinct from that of graphene since it includes both carbon hexagons and pentagons. The basic optical properties, however, are similar to those of regular graphene oxide quantum dots. On the other hand, UFQDs behave quite differently in the presence of heavy-metal ions, in that multiple sensitivity to Cu2+, Pb2+ and As(III) was observed through comparable quenching of the fluorescent emission and different variations of the transmittance spectrum. By dynamic light scattering measurements and transmission electron microscope (TEM) images we confirmed, for the first time in metal sensing, that this response is due to multiple complexation and subsequent aggregation of UFQDs. Nonetheless, the explanation of the distinct behaviour of transmittance in the presence of As(III) and the formation of precipitate with Pb2+ require further studies. These differences, however, also make it possible to discriminate between the three metal ions in view of the implementation of a selective multiple sensor. PMID:29135946

Mesoscopic Elastic Distortions in GaAs Quantum Dot Heterostructures.

PubMed

Pateras, Anastasios; Park, Joonkyu; Ahn, Youngjun; Tilka, Jack A; Holt, Martin V; Reichl, Christian; Wegscheider, Werner; Baart, Timothy A; Dehollain, Juan Pablo; Mukhopadhyay, Uditendu; Vandersypen, Lieven M K; Evans, Paul G

2018-05-09

Quantum devices formed in high-electron-mobility semiconductor heterostructures provide a route through which quantum mechanical effects can be exploited on length scales accessible to lithography and integrated electronics. The electrostatic definition of quantum dots in semiconductor heterostructure devices intrinsically involves the lithographic fabrication of intricate patterns of metallic electrodes. The formation of metal/semiconductor interfaces, growth processes associated with polycrystalline metallic layers, and differential thermal expansion produce elastic distortion in the active areas of quantum devices. Understanding and controlling these distortions present a significant challenge in quantum device development. We report synchrotron X-ray nanodiffraction measurements combined with dynamical X-ray diffraction modeling that reveal lattice tilts with a depth-averaged value up to 0.04° and strain on the order of 10 -4 in the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. Elastic distortions in GaAs/AlGaAs heterostructures modify the potential energy landscape in the 2DEG due to the generation of a deformation potential and an electric field through the piezoelectric effect. The stress induced by metal electrodes directly impacts the ability to control the positions of the potential minima where quantum dots form and the coupling between neighboring quantum dots.

TiO2 quantum dots embedded in bamboo-like porous carbon nanotubes as ultra high power and long life anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Tang, Yakun; Liu, Lang; Wang, Xingchao; Jia, Dianzeng; Xia, Wei; Zhao, Zongbin; Qiu, Jieshan

2016-07-01

TiO2 quantum dots embedded in bamboo-like porous carbon nanotubes have been constructed through the pyrolysis of sulfonated polymer nanotubes and TiO2 hybrids. The TiO2 quantum dots are formed during the pyrolysis, due to the space confinement within the highly cross-linked copolymer networks. The sulfonation degree of the polymer nanotubes is a critical factor to ensure the formation of the unique interpenetrating structure. The nanocomposites exhibit high reversible capacity of 523 mAh g-1 at 100 mA g-1 after 200 cycles, excellent rate capability and superior long-term cycling stability at high current density, which could attain a high discharge capacity of 189 mAh g-1 at 2000 mA g-1 for up to 2000 cycles. The enhanced electrochemical performance of the nanocomposites benefit from the uniform distribution of TiO2 quantum dots, high electronic conductivity of porous carbons and unique interpenetrating structure, which simultaneously solved the major problems of TiO2 anode facing the pulverization, loss of electrical contact and particle aggregation.

Step-by-Step Simulation of Radiation of Radiation Chemistry Using Green Functions for Diffusion-Influenced Reactions

NASA Technical Reports Server (NTRS)

Plante, Ianik; Cucinotta, Francis A.

2011-01-01

The irradiation of biological systems leads to the formation of radiolytic species such as H(raised dot), (raised dot)OH, H2, H2O2, e(sup -)(sub aq), etc.[1]. These species react with neighboring molecules, which result in damage in biological molecules such as DNA. Radiation chemistry is there for every important to understand the radiobiological consequences of radiation[2]. In this work, we discuss an approach based on the exact Green Functions for diffusion-influenced reactions which may be used to simulate radiation chemistry and eventually extended to study more complex systems, including DNA.

ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution.

PubMed

Wu, Aiping; Jing, Liqiang; Wang, Jianqiang; Qu, Yang; Xie, Ying; Jiang, Baojiang; Tian, Chungui; Fu, Honggang

2015-03-09

The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy "controlling competitive reaction" strategy by selecting the thiourea as S(2-) source and Zn(Ac)₂·2H₂O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m(2)g(-1), microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution

NASA Astrophysics Data System (ADS)

Wu, Aiping; Jing, Liqiang; Wang, Jianqiang; Qu, Yang; Xie, Ying; Jiang, Baojiang; Tian, Chungui; Fu, Honggang

2015-03-01

The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy ``controlling competitive reaction'' strategy by selecting the thiourea as S2- source and Zn(Ac)2.2H2O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m2g-1, microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h-1 under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

Synthesis and formation mechanistic investigation of nitrogen-doped carbon dots with high quantum yields and yellowish-green fluorescence

NASA Astrophysics Data System (ADS)

Hou, Juan; Wang, Wei; Zhou, Tianyu; Wang, Bo; Li, Huiyu; Ding, Lan

2016-05-01

Heteroatom doped carbon dots (CDs) have received increasing attention due to their unique properties and related applications. However, previously reported CDs generally show strong emission only in the blue-light region, thus restricting their further applications. And the fundamental investigation on the preparation process is always neglected. Herein, we have developed a simple and solvent-free synthetic strategy to fabricate nitrogen-doped CDs (N-CDs) from citric acid and dicyandiamide. The as-prepared N-CDs exhibited a uniform size distribution, strong yellowish-green fluorescence emission and a high quantum yield of 73.2%. The products obtained at different formation stages were detailedly characterized by transmission electron microscopy, X-ray diffraction spectrometer, X-ray photoelectron spectroscopy and UV absorbance spectroscopy. A possible formation mechanism has thus been proposed including dehydration, polymerization and carbonization. Furthermore, the N-CDs could serve as a facile and label-free probe for the detection of iron and fluorine ions with detection limits of 50 nmol L-1 and 75 nmol L-1, respectively.Heteroatom doped carbon dots (CDs) have received increasing attention due to their unique properties and related applications. However, previously reported CDs generally show strong emission only in the blue-light region, thus restricting their further applications. And the fundamental investigation on the preparation process is always neglected. Herein, we have developed a simple and solvent-free synthetic strategy to fabricate nitrogen-doped CDs (N-CDs) from citric acid and dicyandiamide. The as-prepared N-CDs exhibited a uniform size distribution, strong yellowish-green fluorescence emission and a high quantum yield of 73.2%. The products obtained at different formation stages were detailedly characterized by transmission electron microscopy, X-ray diffraction spectrometer, X-ray photoelectron spectroscopy and UV absorbance spectroscopy. A possible formation mechanism has thus been proposed including dehydration, polymerization and carbonization. Furthermore, the N-CDs could serve as a facile and label-free probe for the detection of iron and fluorine ions with detection limits of 50 nmol L-1 and 75 nmol L-1, respectively. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02701f

Physiological responses and time-motion characteristics of 4-a-side small-sided game in young soccer players: the influence of different team formation methods.

PubMed

Köklü, Yusuf; Ersöz, Gülfem; Alemdaroğlu, Utku; Aşç, Alper; Ozkan, Ali

2012-11-01

The purpose of this study was to examine the influence of different team formation methods on the physiological responses to and time-motion characteristics of 4-a-side small-sided games (SSG4) in young soccer players. Thirty-two young soccer players (age 16.2 ± 0.7 years; height 172.9 ± 6.1 cm; body mass 64.1 ± 7.7 kg) voluntarily participated in this study. Anthropometric measurements, technical tests, and maximum oxygen uptake (V[Combining Dot Above]O2max) tests were carried out on the players. The SSG4 teams were then created using 4 different methods: according to the coaches' subjective evaluation (CE), technical scores (TS), V[Combining Dot Above]O2max (AP), and V[Combining Dot Above]O2max multiplied by TSs (CG). The teams thus created played 4 bouts of SSG4 at 2-day intervals. During the SSG4, heart rate (HR) responses, distance covered, and time spent in HRmax zones were recorded. In addition, rating of perceived exertion (RPE) and blood lactate level (La) were determined at the end of the last bout of each SSG4. Percent of HRmax (%HRmax), La, and RPE responses during SSG4 were significantly higher for teams chosen according to AP and CG compared with that according to CE and TS (p < 0.05). In addition, teams chosen by AP and CG spent significantly more time in zone 4 (>90% HRmax ) and covered a greater distance in the high-intensity running zone (>18 km·h) than did teams formed according to TS. Moreover, AP teams covered significantly greater total distance than TS teams did (p < 0.05). In conclusion, to spend more time in both the high-intensity HR zone and the high-intensity running zone, the teams in SSG4 should be formed according to the players' V[Combining Dot Above]O2max values or the values calculated using both the V[Combining Dot Above]O2max and technique scores.

Investigations into the formation of nanocrystalline quantum dot thin films by mist deposition process

NASA Astrophysics Data System (ADS)

Kshirsagar, Aditya

Semiconductor nanocrystalline quantum dots (NQDs) have material properties remarkably different compared to bulk semiconductors with the same material composition. These NQDs have various novel applications in the electronic and photonic industry, such as light emitting diodes (LEDs) and flat-panel displays. In these applications, ultra-thin films of NQDs in the monolayer regime are needed to ensure optimal current transport properties and device efficiency. There is ongoing search to find a suitable method to deposit and pattern such ultra-thin films of quantum dots with few monolayer thicknesses. Several competing approaches are available, each with its pros and cons. This study explores mist deposition as the technique to fill this void. In this study, ultra-thin films of quantum dots are deposited on diverse substrates and are characterized to understand the mechanics of mist deposition. Various applications of blanket deposited and patterned quantum dot films are studied. The results discussed here include atomic force microscopy analysis of the films to study surface morphology, fluorescence microscopy to study light emission and optical microscope images to study patterning techniques. These results demonstrate the ability of mist deposition to form 1-4 monolayers thick, uniform, defect-free patterned films with root mean square (RMS) surface roughness less than 2 nm. LEDs fabricated using mist deposition show a peak luminescence greater than 500 cd/m2 for matched red, yellow and green devices using Alq3 as the electron transport layer, and over 9000 cd/m2 for red devices using ZnO as the electron transport layer, respectively. In addition to the experimental approach to study the process and explore potential applications, simulation and modeling are carried out to understand the various aspects of mist deposition. A mathematical model is presented which discusses the atomization process of the precursor solution, the physics involved during the deposition process, and the mechanics of film formation. Results of film morphology simulation using Monte Carlo techniques and process simulation using multi-physics approach are discussed. Problems in pattern transfer due to electrostatic effects when using shadow masks are presented in a separate chapter.

Synthesis and characterisation of multifunctional alginate microspheres via the in situ formation of ZnO quantum dots and the graft of 4-(1-pyrenyl) butyric acid to sodium alginate.

PubMed

Luo, Guilin; Wang, Jianxin; Wang, Yingying; Feng, Bo; Weng, Jie

2015-01-01

Growth factor-loaded fluorescent alginate microspheres, which can realise sustained growth factor release and fluorescence imaging, were synthesised by in situ formation of ZnO quantum dots (QDs) and covalent graft of 4-(1-pyrenyl) butyric acid (PBA). BSA was chosen as a growth factor model protein to study the release kinetic of growth factors from alginate microspheres. The microsphere size and fluorescent properties were also investigated. Investigations of cell culture were used for evaluating biocompatibility of BSA-loaded fluorescent microspheres and fluorescence imaging property of ZnO QDs and PBA-grafted sodium alginate from the microspheres. The results show that they have good fluorescent property either to microspheres or to cells and fluorescent microspheres have good biocompatibility and property in sustained release of growth factors. The obtained microspheres will be expected to realise the imaging of cells and materials and also the release of growth factor in tissue engineering or in cell culture.

Theoretical Kinetics Analysis for $$\\dot{H}$$ Atom Addition to 1,3-Butadiene and Related Reactions on the $$\\dot{C}$$ 4H 7 Potential Energy Surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yang; Klippenstein, Stephen J.; Zhou, Chong-Wen

The oxidation chemistry of the simplest conjugated hydrocarbon, 1,3-butadiene, can provide a first step in understanding the role of poly-unsaturated hydrocarbons in combustion and, in particular, an understanding of their contribution towards soot formation. Based on our previous work on propene and the butene isomers (1-, 2- and isobutene), it was found that the reaction kinetics of H-atom addition to the C=C double bond plays a significant role in fuel consumption kinetics and influences the predictions of high-temperature ignition delay times, product species concentrations and flame speed measurements. In this study, the rate constants and thermodynamic properties formore » $$\\dot{H}$$-atom addition to 1,3-butadiene and related reactions on the $$\\dot{C}$$ 4H 7 potential energy surface have been calculated using two different series of quantum chemical methods and two different kinetic codes. Excellent agreement is obtained between the two different kinetics codes. The calculated results including zero point energies, single point energies, rate constants, barrier heights and thermochemistry are systematically compared among the two quantum chemical methods. 1-methylallyl ($$\\dot{C}$$ 4H 71-3) and 3-buten-1- yl ($$\\dot{C}$$ 4H 71-4) radicals and C 2H 4 + $$\\dot{C}$$2H3 are found to be the most important channels and reactivity promoting products, respectively. We calculated that terminal addition is dominant (> 80%) compared to internal $$\\dot{H}$$-atom addition at all temperatures in the range 298 – 2000 K. However, this dominance decreases with increasing temperature. The calculated rate constants for the bimolecular reaction C 4H 6 + $$\\dot{H}$$ → products and C 2H 4 + $$\\dot{C}$$ 2H 3 → products are in excellent agreement with both experimental and theoretical results from the literature. For selected C 4 species the calculated thermochemical values are also in good agreement with literature data. In addition, the rate constants for H-atom abstraction by $$\\dot{H}$$ atoms have also been calculated, and it is found that abstraction from the central carbon atoms is the dominant channel (> 70%) at temperatures in the range 298 – 2000 K. Lastly, by incorporating our calculated rate constants for both H-atom addition and abstraction into our recently developed 1,3-butadiene model, we show that laminar flame speed predictions are significantly improved, emphasizing the value of this study.« less

Molecular screening of the Hbs Constant Spring (codon 142, TAA>CAA, α2) and Paksé (codon 142, TAA>TAT, α2) mutations in Thailand.

PubMed

Pichanun, Dalad; Munkongdee, Thongperm; Klamchuen, Sumonmaln; Butthep, Punnee; Winichagoon, Pranee; Fucharoen, Suthat; Svasti, Saovaros

2010-01-01

Hb Constant Spring [Hb CS, α142(H19)Term] and Hb Paksé [α142(H19)Term] occur from the mutation in the termination codon of the α2-globin gene, TAA>CAA (→Gln) and TAA>TAT (→Tyr), respectively. They are the most common nondeletional α-thalassemia (α-thal) variants causing Hb H disease in Southeast Asia. In this study, 587 cord blood samples were screened for the Hb CS and Hb Paksé mutations by a dot-blot hybridization technique using oligonucleotide probes specific for each mutation. The results showed that the prevalence of Hb CS and Hb Paksé in Central Thailand are 5.80 and 0.51%, respectively, which is in concordance with the results from previous studies.

Analysis of 16 cystic fibrosis mutations in Mexican patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villalobos-Torres, C.; Rojas-Martinez, A.; Barrera-Saldana, H.A.

1997-04-14

We carried out molecular analysis of 80 chromosomes from 40 unrelated Mexican patients with a diagnosis of cystic fibrosis. The study was performed in two PCR steps: a preliminary one to identify mutation AF508, the most frequent cause of cystic fibrosis worldwide, and the second a reverse dot-blot with allele-specific oligonucleotide probes to detect 15 additional common mutations in the Caucasian population. A frequency of 45% for AF508 was found, making it the most common in our sample of Mexican patients. Another five mutations (G542X, 3849 + 10 kb C{r_arrow}T, N1303K, S549N, and 621 + 1 G{r_arrow}T) were detected, andmore » these accounted for 11.25%. The remaining mutations (43.75%) were undetectable with the methodology used. 20 refs., 2 tabs.« less

Mechanisms of optical orientation of an individual Mn2+ ion spin in a II-VI quantum dot

NASA Astrophysics Data System (ADS)

Smoleński, T.; Cywiński, Ł.; Kossacki, P.

2018-02-01

We provide a theoretical description of the optical orientation of a single Mn2+ ion spin under quasi-resonant excitation demonstrated experimentally by Goryca et al (2009 Phys. Rev. Lett. 103 087401). We build and analyze a hierarchy of models by starting with the simplest assumptions (transfer of perfectly spin-polarized excitons from Mn-free dot to the other dot containing a single Mn2+ spin, followed by radiative recombination) and subsequently adding more features, such as spin relaxation of electrons and holes. Particular attention is paid to the role of the influx of the dark excitons and the process of biexciton formation, which are shown to contribute significantly to the orientation process in the quasi-resonant excitation case. Analyzed scenarios show how multiple features of the excitonic complexes in magnetically-doped quantum dots, such as the values of exchange integrals, spin relaxation times, etc, lead to a plethora of optical orientation processes, characterized by distinct dependencies on light polarization and laser intensity, and occurring on distinct timescales. Comparison with experimental data shows that the correct description of the optical orientation mechanism requires taking into account Mn2+ spin-flip processes occurring not only when the exciton is already in the orbital ground state of the light-emitting dot, but also those that happen during the exciton transfer from high-energy states to the ground state. Inspired by the experimental results on energy relaxation of electrons and holes in nonmagnetic dots, we focus on the process of biexciton creation allowed by mutual spin-flip of an electron and the Mn2+ spin, and we show that by including it in the model, we obtain good qualitative and quantitative agreement with the experimental data on quasi-resonantly driven Mn2+ spin orientation.

Pyrite footprinting of RNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlatterer, Joerg C., E-mail: joerg.schlatterer@einstein.yu.edu; Wieder, Matthew S.; Jones, Christopher D.

2012-08-24

Highlights: Black-Right-Pointing-Pointer RNA structure is mapped by pyrite mediated {sup {center_dot}}OH footprinting. Black-Right-Pointing-Pointer Repetitive experiments can be done in a powdered pyrite filled cartridge. Black-Right-Pointing-Pointer High {sup {center_dot}}OH reactivity of nucleotides imply dynamic role in Diels-Alderase catalysis. -- Abstract: In RNA, function follows form. Mapping the surface of RNA molecules with chemical and enzymatic probes has revealed invaluable information about structure and folding. Hydroxyl radicals ({sup {center_dot}}OH) map the surface of nucleic acids by cutting the backbone where it is accessible to solvent. Recent studies showed that a microfluidic chip containing pyrite (FeS{sub 2}) can produce sufficient {sup {center_dot}}OH tomore » footprint DNA. The 49-nt Diels-Alder RNA enzyme catalyzes the C-C bond formation between a diene and a dienophile. A crystal structure, molecular dynamics simulation and atomic mutagenesis studies suggest that nucleotides of an asymmetric bulge participate in the dynamic architecture of the ribozyme's active center. Of note is that residue U42 directly interacts with the product in the crystallized RNA/product complex. Here, we use powdered pyrite held in a commercially available cartridge to footprint the Diels-Alderase ribozyme with single nucleotide resolution. Residues C39 to U42 are more reactive to {sup {center_dot}}OH than predicted by the solvent accessibility calculated from the crystal structure suggesting that this loop is dynamic in solution. The loop's flexibility may contribute to substrate recruitment and product release. Our implementation of pyrite-mediated {sup {center_dot}}OH footprinting is a readily accessible approach to gleaning information about the architecture of small RNA molecules.« less

Determination of graphene's edge energy using hexagonal graphene quantum dots and PM7 method.

PubMed

Vorontsov, Alexander V; Tretyakov, Evgeny V

2018-05-18

Graphene quantum dots (GQDs) are important for a variety of applications and designs, and the shapes of GQDs rely on the energy of their boundaries. Presently, many methods have been developed for the preparation of GQDs with the required boundaries, shapes and edge terminations. However, research on the properties of GQDs and their applications is limited due to the unavailability of these compounds in pure form. In the present computational study, the standard enthalpy of formation, the standard enthalpy of formation of edges and the standard enthalpy of hydrogenation are studied for hexagonal GQDs with purely zigzag and armchair edges in non-passivated and H-passivated forms using the semiempirical quantum chemistry method pm7. The standard enthalpy of formation of the edge is found to remain constant for GQDs studied in the range of 1 to 6 nm, and the enthalpies of edge C atoms are 32.4 and 35.5 kcal mol-1 for armchair and zigzag edges, respectively. In contrast to some literature data, the standard enthalpy of formation of hydrogenated edges is far from zero, and the values are 7.3 and 8.0 kcal mol-1 C for armchair and zigzag edges, respectively. The standard enthalpy of hydrogenation is found to be -10.2 and -9.72 eV nm-1 for the armchair and zigzag edges, respectively.

48 CFR 1201.301-70 - Amendment of (TAR) 48 CFR chapter 12.

Code of Federal Regulations, 2011 CFR

2011-10-01

... from internal DOT personnel, other Government agencies, or the public. Changes shall be submitted in the following format to the Office of the Senior Procurement Executive (OSPE), 400 7th Street, SW... formulate Departmental acquisition policies and procedures. (1) Transportation Acquisition Circular (TAC...

Towards high-throughput molecular detection of Plasmodium: new approaches and molecular markers

PubMed Central

Steenkeste, Nicolas; Incardona, Sandra; Chy, Sophy; Duval, Linda; Ekala, Marie-Thérèse; Lim, Pharath; Hewitt, Sean; Sochantha, Tho; Socheat, Doung; Rogier, Christophe; Mercereau-Puijalon, Odile; Fandeur, Thierry; Ariey, Frédéric

2009-01-01

Background Several strategies are currently deployed in many countries in the tropics to strengthen malaria control toward malaria elimination. To measure the impact of any intervention, there is a need to detect malaria properly. Mostly, decisions still rely on microscopy diagnosis. But sensitive diagnosis tools enabling to deal with a large number of samples are needed. The molecular detection approach offers a much higher sensitivity, and the flexibility to be automated and upgraded. Methods Two new molecular methods were developed: dot18S, a Plasmodium-specific nested PCR based on the 18S rRNA gene followed by dot-blot detection of species by using species-specific probes and CYTB, a Plasmodium-specific nested PCR based on cytochrome b gene followed by species detection using SNP analysis. The results were compared to those obtained with microscopic examination and the "standard" 18S rRNA gene based nested PCR using species specific primers. 337 samples were diagnosed. Results Compared to the microscopy the three molecular methods were more sensitive, greatly increasing the estimated prevalence of Plasmodium infection, including P. malariae and P. ovale. A high rate of mixed infections was uncovered with about one third of the villagers infected with more than one malaria parasite species. Dot18S and CYTB sensitivity outranged the "standard" nested PCR method, CYTB being the most sensitive. As a consequence, compared to the "standard" nested PCR method for the detection of Plasmodium spp., the sensitivity of dot18S and CYTB was respectively 95.3% and 97.3%. Consistent detection of Plasmodium spp. by the three molecular methods was obtained for 83% of tested isolates. Contradictory results were mostly related to detection of Plasmodium malariae and Plasmodium ovale in mixed infections, due to an "all-or-none" detection effect at low-level parasitaemia. Conclusion A large reservoir of asymptomatic infections was uncovered using the molecular methods. Dot18S and CYTB, the new methods reported herein are highly sensitive, allow parasite DNA extraction as well as genus- and species-specific diagnosis of several hundreds of samples, and are amenable to high-throughput scaling up for larger sample sizes. Such methods provide novel information on malaria prevalence and epidemiology and are suited for active malaria detection. The usefulness of such sensitive malaria diagnosis tools, especially in low endemic areas where eradication plans are now on-going, is discussed in this paper. PMID:19402894

Near-field scanning magneto-optical spectroscopy of Wigner molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mintairov, A. M., E-mail: amintair@nd.edu; Rouvimov, S.; Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg, 194021

We study the emission spectra of single self-organized InP/GaInP QDs (size 100-220 nm) using high-spatial-resolution, low-temperature (5 K) near-field scanning optical microscope (NSOM) operating at magnetic field strength B=0-10 T. The dots contain up to twenty electrons and represent natural Wigner molecules (WM). We observed vibronic-type shake-up structure in single electron QDs manifesting formation of two electron (2e) WM in photo-excited state. We found that relative intensities of the shake-up components described well by vibronic Frank-Condon factors giving for dots having parabolic confinement energy ħω{sub 0}=1.2-4 meV molecule bond lengths 40-140 nm. We used measurements of magnetic-field-induced shifts to distinguishmore » emission of 2e-WM and singly charged exciton (trion). We also observed magnetic-field-induced molecular-droplet transition for two electron dot, emitting through doubly charge exciton (tetron) at zero magnetic field.« less

Recent developments in Förster resonance energy transfer (FRET) diagnostics using quantum dots.

PubMed

Geißler, Daniel; Hildebrandt, Niko

2016-07-01

The exceptional photophysical properties and the nanometric dimensions of colloidal semiconductor quantum dots (QD) have strongly attracted the bioanalytical community over the last approximately 20 y. In particular, the integration of QDs in the analysis of biological components and interactions, and the related diagnostics using Förster resonance energy transfer (FRET), have allowed researchers to significantly improve and diversify fluorescence-based biosensing. In this TRENDS article, we review some recent developments in QD-FRET biosensing that have implemented this technology in electronic consumer products, multiplexed analysis, and detection without light excitation for diagnostic applications. In selected examples of smartphone-based imaging, single- and multistep FRET, steady-state and time-resolved spectroscopy, and bio/chemiluminescence detection of QDs used as both FRET donors and acceptors, we highlight the advantages of QD-based FRET biosensing for multiplexed and sensitive diagnostics. Graphical Abstract Quantum dots (QDs) can be applied as donors and/or acceptors for Förster resonance energy transfer- (FRET-) based biosensing for multiplexed and sensitive diagnostics in various assay formats.

Electrically-induced polarization selection rules of a graphene quantum dot

NASA Astrophysics Data System (ADS)

Dong, Qing-Rui; Li, Yan; Jia, Chen; Wang, Fu-Li; Zhang, Ya-Ting; Liu, Chun-Xiang

2018-05-01

We study theoretically the single-electron triangular zigzag graphene quantum dot in uniform in-plane electric fields. The absorption spectra of the dot are calculated by the tight-binding method. The energy spectra and the distribution of wave functions are also presented to analyse the absorption spectra. The orthogonal zero-energy eigenstates are arranged along to the direction of the external field. The remarkable result is that all intraband transitions and some interband transitions are forbidden when the absorbed light is polarized along the direction of the electric field. With x-direction electric field, all intraband absorption is y polarized due to the electric-field-direction-polarization selection rule. Moreover, with y-direction electric field, all absorption is either x or y polarized due to the parity selection rule as well as to the electric-field-direction-polarization selection rule. Our calculation shows that the formation of the absorption spectra is co-decided by the polarization selection rules and the overlap between the eigenstates of the transition.

Synthesis and Characterization of Aqueous Lead Selenide Quantum Dots for Solar Cell Application

NASA Astrophysics Data System (ADS)

Albert, Ancy; Sreekala, C. O.; Prabhakaran, Malini

2018-02-01

High quality, colloidal lead selenide (PbSe) nanoparticles possessing cube shaped morphology have been successfully synthesized by organometallic synthesis method, using oleic acid (OA) as capping agent. The use of non-coordinating solvent, 1-Octadecene (ODE), during the synthesis results in good quality nanocrystals. Morphology analysis by transmission electron microscopy reveals that cube-shaped nanocrystals with a size range of 10 nm have been produced during the synthesis. The absorption and PL spectra analysis showed an emission peak at 675 nm when excited to a wavelength of 610 nm, further confirmed the formation of PbSe nanocrystals. The surface modification of this colloidal quantum dots was then carried out using L- cysteine ligand, to make them water soluble, for solar cell application. The J-V characteristics study of this PbSe quantum dots solar cell (PbSe QDSC) showed a little power conversion efficiency which intern it shows significant advance toward effective utilization of PbSe nanocrystals sensitized in solar cells.

Formation of N, S-codoped fluorescent carbon dots from biomass and their application for the selective detection of mercury and iron ion

NASA Astrophysics Data System (ADS)

Ye, Qianghua; Yan, Fanyong; Luo, Yunmei; Wang, Yinyin; Zhou, Xuguang; Chen, Li

2017-02-01

Biomass is regarded as an excellent candidate for the preparation of heteroatom-doped carbon nanomaterials. We have developed a simple and facile one-pot synthesis of nitrogen and sulfur codoped fluorescent carbon dots from pigeon feathers, egg and manure via the pyrolysis carbonization method. The as-prepared four PCDs have high fluorescence quantum yield about 24.87% (PCDs-f), 17.48% (PCDs-w), 16.34% (PCDs-y), 33.50% (PCDs-m), respectively, which is higher than the other carbon dots preparing from biomass. We found that the preparation of PCDs-m with pigeon manure has no favourable selectively with heavy metal ions. However, other PCDs exhibit highly sensitive and selective detection behavior of Hg2 +/Fe3 + ions with a low detection limit of 10.3 and 60.9 nM. They were applied to imaging of human umbilical vein endothelial cells, showing low cytotoxicity and good biocompatibility.

Infra-red photoresponse of mesoscopic NiO-based solar cells sensitized with PbS quantum dot

PubMed Central

Raissi, Mahfoudh; Pellegrin, Yann; Jobic, Stéphane; Boujtita, Mohammed; Odobel, Fabrice

2016-01-01

Sensitized NiO based photocathode is a new field of investigation with increasing scientific interest in relation with the development of tandem dye-sensitized solar cells (photovoltaic) and dye-sensitized photoelectrosynthetic cells (solar fuel). We demonstrate herein that PbS quantum dots (QDs) represent promising inorganic sensitizers for NiO-based quantum dot-sensitized solar cells (QDSSCs). The solar cell sensitized with PbS quantum dot exhibits significantly higher photoconversion efficiency than solar cells sensitized with a classical and efficient molecular sensitizer (P1 dye = 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid). Furthermore, the system features an IPCE (Incident Photon-to-Current Efficiency) spectrum that spreads into the infra-red region, reaching operating wavelengths of 950 nm. The QDSSC photoelectrochemical device works with the complexes tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) redox mediators, underscoring the formation of a long-lived charge-separated state. The electrochemical impedance spectrocopy measurements are consistent with a high packing of the QDs upon the NiO surface, the high density of which limits the access of the electrolyte and results in favorable light absorption cross-sections and a significant hole lifetime. These notable results highlight the potential of NiO-based photocathodes sensitized with quantum dots for accessing and exploiting the low-energy part of the solar spectrum in photovoltaic and photocatalysis applications. PMID:27125454

Magneto-conductance fingerprints of purely quantum states in the open quantum dot limit

NASA Astrophysics Data System (ADS)

Mendoza, Michel; Ujevic, Sebastian

2012-06-01

We present quantum magneto-conductance simulations, at the quantum low energy condition, to study the open quantum dot limit. The longitudinal conductance G(E,B) of spinless and non-interacting electrons is mapped as a function of the magnetic field B and the energy E of the electrons. The quantum dot linked to the semi-infinite leads is tuned by quantum point contacts of variable width w. We analyze the transition from a quantum wire to an open quantum dot and then to an effective closed system. The transition, as a function of w, occurs in the following sequence: evolution of quasi-Landau levels to Fano resonances and quasi-bound states between the quasi-Landau levels, followed by the formation of crossings that evolve to anti-crossings inside the quasi-Landau level region. After that, Fano resonances are created between the quasi-Landau states with the final generation of resonant tunneling peaks. By comparing the G(E,B) maps, we identify the closed and open-like limits of the system as a function of the applied magnetic field. These results were used to build quantum openness diagrams G(w,B). Also, these maps allow us to determine the w-limit value from which we can qualitatively relate the closed system properties to the open one. The above analysis can be used to identify single spinless particle effects in experimental measurements of the open quantum dot limit.

Gap junction communications influence upon fibroblast synthesis of Type I collagen and fibronectin.

PubMed

Ehrlich, H Paul; Sun, Bonnie; Saggers, Gregory C; Kromath, Fatuma

2006-07-01

In rats polyvinyl alcohol sponge subcutaneous implants treated with gap junctional intercellular communications (GJIC) uncouplers showed reduced deposition of connective tissue. Do uncouplers inhibit the synthesis and deposition of a new connective tissue by fibroblasts? Confluent human dermal fibroblasts in serum-free medium received either endosulfan or oleamide, GJIC uncouplers. Collected media were subjected to Dot Blot analysis for native Type I collagen and fibronectin. Uncoupler-treated fibroblasts released less Type I collagen, while there was no change in fibronectin release. Collagen synthesis was restored to normal, when the uncouplers were removed, showing that these uncouplers were reversible and not toxic to cells. Northern blot analysis revealed procollagen alpha1 (I) mRNA was minimally affected by endosulfan. Oleamide-treated 17-day chick embryo calvaria explants were incubated with Type I collagen antibody, frozen, cryosectioned, and then subjected to rhodamine (Rh) tagged anti-mouse-IgG antibody, to detect newly deposited Type I collagen. Fluorescent antibody-collagen complexes were localized on the periphery of cells in control calvaria, but absent around cells in oleamide-treated calvaria. GJIC optimize collagen synthesis but not fibronectin synthesis. The lack of connective tissue deposited in granulation tissues treated with uncouplers appears related to the inhibition of collagen synthesis. These findings suggest that altering GJIC might control collagen deposition in scarring. 2006 Wiley-Liss, Inc.

Production of specific IgY antibody to the recombinant FanC protein produced in Escherichia coli.

PubMed

Nasiri, Khadijeh; Zibaee, Saeed; Nassiri, Mohammadreza; Tahmoorespur, Mojtaba; Haghparast, Alireza

2016-08-01

Enterotoxigenic Escherichia coli (ETEC) strains are one of the primary causes of diarrhea in newborn calves and in humans, pigs, and sheep. IgY technology has been identified as a promising alternative to generating a mass amount of specific antibody for use in immunotherapy and immunodiagnostics. The purpose of this study was to produce specific antibody by egg yolk antibody (IgY) to recombinant FanC protein from ETEC. FanC (K99) gene was amplified from ETEC by specific primers and polymerase chain reaction. The gene was cloned and subcloned into pTZ57R/T and pET32a (+) vectors, respectively. Recombinant vector was transferred into E. coli BL21 CodonPlus (DE3). Protein expression was investigated by 1 mM IPTG induction. Hens were immunized by the purified recombinant FanC protein. The activity and specificity of the IgY antibody were detected by dot-blotting, Western blotting, and indirect ELISA. We obtained FanC specific IgYs by immunizing the hens with the recombinant FanC protein. The anti-FanC IgY showed binding specifically to the FanC protein of ETEC. The results emphasize that specific IgY against the recombinant FanC protein could be recommended as a candidate for passive immunization against ETEC infection in animals and humans.

Production of specific IgY antibody to the recombinant FanC protein produced in Escherichia coli

PubMed Central

Nasiri, Khadijeh; Zibaee, Saeed; Nassiri, Mohammadreza; Tahmoorespur, Mojtaba; Haghparast, Alireza

2016-01-01

Objective(s): Enterotoxigenic Escherichia coli (ETEC) strains are one of the primary causes of diarrhea in newborn calves and in humans, pigs, and sheep. IgY technology has been identified as a promising alternative to generating a mass amount of specific antibody for use in immunotherapy and immunodiagnostics. The purpose of this study was to produce specific antibody by egg yolk antibody (IgY) to recombinant FanC protein from ETEC. Materials and Methods: FanC (K99) gene was amplified from ETEC by specific primers and polymerase chain reaction. The gene was cloned and subcloned into pTZ57R/T and pET32a (+) vectors, respectively. Recombinant vector was transferred into E. coli BL21 CodonPlus (DE3). Protein expression was investigated by 1 mM IPTG induction. Hens were immunized by the purified recombinant FanC protein. The activity and specificity of the IgY antibody were detected by dot-blotting, Western blotting, and indirect ELISA. Results: We obtained FanC specific IgYs by immunizing the hens with the recombinant FanC protein. The anti-FanC IgY showed binding specifically to the FanC protein of ETEC. Conclusion: The results emphasize that specific IgY against the recombinant FanC protein could be recommended as a candidate for passive immunization against ETEC infection in animals and humans. PMID:27746871

Clinical and epidemiological correlations between the infection with HPV 16 and HPV 18 and female cervical lesions.

PubMed

Stoian, M; Repanovici, R; Corniţescu, F

1995-01-01

A number of 66 specimens from female cervical lesions were examined for infection with human papillomavirus (HPV) types 6, 11, 16, and 18 by nucleic acid hybridization in dot-blot techniques and 35 sera were tested by the immunodot-blot technique, in order to detect the presence of anti E4 and E7 HPV protein antibodies. The findings were compared with the histologic diagnosis. Fifty-six per cent of specimens contained HPV DNA sequences. In 47% of specimens from cervical carcinoma, HPV 11 was detected in 4 cases, HPV 16 in 21 cases, and HPV 18 in 7 cases. Serum antibodies against HPV 16 E4 and HPV 16 E7 occurred in all the cases of uterine carcinoma, in 4 of 10 cases of CIN I-II, and in 3 of 5 sera obtained from apparently healthy women. The analysis of risk factors disclosed the early onset of sexual activity, a relatively high number of births and abortions before the age of 22 years, the use of oral oestroprogestative contraceptive agents, the presence in anamnesis of genital infections with bacterial flora--Candida albicans, Trichomonas vaginalis, Chlamydia trachomatis, Mycoplasma, etc. Our results showed that HPV typing by nucleic acid hybridization was useful for differentiating low- from high-risk cervical lesions and also tried to elucidate the risk factors associated with HPV infections and progression to malignancy.

Response of Staphylococcus aureus isolates from bovine mastitis to exogenous iron sources.

PubMed

Diarra, M S; Petitclerc, D; Lacasse, P

2002-09-01

Staphylococcus aureus can survive in conditions of extremely low iron concentration. The ability of S. aureus to use two exogenous hydroxamate types of siderophores (desferrioxamine and ferrichrome) and four iron-containing proteins found in cattle (hemin, hemoglobin, ferritin, and lactoferrin) were tested on 16 reference and clinical isolates. For all strains tested, ferrichrome and desferrioxamine showed strong growth-promoting activities in a disk diffusion assay and in liquid medium. The heme proteins hemin and hemoglobin were also found to support growth in culture media lacking other iron sources, while lactoferrin failed to do so. On media containing the iron chelator dipyridyl, ferritin induced a growth inhibition effect that was further enhanced in the presence of lactoferrin in seven of the 13 tested strains. Staphylococcus aureus was able to bind hemin and the level of binding activity was not increased after growth in iron-rich or -poor media. Dot-blot competition tests showed that biotin-labeled lactoferrin binds to S. aureus, and this binding can be inhibited by unlabeled lactoferrin. Expression of lactoferrin-binding activity was independent of the level of iron in the medium and the iron saturation status of lactoferrin. For each strain tested, ligand blots showed lactoferrin-binding proteins of molecular weights ranging from 32 to 92 kDa. Possible functions of these lactoferrin-binding proteins could not be related to iron acquisition mechanism in S. aureus.

Bilateral ocular ischemia-induced blindness as a presenting manifestation of Takayasu arteritis: a case report.

PubMed

Pallangyo, Pedro; Epafra, Emmanuel; Nicholaus, Paulina; Lyimo, Frederick; Kazahura, Parvina; Janabi, Mohamed

2017-06-10

Takayasu arteritis is a granulomatous panarteritis that predominantly affects the aorta and its major branches. The initial manifestations of this large-vessel vasculitis are usually nonspecific; however, as the disease progresses, typical symptoms of arterial occlusion, aneurysmal formation, and vascular pain become evident. Ischemic ocular complications of Takayasu arteritis which could lead to complete loss of vision are not uncommon and depend on the obliterated portion(s) of carotid(s), the intensity and rate of progression of ocular vascular insufficiency, and sufficiency of the collateral blood supply to the eye. A 24-year-old woman of African descent with prior normal vision was referred to us with a 3-year history of gradual decline in visual acuity in both eyes and unintentional weight loss (17 kg) within the past 1 year. A physical examination revealed feeble brachial and radial arterial pulses on her left side. She had sinus tachycardia (136 beats/minute) and her blood pressure was 85/59 mmHg on her left and 134/82 mmHg on her right side. Bilateral microaneurysms, dot and blot hemorrhages, and multiple ischemic areas of retina together with neovascularization in her right eye were noted during a funduscopic examination. Computed tomography angiography of her thoracic and abdominal aorta revealed irregular narrowing with variable degrees of stenosis, tapering, and corrugated appearance. Despite its rarity, Takayasu arteritis significantly impairs a patient's quality of life and has a life-threatening potential. Early initiation of appropriate therapy could delay disease progression and reduce the associated complications.

Multiple logic functions from extended blockade region in a silicon quantum-dot transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Youngmin; Lee, Sejoon, E-mail: sejoon@dongguk.edu; Im, Hyunsik

2015-02-14

We demonstrate multiple logic-functions at room temperature on a unit device of the Si single electron transistor (SET). Owing to the formation of the multi-dot system, the device exhibits the enhanced Coulomb blockade characteristics (e.g., large peak-to-valley current ratio ∼200) that can improve the reliability of the SET-based logic circuits. The SET displays a unique feature useful for the logic applications; namely, the Coulomb oscillation peaks are systematically shifted by changing either of only the gate or the drain voltage. This enables the SET to act as a multi-functional one-transistor logic gate with AND, OR, NAND, and XOR functions.

The spatial distribution of umbral dots and granules

NASA Astrophysics Data System (ADS)

Lawrence, J. K.

1983-08-01

It is pointed out that the study of point patterns in two dimensions is of extremely broad interest in both the natural and social sciences. The subjects to which this study has been applied include tree distributions in forests, bird nesting patterns, the growth of towns, crystal formation in rocks, and the distribution of galaxies on the sky. The present investigation is concerned with the particular example of the distribution of umbral dots and their similarity, or dissimilarity, to photospheric granules. Attention is given to a collection of N points in an area A, statistical comparisons of distributions, and studies conducted by Bumba and Suda (1980) and Adjabshirzadeh and Koutchmy (1980, 1982).

Evaluation of quantum confinement effect in nanocrystal Si dot layer by Raman spectroscopy.

PubMed

Mizukami, Y; Kosemura, D; Numasawa, Y; Ohshita, Y; Ogura, A

2012-11-01

Quantum confinement effect in the nanocrystal-Si (nc-Si) was evaluated by Raman spectroscopy. The nc-Si dot layers were fabricated by the H2 plasma treatment for the nucleation site formation followed by the SiH4 irradiation for the nc-Si growth. Post-oxidation annealing was also performed to improve the crystalline quality. After post-oxidation annealing for 5 or 10 min, the asymmetric broadening on the lower frequency sides in Raman spectra were obtained, which can be attributed to the phonon confinement effect in nc-Si. Furthermore we confirmed that hydrostatic stress of approximately 500 MPa was induced in nc-Si after post-oxidation annealing.

Luminescence properties of In(Zn)P alloy core/ZnS shell quantum dots

NASA Astrophysics Data System (ADS)

Thuy, Ung Thi Dieu; Reiss, Peter; Liem, Nguyen Quang

2010-11-01

Chemically synthesized InP/ZnS core/shell quantum dots (QDs) are studied using time-resolved photoluminescence spectroscopy and x-ray diffraction. Zinc stearate, which is added during the synthesis of the InP core, significantly improves the optical characteristics of the QDs. The luminescence quantum yield (QY) reaches 60%-70% and the emission is tunable from 485 to 586 nm by varying the Zn2+:In3+ molar ratio and growth temperature. The observed increased Stokes shift, luminescence decay time, and QY in the presence of Zn are rationalized by the formation of an In(Zn)P alloy structure that causes band-edge fluctuation to enhance the confinement of the excited carriers.

Molecular basis of the fructose-2,6-bisphosphatase reaction of PFKFB3: Transition state and the C-terminal function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavalier, Michael C.; Kim, Song-Gun; Neau, David

2012-03-22

The molecular basis of fructose-2,6-bisphosphatase (F-2,6-P{sub 2}ase) of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB) was investigated using the crystal structures of the human inducible form (PFKFB3) in a phospho-enzyme intermediate state (PFKFB3-P {center_dot} F-6-P), in a transition state-analogous complex (PFKFB3 {center_dot} AlF{sub 4}), and in a complex with pyrophosphate (PFKFB3 {center_dot} PP{sub i}) at resolutions of 2.45, 2.2, and 2.3 {angstrom}, respectively. Trapping the PFKFB3-P {center_dot} F-6-P intermediate was achieved by flash cooling the crystal during the reaction, and the PFKFB3 {center_dot} AlF{sub 4} and PFKFB3 {center_dot} PP{sub i} complexes were obtained by soaking. The PFKFB3 {center_dot} AlF{sub 4} and PFKFB3 {center_dot} PP{sub i}more » complexes resulted in removing F-6-P from the catalytic pocket. With these structures, the structures of the Michaelis complex and the transition state were extrapolated. For both the PFKFB3-P formation and break down, the phosphoryl donor and the acceptor are located within {approx}5.1 {angstrom}, and the pivotal point 2-P is on the same line, suggesting an 'in-line' transfer with a direct inversion of phosphate configuration. The geometry suggests that NE2 of His253 undergoes a nucleophilic attack to form a covalent N-P bond, breaking the 2O-P bond in the substrate. The resulting high reactivity of the leaving group, 2O of F-6-P, is neutralized by a proton donated by Glu322. Negative charges on the equatorial oxygen of the transient bipyramidal phosphorane formed during the transfer are stabilized by Arg252, His387, and Asn259. The C-terminal domain (residues 440-446) was rearranged in PFKFB3 {center_dot} PP{sub i}, implying that this domain plays a critical role in binding of substrate to and release of product from the F-2,6-P{sub 2}ase catalytic pocket. These findings provide a new insight into the understanding of the phosphoryl transfer reaction.« less

Probing the Site for r-Process Nucleosynthesis with Abundances of Barium and Magnesium in Extremely Metal-poor Stars.

PubMed

Tsujimoto; Shigeyama; Yoshii

2000-03-01

We suggest that if the astrophysical site for r-process nucleosynthesis in the early Galaxy is confined to a narrow mass range of Type II supernova (SN II) progenitors, with a lower mass limit of Mms=20 M middle dot in circle, a unique feature in the observed distribution of [Ba/Mg] versus [Mg/H] for extremely metal-poor stars can be adequately reproduced. We associate this feature, a bifurcation of the observed elemental ratios into two branches in the Mg abundance interval -3.7

A K(+)-mediated G-quadruplex formation enhancement fluorescence polarization system based on quantum dots for detection of Hg2+ and biothiols.

PubMed

Zhang, Juanni; Tian, Jianniao; He, Yanlong; Zhao, Yanchun; Zhao, Shulin

2014-02-25

A fluorescence polarization homogenous system based on CdTe/CdS QDs that employed a K(+)-mediated G-quadruplex as an enhancer was identified for sensitive and selective detection of Hg(2+) and biothiols in complex samples.

Tetragonal zirconia quantum dots in silica matrix prepared by a modified sol-gel protocol

NASA Astrophysics Data System (ADS)

Verma, Surbhi; Rani, Saruchi; Kumar, Sushil

2018-05-01

Tetragonal zirconia quantum dots (t-ZrO2 QDs) in silica matrix with different compositions ( x)ZrO2-(100 - x)SiO2 were fabricated by a modified sol-gel protocol. Acetylacetone was added as a chelating agent to zirconium propoxide to avoid precipitation. The powders as well as thin films were given thermal treatment at 650, 875 and 1100 °C for 4 h. The silica matrix remained amorphous after thermal treatment and acted as an inert support for zirconia quantum dots. The tetragonal zirconia embedded in silica matrix transformed into monoclinic form due to thermal treatment ≥ 1100 °C. The stability of tetragonal phase of zirconia is found to enhance with increase in silica content. A homogenous dispersion of t-ZrO2 QDs in silica matrix was indicated by the mapping of Zr, Si and O elements obtained from scanning electron microscope with energy dispersive X-ray analyser. The transmission electron images confirmed the formation of tetragonal zirconia quantum dots embedded in silica. The optical band gap of zirconia QDs (3.65-5.58 eV) was found to increase with increase in zirconia content in silica. The red shift of PL emission has been exhibited with increase in zirconia content in silica.

The design and synthesis of heterostructured quantum dots with dual emission in the visible and infrared

DOE PAGES

Lin, Qianglu; Makarov, Nikolay S.; Koh, Weon-kyu; ...

2014-11-26

The unique optical properties exhibited by visible emitting core/shell quantum dots with especially thick shells are the focus of widespread study, but have yet to be realized in infrared (IR) -active nanostructures. We apply an effective-mass model to identify PbSe/CdSe core/shell quantum dots as a promising system for achieving this goal. We then synthesize colloidal PbSe/CdSe quantum dots with shell thicknesses of up to 4 nm that exhibit unusually slow hole intra-band relaxation from shell to core states, as evidenced by the emergence of dual emission, i.e., IR photoluminescence from the PbSe core observed simultaneously with visible emission from themore » CdSe shell. In addition to the large shell thickness, the development of slowed intraband relaxation is facilitated by the existence of a sharp core-shell interface without discernible alloying. Growth of thick shells without interfacial alloying or incidental formation of homogenous CdSe nanocrystals was accomplished using insights attained via a systematic study of the dynamics of the cation-exchange synthesis of both PbSe/CdSe as well as the related system PbS/CdS. Finally, we show that the efficiency of the visible photoluminescence can be greatly enhanced by inorganic passivation.« less

Highly crystalline carbon dots from fresh tomato: UV emission and quantum confinement.

PubMed

Liu, Weijian; Li, Chun; Sun, Xiaobo; Pan, Wei; Yu, Guifeng; Wang, Jinping

2017-12-01

In this article, fresh tomatoes are explored as a low-cost source to prepare high-performance carbon dots by using microwave-assisted pyrolysis. Given that amino groups might act as nucleophiles for cleaving covalent bridging ester or ether in the crosslinked macromolecules in the biomass bulk, ethylenediamine (EDA) and urea with amino groups were applied as nucleophiles to modulate the chemical composites of the carbon nanoparticles in order to tune their fluorescence emission and enhance their quantum yields. Very interestingly, the carbon dots synthesized in the presence of urea had a highly crystalline nature, a low-degree amorphous surface and were smaller than 5 nm. Moreover, the doped N contributed to the formation of a cyclic form of core that resulted in a strong electron-withdrawing ability within the conjugated C plane. Therefore, this type of carbon dot exhibited marked quantum confinement, with the maximum fluorescence peak located in the UV region. Carbon nanoparticles greater than 20 nm in size, prepared using pristine fresh tomato and in the presence of EDA, emitted surface state controlled fluorescence. Additionally, carbon nanoparticles synthesized using fresh tomato pulp in the presence of EDA and urea were explored for bioimaging of plant pathogenic fungi and the detection of vanillin.

Highly crystalline carbon dots from fresh tomato: UV emission and quantum confinement

NASA Astrophysics Data System (ADS)

Liu, Weijian; Li, Chun; Sun, Xiaobo; Pan, Wei; Yu, Guifeng; Wang, Jinping

2017-12-01

In this article, fresh tomatoes are explored as a low-cost source to prepare high-performance carbon dots by using microwave-assisted pyrolysis. Given that amino groups might act as nucleophiles for cleaving covalent bridging ester or ether in the crosslinked macromolecules in the biomass bulk, ethylenediamine (EDA) and urea with amino groups were applied as nucleophiles to modulate the chemical composites of the carbon nanoparticles in order to tune their fluorescence emission and enhance their quantum yields. Very interestingly, the carbon dots synthesized in the presence of urea had a highly crystalline nature, a low-degree amorphous surface and were smaller than 5 nm. Moreover, the doped N contributed to the formation of a cyclic form of core that resulted in a strong electron-withdrawing ability within the conjugated C plane. Therefore, this type of carbon dot exhibited marked quantum confinement, with the maximum fluorescence peak located in the UV region. Carbon nanoparticles greater than 20 nm in size, prepared using pristine fresh tomato and in the presence of EDA, emitted surface state controlled fluorescence. Additionally, carbon nanoparticles synthesized using fresh tomato pulp in the presence of EDA and urea were explored for bioimaging of plant pathogenic fungi and the detection of vanillin.

Tuning Optoelectronic Properties of the Graphene-Based Quantum Dots C16- xSi xH10 Family.

PubMed

Ramadan, F-Z; Ouarrad, H; Drissi, L B

2018-06-07

The electronic and optical properties of graphene-based quantum dots (QDs) are investigated using DFT and many-body perturbation theory. Formation energy, hardeness and electrophilicity show that all structures, from pyrene to silicene QD passing through 15 CSi QD configurations, are energetically and chemically stable. It is also found that they are reactive which implies their favorable character for the possible electronic transport and conductivity. The electronic and optical properties are very sensitive to the number and position of the substituted silicon atoms as well as the directions of the light polarization. Moreover, quantum confinement effects make the exciton binding energy of CSi quantum dots larger than those of their higher dimensional allotropes such as silicene, graphene, and SiC sheet and nanotube. It is also higher those of other shapes of quantum dots like hexagonal graphene QDs and can be tailored from the ultraviolet region to the visible one. The values of the singlet-triplet splitting determined for the X- and Y-light polarized indicate that all configurations have a high fluorescence quantum yield compared to the yield of typical semiconductors, which makes them very promising for various applications such as the light-emitting diode material and nanomedicine.

Directly observed treatment, short-course strategy and multidrug-resistant tuberculosis: are any modifications required?

PubMed Central

Bastian, I.; Rigouts, L.; Van Deun, A.; Portaels, F.

2000-01-01

Multidrug-resistant tuberculosis (MDRTB) should be defined as tuberculosis with resistance to at least isoniazid and rifampicin because these drugs are the cornerstone of short-course chemotherapy, and combined isoniazid and rifampicin resistance requires prolonged treatment with second-line agents. Short-course chemotherapy is a key ingredient in the tuberculosis control strategy known as directly observed treatment, short-course (DOTS). For populations in which multidrug-resistant tuberculosis is endemic, the outcome of the standard short-course chemotherapy regimen remains uncertain. Unacceptable failure rates have been reported and resistance to additional agents may be induced. As a consequence there have been calls for well-functioning DOTS programmes to provide additional services in areas with high rates of multidrug-resistant tuberculosis. These "DOTS-plus for MDRTB programmes" may need to modify all five elements of the DOTS strategy: the treatment may need to be individualized rather than standardized; laboratory services may need to provide facilities for on-site culture and antibiotic susceptibility testing; reliable supplies of a wide range of expensive second-line agents would have to be supplied; operational studies would be required to determine the indications for and format of the expanded programmes; financial and technical support from international organizations and Western governments would be needed in addition to that obtained from local governments. PMID:10743297

Observation of Mollow Triplets with Tunable Interactions in Double Lambda Systems of Individual Hole Spins.

NASA Astrophysics Data System (ADS)

Lagoudakis, K. G.; Fischer, K. A.; Sarmiento, T.; McMahon, P. L.; Radulaski, M.; Zhang, J. L.; Kelaita, Y.; Dory, C.; Mueller, K. M.; Vuckovic, J.

Although individual spins in quantum dots have been extensively used as qubits, their investigation under strong resonant driving in view of accessing Mollow physics is still an open question. We have grown high quality positively charged quantum dots (QD) embedded in a planar microcavity that enable enhanced light matter interactions. Applying a strong magnetic field in the Voigt configuration, individual positively charged quantum dots provide a double lambda level structure. Using a combination of above band and resonant excitation, we observe the formation of Mollow triplets. We investigate the regime where the Mollow sideband splittings are equal to the Zeeman splitting; we observe strong interactions between the Mollow sidebands of the inner transitions and the outer transitions in the form of very clear anticrossings. We investigated these anticrossings and we were able to modify the observed anticrossing splittings on demand by rotating the polarization of the resonant laser. We also developed a quantum-optical model of our system that fully captures the experimentally observed spectra and provides insight on the complicated level structure that results from the strong driving of our positively charged quantum dot. The authors acknowledge financial support from the Army Research Office (Grant No. W911NF1310309) and support from the National Science Foundation, Division of Materials Research (Grant No. 1503759).

The adaptor protein p62 is involved in RANKL-induced autophagy and osteoclastogenesis.

PubMed

Li, Rui-Fang; Chen, Gang; Ren, Jian-Gang; Zhang, Wei; Wu, Zhong-Xing; Liu, Bing; Zhao, Yi; Zhao, Yi-Fang

2014-12-01

Previous studies have implicated autophagy in osteoclast differentiation. The aim of this study was to investigate the potential role of p62, a characterized adaptor protein for autophagy, in RANKL-induced osteoclastogenesis. Real-time quantitative PCR and western blot analyses were used to evaluate the expression levels of autophagy-related markers during RANKL-induced osteoclastogenesis in mouse macrophage-like RAW264.7 cells. Meanwhile, the potential relationship between p62/LC3 localization and F-actin ring formation was tested using double-labeling immunofluorescence. Then, the expression of p62 in RAW264.7 cells was knocked down using small-interfering RNA (siRNA), followed by detecting its influence on RANKL-induced autophagy activation, osteoclast differentiation, and F-actin ring formation. The data showed that several key autophagy-related markers including p62 were significantly altered during RANKL-induced osteoclast differentiation. In addition, the expression and localization of p62 showed negative correlation with LC3 accumulation and F-actin ring formation, as demonstrated by western blot and immunofluorescence analyses, respectively. Importantly, the knockdown of p62 obviously attenuated RANKL-induced expression of autophagy- and osteoclastogenesis-related genes, formation of TRAP-positive multinuclear cells, accumulation of LC3, as well as formation of F-actin ring. Our study indicates that p62 may play essential roles in RANKL-induced autophagy and osteoclastogenesis, which may help to develop a novel therapeutic strategy against osteoclastogenesis-related diseases. © The Author(s) 2014.

Spatial but not temporal numerosity thresholds correlate with formal math skills in children.

PubMed

Anobile, Giovanni; Arrighi, Roberto; Castaldi, Elisa; Grassi, Eleonora; Pedonese, Lara; Moscoso, Paula A M; Burr, David C

2018-03-01

Humans and other animals are able to make rough estimations of quantities using what has been termed the approximate number system (ANS). Much evidence suggests that sensitivity to numerosity correlates with symbolic math capacity, leading to the suggestion that the ANS may serve as a start-up tool to develop symbolic math. Many experiments have demonstrated that numerosity perception transcends the sensory modality of stimuli and their presentation format (sequential or simultaneous), but it remains an open question whether the relationship between numerosity and math generalizes over stimulus format and modality. Here we measured precision for estimating the numerosity of clouds of dots and sequences of flashes or clicks, as well as for paired comparisons of the numerosity of clouds of dots. Our results show that in children, formal math abilities correlate positively with sensitivity for estimation and paired-comparisons of the numerosity of visual arrays of dots. However, precision of numerosity estimation for sequences of flashes or sounds did not correlate with math, although sensitivities in all estimations tasks (for sequential or simultaneous stimuli) were strongly correlated with each other. In adults, we found no significant correlations between math scores and sensitivity to any of the psychophysical tasks. Taken together these results support the existence of a generalized number sense, and go on to demonstrate an intrinsic link between mathematics and perception of spatial, but not temporal numerosity. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

An unusually massive stellar black hole in the Galaxy.

PubMed

Greiner, J; Cuby, J G; McCaughrean, M J

2001-11-29

The X-ray source known as GRS1915+105 belongs to a group dubbed 'microquasars'. These objects are binary systems which sporadically eject matter at speeds that appear superluminal, as is the case for some quasars. GRS1915+105 is also one of only two known binary sources thought to contain a maximally spinning black hole. Determining the basic parameters of GRS195+105, such as the masses of the components, will help us to understand jet formation in this system, as well as providing links to other objects which exhibit jets. Using X-ray data, indirect methods have previously been used to infer a variety of masses for the accreting compact object in the range 10-30 solar masses (M middle dot in circle). Here we report a direct measurement of the orbital period and mass function of GRS1915+105, which allow us to deduce a mass of 14 +/- 4 M middle dot in circle for the black hole. Black holes with masses >5-7 M middle dot in circle challenge the conventional picture of black-hole formation in binary systems. Based on the mass estimate, we interpret the distinct X-ray variability of GRS1915+105 as arising from instabilities in an accretion disk that is dominated by radiation pressure, and radiating near the Eddington limit (the point where radiation pressure supports matter against gravity). Also, the mass estimate constrains most models which relate observable X-ray properties to the spin of black holes in microquasars.

Control of Wigner localization and electron cavity effects in near-field emission spectra of In(Ga)P/GaInP quantum-dot structures

NASA Astrophysics Data System (ADS)

Mintairov, A. M.; Kapaldo, J.; Merz, J. L.; Rouvimov, S.; Lebedev, D. V.; Kalyuzhnyy, N. A.; Mintairov, S. A.; Belyaev, K. G.; Rakhlin, M. V.; Toropov, A. A.; Brunkov, P. N.; Vlasov, A. S.; Zadiranov, Yu. M.; Blundell, S. A.; Mozharov, A. M.; Mukhin, I.; Yakimov, M.; Oktyabrsky, S.; Shelaev, A. V.; Bykov, V. A.

2018-05-01

Structural and emission properties of few-electron In(Ga)P/GaInP quantum dots (QDs) representing natural Wigner molecules (WM) and whispering gallery mode (WGM) electron (e ) cavities have been investigated. QD structures were grown using self-organized metal-organic vapor phase epitaxy and deposition from ˜3 to 7 monolayers of InP at 700 °C. Using atomic force microscopy, transmission electron microscopy, near-field scanning optical microscopy (NSOM), and μ -photoluminescence (μ -PL) spectra we obtained In(Ga)P/GaInP QDs having lateral size 80-180 nm, height 5-30 nm, Ga content 0.0-0.4, density 2 -10 μm-2 , and electron population up to 20 and demonstrated control of their density and size distribution. Using high-spatial-resolution low-temperature PL spectra, NSOM imaging, and calculations of charge density distributions we observed Wigner localization and e -cavity effects for a series of dots having quantum confinement ℏ ω0=0.5 -6 meV . We used these data together with time-resolved PL measurements to clarify the effect of Coulomb interaction and WM formation on emission spectra of few-electron QDs. We present direct observation of 2 e , 6 e , and 9 e WMs; 2 e and 4 e WGMs; and Fabry-Perot e modes and establish conditions of e -WGM-cavity formation in these QDs.

Photon-induced formation of CdS nanocrystals in selected areas of polymer matrices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athanassiou, Athanassia; Cingolani, Roberto; Tsiranidou, Elsa

2007-10-08

We demonstrate light-induced formation of semiconductor quantum dots in TOPAS registered polymer matrix with very high control of their size and their spatial localization. Irradiation with UV laser pulses of polymer films embedding Cd thiolate precursors results in the formation of cadmium sulfide nanocrystals well confined in the irradiation area, through a macroscopically nondestructive procedure for the host matrix. With increasing number of laser pulses, we accomplish the formation of nanoparticles with gradually increasing dimensions, resulting in the dynamic change of the spectra emitted by the formed nanocomposite areas. The findings are supported by x-ray diffraction and transmission electron microscopymore » measurements.« less

THE STAR FORMATION LAWS OF EDDINGTON-LIMITED STAR-FORMING DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ballantyne, D. R.; Armour, J. N.; Indergaard, J., E-mail: david.ballantyne@physics.gatech.edu

2013-03-10

Two important avenues into understanding the formation and evolution of galaxies are the Kennicutt-Schmidt (K-S) and Elmegreen-Silk (E-S) laws. These relations connect the surface densities of gas and star formation ({Sigma}{sub gas} and {Sigma}-dot{sub *}, respectively) in a galaxy. To elucidate the K-S and E-S laws for disks where {Sigma}{sub gas} {approx}> 10{sup 4} M{sub Sun} pc{sup -2}, we compute 132 Eddington-limited star-forming disk models with radii spanning tens to hundreds of parsecs. The theoretically expected slopes ( Almost-Equal-To 1 for the K-S law and Almost-Equal-To 0.5 for the E-S relation) are relatively robust to spatial averaging over the disks.more » However, the star formation laws exhibit a strong dependence on opacity that separates the models by the dust-to-gas ratio that may lead to the appearance of a erroneously large slope. The total infrared luminosity (L{sub TIR}) and multiple carbon monoxide (CO) line intensities were computed for each model. While L{sub TIR} can yield an estimate of the average {Sigma}-dot{sub *} that is correct to within a factor of two, the velocity-integrated CO line intensity is a poor proxy for the average {Sigma}{sub gas} for these warm and dense disks, making the CO conversion factor ({alpha}{sub CO}) all but useless. Thus, observationally derived K-S and E-S laws at these values of {Sigma}{sub gas} that uses any transition of CO will provide a poor measurement of the underlying star formation relation. Studies of the star formation laws of Eddington-limited disks will require a high-J transition of a high density molecular tracer, as well as a sample of galaxies with known metallicity estimates.« less

Formation of spherical-shaped GaN and InN quantum dots on curved SiN/Si surface.

PubMed

Choi, Ilgyu; Lee, Hyunjoong; Lee, Cheul-Ro; Jeong, Kwang-Un; Kim, Jin Soo

2018-08-03

This paper reports the formation of GaN and InN quantum dots (QDs) with symmetric spherical shapes, grown on SiN/Si(111). Spherical QDs are grown by modulating initial growth behavior via gallium and indium droplets functioning as nucleation sites for QDs. Field-emission scanning electron microscope (FE-SEM) images show that GaN and InN QDs are formed on curved SiN/Si(111) instead of on a flat surface similar to balls on a latex mattress. This is considerably different from the structural properties of In(Ga)As QDs grown on GaAs or InP. In addition, considering the shape of the other III-V semiconductor QDs, the QDs in this study are very close to the ideal shape of zero-dimensional nanostructures. Transmission-electron microscope images show the formation of symmetric GaN and InN QDs with a round shape, agreeing well with the FE-SEM results. Compared to other III-V semiconductor QDs, the unique structural properties of Si-based GaN and InN QDs are strongly related to the modulation in the initial nucleation characteristics due to the presence of droplets, the degree of lattice mismatch between GaN or InN and SiN/Si(111), and the melt-back etching phenomenon.

Nrf2-mediated induction of p62 controls Toll-like receptor-4–driven aggresome-like induced structure formation and autophagic degradation

PubMed Central

Fujita, Ken-ichi; Maeda, Daisuke; Xiao, Qi; Srinivasula, Srinivasa M.

2011-01-01

Toll-like receptors (TLRs) play a crucial role in several innate immune responses by regulating autophagy, but little is known about how TLR signaling controls autophagy. Here we demonstrate that p62/SQSTM1 is required for TLR4-mediated autophagy, which we show as selective autophagy of aggresome-like induced structures (ALIS). Treatment with LPS or Escherichia coli induced LC3+ dot-like structures, and their assembly, but not lysosomal degradation, occurred independently of classic autophagic machinery. Microscopic and ultrastructural analyses showed that p62 is a component of the induced LC3+ dots and these TLR4-induced p62+ structures resemble ALIS. The levels of p62 mRNA and protein were increased in TLR4-activated cells and knockdown of p62 suppressed the ALIS formation and LC3-II conversion. The accumulation of p62 and ALIS required activation of Nrf2 by reactive oxygen species-p38 axis-dependent TLR4/MyD88 signaling, suggesting a link between innate immune and oxidative-stress responses. These findings indicate that TLR4-driven induction of p62 plays an essential role in the formation and the autophagic degradation of ALIS, which might be critical for regulating host defense. PMID:21220332

Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.

PubMed

Tauris; van Den Heuvel EP; Savonije

2000-02-20

We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1

Hypoxia and Prx1 in Malignant Progression of Prostate Cancer

DTIC Science & Technology

2006-09-01

Species (ROS) Formation The rate of ROS formation was determined by flow cytometry analysis using the probe 20,70-dichlorofluorescin diacetate (DCFH-DA...DA were subjected to 4-h hypoxia treatment. After the indicated time, fluorescent cells were analyzed by flow cytometry . Western Blot Analysis Equal...species (ROS) generation was measured by flow cytometry at 0.5, 1, 2, 3, 6, 12, or 24 h after hypoxia treatment. The rate of ROS generation increased

Star Formation in Massive Clusters via Bondi Accretion

NASA Astrophysics Data System (ADS)

Murray, Norman; Chang, Philip

2012-02-01

Essentially all stars form in giant molecular clouds (GMCs). However, inside GMCs, most of the gas does not participate in star formation; rather, denser gas accumulates in clumps in the GMC, with the bulk of the stars in a given GMC forming in a few of the most massive clumps. In the Milky Way, these clumps have masses M cl <~ 5 × 10-2 of the GMC, radii r cl ~ 1 pc, and free-fall times τcl ~ 2 × 105 yr. We show that clumps inside GMCs should accrete at a modified Bondi accretion rate, which depends on clump mass as \\dot{M}_{cl}\\sim M_{cl}^{5/4}. This rate is initially rather slow, usually slower than the initial star formation rate inside the clump (we adopt the common assumption that inside the clump, \\dot{M}_*=\\epsilon _ffM_{cl}/\\tau _{cl}, with epsilonff ≈ 0.017). However, after ~2 GMC free-fall times τGMC, the clump accretion rate accelerates rapidly; formally, the clump can accrete the entire GMC in ~3τGMC. At the same time, the star formation rate accelerates, tracking the Bondi accretion rate. If the GMC is disrupted by feedback from the largest clump, half the stars in that clump form in the final τGMC before the GMC is disrupted. The theory predicts that the distribution of effective star formation rates, measured per GMC free-fall time, is broad, ranging from ~0.001 up to 0.1 or larger and that the mass spectrum of star clusters is flatter than that of clumps, consistent with observations.

About one supplement of teh "Harmony of Universe" by J. Kepler

NASA Astrophysics Data System (ADS)

Smirnov, Vladimir

1999-08-01

In book of J. Kepler "welt harmonik" (Munich-berlin 1939, Verlag R. Oldenburg) musical proportions are amalgamated with geometrical by means of building Platoon's right bodies, enter and described figures. By the physical sense of such association may serve total wave nature those construction. Proportions, received by J. Kepler, are possible in the case of formation of planets (as to J. Kepler constructed Platoon's figures) conform the surfaces to nodes of standing waves having as an the source of central luminary Solar system. By likeness image in experiments of Chladny at the formation of standing wave on the planes of oscillation plate scatter about along it particles collect together, sack from dots, which oscillation plate scatter about along it particles collect together, sack from dots, which oscillation with maximal amplitude, on dots the amplitude fluctuations of fluctuations is equal to zero, fill in nodes lines. Coordinates, count off from the source of wave, must correspond to the distances of planets from Sun, as explaining the physical sense of rule Bode. So, shall adopt the length of base gravitational wave ("basic one") L=0, 52 AU. Then planets the orbits of solar system must distribute in nodes lines in dots, be away from next on multiple L/2 numeral's. From such condition it may be receive the "theoretical" distances of planets from Sun. In Table are presented such distances in compare with true distances. Mecrury 0.39 0.39 Venus 0.72 0,39+0,50L=0,65 Earth 1.00 0,39+1,50L=1,17 Mars 1.52 1,00+1,00L=1.52 Main belt of asteroids 2.90 1.00+4,00L=3.08 Jupiter 5.20 1.00+8,00L=5.16 Saturn9.54 1.00+16,00L=9.32 Uranus 19.20 1.00+35,00L=19.20 Neptun 30.10 1.00+56,00L=30,12 Pluto 39.50 1.00+74,00L=39.48 As visible form Table, with the distance increasing from central body, scale filling "nodes surfaces" in space, or dost in viewed one-dimension accident, grows almost in geometrical progression. Obviously, here tell on mechanics of "gold section", ensuring the harmonious building of this natural formation

Quantum dot formation by molecular beam epitaxy of Ge on Si(100)

NASA Astrophysics Data System (ADS)

Chaparro, Sergio Arturo

1999-11-01

A new technique for producing electron systems with quantum confinement in three dimensions, quantum dots, has been studied. These quantum dots are coherent islands spontaneously formed at the early stages of Ge/Si(100) epitaxy due to the misfit of the system. Our goal is to gain understanding and control of the growth process so uniform quantum dot ensembles can be created for possible use in optoelectronic devices. A UHV Molecular Beam Epitaxy (MBE) growth system was built and calibrated to grow our samples. The samples were prepared by depositing Ge onto a Si(100) surface cleaned by flash desorption of the native oxides. Varying the growth rates from 0.6 ML/min to 4.0 ML/min, the substrate temperature from 450°C to 600°C, and the coverage from 3.5 ML to 14 ML produces different sample morphologies. After growth, the samples were analyzed both in situ and ex situ. The in situ analysis consisted of Auger electron spectroscopy for elemental analysis and reflection high energy electron diffraction, for surface structure analysis. The ex situ analysis included atomic force microscopy (AFM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM). Many digital images were obtained from the microscope analysis. A novel, computer based, analysis was developed to extract the islands parameters from the microscope images. This data, which includes island area and average height for each island on every image, was used for a statistical analysis. Also from the data, island size distributions (histograms of island size) were generated. These measurements confirm that islands form after growth of a 3 ML wetting layer and that islands evolve as they grow. As more Ge is deposited these islands grow and as they grow they evolve from huts, square based pyramids, to domes, truncated pyramids, to dislocated domes. Our results show that the substrate temperature, deposition rate, and amount of deposited material are factors that affect the growth evolution. Higher growth temperature affects the size at which islands evolve from one type of island to another, also introduces new strain release mechanisms such as alloying and trench formation that compete with dislocation formation. Finally a detailed morphological characterization of the observed islands was done.

Detection of the CS20 colonization factor antigen in diffuse-adhering E. coli strains

PubMed Central

Ochoa, Theresa J.; Rivera, Fulton P.; Bernal, Maria; Meza, Rina; Ecker, Lucie; Gil, Ana I.; Cepeda, David; Mosquito, Susan; Mercado, Erik; Maves, Ryan C.; Hall, Eric R.; Svennerholm, Ann-Mari; McVeigh, Annette; Savarino, Stephen; Lanata, Claudio F.

2011-01-01

We analyzed a randomly-selected group of 30 diffusely adherent (DAEC), 30 enteropathogenic, 30 enteroaggregative, and 5 shiga toxin-producing E. coli strains isolated from children with diarrhea. Enterotoxigenic E. coli (ETEC) colonization factors (CFs) were evaluated by dot-blot assay using 21 CF-specific monoclonal antibodies. Out of 95 non-ETEC strains, three DAEC were found to express CS20. No other E. coli expressed CFs. We confirmed the 3 CS20-positive strains as ETEC-negative by repeat PCR and as toxin-negative by GM1-ELISA. To our knowledge, this is the first study that has identified currently-recognized CFs in non-ETEC diarrheagenic E. coli strains identified by molecular methods. CFs may be an unrecognized relevant adherence factor in other E. coli, which may then play a role in pathogenesis and the immune response of the host. PMID:21064230

Comparison of camelpox viruses isolated in Dubai.

PubMed

Pfeffer, M; Meyer, H; Wernery, U; Kaaden, O R

1996-03-01

Between October 1993 and March 1994, outbreaks of pox-like exanthemas were observed in several camel raising farms in Dubai. Scabs from twenty camels with either local or generalized lesions were examined, seven of them had previously been vaccinated with a modified live camelpox virus vaccine. Inspection of scabs by electron microscopy confirmed an infection with orthopox viruses (OPV) in 10 animals and with parapox virus in one camel. Investigation of the scabs by polymerase chain reaction and dot blot assay revealed the presence of OPV in 15 or 13 samples, respectively. OPV could be isolated in cell culture in 14 cases. Restriction enzyme profiles characterized all isolates as camelpox virus. Their DNA patterns were virtually identical displaying only slight variations in the terminal fragments. In contrast, the vaccine strain showed a distinct restriction enzyme profile, indicating that it was not involved in the infections.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yip, Wingkip; Dong, Jianguo,; Yang, Shang Fa

Tomato ACC synthase is inactivated by its substrate SAM, with the moiety of aminobutyrate being covalently linked to ACC synthase during the catalytic reactions. A partial purified ACC synthase (the catalytic activity 100 {mu}mol/h{center dot}mg protein) from pellets of apple extract was incubated with (3,4{sup 14}C) SAM. Only one radioactive peak was revealed in a C-4 reverse phase HPLC and one radioactive band on SDS-PAGE with an M.W. of 48 kDa. Apple ACC synthase in native form is resistant to V8, {alpha}-chromtrypsin and carboxylpeptidase A digestion, but effectively inactivated by trypsin and ficin, as demonstrated by both the activity assaymore » and SAM labeling. The radioactive protein cut from the SDS-PAGE was injected to three mice, two of the mice showed responses to the protein in western blot analysis. The antibodies from mice is currently under characterization.« less

Visual Disturbance as the first Symptom of Chronic Myeloid Leukemia.

PubMed

Huang, Philemon K; Sanjay, Srinivasan

2011-10-01

Chronic myeloid leukemia (CML) is a well-studied entity and advances made in diagnosis and treatment have improved the disease outcome. Patients with ophthalmic manifestation of CML have been reported to have lower 5-year survival rates. Hence, recognizing the early fundus changes may improve outcome by allowing earlier diagnosis and treatment. We report a case of a previously healthy 30-year-old Myanmarese male, who presented with a minor visual disturbance, complaining of seeing a 'black dot' in his left visual field for the past 1 week. Fundoscopic examination revealed bilateral retinal blot hemorrhages, white-centered hemorrhage, and preretinal hemorrhage over the left fovea. The full blood count and peripheral blood film were abnormal, and bone marrow biopsy confirmed the diagnosis of CML. Cytoreduction therapy was promptly commenced and his symptoms resolved, with improvement in visual acuity. No complications were recorded at 1-year follow-up.

Chemiluminescent DNA optical fibre sensor for Brettanomyces bruxellensis detection.

PubMed

Cecchini, Francesca; Manzano, Marisa; Mandabi, Yohai; Perelman, Eddie; Marks, Robert S

2012-01-01

Food and beverage industries require rapid tests to limit economic losses and one way to do so is via molecular tests. In the present work, DNA capture and secondary probes, were designed to target the ITS (Internal Transcribed) sequences of Brettanomyces bruxellensis, a yeast responsible for the production of off flavours in both wine and beer. ITS1 and ITS2 were found to contain distinct regions with sufficient sequence divergence to make them suitable as specific identification target sites. The dot blot technique was used to determine the sensitivity and specificity of the capture probe. Both probes were, thereafter, adapted to construct an optical fibre genosensor, which produced neither false positives nor false negatives, and was both repeatable and faster with respect to traditional methods, the latter requiring at least one week to detect B. bruxellensis. Copyright © 2011 Elsevier B.V. All rights reserved.

Adhesion properties of Lactobacillus rhamnosus mucus-binding factor to mucin and extracellular matrix proteins.

PubMed

Nishiyama, Keita; Nakamata, Koichi; Ueno, Shintaro; Terao, Akari; Aryantini, Ni Putu Desy; Sujaya, I Nengah; Fukuda, Kenji; Urashima, Tadasu; Yamamoto, Yuji; Mukai, Takao

2015-01-01

We previously described potential probiotic Lactobacillus rhamnosus strains, isolated from fermented mare milk produced in Sumbawa Island, Indonesia, which showed high adhesion to porcine colonic mucin (PCM) and extracellular matrix (ECM) proteins. Recently, mucus-binding factor (MBF) was found in the GG strain of L. rhamnosus as a mucin-binding protein. In this study, we assessed the ability of recombinant MBF protein from the FSMM22 strain, one of the isolates of L. rhamnosus from fermented Sumbawa mare milk, to adhere to PCM and ECM proteins by overlay dot blot and Biacore assays. MBF bound to PCM, laminin, collagen IV, and fibronectin with submicromolar dissociation constants. Adhesion of the FSMM22 mbf mutant strain to PCM and ECM proteins was significantly less than that of the wild-type strain. Collectively, these results suggested that MBF contribute to L. rhamnosus host colonization via mucin and ECM protein binding.

Comparative baseline levels of mercury, Hsp 70 and Hsp 60 in subsistence fish from the Yukon-Kuskokwim delta region of Alaska.

PubMed

Duffy, L K; Scofield, E; Rodgers, T; Patton, M; Bowyer, R T

1999-10-01

In subsistence fish; northern pike (Esox lucius), burbot (Lota lota), whitefish (Coregonus nelsoni), grayling (Thymallus arcticus) and sheefish (Stenodus lencichthys), we determined the Hsp 60 and Hsp 70 levels in 31 samples from adult fish gills. A dot-blot analysis using antibodies to either Hsp 70 or Hsp 60 showed the average Hsp 70 concentration was 9.1 microg/mg protein, while the average Hsp 60 concentration was 147.4 microg/mg protein. Mercury levels in muscle tissue in these fish averaged 0.382 ppm. Using a subset of samples (n = 24), we determined that the major component in the muscle of Alaskan subsistence fish was methyl mercury. No correlation was observed between Hsp 60 or Hsp 70 expression in gill tissue and mercury concentrations in muscle tissue. Hsp 60 and Hsp 70 protein levels in the gills were correlated.

High-Level Expression of Recombinant Bovine Lactoferrin in Pichia pastoris with Antimicrobial Activity

PubMed Central

Iglesias-Figueroa, Blanca; Valdiviezo-Godina, Norberto; Siqueiros-Cendón, Tania; Sinagawa-García, Sugey; Arévalo-Gallegos, Sigifredo; Rascón-Cruz, Quintín

2016-01-01

In this study, bovine lactoferrin (bLf), an iron-binding glycoprotein considered an important nutraceutical protein because of its several properties, was expressed in Pichia pastoris KM71-H under AOX1 promoter control, using pJ902 as the recombinant plasmid. Dot blotting analysis revealed the expression of recombinant bovine lactoferrin (rbLf) in Pichia pastoris. After Bach fermentation and purification by molecular exclusion, we obtained an expression yield of 3.5 g/L of rbLf. rbLf and predominantly pepsin-digested rbLf (rbLfcin) demonstrated antibacterial activity against Escherichia coli (E. coli) BL21DE3, Staphylococcus aureus (S. aureus) FRI137, and, in a smaller percentage, Pseudomonas aeruginosa (Ps. Aeruginosa) ATCC 27833. The successful expression and characterization of functional rbLf expressed in Pichia pastoris opens a prospect for the development of natural antimicrobial agents produced recombinantly. PMID:27294912

In vitro evidence for RNA binding properties of the coat protein of prunus necrotic ringspot ilarvirus and their comparison to related and unrelated viruses.

PubMed

Pallás, V; Sánchez-Navarro, J A; Díez, J

1999-01-01

The RNA binding properties of the prunus necrotic ringspot virus (PNRSV) coat protein (CP) were demonstrated by northwestern and dot-blot analyses. The capability to bind PNRSV RNA 4 was compared with viruses representing three different interactions prevailing in the assembly and architecture of virions. The results showed that cucumber mosaic virus (CMV) and PNRSV CPs, which stabilise their virions mainly through RNA-protein interactions bound PNRSV RNA 4 even at very high salt concentrations. The CP of cherry leaf roll nepovirus, whose virions are predominantly stabilised by protein-protein interactions did not bind even at the lowest salt concentration tested. Finally the CP of carnation mottle carmovirus, that has an intermediate position in which both RNA-protein and protein-protein interactions are equally important showed a salt-dependent RNA binding.

78 FR 13933 - Railroad Cost of Capital-2012

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-01

... by May 31, 2013. ADDRESSES: Comments may be submitted either via the Board's e-filing system or in the traditional paper format. Any person using e-filing should comply with the instructions at the E-FILING link on the Board's Web site, at http://www.stb.dot.gov . Any person submitting a filing in the...

76 FR 10430 - Railroad Cost of Capital-2010

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-24

... by June 8, 2011. ADDRESSES: Comments may be submitted either via the Board's e-filing system or in the traditional paper format. Any person using e-filing should comply with the instructions at the E-FILING link on the Board's Web site, at http://www.stb.dot.gov . Any person submitting a filing in the...

75 FR 16894 - Railroad Cost of Capital-2009

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... 15, 2010. ADDRESSES: Comments may be submitted either via the Board's e-filing system or in the traditional paper format. Any person using e-filing should comply with the instructions at the E-FILING link on the Board's Web site, at http://www.stb.dot.gov . Any person submitting a filing in the...

77 FR 6625 - Railroad Cost of Capital-2011

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-08

... railroads are due by May 9, 2012. ADDRESSES: Comments may be submitted either via the Board's e-filing system or in the traditional paper format. Any person using e-filing should comply with the instructions at the E-FILING link on the Board's Web site, at http://www.stb.dot.gov . Any person submitting a...

Quantum dots induce charge-specific amyloid-like fibrillation of insulin at physiological conditions

NASA Astrophysics Data System (ADS)

Sukhanova, Alyona; Poly, Simon; Shemetov, Anton; Nabiev, Igor R.

2012-10-01

Agglomeration of some proteins may give rise to aggregates that have been identified as the main cause of amyloid diseases. For example, fibrillation of insulin is related to diabetes mellitus. Quantum dots (QDs) are of special interest as tagging agents for diagnostic and therapeutic studies due to their broad absorption spectra, narrow emission spectra, and high photostability. In this study, PEGylated CdSe/ZnS QDs have been shown to induce the formation of amyloid-like fibrils of human insulin under physiological conditions, this process being dependent on the variation of the surface charge of the nanoparticles (NPs) used. Circular dichroism (CD), protein secondary structure analysis, thioflavin T (ThT) fluorescence assay, and the dynamic light scattering (DLS) technique have been used for comparative analysis of different stages of the fibrillation process. In particular, insulin secondary structure remodelling accompanied by a considerable increase in the rate of amyloid fiber formation have been observed after insulin was mixed with PEGylated QDs. Nanoparticles may significantly influence the rate of protein fibrillation and induce new mechanisms of amyloid diseases, as well as offer opportunities for their treatment.

Polyamidoamine dendrimers-capped carbon dots/Au nanocrystal nanocomposites and its application for electrochemical immunosensor.

PubMed

Gao, Qi; Han, Jingman; Ma, Zhanfang

2013-11-15

In this work, polyamidoamine dendrimers capped-carbon dots (PAMAM-CDs) were fabricated by one-step microwave assisted pyrolysis of citric acid (CA) and PAMAM, where the formation of CDs and the surface passivation were accomplished simultaneously. The obtained graphitic PAMAM-CDs, with abundant amine groups, were employed as reducing and capping agents for the formation of PAMAM-CDs/Au nanocrystal nanocomposites. The resulting nanocomposites exhibited excellent conductivity, stability and biocompatibility on the surface of electrode and were designed as an immobilized matrix for sensitive immunosensing of alpha-fetoprotein (AFP). The proposed immunosensor showed a wide linear detection range from 100 fg mL(-1) to 100 ng mL(-1). The detection limit for AFP was 0.025 pg mL(-1). Importantly, the immunosensor was evaluated for the analysis of clinical serum samples, obtaining a good correlation with enzyme-linked immunosorbent assay (ELISA). The results indicated that the immunosensor provided a possible application for the detection of AFP in clinical diagnosis. Copyright © 2013 Elsevier B.V. All rights reserved.

Far from the equilibrium crystallization of oxide quantum dots in dried inorganic gels

NASA Astrophysics Data System (ADS)

Costille, B.; Dumoulin, M.; Ntsame Abagha, A. M.; Thune, E.; Guinebretière, R.

2018-06-01

We synthesized, through the sol-gel process, far from the equilibrium amorphous materials in which heterogeneous crystallization allowed the formation of oxide quantum dots. The isothermal evolutions of the mean size of the nanocrystals and the crystallinity of the materials were determined through x-ray diffraction experiments. The heterogeneous crystallization is characterized by a kinetic behavior that is far from that expected, according to the classical nucleation theory. We demonstrate that the evolution of the crystallinity is characterized by an Avrami exponent largely smaller than 1. Finally, nanocrystals exhibiting a size significantly below their Bohr radius are obtained and the number of these nanocrystals increases during isothermal treatment, whereas their mean size remains quasi-constant.

Interdot spacing dependence of electronic structure and properties of multistacked InGaAs quantum dots fabricated without strain compensation technique

NASA Astrophysics Data System (ADS)

Goshima, Keishiro; Tsuda, Norio; Inukai, Keisuke; Amano, Takeru; Sugaya, Takeyoshi

2018-06-01

We report on the electronic properties and band structure of multistacked quantum dots (QDs) fabricated without a strain compensation technique. It is possible to realize a small interdot spacing and introduce a strong quantum mechanical coupling. From the using temperature dependence, polarized photoluminescent spectra, and photoluminescent excitation experiments, we observe a markedly different behavior depending on the interdot spacing. These results evidence that minibands of electrons and holes are formed with interdot spacings of 7 and 3.5 nm, respectively. In addition, thise results are in good agreement with numerical calculations. We describe in detail the miniband formation and electronic structure of multistacked QDs with various interdot spacings of 10 nm or less.

Synthesis of Nitrogen and Sulfur Co-doped Carbon Dots from Garlic for Selective Detection of Fe3+

NASA Astrophysics Data System (ADS)

Sun, Chun; Zhang, Yu; Wang, Peng; Yang, Yue; Wang, Yu; Xu, Jian; Wang, Yiding; Yu, William W.

2016-02-01

Garlic was used as a green source to synthesize carbon dots (CDs) with a systematic study of the optical and structure properties. Ethylenediamine was added into the synthesis to improve the photoluminescence quantum yield (PL QY) of the CDs. Detailed structural and composition studies demonstrated that the content of N and the formation of C-N and C=N were critical to improve the PL QY. The as-synthesized CDs exhibited excellent stability in a wide pH range and high NaCl concentrations, rendering them applicable in complicated and harsh conditions. Quenching the fluorescence of the CDs in the presence of Fe3+ ion made these CDs a luminescent probe for selective detection of Fe3+ ion.

Synthesis of Nitrogen and Sulfur Co-doped Carbon Dots from Garlic for Selective Detection of Fe(3.).

PubMed

Sun, Chun; Zhang, Yu; Wang, Peng; Yang, Yue; Wang, Yu; Xu, Jian; Wang, Yiding; Yu, William W

2016-12-01

Garlic was used as a green source to synthesize carbon dots (CDs) with a systematic study of the optical and structure properties. Ethylenediamine was added into the synthesis to improve the photoluminescence quantum yield (PL QY) of the CDs. Detailed structural and composition studies demonstrated that the content of N and the formation of C-N and C=N were critical to improve the PL QY. The as-synthesized CDs exhibited excellent stability in a wide pH range and high NaCl concentrations, rendering them applicable in complicated and harsh conditions. Quenching the fluorescence of the CDs in the presence of Fe(3+) ion made these CDs a luminescent probe for selective detection of Fe(3+) ion.

Coordinate tropic hormone regulation of mRNAs for insulin-like growth factor II and the cholesterol side-chain-cleavage enzyme, P450scc [corrected], in human steroidogenic tissues.

PubMed Central

Voutilainen, R; Miller, W L

1987-01-01

Insulin-like growth factors (IGFs) are single-chain polypeptides important for cell proliferation and growth. IGFs are produced in several tissues, suggesting that they function in a paracrine or autocrine fashion as well as functioning as endocrine hormones. We studied the hormonal regulation of IGF-I and IGF-II mRNA in human steroidogenic tissues. In cultured human ovarian granulosa cells, follicle-stimulating hormone, human chorionic gonadotropin, and dibutyryl cAMP increased IGF-II mRNA, but corticotropin [adrenocorticotropic hormone (ACTH)], chorionic somatomammotropin, growth hormone, prolactin, dexamethasone, estradiol, and progesterone had no effect. In cultured human fetal adrenal cells, ACTH and dibutyryl cAMP increased IGF-II mRNA accumulation, but human chorionic gonadotropin and angiotensin II did not. The same five size species of IGF-II mRNA were detected in transfer blots of RNA from granulosa cells and fetal adrenal cells, and all of these increased after hormonal stimuli. Dibutyryl cAMP also increased IGF-II mRNA accumulation in cultured human placental cells. Accumulation of mRNA for the cholesterol side-chain-cleavage monooxygenase [P450scc [corrected]; cholesterol, reduced-adrenal-ferredoxin:oxygen oxidoreductase (side-chain-cleaving), EC 1.14.15.6] was regulated in parallel with IGF-II mRNA in all these steroidogenic tissues. IGF-I mRNA was not detected in transfer blots of these RNAs, and the minimal amounts detected in dot blots showed no detectable change after any of the hormonal stimuli studied. The data indicate that the IGF-II gene is expressed in human steroidogenic tissues and is regulated by cAMP. These data suggest that IGF-II may act in an autocrine or paracrine fashion to stimulate the adrenal and gonadal growth stimulated by ACTH and gonadotropins, respectively. Images PMID:3031644

Human alpha-enolase from endothelial cells as a target antigen of anti-endothelial cell antibody in Behçet's disease.

PubMed

Lee, Kwang Hoon; Chung, Hae-Shin; Kim, Hyoung Sup; Oh, Sang-Ho; Ha, Moon-Kyung; Baik, Ja-Hyun; Lee, Sungnack; Bang, Dongsik

2003-07-01

To identify and recombine a protein of the human dermal microvascular endothelial cell (HDMEC) that specifically reacts with anti-endothelial cell antibody (AECA) in the serum of patients with Behçet's disease (BD), and to evaluate the usefulness of this protein in BD. The proteomics technique, with 2-dimensional gel electrophoresis and matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry, was used to identify and recombine HDMEC antigen. Western blotting and enzyme-linked immunosorbent assay (ELISA) of recombinant protein isolated by gene cloning were performed on serum from healthy controls, patients with BD, and patients with other rheumatic diseases (rheumatoid arthritis, systemic lupus erythematosus, and Wegener's granulomatosis). Eighteen of 40 BD patients had serum IgM antibody to HDMEC antigen. The purified protein that reacted with AECA in BD patient sera was found to be alpha-enolase by 2-dimensional gel electrophoresis followed by immunoblotting and MALDI-TOF mass spectrometry. Recombinant alpha-enolase protein was isolated and refined by gene cloning. On Western blots, AECA-positive IgM from the sera of patients with active BD reacted strongly with recombinant human alpha-enolase. BD patient sera positive for anti-alpha-enolase did not react with human gamma-enolase. On dot-blotting, reactivity to human alpha-enolase was detected only in the IgM-positive group. Fifteen of the 18 AECA-positive sera that were positive for the HDMEC antigen showed reactivity to recombinant alpha-enolase IgM antibody by ELISA. The alpha-enolase protein is the target protein of serum AECA in BD patients. This is the first report of the presence of IgM antibodies to alpha-enolase in endothelial cells from the serum of BD patients. Although further studies relating this protein to the pathogenesis of BD will be necessary, alpha-enolase and its antibody may prove useful in the development of new diagnostic and treatment modalities in BD.

THE ASTROPHYSICAL IMPLICATIONS OF DUST FORMATION DURING THE ERUPTIONS OF HOT, MASSIVE STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kochanek, C. S.

2011-12-10

Dust formation in the winds of hot stars is inextricably linked to the classic eruptive state of luminous blue variables because it requires very high mass-loss rates, M-dot {approx}>10{sup -2.5} M{sub sun} year{sup -1}, for grains to grow and for the non-dust optical depth of the wind to shield the dust formation region from the true stellar photosphere. Thus, dusty shells around hot stars trace the history of 'great' eruptions, and the statistics of such shells in the Galaxy indicate that these eruptions are likely the dominant mass-loss mechanism for evolved, M{sub ZAMS} {approx}> 40 M{sub Sun} stars. Dust formationmore » at such high M-dot also explains why very large grains (a{sub max} {approx}> 1 {mu}m) are frequently found in these shells, since a{sub max}{proportional_to} M-dot . The statistics of these shells (numbers, ages, masses, and grain properties such as a{sub max}) provide an archaeological record of this mass-loss process. In particular, the velocities v{sub shell}, transient durations (where known), and ejected masses M{sub shell} of the Galactic shells and the supernova (SN) 'impostors' proposed as their extragalactic counterparts are very different. While much of the difference is a selection effect created by shell lifetimes {proportional_to}(v{sub shell}{radical}(M{sub shell})){sup -1}, more complete Galactic and extragalactic surveys are needed to demonstrate that the two phenomena share a common origin given that their observed properties are essentially disjoint. If even small fractions (1%) of SNe show interactions with such dense shells of ejecta, as is currently believed, then the driving mechanism of the eruptions must be associated with the very final phases of stellar evolution, suggestive of some underlying nuclear burning instability.« less

Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Soo Kang, Jin; Park, Min-Ah; Kim, Jae-Yup; Ha Park, Sun; Young Chung, Dong; Yu, Seung-Ho; Kim, Jin; Park, Jongwoo; Choi, Jung-Woo; Jae Lee, Kyung; Jeong, Juwon; Jae Ko, Min; Ahn, Kwang-Soon; Sung, Yung-Eun

2015-05-01

Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot- sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye-sensitized solar cells (DSCs), with a conversion efficiency (η) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, η = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (η = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (η = 2.80%) when applied to CdSe-based QDSCs.

Physical and electrical characteristics of Si/SiC quantum dot superlattice solar cells with passivation layer of aluminum oxide

NASA Astrophysics Data System (ADS)

Tsai, Yi-Chia; Li, Yiming; Samukawa, Seiji

2017-12-01

In this work, we numerically simulate the silicon (Si)/silicon carbide (SiC) quantum dot superlattice solar cell (SiC-QDSL) with aluminum oxide (Al2O3-QDSL) passivation. By exploiting the passivation layer of Al2O3, the high photocurrent and the conversion efficiency can be achieved without losing the effective bandgap. Based on the two-photon transition mechanism in an AM1.5 and a one sun illumination, the simulated short-circuit current (J sc) of 4.77 mA cm-2 is very close to the experimentally measured 4.75 mA cm-2, which is higher than those of conventional SiC-QDSLs. Moreover, the efficiency fluctuation caused by the structural variation is less sensitive by using the passivation layer. A high conversion efficiency of 17.4% is thus estimated by adopting the QD’s geometry used in the experiment; and, it can be further boosted by applying a hexagonal QD formation with an inter-dot spacing of 0.3 nm.

Physical and electrical characteristics of Si/SiC quantum dot superlattice solar cells with passivation layer of aluminum oxide.

PubMed

Tsai, Yi-Chia; Li, Yiming; Samukawa, Seiji

2017-12-01

In this work, we numerically simulate the silicon (Si)/silicon carbide (SiC) quantum dot superlattice solar cell (SiC-QDSL) with aluminum oxide (Al 2 O 3 -QDSL) passivation. By exploiting the passivation layer of Al 2 O 3 , the high photocurrent and the conversion efficiency can be achieved without losing the effective bandgap. Based on the two-photon transition mechanism in an AM1.5 and a one sun illumination, the simulated short-circuit current (J sc ) of 4.77 mA cm -2 is very close to the experimentally measured 4.75 mA cm -2 , which is higher than those of conventional SiC-QDSLs. Moreover, the efficiency fluctuation caused by the structural variation is less sensitive by using the passivation layer. A high conversion efficiency of 17.4% is thus estimated by adopting the QD's geometry used in the experiment; and, it can be further boosted by applying a hexagonal QD formation with an inter-dot spacing of 0.3 nm.

Observation of Mollow Triplets with Tunable Interactions in Double Lambda Systems of Individual Hole Spins

NASA Astrophysics Data System (ADS)

Lagoudakis, K. G.; Fischer, K. A.; Sarmiento, T.; McMahon, P. L.; Radulaski, M.; Zhang, J. L.; Kelaita, Y.; Dory, C.; Müller, K.; Vučković, J.

2017-01-01

Although individual spins in quantum dots have been studied extensively as qubits, their investigation under strong resonant driving in the scope of accessing Mollow physics is still an open question. Here, we have grown high quality positively charged quantum dots embedded in a planar microcavity that enable enhanced light-matter interactions. Under a strong magnetic field in the Voigt configuration, individual positively charged quantum dots provide a double lambda level structure. Using a combination of above-band and resonant excitation, we observe the formation of Mollow triplets on all optical transitions. We find that when the strong resonant drive power is used to tune the Mollow-triplet lines through each other, we observe anticrossings. We also demonstrate that the interaction that gives rise to the anticrossings can be controlled in strength by tuning the polarization of the resonant laser drive. Quantum-optical modeling of our system fully captures the experimentally observed spectra and provides insight on the complicated level structure that results from the strong driving of the double lambda system.

Suppression of dislocations by Sb spray in the vicinity of InAs/GaAs quantum dots

PubMed Central

2014-01-01

The effect of Sb spray prior to the capping of a GaAs layer on the structure and properties of InAs/GaAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) is studied by cross-sectional high-resolution transmission electron microscopy (HRTEM). Compared to the typical GaAs-capped InAs/GaAs QDs, Sb-sprayed QDs display a more uniform lens shape with a thickness of about 3 ~ 4 nm rather than the pyramidal shape of the non-Sb-sprayed QDs. Particularly, the dislocations were observed to be passivated in the InAs/GaAs interface region and even be suppressed to a large extent. There are almost no extended dislocations in the immediate vicinity of the QDs. This result is most likely related to the formation of graded GaAsSb immediately adjacent to the InAs QDs that provides strain relief for the dot/capping layer lattice mismatch. PACS 81.05.Ea; 81.07.-b; 81.07.Ta PMID:24948897

Structural characterization and observation of variable range hopping conduction mechanism at high temperature in CdSe quantum dot solids

NASA Astrophysics Data System (ADS)

Sinha, Subhojyoti; Kumar Chatterjee, Sanat; Ghosh, Jiten; Kumar Meikap, Ajit

2013-03-01

We have used Rietveld refinement technique to extract the microstructural parameters of thioglycolic acid capped CdSe quantum dots. The quantum dot formation and its efficient capping are further confirmed by HR-TEM, UV-visible and FT-IR spectroscopy. Comparative study of the variation of dc conductivity with temperature (298 K ≤ T ≤ 460 K) is given considering Arrhenius formalism, small polaron hopping and Schnakenberg model. We observe that only Schnakenberg model provides good fit to the non-linear region of the variation of dc conductivity with temperature. Experimental variation of ac conductivity and dielectric parameters with temperature (298 K ≤ T ≤ 460 K) and frequency (80 Hz ≤ f ≤ 2 MHz) are discussed in the light of hopping theory and quantum confinement effect. We have elucidated the observed non-linearity in the I-V curves (measured within ±50 V), at dark and at ambient light, in view of tunneling mechanism. Tunnel exponents and non-linearity weight factors have also been evaluated in this regard.

Ligand-surface interactions and surface oxidation of colloidal PbSe quantum dots revealed by thin-film positron annihilation methods

NASA Astrophysics Data System (ADS)

Shi, Wenqin; Eijt, Stephan W. H.; Suchand Sandeep, C. S.; Siebbeles, Laurens D. A.; Houtepen, Arjan J.; Kinge, Sachin; Brück, Ekkes; Barbiellini, Bernardo; Bansil, Arun

2016-02-01

Positron Two Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) measurements reveal modifications of the electronic structure and composition at the surfaces of PbSe quantum dots (QDs), deposited as thin films, produced by various ligands containing either oxygen or nitrogen atoms. In particular, the 2D-ACAR measurements on thin films of colloidal PbSe QDs capped with oleic acid ligands yield an increased intensity in the electron momentum density (EMD) at high momenta compared to PbSe quantum dots capped with oleylamine. Moreover, the EMD of PbSe QDs is strongly affected by the small ethylenediamine ligands, since these molecules lead to small distances between QDs and favor neck formation between near neighbor QDs, inducing electronic coupling between neighboring QDs. The high sensitivity to the presence of oxygen atoms at the surface can be also exploited to monitor the surface oxidation of PbSe QDs upon exposure to air. Our study clearly demonstrates that positron annihilation spectroscopy applied to thin films can probe surface transformations of colloidal semiconductor QDs embedded in functional layers.

Composition control and localization of S2- in CdSSe quantum dots grown from Li4[Cd10Se4(SPh)16].

PubMed

Lovingood, Derek D; Oyler, Ryan E; Strouse, Geoffrey F

2008-12-17

The development of ternary nanoscale materials with controlled cross-sectional doping is an important step for the use of chemically prepared quantum dots for nanoscale engineering applications. We report cross-sectional, elemental doping with the formation of an alloyed CdSSe nanocrystal from the thermal decomposition of Li(4)[Cd(10)Se(4)(SPh)(16)]. The sulfur incorporation arises from surface-mediated phenylthiolate degradation on the growing quantum dot surface. In the alloy, we identify a pure CdSe nucleus of approximately 1.5 nm, consistent with the predictions of nucleation theory. As the particle grows, S(2-) incorporation increases until the CdSSe reaches approximately 4 nm, where a marked reduction in phenylthiolate content on the nanocrystal is observed by CP-MAS NMR spectroscopy, implying that rapid decomposition of the phenylthiolate arises with subsequent enhanced S(2-) incorporation at the level of the stoichiometry of the reaction (namely approximately 60%). The use of molecular clusters to allow controlled defect ion incorporation can open new pathways to more complex nanomaterials.

Surface Passivation of CdSe Quantum Dots in All Inorganic Amorphous Solid by Forming Cd1-xZnxSe Shell.

PubMed

Xia, Mengling; Liu, Chao; Zhao, Zhiyong; Wang, Jing; Lin, Changgui; Xu, Yinsheng; Heo, Jong; Dai, Shixun; Han, Jianjun; Zhao, Xiujian

2017-02-07

CdSe quantum dots (QDs) doped glasses have been widely investigated for optical filters, LED color converter and other optical emitters. Unlike CdSe QDs in solution, it is difficult to passivate the surface defects of CdSe QDs in glass matrix, which strongly suppress its intrinsic emission. In this study, surface passivation of CdSe quantum dots (QDs) by Cd 1-x Zn x Se shell in silicate glass was reported. An increase in the Se/Cd ratio can lead to the partial passivation of the surface states and appearance of the intrinsic emission of CdSe QDs. Optimizing the heat-treatment condition promotes the incorporation of Zn into CdSe QDs and results in the quenching of the defect emission. Formation of CdSe/Cd 1-x Zn x Se core/graded shell QDs is evidenced by the experimental results of TEM and Raman spectroscopy. Realization of the surface passivation and intrinsic emission of II-VI QDs may facilitate the wide applications of QDs doped all inorganic amorphous materials.

Development of Rapid Diagnostic Kit for Identification of Hanwoo (Korean Native Cattle) Brand Meat by Detecting BIO-TAG

PubMed Central

Park, Sung Kwon; Lee, Myung Hoon; Cho, Soo Hyun

2014-01-01

This study was performed to develop a rapid immuno-assay kit, by using a specific antigen to detect Hanwoo brand meat. We selected a synthetic antigen specific to our target antibody, named BIO-TAG (Tyr-D-Ala-Phe), by utilizing a computer-based analysis and literature review. BIO-TAG tagged with adjuvant was subcutaneously injected in sheep and Hanwoo. The serum and meat juice of the immunized or non-immunized animal were then analyzed, to measure the titer of antibody by ELISA and Western blot. The amount of antibodies against the BIO-TAG increased (p<0.05) in serum by vaccination. Furthermore, meat juice from the immunized Hanwoo showed greater (p<0.05) antibody titer, compared with those from non-immunized groups. To optimze the dilution factor, we performed dot-ELISA, with various combination levels of BIO-TAG. Results from dot-ELISA showed that 2 mg/mL BIO-TAG was sufficient to distinguish the immunized meat from non-immunized groups. These results support our hypothesis that simple immunization of Hanwoo generates a sufficient amount of antibodies to be detectable in the meat juice by means of the immune-assay. Therefore, specific Hanwoo brand meat can be more precisely identified by our rapid diagnostic kit. This technology can deter possible fraud of counterfeit meat brands in the Korean domestic market with ease and rapidity; and offers a new tool that guarantees consumers high quality Hanwoo brand beef. PMID:26761175

Tuning the Formations of Metal-Organic Frameworks by Modification of Ratio of Reactant, Acidity of Reaction System, and Use of a Secondary Ligand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Q; Xie, YB; Li, JR

2012-01-01

Four porous coordination networks (PCNs), {[Zn3O(H2O)(3)(adc)(3)]center dot 2(C2H6NH2)center dot 2(DMF)center dot 3(H2O)}(n) (PCN-131), Zn-2(DMA)(2)(adc)(2)]center dot 2(DMA)}(n) (PCN-132), {[Zn3O(DMF)(adc)(3)(4,4'-bpy)]center dot 2(C2H6NH2)center dot S}(n) (PCN-131'), and {[Zn(adc)(4,4'-bpy)(0.5)]center dot S}(n) (PCN-132'), have been synthesized by the assembly of anthrancene-9,10-dicarboxylic acid (H(2)adc) with Zn(II) under different reaction conditions, including modifications of reactant ratio, acidity variations, and the use of a secondary ligand. Single-crystal X-ray diffraction studies reveal that PCN-131, obtained from the dimethylformamide (DMF) solution under acid condition, has a three-dimentional (3D) framework structure with one-dimensional (1D) honeycomb channels. PCN-132 isolated from dimethylacetamide (DMA) solution without adding acid in synthesis is a two-dimensional (2D)more » layer compound. By employing 4,4'-bipyridyl (4,4'-bpy) as a secondary ligand, PCN-131' and PCN-132' were synchronously synthesized as a mixture outcome with more PCN-131' than PCN-132'. In PCN-131', 4,4'-bpy acting as a secondary ligand is arranged inside the honeycomb channel of the 3D PCN-131, resulting in an effective improvement of thermal stability of the network, while in PCN-132', 4,4'-bpy ligands link 2D layers of PCN-132 to form a pillared-layer 3D framework Gas adsorption has been performed for selected materials. The results show that the framework of PCN-131 is thermally unstable after removing the solvent molecules coordinated to their metal sites. While PCN-131' is stable for gas uptake, with an evaluated Langmuir surface area of 199.04 m(2) g(-1), it shows a selective adsorption of CO2 over CH4.« less

High-throughput and in situ EDXRD investigation on the formation of two new metal aminoethylphosphonates - Ca(O{sub 3}PC{sub 2}H{sub 4}NH{sub 2}) and Ca(OH)(O{sub 3}PC{sub 2}H{sub 4}NH{sub 3}){center_dot}2H{sub 2}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, Corinna; Feyand, Mark; Rothkirch, Andre

2012-04-15

The system Ca{sup 2+}/2-aminoethylphosphonic acid/H{sub 2}O/NaOH was systematically investigated using high-throughput methods. The experiments led to one new compound Ca(O{sub 3}PC{sub 2} H{sub 4}NH{sub 2}) (1) and the crystal structure was determined using in house X-ray powder diffraction data (monoclinic, P2{sub 1}/c, a=9.7753(3), b=6.4931(2), c=8.4473(2) A, {beta}=106.46(2) Degree-Sign , V=514.20(2) A{sup 3}, Z=4). The formation of 1 was investigated by in situ energy dispersive X-ray diffraction measurements (EDXRD) at beamline F3 at HASYLAB (light source DORIS III), DESY, Hamburg. An intermediate, Ca(OH)(O{sub 3}PC{sub 2}H{sub 4}NH{sub 3}){center_dot}2H{sub 2}O (2), was observed and could be isolated from the reaction mixture at ambientmore » temperatures by quenching the reaction. The crystal structure of 2 was determined from XRPD data using synchrotron radiation (monoclinic, P2{sub 1}/m, a=11.2193(7), b=7.1488(3), c=5.0635(2) A, {beta}=100.13(4) Degree-Sign , V=399.78(3) A{sup 3}, Z=2). - Graphical abstarct: The detailed in situ energy dispersive X-ray diffraction (EDXRD) investigation on the formation of the new inorganic-organic hybrid compound Ca(O{sub 3}PC{sub 2}H{sub 4}NH{sub 2}) leads to the discovery of a new crystalline intermediate phase. Both crystal structures were elucidated using X-ray powder diffraction data. Highlights: Black-Right-Pointing-Pointer High-throughput investigation led to new metal aminoethylphosphonate Ca(O{sub 3}PC{sub 2}H{sub 4}NH{sub 2}). Black-Right-Pointing-Pointer The formation of Ca(O{sub 3}PC{sub 2}H{sub 4}NH{sub 2}) was followed by in situ EDXRD measurements. Black-Right-Pointing-Pointer The crystalline intermediate Ca(O{sub 3}PC{sub 2}H{sub 4}NH{sub 3})(OH){center_dot}2H{sub 2}O was discovered. Black-Right-Pointing-Pointer Isolation of Ca(O{sub 3}PC{sub 2}H{sub 4}NH{sub 3})(OH){center_dot}2H{sub 2}O was accomplished by quenching experiments. Black-Right-Pointing-Pointer The structures were determined using X-ray powder diffraction data.« less

Rhipicephalus appendiculatus ticks transmit Theileria parva from persistently infected cattle in the absence of detectable parasitemia: implications for East Coast fever epidemiology.

PubMed

Olds, Cassandra L; Mason, Kathleen L; Scoles, Glen A

2018-03-02

East Coast fever (ECF) is a devastating disease of cattle and a significant constraint to improvement of livestock production in sub-Saharan Africa. The protozoan parasite causing ECF, Theileria parva, undergoes obligate sexual stage development in its tick vector Rhipicephalus appendiculatus. Tick-borne acquisition and transmission occurs transstadially; larval and nymphal ticks acquire infection while feeding and transmit to cattle when they feed after molting to the next stage. Much of the current knowledge relating to tick-borne acquisition and transmission of T. parva has been derived from studies performed during acute infections where parasitemia is high. In contrast, tick-borne transmission during the low-level persistent infections characteristic of endemic transmission cycles is rarely studied. Cattle were infected with one of two stocks of T. parva (Muguga or Marikebuni). Four months post-infection when parasites were no longer detectable in peripheral blood by PCR, 500 R. appendiculatus nymphs were fed to repletion on each of the cattle. After they molted to the adult stage, 20 or 200 ticks, respectively, were fed on two naïve cattle for each of the parasite stocks. After adult ticks fed to repletion, cattle were tested for T. parva infection by nested PCR and dot blot hybridization. Once they had molted to adults the ticks that had fed as nymphs on Muguga and Marikebuni infected cattle successfully transmitted Theileria parva to all naïve cattle, even though T. parva infection was not detectable by nested PCR on salivary gland genomic DNA of a sample of individual ticks. However, a salivary gland homogenate from a single Marikebuni infected tick was able to infect primary bovine lymphocytes. Infection was detected by nested p104 PCR in 3 of 4 calves and detected in all 4 calves by T. parva 18S nested PCR/dot blot hybridization. We show that R. appendiculatus ticks are able to acquire T. parva parasites from infected cattle even in the absence of detectable parasitemia. Although infection was undetectable in a sample of individual ticks, cumulatively as few as 20 ticks were able to transmit T. parva to naïve cattle. These results have important implications for our understanding of T. parva transmission by R. appendiculatus in ECF endemic regions.

Consequences of elastic anisotropy in patterned substrate heteroepitaxy.

PubMed

Dixit, Gopal Krishna; Ranganathan, Madhav

2018-06-13

The role of elastic anisotropy on quantum dot formation and evolution on a pre-patterned substrate is evaluated within the framework of a continuum model. We first extend the formulation for surface evolution to take elastic anisotropy into account. Using a small slope approximation, we derive the evolution equation and show how it can be numerically implemented up to linear and second order for stripe and egg-carton patterned substrates using an accurate and efficient procedure. The semi--infinite nature of the substrate is used to solve the elasticity problem subject to other boundary conditions at the free surface and at the film--substrate interface. The positioning of the quantum dots with respect to the peaks and valleys of the pattern is explained by a competition between the length scale of the pattern and the wavelength of the Asaro--Tiller--Grinfeld instability, which is also affected by the elastic anisotropy. The alignment of dots is affected by a competition between the elastic anisotropy of the film and the pattern orientation. A domain of pattern inversion, wherein the quantum dots form exclusively in the valleys of the patterns is identified as a function of the average film thickness and the elastic anisotropy, and the time--scale for this inversion as function of height is analyzed. © 2018 IOP Publishing Ltd.

Biocide immobilized OMMT-carbon dot reduced Cu2O nanohybrid/hyperbranched epoxy nanocomposites: Mechanical, thermal, antimicrobial and optical properties.

PubMed

De, Bibekananda; Gupta, Kuldeep; Mandal, Manabendra; Karak, Niranjan

2015-11-01

The present work demonstrated a transparent thermosetting nanocomposite with antimicrobial and photoluminescence attributes. The nanocomposites are fabricated by incorporation of different wt.% (1, 2 and 3) of a biocide immobilized OMMT-carbon dot reduced Cu2O nanohybrid (MITH-NH) in the hyperbranched epoxy matrix. MITH-NH is obtained by immobilization of 2-methyl-4-isothiazolin-3-one hydrochloride (MITH) at room temperature using sonication on OMMT-carbon dot reduced Cu2O nanohybid. The nanohybrid is prepared by reduction of cupric acetate using carbon dot as the reducing agent in the presence of OMMT at 70°C. The significant improvements in tensile strength (~2 fold), elongation at break (3 fold), toughness (4 fold) and initial thermal degradation temperature (30°C) of the pristine hyperbranched epoxy system are achieved by incorporation of 3wt.% of MITH-NH in it. The nanocomposites exhibit strong antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae and Pseudomonas aeruginosa bacteria and Candida albicans, a fungus. The nanocomposite also shows significant activity against biofilm formation compared to the pristine thermoset. Further, the nanocomposite films emit different colors on exposure of different wavelengths of UV light. The properties of these nanocomposites are also compared with the same nanohybrid without OMMT. Copyright © 2015. Published by Elsevier B.V.

Reduced graphene oxide-germanium quantum dot nanocomposite: electronic, optical and magnetic properties

NASA Astrophysics Data System (ADS)

Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.

2017-12-01

Graphene provides numerous possibilities for structural modification and functionalization of its carbon backbone. Localized magnetic moments can, as well, be induced in graphene by the formation of structural defects which include vacancies, edges, and adatoms. In this work, graphene was functionalized using germanium atoms, we report the effect of the Ge ad atoms on the structural, electrical, optical and magnetic properties of graphene. Reduced graphene oxide (rGO)-germanium quantum dot nanocomposites of high crystalline quality were synthesized by the microwave-assisted solvothermal reaction. Highly crystalline spherical shaped germanium quantum dots, of diameter ranging between 1.6-9.0 nm, are anchored on the basal planes of rGO. The nanocomposites exhibit high electrical conductivity with a sheet resistance of up to 16 Ω sq-1. The electrical conductivity is observed to increase with the increase in Ge content in the nanocomposites. High defect-induced magnetization is attained in the composites via germanium adatoms. The evolution of the magnetic moments in the nanocomposites and the coercivity showed marked dependence on the Ge quantum dots size and concentration. Quantum confinement effects is evidenced in the UV-vis absorbance spectra and photoluminescence emission spectra of the nanocomposites which show marked size-dependence. The composites manifest strong absorption in the UV region, strong luminescence in the near UV region, and a moderate luminescence in the visible region.

Properties of POPC/POPE supported lipid bilayers modified with hydrophobic quantum dots on polyelectrolyte cushions.

PubMed

Kolasinska-Sojka, Marta; Wlodek, Magdalena; Szuwarzynski, Michal; Kereiche, Sami; Kovacik, Lubomir; Warszynski, Piotr

2017-10-01

The formation and properties of supported lipid bilayers (SLB) containing hydrophobic nanoparticles (NP) was studied in relation to underlying cushion obtained from selected polyelectrolyte multilayers. Lipid vesicles were formed from zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) in phosphate buffer (PBS). As hydrophobic nanoparticles - quantum dots (QD) with size of 3.8nm (emission wavelength of 420nm) were used. Polyelectrolyte multilayers (PEM) were constructed by the sequential, i.e., layer-by-layer (LbL) adsorption of alternately charged polyelectrolytes from their solutions. Liposomes and Liposome-QDs complexes were studied with Transmission Cryo-Electron Microscopy (Cryo-TEM) to verify the quality of vesicles and the position of QD within lipid bilayer. Deposition of liposomes and liposomes with quantum dots on polyelectrolyte films was studied in situ using quartz crystal microbalance with dissipation (QCM-D) technique. The fluorescence emission spectra were analyzed for both: suspension of liposomes with nanoparticles and for supported lipid bilayers containing QD on PEM. It was demonstrated that quantum dots are located in the hydrophobic part of lipid bilayer. Moreover, we proved that such QD-modified liposomes formed supported lipid bilayers and their final structure depended on the type of underlying cushion. Copyright © 2017 Elsevier B.V. All rights reserved.

Double channel emission from a redox active single component quantum dot complex.

PubMed

Bhandari, Satyapriya; Roy, Shilaj; Pramanik, Sabyasachi; Chattopadhyay, Arun

2015-01-13

Herein we report the generation and control of double channel emission from a single component system following a facile complexation reaction between a Mn(2+) doped ZnS colloidal quantum dot (Qdot) and an organic ligand (8-hydroxy quinoline; HQ). The double channel emission of the complexed quantum dot-called the quantum dot complex (QDC)-originates from two independent pathways: one from the complex (ZnQ2) formed on the surface of the Qdot and the other from the dopant Mn(2+) ions of the Qdot. Importantly, reaction of ZnQ2·2H2O with the Qdot resulted in the same QDC formation. The emission at 500 nm with an excitation maximum at 364 nm is assigned to the surface complex involving ZnQ2 and a dangling sulfide bond. On the other hand, the emission at 588 nm-with an excitation maximum at 330 nm-which is redox tunable, is ascribed to Mn(2+) dopant. The ZnQ2 complex while present in QDC has superior thermal stability in comparison to the bare complex. Interestingly, while the emission of Mn(2+) was quenched by an electron quencher (benzoquinone), that due to the surface complex remained unaffected. Further, excitation wavelength dependent tunability in chromaticity color coordinates makes the QDC a potential candidate for fabricating a light emitting device of desired color output.

Self-organised silicide nanodot patterning by medium-energy ion beam sputtering of Si(100): local correlation between the morphology and metal content.

PubMed

Redondo-Cubero, A; Galiana, B; Lorenz, K; Palomares, F J; Bahena, D; Ballesteros, C; Hernandez-Calderón, I; Vázquez, L

2016-11-04

We have produced self-organised silicide nanodot patterns by medium-energy ion beam sputtering (IBS) of silicon targets with a simultaneous and isotropic molybdenum supply. Atomic force microscopy (AFM) studies show that these patterns are qualitatively similar to those produced thus far at low ion energies. We have determined the relevance of the ion species on the pattern ordering and properties. For the higher ordered patterns produced by Xe(+) ions, the pattern wavelength depends linearly on the ion energy. The dot nanostructures are silicide-rich as assessed by x-ray photoelectron spectroscopy (XPS) and emerge in height due to their lower sputtering yield, as observed by electron microscopy. Remarkably, a long wavelength corrugation is observed on the surface which is correlated with both the Mo content and the dot pattern properties. Thus, as assessed by electron microscopy, the protrusions are Mo-rich with higher and more spaced dots on their surface whereas the valleys are Mo-poor with smaller dots that are closer to each other. These findings indicate that there is a correlation between the local metal content of the surface and the nanodot pattern properties both at the nanodot and the large corrugation scales. These results contribute to advancing the understanding of this interesting nanofabrication method and aid in developing a comprehensive theory of nanodot pattern formation and evolution.

Minimization of material inter-diffusion for thermally stable quaternary-capped InAs quantum dot via strain modification

NASA Astrophysics Data System (ADS)

Ghadi, Hemant; Sehara, Navneet; Murkute, Punam; Chakrabarti, Subhananda

2017-05-01

In this study, a theoretical model is developed for investigating the effect of thermal annealing on a single-layer quaternary-capped (In0.21Al0.21Ga0.58As) InAs quantum dot heterostructure (sample A) and compared to a conventional GaAs-capped sample (sample B). Strain, an interfacial property, aids in dot formation; however, it hinders interdiffusion (up to 650 °C), rendering thermal stability to heterostructures. Three diffusing species In/Al/Ga intermix because of the concentration gradient and temperature variation, which is modeled by Fick's law of diffusion. Ground-state energy for both carriers (electron and holes) is calculated by the Schrodinger equation at different annealing temperatures, incorporating strain computed by the concentration-dependent model. Change in activation energy due to strain decreases particle movement, thereby resulting in thermally stable structures at low annealing temperatures. At low temperature, the conduction band near the dot edge slightly decreases, attributed to the comparatively high strain. Calculated results are consistent with the experimental blue-shift i.e. towards lower wavelength of photoluminescence peak on the same sample with increasing annealing temperatures. Cross-sectional transmission microscopy (TEM) images substantiate the existence of dot till 800 °C for sample (A). With increasing annealing temperature, interdiffusion and dot sublimation are observed in XTEM images of samples A and B. Strain calculated from high-resolution X-ray diffraction (HRXRD) peaks and its decline with increasing temperature are in agreement with that calculated by the model. For highlighting the benefits of quaternary capping, InAlGaAs capping is theoretically and experimentally compared to GaAs capping. Concentration-dependent strain energy is calculated at every point and is further used for computing material interdiffusion, band profiles, and photoluminescence peak wavelength, which can provide better insights into strain energy behavior with temperature and help in the better understanding of thermal annealing.

Curcumin Quantum Dots Mediated Degradation of Bacterial Biofilms.

PubMed

Singh, Ashish K; Prakash, Pradyot; Singh, Ranjana; Nandy, Nabarun; Firdaus, Zeba; Bansal, Monika; Singh, Ranjan K; Srivastava, Anchal; Roy, Jagat K; Mishra, Brahmeshwar; Singh, Rakesh K

2017-01-01

Bacterial biofilm has been reported to be associated with more than 80% of bacterial infections. Curcumin, a hydrophobic polyphenol compound, has anti-quorum sensing activity apart from having antimicrobial action. However, its use is limited by its poor aqueous solubility and rapid degradation. In this study, we attempted to prepare quantum dots of the drug curcumin in order to achieve enhanced solubility and stability and investigated for its antimicrobial and antibiofilm activity. We utilized a newer two-step bottom up wet milling approach to prepare Curcumin Quantum Dots (CurQDs) using acetone as a primary solvent. Minimum inhibitory concentration against select Gram-positive and Gram-negative bacteria was performed. The antibiofilm assay was performed at first using 96-well tissue culture plate and subsequently validated by Confocal Laser Scanning Microscopy. Further, biofilm matrix protein was isolated using formaldehyde sludge and TCA/Acetone precipitation method. Protein extracted was incubated with varying concentration of CurQDs for 4 h and was subjected to SDS-PAGE. Molecular docking study was performed to observe interaction between curcumin and phenol soluble modulins as well as curli proteins. The biophysical evidences obtained from TEM, SEM, UV-VIS, fluorescence, Raman spectroscopy, and zeta potential analysis confirmed the formation of curcumin quantum dots with increased stability and solubility. The MICs of curcumin quantum dots, as observed against both select gram positive and negative bacterial isolates, was observed to be significantly lower than native curcumin particles. On TCP assay, Curcumin observed to be having antibiofilm as well as biofilm degrading activity. Results of SDS-PAGE and molecular docking have shown interaction between biofilm matrix proteins and curcumin. The results indicate that aqueous solubility and stability of Curcumin can be achieved by preparing its quantum dots. The study also demonstrates that by sizing down the particle size has not only enhanced its antimicrobial properties but it has also shown its antibiofilm activities. Further, study is needed to elucidate the exact nature of interaction between curcumin and biofilm matrix proteins.

Temperature stability of static and dynamic properties of 1.55 µm quantum dot lasers.

PubMed

Abdollahinia, A; Banyoudeh, S; Rippien, A; Schnabel, F; Eyal, O; Cestier, I; Kalifa, I; Mentovich, E; Eisenstein, G; Reithmaier, J P

2018-03-05

Static and dynamic properties of InP-based 1.55 µm quantum dot (QD) lasers were investigated. Due to the reduced size inhomogeneity and a high dot density of the newest generation of 1.55 µm QD gain materials, ridge waveguide lasers (RWG) exhibit improved temperature stability and record-high modulation characteristics. Detailed results are shown for the temperature dependence of static properties including threshold current, voltage-current characteristics, external differential efficiency and emission wavelength. Similarly, small and large signal modulations were found to have only minor dependences on temperature. Moreover, we show the impact of the active region design and the cavity length on the temperature stability. Measurements were performed in pulsed and continuous wave operation. High characteristic temperatures for the threshold current were obtained with T 0 values of 144 K (15 - 60 °C), 101 K (60 - 110 °C) and 70 K up to 180 °C for a 900-µm-long RWG laser comprising 8 QD layers. The slope efficiency in these lasers is nearly independent of temperature showing a T 1 value of more than 900 K up to 110 °C. Due to the high modal gain, lasers with a cavity length of 340 µm reached new record modulation bandwidths of 17.5 GHz at 20 °C and 9 GHz at 80 °C, respectively. These lasers were modulated at 26 GBit/s in the non-return to zero format at 80 °C and at 25 GBaud using a four-level pulse amplitude format at 21 °C.

Human Factors Design Guidelines for the Army Tactical Command and Control System (ATTCS) Soldier-Machine Interface. Version 2.0

DTIC Science & Technology

1992-05-01

especially true for friend-enemy or danger-safe designations. Dots, dashes, shapes, and video effects are recommended. Care must be taken to avoid visual...MAY 92 10.3 Screen Design - Format 10.3.1.4 Use of Contrasting Features Use contrasting features such as inverse video and color to call attention to...captions. Do not use reverse video or highlighting for labels. 13.2.3.2 Formatting For single fields, locate the caption to the left of the entry fields

Immunodetection of the Bacteriocin Lacticin RM: Analysis of the Influence of Temperature and Tween 80 on Its Expression and Activity

PubMed Central

Keren, Tomer; Yarmus, Merav; Halevy, Galia; Shapira, Roni

2004-01-01

Immunoassays with specific antibodies offer higher sensitivity than do bioassays with indicator strains in the detection and quantification of several bacteriocins. Here we present the purification of lacticin RM and the production of specific polyclonal antibodies to a synthetic peptide resembling an internal fragment of the mature bacteriocin. The specificity and sensitivity of the generated polyclonal antibodies were evaluated in various immunoassays. The detection limits of lacticin RM were found to be 1.9, 0.16, and 0.18 μg ml−1 for Western blot, immuno-dot blot, and noncompetitive indirect enzyme-linked immunosorbent assays, respectively. Immunoassay sensitivities were 12.5-fold higher than that of the agar diffusion test (ADT). The production of lacticin RM showed temperature dependency, with 3, 4.2, 12.7, 28.9, 37.8, and 12 μg ml−1 at 37, 30, 20, 15, 10, and 4°C, respectively. Temperature-stability analysis demonstrated that lacticin RM is sensitive to mild temperature, but the loss of activity does not seem to result from protein degradation. Tween 80 increased the concentration of lacticin RM eightfold and probably affected the results of the ADT either by enhancing the activity of lacticin RM or by increasing the sensitivity of the indicator strain. The use of antibodies for the specific detection and quantification of lacticin RM can expand our knowledge of its production and stability, with important implications for further investigation and future application. PMID:15066801

Relative IGF-1 and IGF-2 gene expression in maternal and fetal tissues from diabetic swine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolverton, C.K.; Leaman, D.W.; White, M.E.

1990-02-26

Fourteen pregnant, crossbred gilts were utilized in this study. Seven gilts were injected with alloxan (50 mg/kg) at day 75 of gestation to induce diabetes. Gilts underwent caesarean section on day 105 of gestation. Samples were collected from maternal skeletal muscle, adipose tissue, uterus and endometrium; and from fetal skeletal muscle, adipose tissue, placenta, liver, lung, kidney, heart, brain and spleen. Tissues were frozen in liquid nitrogen for later analysis of IGF-1 and IGF-2 gene expression. Samples were pooled and total RNA was isolated using the guanidine isothiocynate method. Total mRNA was analyzed by dot blot hybridization. Blots were probedmore » with {sup 32}P-cDNA for porcine IGF-1 and rat IGF-2. IGF-1 gene expression in maternal tissues was unaffected by diabetes. Maternal diabetes increased IGF-2 mRNA in maternal adipose tissue but exhibited no effect in muscle or uterus. Expression of IGF-2 by maternal endometrium was decreased by diabetes. Maternal diabetes induced an increase in IGF-1 gene expression in muscle and placenta while causing an increase in IGF-2 expression in fetal liver and placenta. IGF-2 mRNA was lower in lung from fetuses of diabetic mothers than in controls. These results suggest that maternal diabetes alters IGF-1 and IGF-2 gene expression in specific tissues and differential regulation of these genes appears to exist in the mother and developing fetus.« less

One-step selection of Vaccinia virus-binding DNA aptamers by MonoLEX

PubMed Central

Nitsche, Andreas; Kurth, Andreas; Dunkhorst, Anna; Pänke, Oliver; Sielaff, Hendrik; Junge, Wolfgang; Muth, Doreen; Scheller, Frieder; Stöcklein, Walter; Dahmen, Claudia; Pauli, Georg; Kage, Andreas

2007-01-01

Background As a new class of therapeutic and diagnostic reagents, more than fifteen years ago RNA and DNA aptamers were identified as binding molecules to numerous small compounds, proteins and rarely even to complete pathogen particles. Most aptamers were isolated from complex libraries of synthetic nucleic acids by a process termed SELEX based on several selection and amplification steps. Here we report the application of a new one-step selection method (MonoLEX) to acquire high-affinity DNA aptamers binding Vaccinia virus used as a model organism for complex target structures. Results The selection against complete Vaccinia virus particles resulted in a 64-base DNA aptamer specifically binding to orthopoxviruses as validated by dot blot analysis, Surface Plasmon Resonance, Fluorescence Correlation Spectroscopy and real-time PCR, following an aptamer blotting assay. The same oligonucleotide showed the ability to inhibit in vitro infection of Vaccinia virus and other orthopoxviruses in a concentration-dependent manner. Conclusion The MonoLEX method is a straightforward procedure as demonstrated here for the identification of a high-affinity DNA aptamer binding Vaccinia virus. MonoLEX comprises a single affinity chromatography step, followed by subsequent physical segmentation of the affinity resin and a single final PCR amplification step of bound aptamers. Therefore, this procedure improves the selection of high affinity aptamers by reducing the competition between aptamers of different affinities during the PCR step, indicating an advantage for the single-round MonoLEX method. PMID:17697378

Induction of the c-myc protooncogene following antigen binding to hapten-specific B cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snow, E.C.; Fetherston, J.; Zimmer, S.

1986-03-01

Considerable controversy has centered on the role that the surface immunoglobulin (sIg) receptor for antigen plays during the induction of B cell activation. Stimulation by anti-Ig reagents has been shown to activate G/sub 0/ B cells to enter the cell cycle. The binding of thymus-dependent antigens to hapten-specific B cell populations apparently does not result in the movement of the antigen-binding cells (ABC) into the G/sub 1/ stage of the cell cycle. However, the authors have recently demonstrated that antigen binding to such hapten-specific B cells does result in the initiation of the membrane phosphatidylinositol cycle. In the present experiments,more » hapten-specific B cells (80-90% ABC, 99% in G/sub 0/) were incubated with either the correct hapten-carrier conjugate, with the carrier protein, or only media for 2 hours at 37/sup 0/C. At that time, total cellular RNA was isolated and subsequently analyzed by either dot blots or Northern gel techniques. The blots were probed with a (/sup 32/P)-c-myc SstI-Xhol fragment. The results indicate that hapten carrier stimulation of the hapten-specific B cells induces enhanced transcription of the c-myc gene. These observations lend further support to the premise that antigen binding to the sIg receptor results in the transduction to the cell of important signals and implicates the active participation of sIg during the process of antigen-mediated B cell activation.« less

Directory of Academic Institutions and Organizations Offering Drug, Alcohol, and Employee Assistance Program Educational Resources.

ERIC Educational Resources Information Center

National Inst. on Drug Abuse (DHHS/PHS), Rockville, MD.

This directory lists academic institutions, State offices of alcohol and drug abuse, and national organizations which offer drug, alcohol, and employee assistance program (EAP) educational resources. A matrix format is used. Entries include name, address, telephone number, and contact person. A dot appears directly under column headings which are…

Losartan Attenuates Scar Formation in Filtering Bleb After Trabeculectomy.

PubMed

Shi, Huimin; Wang, Huiying; Fu, Shuhao; Xu, Kang; Zhang, Xiaoyan; Xiao, Yiqin; Ye, Wen

2017-03-01

To examine the effects of losartan on scar formation after trabeculectomy and on fibrotic changes of human Tenon's fibroblasts (HTFs). Trabeculectomy was performed on New Zealand rabbits. They were randomized to receive one of the following treatments: 0.9% normal saline, mitomycin-C, or one of the three doses of losartan. Bleb morphology, IOP, and histopathology examination were performed. Primary cultured HTFs were treated with losartan or vehicle, with or without angiotensin II (Ang II). Cell proliferation was assessed by Cell Counting Kit-8 assay, and cell migration was detected by scratch wound and transwell assay. Transdifferentiation was evaluated through the expression of α-smooth muscle actin (α-SMA) by immunofluorescence, real-time PCR, and Western blot. The expression of fibronectin (FN) was evaluated by real-time PCR and Western blot. An amount of 5 mg/mL of losartan subconjunctival injection significantly decreased IOP postoperatively and attenuated wound healing of the filtering bleb in the rabbit model. Immunostaining results showed less myofibroblast and collagen deposition around the bleb area in the losartan-treated eyes. Losartan (10-5 M) in vitro significantly attenuated Ang II's stimulatory effects on proliferation and migration of HTFs. Expressions of α-SMA and FN in these cells were also decreased by losartan pretreatment. Losartan attenuates scar formation of filtering bleb after trabeculectomy likely via decreasing proliferation, migration, transdifferentiation, and extracellular matrix deposition of Tenon's fibroblasts. These results indicate that losartan may be an effective therapeutic agent in preventing bleb scar formation and in improving surgical outcome after trabeculectomy.

The Anticancer Effects of Radachlorin-mediated Photodynamic Therapy in the Human Endometrial Adenocarcinoma Cell Line HEC-1-A.

PubMed

Kim, Su-Mi; Rhee, Yun-Hee; Kim, Jong-Soo

2017-11-01

We investigated the effect of photodynamic therapy (PDT) using radachlorin on invasion, vascular formation and apoptosis by targeting epidermal growth factor receptor (EGFR)/vascular endothelial growth factor receptor 2 (VEGFR2) signaling pathways in the HEC-1-A endometrial adenocarcinoma cell line. To investigate the apoptotic pathway, we performed the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, and western blot analysis. We also evaluated the effects of PDT on tubular capillary formation in and invasion by HEC-1-A cells with a tube formation assay, invasion assay, prostaglandin E2 (PGE2) assay, and western blot analysis. PDT had anticancer effects on HEC-1-A through activation of the intrinsic pathway of apoptosis via caspase-9 and poly-(ADP-ribose) polymerase (PARP). PDT also inhibited tubular capillary formation in and invasion by HEC-1-A under VEGF pretreatment, that resulted from down-regulation of VEGFR2, EGFR, Ras homolog gene family/ member A (RhoA) and PGE2. These results are indicative of the specificity of radachlorin-mediated PDT to VEGF. The major advantage of radachlorin-mediated PDT is its selectivity for cancer tissue while maintaining adjacent normal endometrial tissue. Therefore, radachlorin-mediated PDT might offer high anticancer efficacy for endometrial adenocarcinoma and an especially useful modality for preserving fertility. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

The cotton centromere contains a Ty3-gypsy-like LTR retroelement.

PubMed

Luo, Song; Mach, Jennifer; Abramson, Bradley; Ramirez, Rolando; Schurr, Robert; Barone, Pierluigi; Copenhaver, Gregory; Folkerts, Otto

2012-01-01

The centromere is a repeat-rich structure essential for chromosome segregation; with the long-term aim of understanding centromere structure and function, we set out to identify cotton centromere sequences. To isolate centromere-associated sequences from cotton, (Gossypium hirsutum) we surveyed tandem and dispersed repetitive DNA in the genus. Centromere-associated elements in other plants include tandem repeats and, in some cases, centromere-specific retroelements. Examination of cotton genomic survey sequences for tandem repeats yielded sequences that did not localize to the centromere. However, among the repetitive sequences we also identified a gypsy-like LTR retrotransposon (Centromere Retroelement Gossypium, CRG) that localizes to the centromere region of all chromosomes in domestic upland cotton, Gossypium hirsutum, the major commercially grown cotton. The location of the functional centromere was confirmed by immunostaining with antiserum to the centromere-specific histone CENH3, which co-localizes with CRG hybridization on metaphase mitotic chromosomes. G. hirsutum is an allotetraploid composed of A and D genomes and CRG is also present in the centromere regions of other AD cotton species. Furthermore, FISH and genomic dot blot hybridization revealed that CRG is found in D-genome diploid cotton species, but not in A-genome diploid species, indicating that this retroelement may have invaded the A-genome centromeres during allopolyploid formation and amplified during evolutionary history. CRG is also found in other diploid Gossypium species, including B and E2 genome species, but not in the C, E1, F, and G genome species tested. Isolation of this centromere-specific retrotransposon from Gossypium provides a probe for further understanding of centromere structure, and a tool for future engineering of centromere mini-chromosomes in this important crop species.

Detergent Screening and Purification of the Human Liver ABC Transporters BSEP (ABCB11) and MDR3 (ABCB4) Expressed in the Yeast Pichia pastoris

PubMed Central

Stindt, Jan; Smits, Sander H. J.; Schmitt, Lutz

2013-01-01

The human liver ATP-binding cassette (ABC) transporters bile salt export pump (BSEP/ABCB11) and the multidrug resistance protein 3 (MDR3/ABCB4) fulfill the translocation of bile salts and phosphatidylcholine across the apical membrane of hepatocytes. In concert with ABCG5/G8, these two transporters are responsible for the formation of bile and mutations within these transporters can lead to severe hereditary diseases. In this study, we report the heterologous overexpression and purification of human BSEP and MDR3 as well as the expression of the corresponding C-terminal GFP-fusion proteins in the yeast Pichia pastoris. Confocal laser scanning microscopy revealed that BSEP-GFP and MDR3-GFP are localized in the plasma membrane of P. pastoris. Furthermore, we demonstrate the first purification of human BSEP and MDR3 yielding ∼1 mg and ∼6 mg per 100 g of wet cell weight, respectively. By screening over 100 detergents using a dot blot technique, we found that only zwitterionic, lipid-like detergents such as Fos-cholines or Cyclofos were able to extract both transporters in sufficient amounts for subsequent functional analysis. For MDR3, fluorescence-detection size exclusion chromatography (FSEC) screens revealed that increasing the acyl chain length of Fos-Cholines improved monodispersity. BSEP purified in n-dodecyl-β-D-maltoside or Cymal-5 after solubilization with Fos-choline 16 from P. pastoris membranes showed binding to ATP-agarose. Furthermore, detergent-solubilized and purified MDR3 showed a substrate-inducible ATPase activity upon addition of phosphatidylcholine lipids. These results form the basis for further biochemical analysis of human BSEP and MDR3 to elucidate the function of these clinically relevant ABC transporters. PMID:23593265

The Cotton Centromere Contains a Ty3-gypsy-like LTR Retroelement

PubMed Central

Luo, Song; Mach, Jennifer; Abramson, Bradley; Ramirez, Rolando; Schurr, Robert; Barone, Pierluigi; Copenhaver, Gregory; Folkerts, Otto

2012-01-01

The centromere is a repeat-rich structure essential for chromosome segregation; with the long-term aim of understanding centromere structure and function, we set out to identify cotton centromere sequences. To isolate centromere-associated sequences from cotton, (Gossypium hirsutum) we surveyed tandem and dispersed repetitive DNA in the genus. Centromere-associated elements in other plants include tandem repeats and, in some cases, centromere-specific retroelements. Examination of cotton genomic survey sequences for tandem repeats yielded sequences that did not localize to the centromere. However, among the repetitive sequences we also identified a gypsy-like LTR retrotransposon (Centromere Retroelement Gossypium, CRG) that localizes to the centromere region of all chromosomes in domestic upland cotton, Gossypium hirsutum, the major commercially grown cotton. The location of the functional centromere was confirmed by immunostaining with antiserum to the centromere-specific histone CENH3, which co-localizes with CRG hybridization on metaphase mitotic chromosomes. G. hirsutum is an allotetraploid composed of A and D genomes and CRG is also present in the centromere regions of other AD cotton species. Furthermore, FISH and genomic dot blot hybridization revealed that CRG is found in D-genome diploid cotton species, but not in A-genome diploid species, indicating that this retroelement may have invaded the A-genome centromeres during allopolyploid formation and amplified during evolutionary history. CRG is also found in other diploid Gossypium species, including B and E2 genome species, but not in the C, E1, F, and G genome species tested. Isolation of this centromere-specific retrotransposon from Gossypium provides a probe for further understanding of centromere structure, and a tool for future engineering of centromere mini-chromosomes in this important crop species. PMID:22536361

Augmented Expression of Polysaccharide Intercellular Adhesin in a Defined Staphylococcus epidermidis Mutant with the Small-Colony-Variant Phenotype▿

PubMed Central

Al Laham, Nahed; Rohde, Holger; Sander, Gunnar; Fischer, Andreas; Hussain, Muzaffar; Heilmann, Christine; Mack, Dietrich; Proctor, Richard; Peters, Georg; Becker, Karsten; von Eiff, Christof

2007-01-01

While coagulase-negative staphylococci (CoNS), with their ability to form a thick, multilayered biofilm on foreign bodies, have been identified as the major cause of implant-associated infections, no data are available about biofilm formation by staphylococcal small-colony variants (SCVs). In the past years, a number of device-associated infections due to staphylococcal SCVs were described, among them, several pacemaker infections due to SCVs of CoNS auxotrophic to hemin. To test the characteristics of SCVs of CoNS, in particular, to study the ability of SCVs to form a biofilm on foreign bodies, we generated a stable mutant in electron transport by interrupting one of the hemin biosynthetic genes, hemB, in Staphylococcus epidermidis. In fact, this mutant displayed a stable SCV phenotype with tiny colonies showing strong adhesion to the agar surface. When the incubation time was extended to 48 h or a higher inoculum concentration was used, the mutant produced biofilm amounts on polystyrene similar to those produced by the parent strain. When grown under planktonic conditions, the mutant formed markedly larger cell clusters than the parental strain which were completely disintegrated by the specific β-1,6-hexosaminidase dispersin B but were resistant to trypsin treatment. In a dot blot assay, the mutant expressed larger amounts of polysaccharide intercellular adhesin (PIA) than the parent strain. In conclusion, interrupting a hemin biosynthetic gene in S. epidermidis resulted in an SCV phenotype. Markedly larger cell clusters and the ability of the hemB mutant to form a biofilm are related to the augmented expression of PIA. PMID:17449620

Transcriptome Analysis of Arbuscular Mycorrhizal Roots during Development of the Prepenetration Apparatus1[W

PubMed Central

Siciliano, Valeria; Genre, Andrea; Balestrini, Raffaella; Cappellazzo, Gilda; deWit, Pierre J.G.M.; Bonfante, Paola

2007-01-01

Information on changes in the plant transcriptome during early interaction with arbuscular mycorrhizal (AM) fungi is still limited since infections are usually not synchronized and plant markers for early stages of colonization are not yet available. A prepenetration apparatus (PPA), organized in epidermal cells during appressorium development, has been reported to be responsible for assembling a trans-cellular tunnel to accommodate the invading fungus. Here, we used PPAs as markers for cell responsiveness to fungal contact to investigate gene expression at this early stage of infection with minimal transcript dilution. PPAs were identified by confocal microscopy in transformed roots of Medicago truncatula expressing green fluorescent protein-HDEL, colonized by the AM fungus Gigaspora margarita. A PPA-targeted suppressive-subtractive cDNA library was built, the cDNAs were cloned and sequenced, and, consequently, 107 putative interaction-specific genes were identified. The expression of a subset of 15 genes, selected by reverse northern dot blot screening, and five additional genes, potentially involved in PPA formation, was analyzed by real-time reverse transcription-polymerase chain reaction and compared with an infection stage, 48 h after the onset of the PPA. Comparison of the expression profile of G. margarita-inoculated wild type and the mycorrhiza-defective dmi3-1 mutant of M. truncatula revealed that an expansin-like gene, expressed in wild-type epidermis during PPA development, can be regarded as an early host marker for successful mycorrhization. A putative Avr9/Cf-9 rapidly elicited gene, found to be up-regulated in the mutant, suggests novel regulatory roles for the DMI3 protein in the early mycorrhization process. PMID:17468219

Development of field-applicable tests for rapid and sensitive detection of Candidatus Phytoplasma oryzae.

PubMed

Wambua, Lillian; Schneider, Bernd; Okwaro, Allan; Wanga, Joseph Odhiambo; Imali, Olive; Wambua, Peninah Nduku; Agutu, Lavender; Olds, Cassandra; Jones, Chris Stephen; Masiga, Daniel; Midega, Charles; Khan, Zeyaur; Jores, Joerg; Fischer, Anne

2017-10-01

Napier grass Stunt Disease (NSD) is a severe disease of Napier grass (Pennisetum purpureum) in Eastern Africa, caused by the leafhopper-transmitted bacterium Candidatus Phytoplasma oryzae. The pathogen severely impairs the growth of Napier grass, the major fodder for dairy cattle in Eastern Africa. NSD is associated with biomass losses of up to 70% of infected plants. Diagnosis of NSD is done by nested PCR targeting the phytoplasma DNA, which is difficult to perform in developing countries with little infrastructure. We report the development of an easy to use, rapid, sensitive and specific molecular assay for field diagnosis of NSD. The procedure is based on recombinase polymerase amplification and targets the imp gene encoding a pathogen-specific immunodominant membrane protein. Therefore we followed a two-step process. First we developed an isothermal DNA amplification method for real time fluorescence application and then transferred this assay to a lateral flow format. The limit of detection for both procedures was estimated to be 10 organisms. We simplified the template preparation procedure by using freshly squeezed phloem sap from Napier grass. Additionally, we developed a laboratory serological assay with the potential to be converted to a lateral flow assay. Two murine monoclonal antibodies with high affinity and specificity to the immunodominant membrane protein IMP of Candidatus Phytoplasma oryzae were generated. Both antibodies specifically reacted with the denatured or native 17 kDa IMP protein. In dot blot experiments of extracts from infected plant, phytoplasmas were detected in as little as 12,5 μg of fresh plant material. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Javahery, G.; Petrie, S.; Wang, J.

Results are reported for the reactions of the fullerene ions C[sub 60[center dot]+], C[sub 70[center dot]+], C[sub 60][sup 2+], C[sub 70][sup 2+], and C[sub 60[center dot]3+] with the nitriles HCN, CH[sub 3]CN, CH[sub 2]CHCN, CH[sub 3]CH[sub 2]CN, CH[sub 2]CHCH[sub 2]CN, CH[sub 3]CH[sub 2]CH[sub 2]CN, (CH[sub 3])[sub 2]CHCN, C[sub 2]N[sub 2], and CH[sub 2](CN)[sub 2]. The reactions were studied using a selected-ion flow tube (SIFT) at 294 [+-] 2 K and a helium buffer gas pressure of 0.35 [+-] 0.01 Torr and exhibited a wide range of chemical behavior. For the monocations C[sub 60][sup [center dot]+] and C[sub 70][sup [center dot]+],more » no detectable reaction occurred with any of the nitriles. For the dications C[sub 60][sup 2+], and C[sub 70][sup 2+], the only primary or secondary product channel evident in all instances was addition: tertiary association was seen to be considerably less efficient than the primary and secondary reactions, and the formation of a quadruple adduct C[sub 60](RCN)[sub 4][sup 2+] was only detected in the reaction with butyronitrile, CH[sub 3]CH[sub 2]CH[sub 2]CN. The observed primary rate coefficients show a very clear dependence upon the molecular complexity of the nitrile: association proceeds more efficiently for nitriles with a higher number of hydrogen atoms. This observation is explained in terms of a model which relates the number of C-H bonds - or, alternatively, the number of internal rotational modes - in the collision complex to the lifetime and probability of stabilization of this complex. 42 refs., 5 figs., 3 tabs.« less

The growth efficiency of high-redshift black holes

NASA Astrophysics Data System (ADS)

Pacucci, Fabio; Volonteri, Marta; Ferrara, Andrea

2015-09-01

The observational evidence that Super-Massive Black Holes (M• ˜ 109-10 M⊙) are already in place less than 1 Gyr after the big bang poses stringent time constraints on the growth efficiency of their seeds. Among proposed possibilities, the formation of massive (˜103-6 M⊙) seeds and/or the occurrence of super-Eddington (dot{M}>dot{M}_{Edd}) accretion episodes may contribute to the solution of this problem. In this work, using a set of astrophysically motivated initial conditions, we analytically and numerically investigate the accretion flow on to high-redshift (z ˜ 10) black holes to understand the physical requirements favouring rapid and efficient growth. Our model identifies a `feeding-dominated' accretion regime and a `feedback-limited' one, the latter being characterized by intermittent (duty cycles D ≲ 0.5) and inefficient growth, with recurring outflow episodes. We find that low-mass seeds (≲103-4 M⊙) evolve in the feedback-limited regime, while more massive seeds (≳105-6 M⊙) grow very rapidly as they are found in the feeding-dominated regime. In addition to the standard accretion model with a fixed matter-energy conversion factor (ɛ = 0.1), we have also explored slim disc models, appropriate for super-Eddington accretion, where radiation is trapped in the disc and the radiative efficiency is reduced (ɛ ≲ 0.04), which may ensure a continuous growth with dot{M} ≫ dot{M}_{Edd} (up to {˜ } 300 dot{M}_{Edd} in our simulations). Under these conditions, outflows play a negligible role and a black hole can accrete 80-100 per cent of the gas mass of the host halo (˜107 M⊙) in ˜10 Myr, while in feedback-limited systems we predict that black holes can accrete only up to ˜15 per cent of the available mass.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Huajuan; Zhao, Yanbao, E-mail: zhaoyb902@henu.edu.cn; Sun, Lei

Graphical abstract: A simple method for the synthesis of novel micrometer flower-like Cu/PVP architectures was introduced. Highlights: {yields} Micrometer flower-like copper/polyvinylpyrrolidone architectures were obtained by a simple chemical route. {yields} The amount of N{sub 2}H{sub 4}{center_dot}H{sub 2}O, the reaction temperature, the molar ratio of CuCl{sub 2} to PVP and different molecular weights of PVP play an important role in the controlling the morphology of the Cu/PVP architectures. {yields} A possible mechanism of the formation of Cu/PVP architectures was discussed. -- Abstract: Micrometer-sized flower-like Cu/polyvinylpyrrolidone (PVP) architectures are synthesized by the reduction of copper (II) salt with hydrazine hydrate in aqueousmore » solution in the presence of PVP capping agent. The resulting Cu/PVP architectures are investigated by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The Cu/PVP flowers have uniform morphologies with an average diameter of 10 {mu}m, made of several intercrossing plates. The formation of Cu/PVP flowers is a new kinetic control process, and the factors such as the amount of N{sub 2}H{sub 4}{center_dot}H{sub 2}O, reaction temperature, molar ratio of CuCl{sub 2} to PVP and molecular weight of PVP have significant effect on the morphology of Cu/PVP architectures. A possible mechanism of the formation of micrometer Cu/PVP architectures was discussed.« less

Theory of multiple quantum dot formation in strained-layer heteroepitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Lin; Maroudas, Dimitrios, E-mail: maroudas@ecs.umass.edu

2016-07-11

We develop a theory for the experimentally observed formation of multiple quantum dots (QDs) in strained-layer heteroepitaxy based on surface morphological stability analysis of a coherently strained epitaxial thin film on a crystalline substrate. Using a fully nonlinear model of surface morphological evolution that accounts for a wetting potential contribution to the epitaxial film's free energy as well as surface diffusional anisotropy, we demonstrate the formation of multiple QD patterns in self-consistent dynamical simulations of the evolution of the epitaxial film surface perturbed from its planar state. The simulation predictions are supported by weakly nonlinear analysis of the epitaxial filmmore » surface morphological stability. We find that, in addition to the Stranski-Krastanow instability, long-wavelength perturbations from the planar film surface morphology can trigger a nonlinear instability, resulting in the splitting of a single QD into multiple QDs of smaller sizes, and predict the critical wavelength of the film surface perturbation for the onset of the nonlinear tip-splitting instability. The theory provides a fundamental interpretation for the observations of “QD pairs” or “double QDs” and other multiple QDs reported in experimental studies of epitaxial growth of semiconductor strained layers and sets the stage for precise engineering of tunable-size nanoscale surface features in strained-layer heteroepitaxy by exploiting film surface nonlinear, pattern forming phenomena.« less

Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices

PubMed Central

Cirlin, GE; Tonkikh, AA; Zakharov, ND; Werner, P; Gösele, U; Tomm, JW; Elsaesser, T

2006-01-01

The luminescence properties of highly strained, Sb-doped Ge/Si multi-layer heterostructures with incorporated Ge quantum dots (QDs) are studied. Calculations of the electronic band structure and luminescence measurements prove the existence of an electron miniband within the columns of the QDs. Miniband formation results in a conversion of the indirect to a quasi-direct excitons takes place. The optical transitions between electron states within the miniband and hole states within QDs are responsible for an intense luminescence in the 1.4–1.8 µm range, which is maintained up to room temperature. At 300 K, a light emitting diode based on such Ge/Si QD superlattices demonstrates an external quantum efficiency of 0.04% at a wavelength of 1.55 µm.

Droplet heteroepitaxy of zinc-blende vs. wurtzite GaN quantum dots

NASA Astrophysics Data System (ADS)

Reese, C.; Jeon, S.; Hill, T.; Jones, C.; Shusterman, S.; Yacoby, Y.; Clarke, R.; Deng, H.; Goldman, Rs

We have developed a GaN droplet heteroepitaxy process based upon plasma-assisted molecular-beam epitaxy. Using various surface treatments and Ga deposition parameters, we have demonstrated polycrystalline, zinc-blende (ZB), and wurtzite (WZ) GaN quantum dots (QDs) on Si(001), r-Al2O3, Si(111), and c-GaN substrates. For the polar substrates (i.e. Si(111) and c-GaN), high-resolution transmission electron microscopy and coherent Bragg rod analysis reveals the formation of coherent WZ GaN QDs with nitridation-temperature-dependent sizes and densities. For the non-polar substrates (i.e. Si(001) and r-Al2O3) , QDs with strong near-band photoluminescence emission are observed and ZB GaN QD growth on Si(001) is demonstrated for the first time.

Multifunctional quantum dots-based cancer diagnostics and stem cell therapeutics for regenerative medicine.

PubMed

Onoshima, Daisuke; Yukawa, Hiroshi; Baba, Yoshinobu

2015-12-01

A field of recent diagnostics and therapeutics has been advanced with quantum dots (QDs). QDs have developed into new formats of biomolecular sensing to push the limits of detection in biology and medicine. QDs can be also utilized as bio-probes or labels for biological imaging of living cells and tissues. More recently, QDs has been demonstrated to construct a multifunctional nanoplatform, where the QDs serve not only as an imaging agent, but also a nanoscaffold for diagnostic and therapeutic modalities. This review highlights the promising applications of multi-functionalized QDs as advanced nanosensors for diagnosing cancer and as innovative fluorescence probes for in vitro or in vivo stem cell imaging in regenerative medicine. Copyright © 2015 Elsevier B.V. All rights reserved.

Getting There is Half the Fun

NASA Technical Reports Server (NTRS)

2004-01-01

This map shows the Mars Exploration Rover Spirit's past and future routes across the Gusev Crater floor. The solid red line shows where the rover has traveled so far, from lander to the rim of the large crater dubbed 'Bonneville.' The dotted red line indicates proposed future paths to the Columbia Hills. Rover team members have not yet decided which direction Spirit will travel across Bonneville's ejecta (the blanket of material expelled from it during formation) and toward the hills, as illustrated by the two diverging dotted lines. Along the way, Spirit will stop to investigate interesting targets, including craters and plain deposits. The journey to the hills is estimated to about two months, or 60 sols. The underlying image in this map was taken by the camera on NASA's Mars Global Surveyor orbiter.

One-pot synthesis of polythiol ligand for highly bright and stable hydrophilic quantum dots toward bioconjugate formation

NASA Astrophysics Data System (ADS)

Dezhurov, Sergey V.; Krylsky, Dmitry V.; Rybakova, Anastasia V.; Ibragimova, Sagila A.; Gladyshev, Pavel P.; Vasiliev, Alexey A.; Morenkov, Oleg S.

2018-03-01

A fast and efficient one-pot synthesis of thiol-terminated poly(vinylpirrolidone-co-maleic anhydride-co-ethylene glycol dimethacrylate) based heterobifunctional polymer (PTVP) has been developed. The polymer was used for the modification of quantum dots (QDs) to prepare water soluble and stable QDs with emission quantum yield as high as 80%. Using carbodiimide method, PTVP-capped red light-emitting QDs were conjugated to model monoclonal antibodies specific to glycoprotein B (gB) of Aujeszky’s disease virus (ADV) and successfully used in the lateral flow assay (LFA) for the detection of ADV gB in biological fluids. A comparative analysis of the sensitivity of the method was carried out using three types of QDs emitting in the red and far-red region.