Ag Columns Research Articles

Enantioselectivity and residue analysis of cycloxaprid and its metabolite in the pile and fermentation processing of Puer tea by ultraperformance liquid chromatography-high-resolution mass spectrometry.

The residues of cycloxaprid enantiomers and metabolites are investigated by ultraperformance liquid chromatography–high‐resolution mass spectrometry (UPLC‐HRMS) during raw and ripen Puer tea processing. A Chiralpak AG column with chiral stationary phase of amylose tris (3‐chloro‐5‐methylphenylcarbamate) is succeed to separate the 1R, 2S‐cycloxaprid, 1S, 2R‐cycloxaprid, and their metabolite, which is identified as nitrylene‐imidazolidine. It is not conversed 1R, 2S ‐cycloxaprid into 1S,2R‐cycloxaprid during Puer tea processing. The estimated half‐lives of the 1R,2S‐cycloxaprid and 1S,2R‐cycloxaprid are 0.97 and 1.1 h, respectively, and 1R,2S‐cycloxaprid decreases more quickly than the 1S,2R‐cycloxaprid. During raw Puer tea processing, the half‐lives of 1R, 2S‐cycloxaprid and 1S, 2R‐cycloxaprid are 1.68 h and 1.77 h, but the residue is still detected even if it is over 730 day. However, the half‐lives of 1R,2S ‐cycloxaprid and 1S,2R‐cycloxaprid are 0.60 day and 0.63 day during ripen tea processing. The amounts of metabolite are more in raw tea than in ripen tea; the terminal residues are still detected until 730 days during raw tea. A significant enantioselectivity of 1R, 2S‐cycloxaprid and 1S, 2R‐cycloxaprid is observed during raw tea or ripen tea processing. The degration result shows the enantioselectivity of cycloxaprid in raw or ripen Puer tea processing.

Morphological and Near-Field Properties of Silver Columnar Thin Film for Surface-Enhanced Raman Scattering

Noble metal sculptured thin films have attracted great research interest last decade as competitive surface-enhanced Raman scattering (SERS) substrates. However, the influences of the deposition conditions and the morphology on the plasmonic properties and SERS performance of the metal sculptured thin films have not been well understood due to the complexities of the morphology. In this work, the influences of the deposition angle and the height are investigated in both experiment and numerical simulation. A more accurate geometrical model based on the binarized scanning electron microscope images has been utilized to study the near-field plasmonic properties of Ag column thin films by taking account of the geometry irregularities, size distributions and random arrangement of the columns. It's found that the cross-sectional electric field enhancement is mainly dominated by the column density. When the deposition angle increases from 68° to 82° the SERS enhancement factors increases monotonously due to the increase of the self-shadow effect. While with the increase of height the SERS enhancement factors firstly increase to the largest value of 3.05 × 108 at the thickness of 694 nm then decrease because of competitive growth mechanism during the deposition. The detection limit of the optimized sample is found to be lower than 10-12 M. Our work could be helpful in understanding the SERS mechanism and useful to the optimization of metal sculptured thin films as SERS substrates.

Beam-induced atomic migration at Ag-containing nanofacets at an asymmetric Cu grain boundary

Abstract

Formation mechanism of plasmonic silver nanohexagonal particles made by galvanic displacement reaction

Multi-element XPS depth profile analysis made clear that Ag nanoscale hexagonal columns formed by newly-discovered galvanic displacement reaction are covered with Cu compounds which prevent Ag columns from fusion, resulting in stable hotspots.

Determination of glyphosate in heart blood of corpse by ion chromatography

A method for the determination of glyphosate in human blood by ion chromatography was established. The protein in heart blood from a corpse was precipitated with acetonitrile. The large molecules and Cl(-) in the supernatant were removed by a Dionex OnGuard II RP column and a Dionex OnGuard II Ag column, respectively. The filtrate was separated on an IonPac AS-19 column with KOH solution as eluent produced online by an eluent generator (EG). A suppressor with external water mode and a conductivity detector for the detection were used. The linear range of this method was 10 - 100 mg/L with a correlation coefficient (r2) of 0.9999. The limits of detection (LOD, S/N = 3) and quantification (LOQ, S/N = 10) of glyphosate in blood were 0.12 mg/L and 0.39 mg/L, respectively. The recoveries ranged between 95.2% -109.1% with the relative standard deviations (RSDs, n = 5) of 1.2% - 3.7%. The glyphosate content in a heart blood sample from a corpse in an actual case was 508 mg/L detected by this method. This method is simple, sensitive, accurate, and can rapidly provided reliable clues and evidences for glyphosate poisoning cases. This method can meet the needs of public security work.

Demonstration of silver micro-joints for flip-chip interconnect

► Silver micro-joints for flip-chip interconnect are formed between silicon chips and copper substrates by solid state bonding. ► No flux is used during bonding. ► Bonding temperature is compatible with typical reflow temperature of lead-free solders used in industries. ► Solid state bonding occurs when silver and copper atoms are brought within atomic distance so as to share electrons. ► Silver joints do not contain intermetallic compound, avoiding reliability issues associated with its growth. We report formation of silver (Ag) micro-joints for flip-chip interconnect. For demonstration, the micro-joints were made between silicon (Si) chips and copper (Cu) substrates. Two different Ag joint sizes, 40 and 15 μm, respectively, were produced. In experiment, arrays of cylindrical cavities were fabricated in thick photoresist on 2-in. Si wafers that were coated with chromium (Cr) and gold (Au) dual layer. The Si wafers are diced into 6 mm × 6 mm chips. The cavities were filled up with pure Ag by electroplating process. The photoresist was then stripped off. The Si chip with Ag columns was bonded to Cu substrate at 260 °C in 80 mTorr vacuum. During bonding, Ag columns deform and their surfaces conform to and mate with the surface of Cu substrate. Solid state bonding can incur when the Ag atoms and the Cu atoms are brought within atomic distance so that they share electrons. The Ag columns were well bonded to Cu. The ductile Ag joints are able to accommodate the thermal expansion mismatch between Si and Cu. The Ag joints do not contain any intermetallic compound (IMC). Accordingly, this interconnect technology avoids all reliability issues associated with IMC growth in solder-based flip-chip joints. Compared to solders, Ag joints have superior electrical and thermal properties. Pull test results show that the strength of 40 μm Ag joints passed MIL-STD-883H by wide margin.

40 μm Copper–Silver Composite Flip-Chip Interconnect Technology Using Solid-State Bonding

Copper–silver (Cu–Ag) composite flip-chip interconnect between silicon (Si) chips and Cu substrates is demonstrated. Array of Cu–Ag columns, each 28 μm in height and 40 μm in diameter, is electroplated on 2-in. Si wafers coated with chromium (Cr)/gold (Au) dual layer. The Si wafers are diced into 6 mm × 6 mm chips, each containing 50 × 50 Cu–Ag columns. The Si chip with Cu–Ag columns is bonded to Cu substrates at 260 °C in 80 mTorr vacuum. A bonding force of only 1.8 kg is applied, corresponding to 0.71 g per Cu–Ag column. During bonding, Ag atoms in Cu–Ag columns deform and their surfaces conform to and mate with the surface of Cu substrate. Solid-state bonding incurs when Ag atoms in Cu–Ag columns and Cu atoms in Cu substrates are brought within atomic distance so that they share conduction electrons. The Cu–Ag columns are indeed bonded to the Cu. No molten phase is involved in the bonding. The joint consists of 60% Cu section and 40% Ag section. The ductile Ag is able to accommodate the thermal expansion mismatch between Si and Cu. The Cu–Ag joints do not contain any intermetallic compound (IMC). This interconnect technology avoids all reliability issues associated with IMC growth in conventional soldering processes. Compared to tin-based lead-free solder joints, Cu–Ag composite joints have superior electrical and thermal properties.

40 $\mu{\rm m}$ Flip-Chip Process Using Ag–In Transient Liquid Phase Reaction

A flip-chip interconnect process at 180°C using the silver-indium (Ag-In) binary system is reported. An array of 50 × 50 flip-chip joints with 100 μm pitch and 40 μm joint diameter was fabricated. Each joint has the column structure of Ag/(Ag)/Ag2In/(Ag) that connects the silicon (Si) chip to the copper (Cu) substrate. The joint height is approximately 50 μm. In this structure, Ag2In is a dominating intermetallic compound in the Ag-In system with melting temperature of 660°C. (Ag) is a solid solution phase of Ag with In composition up to 20 at.%. It has a solidus temperature range of 695 to 962°C depending on In composition. In long-term operation, (Ag)/Ag2In/(Ag) is expected to gradually convert to a single (Ag) phase, which is more reliable. Thus, the flip-chip joints will get better in use. In fabrication, 50 × 50 Ag columns were made on Si wafer coated with chromium (Cr) and gold (Au). The Cu substrate was electroplated with Ag(10 μm)/In(5 μm)/Ag(thin). Si chips with Ag columns were bonded to Cu substrates at 180°C for 5 min. No flux was used. Cross-sectional scanning electron microscopy images show that all 50 Ag columns in one row are well bonded to the Cu substrate without visible voids or cracks. Energy-dispersive X-ray spectroscopy data indicate that the resulting column structure is Ag/(Ag)/Ag2In/(Ag). The process temperature of this new interconnect method is 80 °C below the typical reflow temperature of tin-based lead-free solders.

40 μm Silver Flip-Chip Interconnect Technology With Solid-State Bonding

Formation of pure silver (Ag) flip-chip interconnect of silicon (Si) chips on copper (Cu) substrates is reported. Arrays of Ag columns, each 36 μm in height and 40 μm in diameter, are fabricated on 2-in. Si wafers which are first coated with chromium (Cr)/gold (Au) dual layers. The Si wafers are diced into 6 mm × 6 mm chips, each having 50 × 50 Ag columns. The Si chip with Ag columns is directly bonded to Cu substrate at 260 °C in 80 mTorr vacuum to inhibit oxidation. The static bonding pressure is as low as 680 psi (4.69 MPa), corresponding to a load of 0.021 oz (0.60 g) per column. During bonding, the Ag columns deform and conform to the Cu substrate. They are well bonded to the Cu. No molten phase is involved in the bonding process. The joints consist of pure Ag only. The ductile Ag joints are able to accommodate the thermal expansion mismatch between Si and Cu. It is well known that in nearly all soldering processes used in electronic industries, intermetallic compound (IMC) formation is essential to make a solder joint. In the pure Ag interconnect, no IMCs exist. Thus, reliability issues associated with IMCs are eliminated. Compared to tin-based lead-free solders, pure Ag joints have superior electrical and thermal properties.

Suppressor T cell exosomes via miR-150* and antigen specific Ig light chains. (50.13)

Abstract Tolerance in contact sensitivity (CS) is due to CD8+ suppressor T cell (Ts) released factor (TsF) that is phenol chloroform extractable (PCE), in RNA fraction of Qiagen DNA/RNA separation column, sensitive to RNase A, not DNase nor trypsin, and also sensitive to RNase III; a property of double stranded RNA (dsRNA) like miRNA. Sizing electrophoresis indicated the active inhibitory RNA was about 75bp; the size of pre-miRNA. TsF RNA also inhibited in vitro IL-2 responses of T cell lines. We concluded that the small suppressive dsRNA was in the miRNA family TsF RNA is transported systematically in vivo in exosomes in the blood plasma of Ts donors. Remarkably, the exosomes act antigen (Ag) specifically due to surface coat of Ag-specific immunoglobulin free light chains, likely derived from activated B-1 B cells, and absorbed to receptors on the exosome surface. Ag specificity of the exosomes that eluted from the Ag column provided enriched exosome RNA for cDNA cloning and deep sequencing to identify candidate miRNA-150*. We postulate that the suppressive Ag-specific exosomes act systemically in an endocrine manner, via the blood, to target Ag specific effector T cells at distant sites, and inhibit their function via transfer of the inhibitory miRNA. This is the first demonstration of systemic immunoregulation by exosomes delivering inhibitory miRNA Ag specifically from donor suppressor T cells to distant target effector T cells in an endocrine manner.

吸着・加熱脱着分析におけるサンプリング前処理に関する検討

For adsorption—thermal desorption analysis, three ways of gas sampling pretreatments: 1) two water impingers (“Two impingers”); 2) two water impingers and two empty impingers (“Four impingers”); 3) cooling dehumidifier with Ag column (“Cooling dehumidifier”), were compared using aliphatic organic chlorinated compounds, chlorobenzenes and chlorophenols. Since the gas pretreatment system combines gas—liquid contact, distribution of chemicals between air and water was examined by a tank analogy model employing water volume, gas volume and Henry's constant. The compounds, Henry's constant of which is relatively low (those distribute more to water than to air) such as chlorophenols can neither pass “Two impingers” nor “For impingers” efficiently, while can survive at a rate of 70 % through “Cooling humidifier”, because it does not use water. Those compounds, the water solubility of which is high, such as chloroform and dichloromethane did not pass “Four impingers” although the estimated Henry's constant is adequately large. That suggests Henry's constant estimation involves considerable error for those compounds. Pretreatment loss caused by condensation and adsorption is sensitively affected by the property and the condition of the pretreatment device, namely, tetrachlorobenzene and larger compounds were significantly lost in “Four impingers” and “Cooling dehumidifier”, while “Two impingers” can pass pentachlorobenzene efficiently. Adsorption—thermal desorption property was studied using Carbotrap C. If the suctioned gas volume is increased, the recovery loss did not show exponential decrease, but the thermal desorption chart became split two peaks, main and shoulder, and desorption velocity went slow. That suggests the chemicals has diffused into the inner of the adsorbent. For the sake of the optimization of adsorption—thermal desorption analysis, limitation of analyzed chemical to avoid instrumental memory, and sensitive detection to quick determination and down-sizing of sampled gas volume.

Antibodies reactive to Trypanosoma cruzi epimastigotes or amastigotes express different idiotypic patterns if from patients with different clinical forms of Chagas' disease.

Antibodies (Abs) were purified from pooled sera of patients with either indeterminate (IND or I) or cardiac (CARD or C) Chagas' disease, on either epimastigote (EPI or E) or amastigote-enriched (AMAST or A) antigen (Ag) columns and their idiotypic (Id) expression examined. Anti-Id rabbit Abs were raised to the different preparations (E-IdI, E-IdC, A-IdI and A-IdC). Competitive ELISAs using anti-Ids were able to discriminate between IdI and IdC, disregarding Ag reactivity. E-IdI and A-IdI present different inhibitory abilities, as do E-IdC and A-IdC, but IdC always competes with IdI for anti-IdI comparably. In contrast, a 4-8-fold increase of IdI is required to compete in parallel with IdC for anti-IdC. Therefore, Ids from IND patients share only low levels of the Ids that are most characteristic of CARD patients. While some CARD Abs also express Ids in common with IND patients, these studies reveal that CARD Abs express some Ids that are characteristic to only CARD patients, and these Ids are present on Abs purified with either EPI or AMAST.

Utilization of Soft Acid/Base Interactions in Low Molecular Weight Biochemical Separations

Categorization of acid/base interactions using hard soft acid base (HSAB) theory suggested that sulfur-containing low molecular weight biological molecules could be specifically targeted for reversible complexation using soft metal ions. A viable method of employing soft metal ions for bioseparations is to immobilize Ag(I) and Pt(II) ions using a soft ligand such as thiourea. This immobilization chemistry allows for the use of Ag(I) columns that are stable in the presence of chloride and phosphate ions in the mobile phase, and it enhances the complexation chemistry of Ag(I) and Pt(II) ions toward solutes which are soft bases. Because chloride ions are soft bases, NaCl can be used for competitive elution. However, in amino acid separations, electrostatic and hydrophobic interactions influence the selectivity and capacity of Ag(I) and Pt(II) columns. A detailed study of the effects of Ag(I) ion loading and pH on the retention time of methionine, histidine, and tryptophan illustrates the need for accounting for Lewis acid/base, electrostatic, and hydrophobic interactions in biological molecule separations.

Retention Behavior of Amino Acids Using Immobilized Ag(I) Chromatography

AbstractA mathematical description of retention times for several amino acids on a polyacrylamide resin containing immobilized Ag(I) is presented in this paper. Immobilization of Ag(I) ions onto a chromatography support allows for the expansion of immobilized metal affinity chromatography (IMAC) to include soft acid/soft base interactions. For the retention of methionine, histidine, and tryptophan, a mathematical model is presented that rationalizes the retention behavior of these amino acids on a Ag(I) column as a function of silver ion loading and pH. The pH effect is important in that methionine is retained longer than histidine at pH values below 5, while at pH 7 histidine is retained longer than methionine. The effects of nonspecific interactions with the modified polymer, electrostatic interactions, and soft acid/soft base interactions are also taken into account by the model. This approach may also be useful for modeling the retention times of amino acids on other types of IMAC columns.

Monoclonal, antigen-specific, T cell contrasuppressor factor expresses determinants of TCR alpha-chain (not necessarily TCR beta-chain), having a molecular mass of about 40 kDa.

Contrasuppression is a regulatory T cell activity that acts on helper and contact sensitivity effector T cells to protect them from the action of suppressor T cells. In this study, we examined a monoclonal Ag-specific T cell-secreted contrasuppressor factor (TcsF) with Ag specificity for the hapten TNP (trinitrophenyl). This factor positively influences the adoptive cell transfer of contact sensitivity in the presence of active suppression. Results presented in this report demonstrate a relationship between TcsF and the alpha,beta-T cell receptor (TCR). We found that TcsF bound to mAb anti-TCR-alpha (H28) and to mAb anti-TCR-beta (H57) immunoaffinity columns, but not to a mAb anti-TCR-gamma,delta (UC7) column. The bound contrasuppressor activity could be recovered from these affinity columns by base elution. Reduction of TcsF with DTT followed by alkylation with methylmethanethiosulfonate (MMTS), demonstrated that the active subunit of TcsF bound to and eluted from anti-TCR-alpha, but not to anti-TCR-beta columns. The active TcsF that bound to anti-TCR-alpha but not to the anti-TCR-beta column was shown subsequently to have the ability to bind to specific Ag columns TNP-BSA and TNP-BGG Sepharose 4B. The TcsF could be successfully recovered later from Ag columns; thus suggesting that the Ag-binding domain for mAb, and the biologic activity, resides on the TCR-alpha chain of TcsF. Separation of TcsF on SDS-PAGE under reducing conditions, followed by elution and renaturation of proteins from the gel slices, showed that a 35 to 40 kDa protein had the T cell contrasuppressive activity. Western blot analysis of nonreduced TNP-binding TcsF revealed TCR-alpha,beta determinants on an 80-kDa native molecule similar to TCR-alpha,beta from a helper T cell clone. In summary, Ag-specific, Ag-binding T cell-derived contrasuppressor factor has serologic determinants of TCR-alpha and TCR-beta chains, but the TCR-alpha chain and not the TCR-beta chain is required for biologic function. This TCR-alpha determinant-containing factor is absorbed by specific Ag (TNP) columns. SDS-PAGE analysis under reducing conditions suggested a molecular weight of about 35 to 40 kDa for the TNP-specific TcsF. The mechanism of action of the TCR-alpha-containing contrasuppressor factor in the regulation contact sensitivity is discussed.

A monoclonal antibody raised to lipomodulin recognizes T suppressor factors in two independent hapten-specific suppressor networks.

Five different Ag-binding suppressor factors from two types of hapten-specific Ts cell hybridomas (TsF1 inducer and TsF3 effector factors) were bound by an anti-lipomodulin mAb (141-B9), that crossreacts with rodent glycosylation inhibition factor (GIF). The Ag-specific suppressor activity in these hybridoma supernatants was bound by anti-lipomodulin columns and could be recovered by elution at acid pH. Additional evidence for the expression of lipomodulin/GIF activity on these TsF molecules was demonstrated by the ability of the eluted fractions to inhibit the glycosylation of IgE-binding peptides during their biosynthesis. The same biologic activity is associated with GIF and lipomodulin. The relationship between TsF and lipomodulin/GIF was confirmed in a serologic assay, which showed that TsF1 and TsF3 molecules, whether purified over Ag, anti-IJ or anti-TsF columns, are recognized by the mAb. 141-B9. The combined results indicate that Ag-binding Ts factors share a common antigenic determinant with phospholipase inhibitory proteins such as lipomodulin and GIF. In addition, the demonstration of glycosylation regulatory activity carried on these TsF molecules suggests a possible mode for their bioactivity.