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排序方式: 共有170条查询结果,搜索用时 31 毫秒
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104.
Stroink T Schravendijk P Wiese G Teeuwsen J Lingeman H Waterval JC Bult A de Jong GJ Underberg WJ 《Electrophoresis》2003,24(6):1126-1134
Since biologically active peptides usually exhibit their effects in low concentrations, the development of sensitive analytical methods has become a challenge. In this paper, a multidimensional system is presented, consisting of a size-exclusion chromatographic (SEC) separation followed by a trapping procedure on a 4 mm x 3 mm ID reversed-phase C18 (RP18) column with subsequent elution of the trapped fraction and separation by capillary zone electrophoresis (CZE). The system has been tested with mixtures of six enkephalins and albumin, mimicking biological matrices such as plasma and cerebrospinal fluid. After separation of albumin from the enkephalins in the SEC dimension a heart-cut of 200 micro L, containing the enkephalin peak, is taken, concentrated on the RP18 microcolumn and, after elution with a 20 micro L plug of 80% acetonitrile, electrokinetically injected into the CZE system, where stacking and separation is achieved. While validation shows generally good linearity and reproducibility, the quantitation limit with UV detection is acceptable (2.5 micro g/ mL with an injection volume of 50 micro L). 相似文献
105.
Saxton OH Schalk T Schumm BA Schwiening J Serbo VV Shapiro G Sinev NB Snyder JA Staengle H Stahl A Stamer P Steiner H Su D Suekane F Sugiyama A Suzuki A Swartz M Taylor FE Thom J Torrence E Usher T Va'vra J Verdier R Wagner DL Waite AP Walston S 《Physical review letters》2000,85(24):5059-5063
We present the first direct measurement of A(s), the parity-violating coupling of the Z0 boson to the strange quark, using approximately 550 000 e(+)e(-)-->Z0-->hadrons events recorded by the SLC Large Detector with a polarized e(-) beam. We tagged Z0-->s&smacr; events by the absence of B or D hadrons and the presence in each hemisphere of a high momentum K+/- or K(0)(s). Fitting the polar angle distributions of the strangeness-signed thrust axis gave A(s) = 0.895+/-0.066(stat)+/-0.062(syst). The analyzing power and uu+d&dmacr; background were constrained using the data, greatly reducing any model dependence. 相似文献
106.
Saxton OH Schalk T Schumm BA Schwiening J Serbo VV Shapiro G Sinev NB Snyder JA Staengle H Stahl A Stamer P Steiner H Su D Suekane F Sugiyama A Swartz M Taylor FE Thom J Usher T Va'vra J Verdier R Wagner DL Waite AP Walston S Wang J Weidemann AW 《Physical review letters》2000,84(19):4300-4304
We have developed a new technique for inclusive reconstruction of the energy of B hadrons. The excellent efficiency and resolution of this technique allow us to make the most precise determination of the b-quark fragmentation function, using e(+)e(-)-->Z0 decays recorded in the SLAC Large Detector experiment. We compared our measurement with the predictions of a number of fragmentation models. We excluded several of these models and measured the average scaled energy of weakly decaying B hadrons to be = 0.714+/-0. 005(stat)+/-0.007(syst)+/-0.002 (model dependence). 相似文献
107.
Andreas Thom 《Israel Journal of Mathematics》2017,219(1):469-478
We prove new upper bounds of the form O(n/log(n)2?ε ) for the length of laws that hold for all groups of size at most n — improving on previous results of Bou-Rabee and Kassabov–Matucci. The methods make use of the classification of finite simple groups. Stronger bounds are proved in case the groups are assumed to be nilpotent or solvable. 相似文献
108.
Tatijana Markoska Davor Daniloski Todor Vasiljevic Thom Huppertz 《Molecules (Basel, Switzerland)》2021,26(24)
This study investigated structural changes in β-casein as a function of temperature (4 and 20 °C) and pH (5.9 and 7.0). For this purpose, nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy were used, in conjunction with chemometric analysis. Both temperature and pH had strongly affected the secondary structure of β-casein, with most affected regions involving random coils and α-helical structures. The α-helical structures showed great pH sensitivity by decreasing at 20 °C and diminishing completely at 4 °C when pH was increased from 5.9 to 7.0. The decrease in α-helix was likely related to the greater presence of random coils at pH 7.0, which was not observed at pH 5.9 at either temperature. The changes in secondary structure components were linked to decreased hydrophobic interactions at lower temperature and increasing pH. The most prominent change of the α-helix took place when the pH was adjusted to 7.0 and the temperature set at 4 °C, which confirms the disruption of the hydrogen bonds and weakening of hydrophobic interactions in the system. The findings can assist in establishing the structural behaviour of the β-casein under conditions that apply as important for solubility and production of β-casein. 相似文献
109.
David Chukwuma Izuogu Takefumi Yoshida Goulven Cosquer Jonnie N. Asegbeloyin Haitao Zhang Alex J. W. Thom Masahiro Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(27):6036-6049
Acetato-bridged palladium–lanthanide tetranuclear heterometallic complexes of the form [Pd2Ln2(H2O)2(CH3COO)10] ⋅ 2 CH3COOH [Ln2=Ce2 ( 1 ), Pr2 ( 2 ), Nd2 ( 3 ), Sm2 ( 4 ), Tb2 ( 5 ), Dy2 ( 6 ), Dy0.2Y1.8 ( 6′′ ), Ho2 ( 7 ), Er2 ( 8 ), Er0.24Y1.7 ( 8′′ ), Tm2 ( 9 ), Yb2 ( 10 ), Y2( 11 )] were synthesised and characterised by experimental and theoretical techniques. All complexes containing Kramers lanthanide ions [Ln3+=Ce ( 1 ), Nd ( 3 ), Sm ( 4 ), Dy ( 6 ), DyY ( 6′′ ), Er ( 8 ), ErY ( 8′′ ), Yb ( 10 )] showed field-induced slow magnetic relaxation, characteristic of single-molecule magnetism and purely of molecular origin. In contrast, all non-Kramers lanthanide ions [Ln3+=Pr ( 2 ), Tb ( 5 ), Ho ( 7 ), Tm ( 9 ), Y3+ ( 11 ) is diamagnetic and non-lanthanide] did not show any slow magnetic relaxation. The variation in the electronic structure and accompanying consequences across the complexes representing all Kramers and non-Kramers lanthanide ions were investigated. The origin of the magnetic properties and the extent to which the axial donor–acceptor interaction involving the lanthanide ions and an electron-deficient orbital of palladium affects the observed magnetic and electronic properties across the lanthanide series are presented. Unique consistent electronic and magnetic properties of isostructural complexes spanning the lanthanide series with properties dependent on whether the ions are Kramers or non-Kramers are reported. 相似文献
110.
This article presents a model of damage accumulation in irradiated crystals. This model is based on the assumption that the
damage accumulation occurs through a series of structural transformations triggered by the destabilization of the current
structure of crystals. Formal equations describing the damage accumulation build-up and experimental assessment of the model
are presented and discussed in the framework of the actual knowledge of radiation effects in oxide crystals (yttria-stabilized
zirconia (YSZ) and magnesium-aluminate spinel (MAS)), silicon carbide crystals and zirconia implanted nickel crystals. 相似文献