Разработка приспособления для сборки и сварки балки навески

Цель работы –разработка приспособления для сборки и сварки балки навески, которое позволит ускорить процесс подготовки деталей перед сваркой, будет иметь возможность поворота изделия и доступ к сварке со всех сторон. Проведен технико-экономический анализ процесса сборки и сварки балки навески. Дано обоснование эффективности предлагаемого приспособления и малый срок его окупаемости.The object of this study is to build technology and welding hinge beams. Purpose - improving the technology of assembling and welding of sample beams, so as to speed up the process of preparing the parts prior to welding, and have the ability to rotate the product and access to welding on all sides. Spend a technical and economic analysis of the process of assembly and welding hinge beams. The substantiation of the effectiveness of the proposed adaptations and short term payback

Multistep photoinduced electron transfer in self-organised nano-scale porphyrin triads

Well-defined structurally organised porphyrin triads of a controlled geometry andnanoscale size have been formed in liquid solutions using the combination of a covalent approach and non-covalent self-assembly. The triads contain zinc-octaethylporphyrin chemical dimer, (ZnOEP)₂Ph, with covalently linked electron acceptors (p-benzoquinone, Q or pyromellitimide, Pim), and additional dipyridyl-substituted tetrapyrrole extra-ligands. Steady-state, picosecond fluorescence (∆ₜ½ ≈ 75 ps) and femtosecond pump–probe (⊿½ ≈ 280 fs) data show that non-radiative deactivation of the dimer S₁-states (τₛ < 1 ps) is due to both the S–S energy transfer (ZnOEP)₂Ph→extra-ligand and the sequential photoinduced electron transfer (ZnOEP)₂Ph→Q (or Pim) at r_DA = 10.8 Å. The additional decay shortening of the extra-ligand S₁-states by 3–6 times (toluene, 293 K) is attributed to the increased “superexchange” mediated long distant (r_DA ≈ 18–21 Å) one-step electron transfer extra-ligand→Q (or Pim). © 2002 Elsevier Science B.V. All rights reserved

Influence of Single Dye Molecules on Temperature and Time Dependent Optical Properties of CdSe/ZnS Quantum Dots: Ensemble and Single Nanoassembly Detection

Optical spectroscopy on ensembles and single CdSe/ZnS semiconductor quantum dots (QDs) demonstrates a competition of trap and near band edge photoluminescence (PL). This competition can be markedly influenced by a few surface attached pyridyl functionalized dye molecules (porphyrins or perylene diimides) forming nanoassemblies with well defined geometries. Temperature variation and related changes in absorption and emission reveal sharp changes of the ligand shell structure in a narrow temperature range for organic (TOPO and amine) surfactants (phase transition). The effects on QD PL at this transition become considerably pronounced upon attachment of only a few dye molecules to QD surface. Moreover, under ambient conditions amine capped QDs are photodegraded in the course of time. This process is enhanced by attached dye molecules both on the ensemble and single particle/dye level. This investigation elaborates the importance of (switchable) surface states for the characterization of the PL of QDs. © 2012 Elsevier B.V. All rights reserved

Formation and optical properties of self-organized pentameric porphyrin arrays

Principles of formation, electronic absorption and fluorescence spectra are reported for self-organized pentameric arrays of tetrapyrrolic macrocycles. In these arrays two molecules of Zn-porphyrin dimers, Zn(II)l,4-bis[5-(10,15,20-tri-p-hexylphenylporphyrinyl)]-benzene ((ZnHTPP)₂) are bound via one molecule of a tetrapyridyl-substituted free base of porphyrin or tetrahydroporphyrin. The process of self-assembly is based on the twofold coordination of the central Zn ions !n the dimer with the nitrogen atoms of the pyridyl rings in the free base which is strong enough to make the complexes stable at room temperature. The formation of the complexes can be followed by changes in the absorption bands of (ZnHTPP)₂ characteristic of an axial extra-ligation of Zn-porphyrins with pyridine or pyridyl-substituted compounds. The spectral behavior of the free bases in the pentads is determined by a non-planar distortion of their macrocycle caused by the two-point binding with the dimers. The fluorescence intensity of the Zn-porphyrin dimer decreases essentially upon complexation with the tetrapyridyl-substituted free bases. This quenching effect is assigned to a singlet-silaglet energy transfer from the complexed Zn-porphyrin dimers to the free base subunit in the pentad

Time-resolved spectroscopy of single quantum dots.

We have performed a series laser time-resolved experiments for single CdSe/ZnS QDs spin coated onto a quartz substrate at 293 K.DFG Priority Unit FOR 877 and BSPSR “Convergence 3.2.08

Complexation and interchromophoric interactions in self-organized porphyrin and chlorin triads

Spectral properties and equilibrium constants of multimolecular complexes (triads) formed by 2-fold coordination of dipyridyl-substituted free bases of porphyrin, chlorin, or tetrahydroporphyrin with Zn-porphyrin and Zn-chlorin dimers bridged by either of two different spacers between the monomeric entities have been studied in methylcyclohexane at room temperature. The ability of the dimers bridged by a -CH2-CH2- spacer to form complexes with the free bases is found to be much lower than that for the dimers with a phenyl spacer having complexation constants up to Kc = 5 × 10⁷ M⁻¹. The complexation equilibrium is also affected strongly by the chemical nature of the free base and the position of the pyridyl substituents. Spectral effects occurring upon complexation in absorption spectra of the dimers are mainly due to ligation effects. Strong quenching of the dimer fluorescence in the complexes is attributed to effective singlet-singlet energy transfer (ET) to the ligands

Spectroscopy of interchromophoric interactions in self-organized porphyrin and chlorin complexes

Spectral-luminescent properties of multimolecular complexes (triads and pentads, complexation constants range from 5∙10⁶ to 5∙10⁷ M⁻¹) formed by two-fold coordination of dipyridyl and tetra-pyridyl substituted porphyrin or related molecules with Zn-porphyrin and Zn-chlorin dimers having various spacers between macrocycles (-CH₂-CH₂- or phenyl ring) have been studied in methylcyclohexane solutions in a temperature range from 140 to 360 K. The red shift of Zn-dimer electronic Q- and B-bands (∆ν≤550 cm⁻¹) upon complexation with pyridyl containing ligands is explained in terms of extra-ligation which influences the relative position for HOMO’s a₁ᵤ, and a₂ᵤ according to the four-orbital model. The splitting of Zn-dimer B-bands (∆E≥600 cm⁻¹) as well as the significant transformation of these bands in trimeric and pentameric complexes (redistribution of the absorption band intensities in Soret region and appearance of complicated splitted spectral manifolds ∆ν≤1900 cm⁻¹) is connected with excitonic interactions of strong B-transitions of π-conjugated macrocycles included in the complex. Observed experimental splittings are compared with theoretical values calculated using the point dipole approximation and a computer-simulated geometry of the complexes under investigation. It has been observed that mutual influence of π-electronic macrocycles in the complexes leads to the red shift of porphyrin extra-ligand free base Q-bands (∆ν≈120 cm⁻¹) and is accompanied by quenching a fluorescence of certain components

Identification and assignment of porphyrin-CdSe Hetero-nanoassemblies

Hetero-nanoassemblies in toluene solution are formed via anchoring pyridyl substituted free base porphyrin molecules on the colloidal core-shell semiconductor nanocrystals CdSe/ZnS. The formation can be identified via quenching of semiconductor photoluminescence and followed via spectral changes of porphyrin spectral properties such as fluorescence, fluorescence decay and absorption. Interpreting these changes we estimate that even at high molar ratios on average only one molecule is anchored on one nanocrystal. Experimentally determined complexation constants are comparable to those observed for multi-porphyrin complexes. © 2007 Elsevier B.V. All rights reserved

Excess Mortality Rate During Adulthood Among Danish Adoptees

BACKGROUND AND OBJECTIVE: Adoption studies have been used to disentangle the influence of genes from shared familial environment on various traits and disease risks. However, both the factors leading to adoption and living as an adoptee may bias the studies with regard to the relative influence of genes and environment compared to the general population. The aim was to investigate whether the cohort of domestic adoptees used for these studies in Denmark is similar to the general population with respect to all-cause mortality and cause-specific mortality rates. METHODS: 13,111 adoptees born in Denmark in 1917, or later, and adopted in 1924 to 1947 were compared to all Danes from the same birth cohorts using standardized mortality ratios (SMR). The 12,729 adoptees alive in 1970 were similarly compared to all Danes using SMR as well as cause-specific SMR. RESULTS: The excess in all-cause mortality before age 65 years in adoptees was estimated to be 1.30 (95% CI 1.26-1.35). Significant excess mortality before age 65 years was also observed for infections, vascular deaths, cancer, alcohol-related deaths and suicide. Analyses including deaths after age 65 generally showed slightly less excess in mortality, but the excess was significant for all-cause mortality, cancer, alcohol-related deaths and suicides. CONCLUSION: Adoptees have an increased all-cause mortality compared to the general population. All major specific causes of death contributed, and the highest excess is seen for alcohol-related deaths

Self-assembled nanoscale photomimetic models: structure and related dynamics

Using static and time-resolved measurements, dynamics of non-radiative relaxation processes have been studied in self-assembled porphyrin triads of various geometry, containing the main biomimetic components, Zn–porphyrin dimers, free-base extra-ligands (porphyrin, chlorin or tetrahydroporphyrin), and electron acceptors A (quinone or pyromellitimide). The strong quenching of the dimer fluorescence is due to energy and sequential electron transfer (ET) processes to the extra-ligand (~0.9–1.7 ps), which are faster than a slower ET (34–135 ps) from the dimer to covalently linked A in toluene at 293 K. The extra-ligand S₁-state decay (τₛ = 940–2670 ps) is governed by competing processes: a bridge (dimer) mediated long-range (r_DA = 18–24 Å) superexchange ET to an acceptor, and photoinduced hole transfer from the excited extra-ligand to the dimer followed by possible superexchange ET steps to low-lying charge transfer states of the triads. The subsequent ET steps dimer → monomer → A taking place in the triads, mimic the sequence of primary ET reactions in photosynthetic reaction centers in vivo. © 2002 Elsevier Science B.V. All rights reserved