Разработка и исследования ионного Br - диода

Объектом исследования является ионный Br–диод с внешним магнитным полем. Целью работы является разработка конструкции ионного Br–диода и проведение на нем исследовании по генерации мощных ионных пучков различного массового состава и фокусировки ионного пучка, для повышения эффективности работы ионного диода и ресурса работы анодного покрытия. В процессе исследования проводились расчеты по определению размеров и конструкции ионного Br-диода, параметров магнитного поля, создаваемого внешним источником питания. По разработанному Br-ионному диоду проводились экспериментальные исследования различных эмиссионных покрытий анода, а также опыты по улучшению фокусировки ионного пучка.The object of investigation is an ion Br-diode with an external magnetic field. The aim of the work is to develop the design of the ion Br-diode and to carry out research on the generation of powerful ion beams of various mass composition and focusing of the ion beam, in order to increase the efficiency of the ion diode and the life of the anode coating. During the research, calculations were made to determine the size and design of the ion Br-diode, the parameters of the magnetic field created by an external power source. Based on the developed Br-ion diode, experimental studies of various emission coatings of the anode, as well as experiments to improve the focusing of the ion beam, were carried out

Synthesis and characterization of organic high-spin molecules

$\it m$-Xylylene und 1,3,5-Trimethylenbenzol sind non-Kekulé Kohlenwasserstoffe mit Triplett- bzw. Quartettgrundzuständen, die als $\pi$,$\pi$-Diradikal bzw. $\pi$,$\pi$,$\pi$-Triradikal klassifiziert werden können. Sowohl $\it m$-Xylylene als auch 1,3,5-Trimethylenbenzol konnten durch Pyrolyse der in benzylischer Position iodierten Vorstufen bei kryogenen Temperaturen isoliert und IR, UV/Vis und EPR spektroskopisch charakterisiert werden. Bestrahlung von $\it m$-Xylylene führt zur Isomerisierung in drei $C_{8}H_{8}$-Kohlenwasserstoffen, die im photostationären Gleichgewicht vorliegen. Die $C_{2v}$-Symmetrie von $\it m$-Xylylene konnte durch IR-Dichroismus Messungen nachgewiesen werden. Abfangexperimente mit Sauerstoff führen zu einem neuen Peroxiddiradikal. Die $\sigma$,$\pi$-Diradikale $\alpha$,2- und $\alpha$,4-Dehydrotoluol sowie die $\sigma$,$\pi$,$\pi$-Triradikale 2-Dehydro- und 4-Dehydro-$\it m$-xylylene konnten mittels EPR in ihren Triplett- bzw. Quartettzuständen identifiziert werden. Das 5-Nitreno-$\it m$-xylylene Tetraradikal konnte im Quintettzustand nachgewiesen werden

Heterozygous mutation in OTX2 associated with early-onset retinal dystrophy with atypical maculopathy

Purpose: Heterozygous mutations in OTX2 have been associated with a range of ocular and pituitary abnormalities. We report a novel heterozygous deletion in OTX2 underlying early-onset retinal dystrophy with atypical maculopathy. Methods: Clinical examination included electroretinography and multimodal retinal imaging. Molecular genetic testing was composed of next-generation sequencing of a panel of retinal dystrophy genes. Results: A now 17-year-old boy presented 12 years earlier with a history of progressively poor vision since birth, nyctalopia, and early-onset retinal dystrophy with atypical maculopathy. He also had bilateral microphthalmos and a slim prepubertal appearance; growth hormone levels were within normal ranges. Next-generation sequencing of a retinal dystrophy gene panel revealed a heterozygous deletion c.485delC (p.Pro162G.Infs*24) in exon 5 of OTX2. Conclusions: This second report of maculopathy associated with a heterozygous mutation in OTX2 confirms that mutations in OTX2 should be considered in the differential diagnosis of atypical hereditary maculopathy, with or without rod-cone dystrophy

Long-term follow-up of retinal function and structure in trpm1-associated complete congenital stationary night blindness

Purpose: TRPM1-associated congenital stationary night blindness (CSNB) is characterized by nystagmus and high myopia. We assessed retinal function and structure over long-term follow-up up to 10 years in two siblings from a family with the homozygous deletion c.2394delC in exon 18 that we previously identified. In addition, we describe retinal function and structure in two other siblings with the novel homozygous c.1394T>A (p.Met465Lys) missense mutation. Methods: Clinical examination included full-field electroretinography, axial length measurements, and multimodal retinal imaging. Molecular genetic tests included next-generation sequencing and Sanger sequencing. Results: All patients had non-recordable rod responses and electronegative configuration of the rod-cone responses at presentation. There was a median of 26% reduction in the dark-and light-adapted electroretinographic (ERG) amplitudes over 4 years. Myopia progressed rapidly in childhood but showed only a mild progression after the teenage years. Visual acuities were stable over time, and there was no sign of progressive retinal thinning. All patients had axial myopia. A novel homozygous c.1394T>A (p.Met465Lys) missense mutation in TRPM1 was identified in two siblings. Conclusions: Further prospective study in larger samples is needed to establish whether there is progressive retinal degeneration in TRPM1-associated CSNB. The associated myopia was found to be mainly axial, which has not been described previously. The mechanism of myopia development in this condition remains incompletely understood; however, it may be related to altered retinal dopamine signaling and amacrine cell dysfunction

Triplet State Delocalization in a Conjugated Porphyrin Dimer Probed by Transient Electron Paramagnetic Resonance Techniques

The delocalization of the photoexcited triplet state in a linear butadiyne-linked porphyrin dimer is investigated by time-resolved and pulse electron paramagnetic resonance (EPR) with laser excitation. The transient EPR spectra of the photoexcited triplet states of the porphyrin monomer and dimer are characterized by significantly different spin polarizations and an increase of the zero-field splitting parameter <i>D</i> from monomer to dimer. The proton and nitrogen hyperfine couplings, determined using electron nuclear double resonance (ENDOR) and X- and Q-band HYSCORE, are reduced to about half in the porphyrin dimer. These data unequivocally prove the delocalization of the triplet state over both porphyrin units, in contrast to the conclusions from previous studies on the triplet states of closely related porphyrin dimers. The results presented here demonstrate that the most accurate estimate of the extent of triplet state delocalization can be obtained from the hyperfine couplings, while interpretation of the zero-field splitting parameter <i>D</i> can lead to underestimation of the delocalization length, unless combined with quantum chemical calculations. Furthermore, orientation-selective ENDOR and HYSCORE results, in combination with the results of density functional theory (DFT) calculations, allowed determination of the orientations of the zero-field splitting tensors with respect to the molecular frame in both porphyrin monomer and dimer. The results provide evidence for a reorientation of the zero-field splitting tensor and a change in the sign of the zero-field splitting <i>D</i> value. The direction of maximum dipolar coupling shifts from the out-of-plane direction in the porphyrin monomer to the vector connecting the two porphyrin units in the dimer. This reorientation, leading to an alignment of the principal optical transition moment and the axis of maximum dipolar coupling, is also confirmed by magnetophotoselection experiments

HYSCORE on Photoexcited Triplet States

HYperfine Sublevel CORrElation spectroscopy (HYSCORE) is one of the most widely applied EPR techniques for the investigation of hyperfine couplings in a wide range of spin systems; here, it is applied for the first time to a photoexcited triplet state. The analytical expressions describing the electron spin echo envelope modulations in a HYSCORE experiment on a triplet state coupled to spin ½ nuclei and spin 1 nuclei with weak nuclear quadrupole interactions were derived employing the density matrix formalism and used to determine the characteristic features of this experiment when applied to a triplet state. Experimental HYSCORE spectra recorded on the photoexcited triplet state of a meso-substituted zinc porphyrin are used to investigate the 14N hyperfine interactions in this system. The results are compared to one-dimensional three-pulse Electron Spin Echo Envelope Modulation (ESEEM) experiments and the comparison clearly shows the advantage of the HYSCORE experiment for investigation of the hyperfine couplings of a spin 1 nucleus for triplet states in disordered powder samples. The experimental HYSCORE data are discussed and interpreted in light of the properties of triplet state HYSCORE spectra identified using our theoretical approach

Tunneling Rearrangement of 1‑Azulenylcarbene

1-Azulenylcarbene was synthesized by photolysis of 1-azulenyldiazomethane in argon or neon matrices at 3–10 K. The highly polar singlet carbene is only metastable and undergoes a tunneling rearrangement to 8-methylene-bicyclo[5.3.0]­deca-1,3,5,6,9-pentaene. After substitution of the 4 and 8 positions with deuterium, the rearrangement is completely inhibited. This indicates a very large kinetic isotope effect, as expected for a tunneling reaction

Discrimination of Diverse Coherences Allows Identification of Electronic Transitions of a Molecular Nanoring

The role of quantum coherence in photochemical functions of molecular systems such as photosynthetic complexes is a broadly debated topic. Coexistence and intermixing of electronic and vibrational coherences has been proposed to be responsible for the observed long-lived coherences and high energy transfer efficiency. However, clear experimental evidence of coherences with different origins operating at the same time has been elusive. In this work, multidimensional spectra obtained from a six-porphyrin nanoring system are analyzed in detail with support from theoretical modeling. We uncover a great diversity of separable electronic, vibrational, and mixed coherences and show their cooperation in shaping the spectroscopic response. The results permit direct assignment of electronic and vibronic states and characterization of the excitation dynamics. The clear disentanglement of coherences in molecules with extended π-conjugation opens up new avenues for exploring coherent phenomena and understanding their importance for the function of complex systems