Structural diversity and solution behavior of low-valent iridium complexes bearing 1,4-diazabutadiene ligands

Three types of 1,4-diazabutadiene stabilized low-valent iridium complexes, namely [IrCl(cod)(MesDAB)] (1), [IrCl(coe)(MesDAB)] (2) and [IrCl(MesDAB)₂] (3), have been prepared from 1,4-bis(2,4,6-trimethylphenyl)-1,4-diaza-1,3-butadiene (MesDAB) and [IrCl(cod)]₂ or [IrCl(coe)₂]₂, respectively. The complexes have been investigated by NMR spectroscopy and X-ray diffraction experiments. While tetra-coordinated 2 and penta-coordinated 3 maintain their solid state structure in solution, penta-coordinated 1 shows fluxional behavior. The crystal structures determined indicate strong π-backbonding towards the MesDAB ligand in all cases.     

A fully automated calibration method for an optical see-through head-mounted operating microscope with variable zoom and focus

Ever since the development of the first applications in image-guided therapy (IGT), the use of head-mounted displays (HMDs) was considered an important extension of existing IGT technologies. Several approaches to utilizing HMDs and modified medical devices for augmented reality (AR) visualization were implemented. These approaches include video-see through systems, semitransparent mirrors, modified endoscopes, and modified operating microscopes. Common to all these devices is the fact that a precise calibration between the display and three-dimensional coordinates in the patient's frame of reference is compulsory. In optical see-through devices based on complex optical systems such as operating microscopes or operating binoculars-as in the case of the system presented in this paper-this procedure can become increasingly difficult since precise camera calibration for every focus and zoom position is required. We present a method for fully automatic calibration of the operating binocular Varioscope M5 AR for the full range of zoom and focus settings available. Our method uses a special calibration pattern, a linear guide driven by a stepping motor, and special calibration software. The overlay error in the calibration plane was found to be 0.14-0.91 mm, which is less than 1% of the field of view. Using the motorized calibration rig as presented in the paper, we were also able to assess the dynamic latency when viewing augmentation graphics on a mobile target; spatial displacement due to latency was found to be in the range of 1.1-2.8 mm maximum, the disparity between the true object and its computed overlay represented latency of 0.1 s. We conclude that the automatic calibration method presented in this paper is sufficient in terms of accuracy and time requirements for standard uses of optical see-through systems in a clinical environment.     

Photonic Side-Channel Analysis of Arbiter PUFs

As intended by its name, physically unclonable functions (PUFs) are considered as an ultimate solution to deal with insecure storage, hardware counterfeiting, and many other security problems. However, many different successful attacks have already revealed vulnerabilities of certain digital intrinsic PUFs. This paper demonstrates that legacy arbiter PUF and its popular extended versions (i.e., feed-forward and XOR-enhanced) can be completely and linearly characterized by means of photonic emission analysis. Our experimental setup is capable of measuring every PUF internal delay with a resolution of 6 ps. Due to this resolution, we indeed require only the theoretical minimum number of linear independent equations (i.e., physical measurements) to directly solve the underlying inhomogeneous linear system. Moreover, it is not required to know the actual PUF responses for our physical delay extraction. We present our practical results for an arbiter PUF implementation on a complex programmable logic device manufactured with a 180 nm process. Finally, we give an insight into photonic emission analysis of arbiter PUF on smaller chip architectures by performing experiments on a field programmable gate array manufactured with a 60 nm process.     

Erratum to “Experimental study on the air/water counter-current flow limitation in a model of the hot leg of a pressurized water reactor”

This paper replaces the paper published in the journal by Deendarlianto et al. (2008). Because of an error in the implementation of the air flow meter some of the data given by Deendarlianto et al. (2008) are wrong. They are corrected within the present paper. The general results and conclusions remain unchanged.An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25 m × 0.05 m) and 2.59 m, respectively, whereas the inclination angle of the riser is 50°. The flow was captured by a high speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Counter-current flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate.From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a slight hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of HZDR, since the other investigations were done for pipes.     

连续相黏度对膜乳化结果的影响

Oil-in-water(o/w) emulsions were produced with a membrane emulsification system. The effect of the continuous phase viscosity on the emulsification was studied. The theoretical analyses show that the continuous phase viscosity influences not only the flow field of the continuous phase but also the interfacial tension. The droplet size distribution and disperse phase flux for different continuous phase viscosity were investigated experimentally at constant wall shear stress and constant volume flow rate of the continuous phase respectively.     

Synthesis of β‐Aminonitrones by Regioselective Oxidation of 4H‐Imidazoles

A new regioselective synthesis for aminonitrones of type 4 via oxidative modification of 4H‐imidazoles 1 has been developed. An X‐ray structural analysis revealed an unexpected tautomeric fixation of the hydrogen atom in 4 . NMR investigations of the ¹⁵N‐labelled derivative 4b showed that this fixation is also present in solution. All new synthesized aminonitrones reported here are unusually stable which can be explained by contribution of anionic as well as cationic delocalized mesomeric structures. Treatment of 4 with acetic anhydride leads to formation of the O‐acylated hydroxylamine derivatives 5 .     

Komplexbildung und selektive Cyclisierung substituierter Oxalamidine

Crystallographic data for the acyclic benzylic substituted oxalamidine 3 and the alkyl substituted oxalamidine 4 reveal different structures for compound 3 (s‐trans(E/E) configuration and intramolecular hydrogen bridges) and compound 4 (s‐cis(E/E) configuration without hydrogen bridges). On the basis of the different configurations of these isomeric oxalamidines, the complexation on a (CO)₄Mo‐fragment varies remarkably: Complex formation of ligand 3 takes place at the sp²‐hybridized nitrogen atoms by rotation of the central C–C‐axis, isomerisation of the C N bonds, and by breaking of the hydrogen bridges. Because of the steric hindrance in 4 , the initiating coordination should occur on the sp³‐nitrogen atoms, followed by a intramolecular proton transfer and rehybridization. This complexation is favoured in the cases of cyclic oxalamidines. The molecular structures of the oxalamidines 3 and 4 , their (CO)₄Mo‐complexes 5 , 6 , and of the coordination compound of the cyclic 2,3‐bis(phenyl‐amino)chinoxaline 8 were unambiguously clarified by X‐ray analysis. The cyclization of the different substituted oxalamidines 3 and 4 by phosgene or thiophosgene in the presence of NaN[Si(CH₃)₃]₂ in THF proceeds regioselectively to the asymmetric 2‐imidazolidinones and ‐thiones 11 and 14 , respectively. In contrast to 3 , 4 cyclizes in toluene selectively to the isomeric symmetric 2‐imidazolidinthione 13 . Furthermore, the cyclization on the coordinated oxalamidines with oxalyl chloride provides exclusively the coordinated 2‐imidazolidinones 12 and 15 , which retain the substituent pattern of the starting complexes 5 and 6 – the (CO)₄Mo‐fragment acts as a protecting group.