An experimental set-up to apply polarization modulation to infrared reflection absorption spectroscopy for improved in situ studies of atmospheric corrosion processes.

A new set-up for improved monitoring of atmospheric corrosion processes in situ and in real-time is presented. To characterize chemical structures of thin films on metal surfaces surface sensitive analytical techniques are required. One possible technique is Infrared Reflection Absorption Spectroscopy (IRRAS) which has become an established method to investigate surface corrosion films of thicknesses less than 200 nm. However, there are limitations related to the sensitivity of these measurements, in case of investigating ultrathin films or absorption bands of interest, surface species are superimposed by atmospheric background absorption, which changes during in situ measurements in ambient atmospheres. These difficulties of in situ surface reflection measurements can be eliminated by availing the polarization selectivity of adsorbed surface species. At grazing angles of incidence the absorption of p-polarized infrared radiation by thin surface films on metals is enhanced, while the absorption of s-polarized light by this film is nearly zero. This different behavior of the polarization properties leads to strong selection rules at the surface and can therefore be used to identify molecules adsorbed on metal surfaces. Polarization Modulation (PM) of the infrared (IR) light takes advantage of this disparity of polarization on sample surfaces and in combination with IRRAS yielding a very sensitive and surface-selective method for obtaining IR spectra of ultra-thin films on metal surfaces. An already existing in situ IRRAS/Quartz Crystal Microbalance weathering cell was combined with PM and evaluated according to its applicability to study in situ atmospheric corrosion processes. First real-time measurements on silver samples exposed to different atmospheres were performed showing the advantage of PM-IRRAS compared to conventional IRRAS for such investigations.

A new experimental setup for in situ infrared reflection absorption spectroscopy studies of atmospheric corrosion on metal surfaces considering the influence of ultraviolet light.

The knowledge available regarding the influence of ultraviolet (UV) light on the atmospheric corrosion of materials is very rudimentary. Therefore, a new experimental setup consisting of a cell for studying in situ reactions occurring at the metal/atmosphere interface by simultaneously applying infrared reflection absorption spectroscopy (IRRAS) and quartz crystal microbalance (QCM) measurements was designed and built. The cell presented consists of an acrylic glass body with a UV-light-transparent window mounted in such a way that the sample can be irradiated and weathered under controlled atmospheric conditions under a grazing angle of incidence of the IR beam. This new setup was tested by using a specimen of polycrystalline silver, where the growth of Ag(2)CO(3) and AgOH as basic silver carbonate on the surface could be observed. The weathering tests were carried out in synthetic air containing 90% relative humidity (RH) and 250 ppm CO(2), with and without UV light. The results obtained from the IRRAS spectra could be perfectly correlated with the in situ QCM data.

TOF-SIMS investigations on weathered silver surfaces.

Silver-coated quartz crystal microbalance (QCM) disks were treated under different environmental conditions (including changes in parameters such as relative humidity (%RH) and SO(2)/H(2)S content) in atmospheres of synthetic air and pure N(2) for 24 h in a weathering chamber. The corroded surfaces were subjected to depth profiling by a time of flight (TOF) secondary ion mass spectrometry (SIMS) instrument, equipped with a Bi(+) analysis gun and Cs(+) sputter gun. The evaluation of the in-depth distribution of several elements and species provides evidence for the formation of a corrosion layer containing Ag(2)SO(3), even in the absence of oxidizing agents, such as H(2)O(2) or NO(2). Furthermore it could be elucidated that the thickness of the formed Ag(2)SO(3) layer does not depend on the SO(2) concentration but rather on the humidity and oxygen content of the ambient atmosphere. In weathering experiments in atmospheres composed of synthetic air, humidity, and H(2)S, the presence of different oxygen species (surface and bulk) and silver sulfide could be detected by TOF-SIMS depth profiling experiments. The obtained results for both acidifying gases are in good correlation with the corresponding tapping mode atomic force microscopy (TM-AFM) investigations and in situ QCM measurements.

Laser-assisted zona pellucida thinning prior to routine ICSI.

BACKGROUND: In MII oocytes showing difficult oolemma breakage, ICSI can cause an increase in the degeneration rate. This may be overcome by laser-assisted ICSI using a 5-10 micro m opening in the zona pellucida for injection. However, such a small opening might impair the hatching process, especially if assisted hatching is applied in addition. In order to prevent this, the present study used routine injection through an area of zona pellucida in which laser zona thinning had been applied, providing for both a reduced mechanical stress to the oocyte and assisted hatching. METHODS: This prospective study involved 100 cycles with 1016 MII oocytes. Conventional ICSI (control group) was compared with a modified laser-assisted ICSI (study group) in sibling oocytes. In the latter group oocytes were injected through an extended area of zona thinning. RESULTS: Degeneration rate was significantly lower in the study group (P < 0.004). There were no differences in fertilization, or formation and quality of blastocysts. In the study group embryo quality on day 2 was significantly better (P = 0.004) and herniation of day 5 blastocysts was increased (P = 0.005). Rates of implantation and pregnancy were not affected. However, on day 3 laser-assisted ICSI proved beneficial (P = 0.038) in terms of clinical pregnancy rate. CONCLUSIONS: The new method combines a less invasive ICSI technique with assisted hatching. Our preliminary data indicate that in addition to an improved oocyte survival, this new approach increases the hatching rate in vitro, which may explain the increase in pregnancy rate, at least in day 3 transfers.

Presence, but not type or degree of extension, of a cytoplasmic halo has a significant influence on preimplantation development and implantation behaviour.

BACKGROUND: Since there is considerable disagreement in grading cytoplasmic haloes, this prospective study was set up to evaluate if certain subtypes of haloes are related to further development. METHODS: Out of a total of 152 patients, 713 zygotes could be checked for the formation of a halo. Where present, haloes were subdivided into concentric (symmetric) and polar (asymmetric) types. In addition, each halo was measured accurately to see if the extension of the halo might influence further development. In parallel, pronuclear patterns were checked. RESULTS: Halo-positive zygotes did not differ from halo-negative ones in terms of embryo quality and blastocyst formation rate. However, quality of blastocysts (assessed by their inner cell mass consistency) was significantly increased (P < 0.001) if a halo appeared at zygote stage. This phenomenon was not related to type of halo or degree of halo. In terms of pronuclear pattern, pattern 0 (0A, 0B) led to significantly more blastocysts (P < 0.001) of better quality (P = 0.002) compared with patterns 1-5. A stepwise logistic regression showed no relationship between different halo types and pronuclear pattern 0. CONCLUSIONS: The present study indicates that any halo has a positive prognostic value on blastocyst quality, irrespective of the fact that it is light or extreme, polar or concentric. In addition, the developmental advantage of pattern 0 is confirmed.

Developmental competence of oocytes showing increased cytoplasmic viscosity.

BACKGROUND: The objective of the study was to investigate the developmental fate of oocytes with increased cytoplasmic viscosity as assessed by the persistence of the injection funnel after withdrawal of the ICSI pipette. METHODS: For this purpose, 1008 oocytes showing a characteristic injection funnel during ICSI were subdivided into two groups according to the oocyte's ability to restore its spherical shape within 2-3 min after ICSI. Fertilization and further development was evaluated in both groups. In addition, implantation and pregnancy rates were analysed. RESULTS: In the funnel positive cohort (group 1) significantly fewer oocytes degenerated after injection (P < 0.01) compared with oocytes without persistent funnel (group 2). However, at zygote stage, presence of a halo (P < 0.05) and a optimal pronuclear pattern 0 (P < 0.01) was increased in group 2. In addition, significantly fewer poor quality embryos were found in this group (P < 0.01). The number of good quality blastocysts but not blastocyst formation was increased in group 2 (P < 0.05). This resulted in an increased clinical pregnancy rate if embryos which derived exclusively from funnel negative oocytes were transferred (P < 0.05). CONCLUSIONS: Our data suggest that cytoplasm of higher viscosity delays development up to cleavage stage and impairs optimal development. Injection funnel persistence was found to be a negative prognostic marker of preimplantation development.