Coherent control of the ultrafast dissociative ionization dynamics of bromochloroalkanes.

We report on the coherent control of the ultrafast ionization and fragmentation dynamics of the bromochloroalkanes C(2)H(4)BrCl and C(3)H(6)BrCl using shaped femtosecond laser pulses. In closed-loop control experiments on bromochloropropane (C(3)H(6)BrCl) the fragment ion yields of CH(2)Cl(+), CH(2)Br(+), and C(3)H(3)(+) are optimized with respect to that of the parent cation C(3)H(6)BrCl(+). The fragment ion yields are recorded in additional experiments in order to reveal the energetics of cation fragmentation, where laser-produced plasma radiation is used as a tunable pulsed nanosecond vacuum ultraviolet radiation source along with photoionization mass spectrometry. The time structure of the optimized femtosecond laser pulses leads to a depletion of the parent ion and an enhancement of the fragment ions, where a characteristic sequence of pulses is required. Specifically, an intense pump pulse is followed by a less intense probe pulse where the delay is 0.5 ps. Similarly optimized pulse shapes are obtained from closed-loop control experiments on bromochloroethane (C(2)H(4)BrCl), where the fragment ion yield of CH(2)Br(+) is optimized with respect to that of C(2)H(4)BrCl(+) as well as the fragment ion ratios C(2)H(2)(+)/CH(2)Br(+) and C(2)H(3)(+)/C(2)H(4)Cl(+). The assignment of the underlying control mechanism is derived from one-color 804 nm pump-probe experiments, where the yields of the parent cation and several fragments show broad dynamic resonances with a maximum at Δt = 0.5 ps. The experimental findings are rationalized in terms of dynamic ionic resonances leading to an enhanced dissociation of the parent cation and some primary fragment ions.

Novel monogenic diabetes mutations in the P2 promoter of the HNF4A gene are associated with impaired function in vitro.

AIMS: Mutations in HNF4A cause a form of monogenic beta-cell diabetes. We aimed to identify mutations in the pancreas-specific P2 promoter of HNF4A in families with suspected HNF4A diabetes and to show that they impaired the function of the promoter in vitro. METHODS: We screened families with a clinical suspicion of HNF4A monogenic beta-cell diabetes for mutations in the HNF4A P2 promoter. We investigated the function of the previously reported HNF4A P2 promoter mutation -192C>G linked to late-onset diabetes in several families, along with two new segregating mutations, in vitro using a modified luciferase reporter assay system with enhanced sensitivity. RESULTS: We identified two novel HNF4A P2 promoter mutations that co-segregate with diabetes in two families, -136A>G and -169C>T. Both families displayed phenotypes typical of HNF4A monogenic beta-cell diabetes, including at least two affected generations, good response to sulphonylurea treatment and increased birthweight and/or neonatal hypoglycaemia. We show that both of these novel mutations and -192C>G impair the function of the promoter in transient transfection assays. CONCLUSIONS: Two novel mutations identified here and the previously identified late-onset diabetes mutation, -192C>G, impair the function of the HNF4A P2 promoter in vitro.

Chirped pulse multiphoton ionization of nitrogen: control of selective rotational excitation in N(2)(+)(B 2Sigma(u)(+)).

We report on fluorescence spectra of N(2)(+)(B (2)Sigma(u)(+)) --> N(2)(+)(X (2)Sigma(g)(+)) obtained from multiphoton ionization of molecular nitrogen by 804 nm femtosecond laser pulses. The analysis of the fluorescence spectra reveals that the vibrational levels v = 0 and v = 4 in the B (2)Sigma(u)(+)-state of N(2)(+) are primarily populated. The rotational state distribution of N(2)(+)(B (2)Sigma(u)(+), v = 0) is determined from the rotationally resolved fluorescence spectra. It is demonstrated that the linear chirp of the 804 nm femtosecond laser pulse has a strong influence on the rotational state distribution of the vibrational ground state of the molecular cation N(2)(+)(B (2)Sigma(u)(+), v = 0). Possible mechanisms leading to the experimental results are discussed. The particular population of the vibrational levels as well as the linear chirp dependence of the fluorescence signal gives evidence for the importance of a resonant intermediate state. The N(2) a (1)Pi-state is likely involved in a resonant multiphoton excitation process. This permits to selectively control the rotational population of the cation that is formed via chirped pulse multiphoton ionization.

Bradyzoite-specific gene expression in Toxoplasma gondii requires minimal genomic elements.

BAG1 is a small heat-shock protein of Toxoplasma gondii that is specifically expressed in the cyst-forming bradyzoite stage of the parasite. Upregulation of BAG1 mRNA occurs early during the differentiation pathway from tachyzoites to bradyzoites. In order define genomic elements involved in bradyzoite-specific gene regulation, chloramphenicol acetyltransferase (CAT)-reporter gene studies were performed with 5' flanking sequences of the BAG1 gene. Tachyzoites, transiently transfected with the BAG1/cat construct, exhibited very low CAT activity (200 fold less than in parasites transfected with a tubulin promoter/cat construct). After induction of bradyzoite differentiation by alkaline pH shift, however, CAT activity increased 50 fold, demonstrating bradyzoite-specific expression of the CAT reporter gene under control of 5' flanking sequences of BAG1. Stage-specific regulation of BAG1/CAT was independent of the 3'-flanking region, since constructs containing 3'-flanking sequences of the tachyzoite-specific SAG1 gene showed identical regulation to those containing the BAG1 3'-flanking region. The kinetics of BAG1/CAT induction in stably transfected parasites is similar to the kinetics of endogenous BAG1 expression: increased CAT activity was first detected on day 3 after alkaline pH shift (20 fold) and was dramatically upregulated 250 fold on day 4. A series of deletions in the BAG1 5'-flanking sequences demonstrated that a 324 nucleotide (nt) fragment, starting 60 nt upstream of the BAG1 transcription start, is sufficient to confer stage-specific regulation on the CAT reporter. These deletion analyses demonstrate that bradyzoite-specific expression of a heterologeous reporter gene requires only minimal genomic sequences.

Is the [15N]methacetin liver function test suited to estimate environmental effects on the maturity of neonates?

Clinical and paraclinical data of 91 neonates of the Saxon regions of Leipzig and of Torgau/Elbe were reviewed and correlated to the environmental conditions of the places of residence of their mothers during pregnancy. One of the parameters investigated was the hepatic detoxification capacity of the neonates measured by 15N elimination rates in the [15N]methacetin urine test. Because of heavy air pollution in the places of residence of some of the pregnant women, a distinct reflection of environmental influence in the parameters was expected. While some of the parameters considered, such as birth weight and bilirubin levels, did not correlate with mean exposure data of the residences of the pregnant women, the mean rate of the age-dependent maturation of hepatic 15N elimination did. This maturation was seen to be significantly decreased in heavily polluted districts of the Leipzig region compared to lower polluted places of Leipzig and to the lowly polluted region of Torgau/Elbe.

Inner-valence photoionization of O((1)D): experimental evidence for the 2s(2)2p(4)((1)D)-->2s(1)2p(5)((1)P) transition.

Photoionization and autoionization of electronically excited atomic oxygen O((1)D) are investigated in the energy range between 12 and 26 eV using tunable laser-produced plasma radiation in combination with time-of-flight mass spectrometry. A broad, asymmetric, and intense feature is observed that is peaking at 20.53+/-0.05 eV. It is assigned to the 2s(2)2p(4)((1)D)-->2s(1)2p(5)((1)P) transition, which subsequently autoionizes by a Coster-Kronig transition, as predicted by the previous theoretical work [K. L. Bell et al., J. Phys. B 22, 3197 (1989)]. Specifically, the energy of the unperturbed transition occurs at 20.35+/-0.07 eV. Its shape is described by a Fano profile revealing a q parameter of 4.25+/-0.8 and a width of gamma=2.2+/-0.15 eV. Absolute photoionization cross section sigma is derived, yielding sigma=22.5+/-2.3 Mb at the maximum of the resonance. In addition, weak contributions to the O((1)D) yield from dissociative ionization originating from molecular singlet oxygen [O(2)((1)Delta(g))] are identified as well. Possible applications of the 2s(2)2p(4)((1)D)-->2s(1)2p(5)((1)P) transition as a state-selective and sensitive probe of excited oxygen in combination with photoionization mass spectrometry are briefly discussed.

Phenotypically plastic responses of green frog embryos to conflicting predation risk.

Predators have been shown to alter the timing of switch points between life history stages, but few studies have addressed switch point plasticity in prey exposed simultaneously to conflicting predation pressure. We tested hatching responses of green frog (Rana clamitans) embryos subject to perceived predation risk from chemical cues released by two stage-specific predators, predicting that these predators would elicit: (1) directional hatching responses when presented independently, and (2) intermediate phenotypic responses when presented simultaneously. R. clamitans embryos in outdoor exclosures were exposed to cues from an egg predator (freshwater leeches; Nephelopsis obscura), a larval predator (dragonfly nymphs, Aeschna canadensis), and both predators in a 2 x 2 factorial experiment, and changes in hatchling size, hatchling developmental stage, and hatching time were compared to those for control embryos. Leeches alone induced embryos to hatch at a smaller size and an earlier developmental stage than controls, while dragonfly nymphs elicited a delay in egg hatching time that was associated with larger size and later developmental stage at hatching. Embryos failed to respond to simultaneous exposure to both predators, implying that responses to each occurred concurrently and were therefore dampened. Our results indicate that prey under threat from conflicting predators may manifest intermediate defensive phenotypes. Such intermediate responses may result in elevated rates of prey mortality with possible consequences at the population level.

[Indoor climatic conditions of the floor zone in child nurseries]. / Untersuchungen zu den raumklimatischen Verhältnissen der bodennahen Zone in Kinderkrippen.

The room climatic conditions in the near floor zone were measured in creches. The surface temperature of the floor during the heating season did not reach the desired range of 20 to 22 degrees C. 59% of the measured minimal values, 39% of the mean values, and 18% of the maximal ones were about 15 degrees C or even drastically lower. Of the air temperature in the near floor zone (at a level between 0.15 m and 0.50m) 31% of their minimal values at the level of 0.15 m and 27% of their minimal values at the level of 0.50 m values were below 16 degrees C. The investigations of the vertical temperature gradients during the heating season showed that only 9% of the values measured between 0.50 m and 1.50 m meet the required standard of 1 degree C temperature difference per meter. Conclusions are drawn and discussed.