Reviews

Michal Kokowski, Copernicus’s Originality: Towards Integration of Contemporary Copernican Studies (Warsaw: Wydawnictwa Ihn Pan, 2004). 314 pp. pb. ISBN 83‐86062‐27‐4. Sharon E. Kingsland, The Evolution of American Ecology 1890–2000 (Baltimore: Johns Hopkins University Press, 2005). 313 pp. hc. $50. ISBN 0‐8018‐8171‐4. Graeme J.N. Gooday. The Morals of Measurement: Accuracy, Irony, and Trust in Late Victorian Electrical Practice (Cambridge: Cambridge University Press, 2004). xxv, 285 pp. hc. £55. ISBN 0‐521‐43098. Joan Vernet; Ramon Parés (eds.), La Ciència en la Història del Països Catalans. Vol. 1. Dels Àrabs al Renaixement (Valencia: University of Valencia, 2004). 630 pp. hc. €50. ISBN 84‐370‐ 6047‐8. Giuliano Pancaldi, Volta. Science and Culture in the Age of Enlightenment (Princeton and Oxford: Princeton University Press, 2003). 381 pp. hc. £32.50. ISBN 0‐691‐09685‐6. Wolfgang Lefèvre; Jürgen Renn; Urs Schoepfin (eds.), The Power of Images in Early Modern Science (Basel: Birkhäuser Verlag, 2003). 320 pp. pb. CHF 184, € 118. ISBN 3‐7643‐2434‐1. Olivier Darrigol, Worlds of Flow: A History of Hydrodynamics from the Bernoullis to Prandtl (Oxford: Oxford University Press, 2005). 356 pp. hc. L35.00. ISBN 0‐19‐856843‐6. Ad Meskens, Joannes della Faille s.j.: Mathematics, Modesty and Missed Opportunities (Brussel: Institut Historique Belge de Rome, 2005). 175 pp. hc. ISBN 90‐74461‐53‐0. Aant Elzinga; Torgny Nordin; David Turner; Urban Wråkberg (eds.), Antarctic Challenges. Historical and Current Perspectives on Otto Nordenskjöld’s Antartic Expedition 1901–1903 (Göteborg: Royal Society of Arts and Sciences, 2004). 330 pp. hc. $93. ISBN 91‐85252‐64‐6. Klaus‐Heinrich Peters, Schönheit, Exaktheit, Wahrheit: Der Zusammenhang von Mathematik und Physik am Beispiel der Geschichte der Distributionen (Berlin: GNT‐Verlag, 2005). 272 pp. pb. € 32.00. ISBN 3‐928186‐74‐4.     

Effects of molecular weight and elastic segment flexibility on syneresis in Ca-alginate gels

Syneresis in Ca-alginate gels was studied as a function of the alginate molecular weight and the degree of flexibility of the elastic segments. Small angle X-ray scattering of alginate gels reveals an increased lateral association of junction zones when entering a Ca²⁺ regime giving syneresis. This suggests growth of junction zones to be the primary driving force for syneresis. Ca-alginate gels prepared from alginates with different molecular weights show a reduced syneresis with decreasing M_w. A reduced syneresis is also observed when fractions of a high M_w alginate is replaced by short alginate molecules enriched in guluronate residues. The effect of altering the monomer sequence of the elastic segments spanning the junction zones was studied by converting poly-mannuronate regions to alternating guluronate/mannuronate sequences by the mannuronan C5-epimerase AlgE4. This epimerisation reaction gives a more flexible elastic segment. The epimerased alginates yielded gels with larger syneresis compared to the non-epimerased, native alginate samples. Thus, both molecular weight and elastic segment flexibility are needed in a molecular model for describing syneretic behaviour in alginate gels. These parameters will to a large extent determine to which degree the non-equilibrium nature of the alginate gel is macroscopically expressed (syneresis).     

Responsiveness of the major birch allergen Bet v 1 scaffold to the gastric environment: Impact on structure and allergenic activity

Scope: Four Bet v 1 homologous food allergens from celeriac (rApi g 1), apple (rMal d 1), peach (rPru p 1) and hazelnut (rCor a 1), were used to probe the structural responsiveness of the Bet v 1 scaffold to gastric digestion conditions and its impact on allergenicity. Methods and results: Low pH induced conformational changes of all homologues, which was reduced at physiological ionic strength for all except rPru p 1 as observed by circular dichroism (CD)‐spectroscopy. The homologues were rapidly digested by pepsin, losing their IgE binding activity, although the kinetics and patterns of digestion varied subtly between homologues, rApi g 1 being the most stable. We have demonstrated for the first time that gastric phosphatidyl‐choline (PC) induced conformational changes in all homologues but only rMal d 1 penetrated the PC vesicles as detected by fluorescence polarization, slowing its digestion and retaining more of its allergenic activity. PC enhanced basophil activation of all digested allergens except rApi g 1. Conclusion: The Bet v 1 scaffold is generally susceptible to low pH and pepsinolysis and interacts with PC vesicles, properties which can explain effects of the gastric environment on their allergenicity. These data show the importance of including surfactants in model digestion systems.     

Comparative Studies of Carrier Dynamics in 3C-SiC Layers Grown on Si and 4H-SiC Substrates

Time-resolved nonlinear optical techniques were applied to determine the electronic parameters of cubic silicon carbide layers. Carrier lifetime, τ, and mobility, μ, were measured in a free-standing wafer grown on undulant Si and an epitaxial layer grown by hot-wall chemical vapor deposition (CVD) on a nominally on-axis 4H-SiC substrate. Nonequilibrium carrier dynamics was monitored in the 80 K to 800 K range by using a picosecond free carrier grating and free carrier absorption techniques. Correlation of τ(T) and μ _a(T) dependencies was explained by the strong contribution of diffusion-limited recombination on extended defects in the layers. A lower defect density in the epitaxial layer on 4H-SiC was confirmed by a carrier lifetime of 100 ns, being ~4 times longer than that in free-standing 3C.     

Effect of exogenous phytase on feed inositol phosphate hydrolysis in an in vitro rumen fluid buffer system

Three in vitro experiments using a rumen fluid buffer system were performed to investigate the effect of addition of 4 experimental phytases (Phy1, Phy2, Phy3, and Phy4) compared with no addition of phytase on feed inositol phosphate hydrolysis in wheat and rapeseed cake to determine which of the 4 phytases was most suitable under rumen-like conditions. The feedstuffs were incubated with a mixture of physiological buffer, ruminal fluid, and exogenous phytase at pH 6.2, after which the samples were incubated for different periods. Incubations were stopped using HCl, and the samples were analyzed for inositol phosphates via high performance ion chromatography. Addition of phytase (Phy1) resulted in enhanced degradation of myo-inositol hexakisphosphate (InsP₆) in rapeseed cake, whereas addition of exogenous phytase did not improve the degradation of InsP₆ in wheat. Only rapeseed cake was therefore used subsequently. All 4 phytases increased degradation of InsP₆ in rapeseed cake in the in vitro system, and degradability of InsP₆ increased with higher incubation time and higher phytase dosages, independent of phytase. Addition of 2 units of phytase per gram of substrate of the phytases Phy1, Phy2, Phy3, and Phy4 led to an undegraded InsP₆ content of 56, 49, 70, and 18%, respectively, when incubated with rapeseed cake for 6 h, indicating that Phy2 and Phy4 were the most effective phytases. However, Phy2 had a higher specific activity than Phy4, as 60% of the original InsP₆ content was remaining after 3 h when 5 mg of enzyme protein per gram of substrate of Phy2 was added to rapeseed cake, whereas 150 mg of enzyme protein per gram of substrate of Phy4 was necessary to achieve a similar result. Therefore, Phy2 appeared to be most applicable under rumen-like conditions.     

Characterization Of Ofice Dust By VOCs And TVOC Release - Identification Of Potential Irritant VOCs By Partial Least Squares Analysis

Floor dust from nine city hall office buildings was separated into fiber and particulate fractions and analyzed for volatile organic compounds (VOCs) and total VOC (TVOC) by thermal desorption/high resolution gas chromatography (HRGC). Components were identified by HRGC/mass spectroscopy (MS). Principal component analysis was applied to VOC emission profiles revealing similarities between buildings and correlations between profiles and SBS symptoms of mucous membrane irritation and “concentration difficulty”. While the dominant pattern in emission profiles was not correlated with SBS irritation complaints, partial least squares analysis in latent variables (PLS analysis) identified VOCs for which peak areas were correlated with SBS irritation complaints and the CNS Complaint, “concentration difficulty”     

Characterization of slice-based H.264/AVC encoded video traffic using token buckets

An explicit slice-based mode type selection scheme for use in H.264/AVC has recently been developed, which reduces the burstiness effect of standard frame-based H.264/AVC by breaking up the Group of Picture structure. In this paper, slice-based encoded video streams are characterized using the token bucket traffic model and compared to standard frame-based encoded streams. Both lossless, loss bounded and delay bounded token bucket models are investigated and the high quantiles are found for the amount of loss. Loss above the amount given by the high quantiles will happen only with a very small probability. It is shown that the reduced burstiness for the slice-based video encoding leads to lower token bucket parameters compared to frame-based video encoding for a stream without scene changes, and a larger reduction in the token bucket parameters compared to the frame-based video encoding when a small amount of delay or loss is allowed for the stream with scene changes. Next, reshuffling of the frames of the video streams with scene changes is employed to better understand the effects of long-range dependence on the token bucket parameters. Only small effects are found from reshuffling the scenes, but reshuffling of the frames inside the scenes leads to lower token bucket parameters. Finally, an approach to estimate the parameters for the token bucket model using simple characteristics of the slice-based stream is developed.     

Susceptibility to effects of UVB irradiation on induction of contact sensitivity, relevance of number and function of Langerhans cells and epidermal macrophages

Sensitization on skin exposed to acute low-dose UVB irradiation separates normal humans into two phenotypically distinct groups: One group, following sensitization on UVB-irradiated skin, develops contact sensitivity, designated UVB resistant (UVB-R) and the second group, following sensitization on UVB-irradiated skin, fails to develop contact sensitivity, designated UVB susceptible (UVB-S). To investigate whether UVB susceptibility in humans in related to antigen-presenting activity in the skin we studied the effect of UVB irradiation on the number and function of the epidermal antigen-presenting cells in volunteers identified as UVB-R and UVB-S. Single cell suspensions of epidermal cells from control skin and skin exposed to 3 minimal erythema doses (MED) of UVB 3 days previously were stained for Langerhans cells (CD1a+HLA-DR+) and epidermal macrophages (CD1a-HLA-DR+). The UVB exposure of the skin significantly decreased the percentage of Langerhans cells (UVB-R: n = 7, P < 0.02, UVB-S: n = 6, P < 0.03) and increased the percentage of epidermal macrophages (UVB-R: n = 7, P < 0.03, UVB-S: n = 6, P < 0.03) however to the same degree in both the UVB-R and the UVB-S group. To study the effect on Langerhans cell alloreactivity, epidermal cells were harvested immediately after UVB irradiation. However, in both UVB-R and UVB-S subjects the Langerhans cell alloreactivity was blocked to the same degree immediately after UVB irradiation compared to nonirradiated epidermal cells. To determine the effect of UVB irradiation on epidermal macrophages, epidermal cells were harvested 3 days after UVB irradiation. Irradiated epidermal cells from both UVB-R and UVB-S subjects demonstrated a strong antigen-presenting capacity compared to epidermal cells from control skin leading to activation of T cells that mainly secrete interferon (IFN)-gamma and not interleukin (IL)-4. In conclusion we found that UVB susceptibility was not correlated with the number of Langerhans cells or epidermal macrophages in the skin at the same time of sensitization. Neither was it correlated with the capacity of Langerhans cells nor UVB-induced epidermal macrophages to activate T cells in vitro.     

Flow-dependent effect of formoterol dry-powder inhaled from the Aerolizer

The output and size distribution of aerosols from dry powder inhalers are dependent on the flow rate through the device. Therefore, in an in vivo study, we examined the flow-dependency of the effect of formoterol when delivered from a dry powder inhaler, the Aerolizer, in a flow range relevant to schoolchildren. In a preliminary study comprising 126 asthmatic children aged 3-10 yrs, the relationship between age and peak inspiratory flow (PIF) rate through the Aerolizer was determined. Mean PIF was 104 L.min-1 and all children aged > 5 yrs performed a PIF > 60 L.min-1. Sixteen children aged 8-15 yrs with exercise-induced asthma (EIA) took part in the main trial comparing the protective effect of 12 micrograms formoterol inhaled at 60 and 120 L.min-1. The effect from high and low inspiratory flow was judged from the protective effect against EIA 12 h after drug administration. The decrease in forced expiratory volume in one second (FEV1) after exercise was 34% on the placebo day, but only 15% when formoterol was inhaled at the high flow rate. This difference was statistically significant. The decrease in FEV1 was 23% after treatment with formoterol inhaled at the low flow rate, that was not significantly different from placebo or from high-flow formoterol treatment. These clinical findings correspond with the in vitro findings of flow-dependent fine particle mass from the Aerolizer, and corroborate the relationship between fine particle mass of aerosol and clinical effect. The results indicate a flow-dependent effect of formoterol dry powder inhaled from the Aerolizer, within the range of inspiratory flow rate obtainable by school-children. This questions its applicability in children with asthma.     

Effects of leader contingent and noncontingent reward and punishment behaviors on subordinate performance and satisfaction.

This study investigated the nature of the relationships between leader reward and punishment behaviors and subordinate performance and satisfaction. Only performance-contingent reward behavior was found to affect subordinate performance significantly. Positive relationships were found between leader contingent reward behavior and employee satisfaction. Contingent punishment had no effects on subordinate performance or satisfaction.