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This paper presents results of a statistical investigation of the grain size-, grain orientation- and grain boundary type distribution of six industrially grown conventional multicrystalline (mc-Si) silicon bricks and six high performance (hp) mc-Si bricks of different producers. It was found that hp mc-Si wafers have a more uniform initial grain size (coefficient of variation CV < 2.5) and grain orientation (CV < 1.5) distribution, with a smaller mean grain size (60%) in comparison to the conventional mc-Si wafers. Despite the totally different initial grain structures between the hp and conventional me-Si bricks the grain structure of the top wafers is more or less comparable. It was concluded that the grain structure development of the hp mc-Si bricks is driven by an energy minimization due to the surface energy as well as the grain boundary energy. The grain structure investigations show clearly that especially the initial grain structure of the bricks significantly influences the area fraction of electrical active defects as well as the solar cell efficiency. The hp mc-Si bricks show the lowest area fraction of electrical active defects up to 4% and the highest solar cell efficiency of 18.8%, whereas the conventional mc-Si bricks have an area fraction of electrical active defects up to 14% and a maximum solar cell efficiency of about 18.4%.

The grain structure, especially the grain orientation, number and type of grain boundaries, influences many of the properties of multicrystalline (mc) silicon (Si) wafers used for manufacturing solar cells. In order to increase the efficiency of silicon solar cells, the relation between material defects, such as dislocations, impurities and precipitates, and the grain structure must be understood. Currently no measurement system exists that can determine the grain orientation on a full mc Si wafer with an area of 156 × 156 mm2. The most widely used measuring method is electron backscatter diffraction (EBSD). However, it is only possible to measure small sample sizes by EBSD depending on the scanning electron microscopy stage, and moreover a time-consuming surface preparation is needed. In this paper an innovative fast characterization method is presented that allows the orientation measurement of as-cut and polished Si samples up to 380 × 400 mm2. This method, known as the Laue scanner, is based on X-ray diffraction. Experimental and theoretical considerations, limits of the system and example results of possible tasks are shown and discussed.

Propylene production from current sources will not suffice in the long run to meet market requirements. The transformation of either ethylene or ethanol into propylene is hence an interesting alternative to conventional production routes. These two chemical processes were thermodynamically analyzed employing Gibbs energy minimization. Investigated process parameters included system pressures ranging from 1 to 20 bar and reaction temperatures between 250 and 750 °C. Regarding initial compositions, pure ethylene or ethanol feeds were considered as well as binary mixtures of aqueous ethanol containing water mass fractions up to 95%. The effect of catalyst-caused shape selectivity on the product spectrum was accounted for by using different species lists. Non-ideal behavior was incorporated using the virial equation but found to be negligible. Both ethanol and ethylene feeds gave a maximum propylene yield of approximately 42% (carbon atom basis) at a system pressure of 1 bar. Optimal reaction temperatures were found at 600 °C (ethanol feed) and 650 °C (ethylene feed), respectively. In addition, chemical equilibria revealed room for improvement as far as currently available catalysts are concerned. The results of this study are thus useful as a benchmark for future catalyst developments. The potential attractiveness of ethylene- or ethanol-based propylene production is pointed out from a general thermodynamic point of view.

In this work one high performance multi-crystalline silicon ingot and one conventional multi-crystalline silicon ingot, each with an extraordinary ingot height of 710 mm, were replicated by the successive growth of eight G1 ingots to evaluate the potential advantage of extraordinary tall HPM ingots in industrial production. By analyzing different grain structure parameters like mean grain size, grain orientation and grain boundary type distribution as well as the recombination active dislocation area over the complete ingot height, it was observed that the material properties strongly differ in the initial state of growth for the two material types. However, at ingot heights above 350 mm, the difference has vanished and the grain structure properties for both materials appear similar. It is shown that the evolution of the grain structure in both material types can be explained by the same grain selection and grain boundary generation/annihilation mechanisms whereas the current grain structure determines which mechanisms are the most dominant at a specific ingot height. Since the grain structure directly influences the dislocation content in the silicon material, also the recombination active dislocation area becomes equal in high performance and conventional multi-crystalline silicon material at ingot heights above 350 mm. From these results it is concluded that the advantage of high performance silicon material is limited to the first grown 350 mm of the ingot.

A template ion exchange approach has been employed to prepare Ni/MCM-41 with varying nickel loadings. The synthesized samples were studied by nitrogen physisorption, X-ray diffraction, atomic absorption spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction and Fourier transform infrared spectroscopy. Extensive compound formation was found to result from the adopted preparation method. The Ni(II) phase was elucidated to be a nickel silicate with layer structure. Corresponding layers were comprised of an octahedral Ni(II) sheet in between two tetrahedral SiO4 sheets. Nickel compound formation was accompanied by simultaneous dissolution of the support material. The nickel phase was most likely deposited onto the external surface of the MCM-41 particles. Temperature-programmed desorption of ammonia was used to investigate the influence of nickel content on acidity. Moderate acidity was found for the undoped support material. Introduction of nickel led to the formation of two additional types of acid sites with weak and moderate acidity characteristics.

Ni-MCM-41 has been prepared by equilibrium adsorption of different nickel precursors. Nickel citrate and nickel nitrate gave the most active catalysts for the direct transformation of ethene into propene above 250 °C at atmospheric pressure. The maximal ethene conversion at 400 °C was 36% while propene selectivity reached 45%. Analysis of product formation spectra at different temperatures, residence times and inlet compositions revealed reaction kinetics consistent with a sequence of ethene dimerization, positional butene isomerization and propene retro-metathesis.

A molecular model of the active site of the serine protease dipeptidyl peptidase IV (DPP IV or CD26) has been developed on the basis of comparative molecular field analysis (CoMFA) of competitive inhibitors and by force field calculations. By application of CoMFA experimentally obtained inhibition constants Ki have been successfully predicted. The resulting steric and electrostatic coefficients of CoMFA were used for the development of the molecular model. The main assumptions of the model are the recognition of substrates or inhibitors by the side chains of a tyrosine (S1-position) and a tryptophan residue (S2-position). The model helps us to understand a multitude of experimental data regarding the substrate specificity of this enzyme as well as results obtained by genetic engineering experiments by other authors. General conclusions concerning a new family of serine proteases are drawn and discussed.

Different silicon feedstock materials, Single Crystalline Crushed (SCS), Fluidized-Bed-Reactor (FBR) and Siemens (SIE) feedstock, were used as seeding layer for growing cylindrical shaped, high performance multi-crystalline ingots with a weight of 1.2 kg. Within the investigations a systematic variation of the particle size of the seeding material in the range of

Pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) play a key role in the pathogenesis of osteoarthritis (OA). Anti-inflammatory agents capable of suppressing the production and catabolic actions of these cytokines may have therapeutic potential in the treatment of OA and a range of other osteoarticular disorders. The purpose of this study was to examine the effects of curcumin (diferuloylmethane), a pharmacologically safe phytochemical agent with potent anti-inflammatory properties on IL-1beta and TNF-alpha signalling pathways in human articular chondrocytes maintained in vitro. The effects of curcumin were studied in cultures of human articular chondrocytes treated with IL-1beta and TNF-alpha for up to 72h. Expression of collagen type II, integrin beta1, cyclo-oxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) was monitored by western blotting. The effects of curcumin on the expression, phosphorylation and nuclear translocation of protein components of the NF-kappaB system were studied by western blotting and immunofluorescence, respectively. Treatment of chondrocytes with curcumin suppressed IL-1beta-induced NF-kappaB activation via inhibition of IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation and p65 nuclear translocation. Curcumin inhibited the IL-1beta-induced stimulation of up-stream protein kinase B Akt. These events correlated with down-regulation of NF-kappaB targets including COX-2 and MMP-9. Similar results were obtained in chondrocytes stimulated with TNF-alpha. Curcumin also reversed the IL-1beta-induced down-regulation of collagen type II and beta1-integrin receptor expression. These results indicate that curcumin has nutritional potential as a naturally occurring anti-inflammatory agent for treating OA through suppression of NF-kappaB mediated IL-1beta/TNF-alpha catabolic signalling pathways in chondrocytes.

We present a new molecular engineering approach in which a polymer-supported phospholipid bilayer is vertically stabilized by controlled covalent tethering at both the polymer-substrate and polymer-bilayer interfaces. This approach is based on lipopolymer molecules, which not only form a polymer cushion between the phospholipid bilayer and a solid glass substrate but also act as covalent connections (tethers) between the bilayer and cushion. Our approach involves Langmuir-Blodgett transfer of a phospholipid-lipopolymer monolayer followed by Schaefer transfer of a pure phospholipid monolayer and is capable of varying the tethering density between the polymer layer and the phospholipid bilayer in a very controlled manner. Further stabilization is achieved if the glass substrate is surface-functionalized with a benzophenone silane. In this case, a photocross-linking reaction between the polymer and benzophenone group allows for the covalent attachment of the polymer cushion to the glass substrate. This approach is similar to that recently reported by Wagner and Tamm in which double tethering is achieved via lipopolymer silanes (Wagner, M. L.; Tamm, L. K. Biophys. J. 2000, 79, 1400). To obtain a deeper understanding of how the covalent tethering affects the lateral mobility of the bilayer, we performed fluorescence recovery after photobleaching (FRAP) experiments on polymer-tethered bilayers at different tethering densities (lipopolymer/phospholipid molar ratios). The FRAP data clearly indicate that the hydrophobic lipopolymer moieties act as rather immobile obstacles within the phospholipid bilayer, thereby leading to hindered diffusion of phospholipids. Whereas the high lateral diffusion coefficient of D = 17.7 mum(2)/s measured at low tethering density (5 mol % lipopolymer) indicates rather unrestricted motion within the bilayer, corresponding values at moderate (10 mol % lipopolymer) and high (30 mol % lipopolymer) tethering densities of D = 9.7 mum(2)/s and D = 1.1 mum(2)/s, respectively, show significant hindered diffusion. These results are contrary to the recent findings on similar membrane systems reported by Wagner and Tamm in which no significant change in phospholipid diffusion was found between 0 and 10 mol % lipopolymer. Our experimental report leads to a deeper understanding of the complex problem of interlayer coupling and offers a path toward a compromise between stability of the whole system and lateral mobility within the bilayer. Furthermore, the FRAP measurements show that polymer-tethered membranes are very interesting model systems for studying problems of restricted diffusion within two-dimensional fluids.

Recent surface rheology and film balance experiments on monolayers of PEG lipopolymers and phospholipid/PEG lipopolymer mixtures at the air−water interface have revealed a new class of quasi two-dimensional physical networks. Two different kinds of associative interactions are necessary to form the network: microcondensation of alkyl chains of lipopolymers to form small clusters and water molecule mediation of the interaction between adjacent PEG clusters via hydrogen bonding. In the experiments presented here, we are interested to learn whether the physical gelation is PEG specific or whether it is a more general characteristic of lipopolymers at the air−water interface. To address this topic, we have expanded our surface rheology and film balance experiments to poly(oxazoline) lipopolymers. Our experiments indicate the occurrence of a rheological transition if the poly(oxazoline) lipopolymers consist of a dioctadecylglycerol anchor. This shows that the physical gelation among lipopolymers is not a PEG-...

OBJECTIVE: To investigate possible relationships between leptin and energy expenditure (EE), both in the condition of stable body weight and during weight loss. SUBJECTS: Seventy four Caucasian, adult obese women with stable body weight (including 10 obese women studied before and during a body weight-reducing program). MEASUREMENTS: Resting EE (REE) and substrate oxidation rates by indirect calorimetry; plasma leptin concentrations by radioimmunoassay (RIA). RESULTS: In conditions of stable body weight, leptin values showed a significant, negative relationship with REE, as expressed in absolute values (P = 0.030) and as adjusted for the variation in lean body mass (LBM) (P = 0.017). This negative relationship was independent of both LBM and fat mass (FM). Linear regression analysis was used to obtain the equation linking REE and LBM; then both predicted REE and the percent deviation from predicted REE were calculated for each subject. Leptin values were negatively related (P < 0.0001) to the deviation from predicted REE. During active body weight loss, the modifications of both REE (delta REE) and lipid oxidation (delta lipid oxidation) were significantly negatively related to leptin concentrations, which were measured before the dieting period (P < 0.03 for both). CONCLUSION: In obese women, high plasma leptin concentrations are associated with a low rate of REE, when body weight is stable, and with a reduction of REE and lipid oxidation, in response to a hypocaloric diet. This suggests that, in severely obese women, leptin is a marker of sparing energy mechanisms operating in both basal and reducing weight conditions.

Silicon ribbons for photovoltaic applications grown under typical industrial processing conditions by the String Ribbon and the Edge-defined Film-fed Growth (EFG) methods were quantitatively analyzed by newly developed scanning technologies with respect to the grain structure and orientation. As a result the grain structure consists typically of elongated grains with a 〈2 1 1〉 orientation nearly parallel to the growth direction and a {1 1 0} ribbon surface. These grains are mainly separated by Σ3 twin boundaries which are nearly perpendicular to the {1 1 0} ribbon surface. This result is found to be independent from the orientation of seed crystals and is in agreement with earlier studies on silicon ribbon growth. The experimental observations will be explained by a growth model which considers the surface energies of the growing grains and the need for undercooling in front of the phase boundary.

OBJECTIVE: To examine the relationships between the distribution and composition of subfractions of very low density (VLDL), low density (LDL) and high density (HDL) lipoproteins and central fat deposition as measured by the waist-to-hip ratio (WHR). DESIGN: Participants (n=62, 44 women and 18 men; body mass index (BMI)≥25.0) were recruited from those consecutively attending the outpatient obesity clinic at the University Hospital, Geneva. MEASUREMENTS: Lipoprotein subfractions were isolated from fasting blood samples by cumulative flotation or density gradient ultracentrifugation. Concentration and composition were analysed as a function of obesity indices. RESULTS: There were significant correlations between the WHR and the profiles of the three major lipoprotein subclasses. Central obesity was associated with larger VLDL, small, dense LDL and lower levels of HDL-2 independently of other indices of obesity and plasma triglycerides. Central obesity was also significantly and independently associated with compositional anomalies, specifically an increased free cholesterol content of VLDL and LDL. CONCLUSIONS: Central body fat was associated with modifications of an atherogenic nature to lipoprotein distribution and composition. The data are consistent with an impact of body fat distribution on cardiovascular disease (CVD) via the agency of modified lipoprotein metabolism independently of raised triglycerides.

A rapid and selective reversed-phase high-performance liquid chromatographic assay with gradient elution and diode-array detection for diacetylmorphine, morphine, codeine, and their free and glucuronidated metabolites in plasma, was developed. After addition of ethylmorphine as internal standard the plasma samples were extracted using C18 ODS-2 solid-phase columns with a recovery better than 80%. The limit of quantitation using an injection volume of 2 microl was 25 ng/ml for each compound. The intra- and inter-day precision was better than 5%. The described method cannot only be used for pharmacokinetic studies but also for intoxication cases to monitor a wide range of opiates.

An HPLC method with photodiode array detection (DAD) is described for the qualitative and quantitative determination of neutral and acidic cannabinoids in Cannabis sativa L. The complex chromatographic pattern can be used for the classification of Cannabis chemotypes, the monitoring of the psychotropic potency and the comparison of Cannabis products of different origin.

A rapid and sensitive method for identification of Catha edulis (khat) basing on a simple extraction and TLC separation is described. The test is specific for the main khatamines cathinone and norpseudoephedrine.

Results of spectral and photometric measurements are presented for pulsed operated high-pressure-sodium lamps. Choosing for the colour temperature a value of 3000 K, the output spectrum was optimized with respect to colour rendition and lamp efficacy taking the pulse parameters, the sodium mole fraction, and the cold spot temperature as quantities to be varied. For the nominal rating of 70 W a maximum lamp efficacy of 70 lm/W and a colour rendering index of 40 can be obtained. Further improvements of the colour rendition require an enhanced sodium vapour pressure which can be achieved by operating the lamp at rised cold spot temperature.

Gas chromatographic-mass spectrometric (GC-MS) quantitation of 25 cannabis sed oils determined delta 9-tetrahydrocannabinol (THC) concentrations from 3 to 1500 micrograms/g oil. In a pilot study, the morning urine of six volunteers who had ingested 11 or 22 g of the oil, which contained the highest THC content (1500 micrograms/g), was collected for six days. The urine samples were screened by immunoassay, and the content of 11-nor-9-carboxy-delta 9-THC (THCCOOH) was determined by GC-MS. Urine samples were found cannabis positive for up to six days with THCCOOH-equivalent concentrations up to 243 ng/mL. by the Abuscreen OnLine immunoassay and THCCOOH contents from 5 to 431 ng/mL by the GC-MS method. All subjects reported THC-specific psychotropic effects.

In this note we report the first observation of salient features of the Si(1 1 1)7×7 reconstructed surface across monatomic steps by dynamic atomic force microscopy (AFM) in ultrahigh vacuum (UHV). Simultaneous measurements of the resonance frequency shift Δf of the Si-cantilever and of the mean tunneling current Ī i from the cleaned Si tip indicate a restricted range for stable imaging with true atomic resolution. The corresponding characteristics vs. distance reveal why feedback control via Δf is problematic, whereas it is as successful as in conventional STM via Ī i .

(−)-Δ9-(trans)-Tetrahydrocannabinolic acid A (THCA-A), which is the main cannabinoid in ripe plants and the biogenetk precursor of the psychoactive (−)-Δ9-(trans)-tetrahydrocannabinol, has been isolated from Cannabis sativa L. After extraction with petroleum ether and subsequent fractionation using alkali and diethyl ether, purification was performed by medium pressure liquid chromatography to yield an amorphous >99% pure powder. THCA-A was characterized by its chromatographic and spectroscopic data.

The impact of energy economy on body weight loss was investigated in 20 obese women, submitted to Roux-en-Y gastric bypass. Resting energy expenditure (REE), substrate oxidation rates, plasma glucose, free fatty acid, and insulin and leptin levels were measured before and 3, 6, and 12 months after surgery. Predicted REE was obtained from linear regression analysis of REE and fat free mass, in a group of 85 women, whose body mass index ranged between 20 and 60 kg/m2. The deviation from predicted REE, calculated as area under the curve (AUC) over the 12-month period for each patient, was considered as the expression of energy economy. Energy economy AUC was significantly (P < 0.005) negatively related to the weight lost during 12 months after surgery.Energy intake, calculated from self-reported food consumption, was also expressed as AUC. Energy intake AUC showed a significant (P < 0.002) positive correlation with weight loss.Lipid oxidation rate, also calculated as AUC, significantly correlated, negatively, with energy economy (P < 0.001) and, positively, with energy intake (P < 0.002). Preoperative leptin values were significantly (P < 0.01) linked to individual energy economy capacity.In conclusion, after Roux-en-Y gastric bypass, energy economy hampers the weight loss process, probably through a low fat oxidation rate.

OBJECTIVES: To evaluate energy balance after three isocaloric oral loads of different composition and to establish possible relationships between the substrates oxidative patterns and the modifications of insulin and free fatty acids (FFA) plasma profiles. DESIGN: Each subject received, in a randomized order, three oral loads of 2658 +/- 45 kJ (636 +/- 11 Kcal) either as glucose, lipids (cream) or a mixture (glucose+cream). SETTING: The experiments were performed at the University Hospital of Geneva. SUBJECTS: Ten normal body-weight volunteers. METHODS: Energy expenditure (EE) and substrates oxidation were measured by indirect calorimetry during 8 h following each load. Plasma glucose, insulin and FFA were also measured. RESULTS: EE was 1776 +/- 107, 1818 +/- 125 and 1785 +/- 117 KJ over 8 h after glucose, mixed and lipids load, respectively. Glucose oxidation was the highest after oral glucose as compared to mixed and lipids load, while the highest value of lipids oxidation was measured after fat load. A significant relationship linked fat oxidation to plasma FFA (r = 0.54, P < 0.002) as well as to insulin (r = -0.40, P < 0.002). CONCLUSIONS: (a) The energetic cost of glucose and fat intake is the same; (2) after each load, the main source of energy corresponds to the substrate administered; (3) both plasma insulin and FFA influence the substrate oxidative patterns observed after each load; (4) alimentary fat may contribute to fat oxidation by maintaining elevated plasma FFA levels.

In this study we investigated the influence of N-acetylcysteine (NAC) on the hepatic microcirculation after warm ischemia by intravital fluorescence microscopy. Clamping of the left liver lobe was performed in 20 male Wistar rats for 70 min. The treatment group (n = 10) received 400 mg NAC/kg body weight 20 min prior to clamping. After reperfusion, acinar and sinusoidal perfusions were observed as well as the leukocyte-endothelium interaction. Phagocytic activity was assessed after application of latex beads. NAC reduced the number of nonperfused sinusoids in all acinar zones. A reduction in zone 1 (portal) was achieved from 15.5 to 7.1% (p0.0001), in zone 2 (midzonal) from 14.6 to 6.1% (p0.0001) and in zone 3 (central) from 11.9 to 2.9% (p0.0001). There were no significant differences in leukocyte adherence as well as in phagocytic activity detectable. We conclude that NAC improves hepatic microcirculation after warm ischemia by increasing sinusoidal blood flow.

Comparative molecular field analysis (CoMFA) is shown to be a very useful tool in treating two series of artificial substrate analogue inhibitors, peptide methyl ketones and chloromethyl ketones, of the serine protease thermitase. The backbone structure of the native polypeptide eglin c found in the X-ray structure of its complex with the enzyme served as a template for the alignment of the inhibitors, which could be shown to be the key for success. Restricted only by the relatively small number of different amino acids representing the peptide sequence we were able to determine the regions of the compounds that are important for the value of the inhibitor constant K(i). On the basis of these results we have suggested some new structures with possibly increased inhibitory activity. One such structure was synthesized and is shown to be the most active compound tested up to now, with an experimental K(i)-value in the predicted range.

By theoretical conformational investigations of substrates and nonsubstrates of the enzyme dipeptidyl-peptidase IV (DP IV) as well as dipeptide-esters using the ECEPP83 method we determined the structure of peptides recognized and cleaved by the enzyme. From a comparison of all possible structures for the substrates with conformations not possible in nonsubstrates we concluded that a single conformation explains substrate specificities of DP IV. This conformation is characterized by the following dihedral angles: psi 1 = 85 degrees, omega 1 = 180 degrees, phi 2 = -75 degrees, psi 2 = 80 degrees, and omega 2 = 180 degrees. The conclusions were supported by comparisons of molecular electrostatic potentials calculated with the molecular graphics program HAMOG.

Zinc meso-tetraphenylporphyrin (ZnTPP) forms triplet exciplexes with different arenediazonium salts (p-Et2N, p-MeO, p-Me, p-t-Bu, p-H, p-Cl, p-Br) and p-benzoquinone, and a singlet exciplex with oxygen (probably formed after energy transfer from excited ZnTPP to 3O2 to yield 1O2). The absorption spectra of these exciplexes are nearly identical and – except of pronounced fine structures – similar to the spectrum of 3(ZnTPP)*. By means of WARE treatment of flash-photolytically determined rate constants or of quantum yields equilibrium constants, lifetimes and further data of diazonium salt exciplexes are determined. The equilibrium constants and lifetimes are very similar and amount to about 104 M−1 and 20 μs, respectively. The equilibrium constants of the oxygen and p-benzoquinone exciplexes are determined by competition experiments; they amount also to about 104 M−1. The diazonium salt exciplexes belong to the charge-shift type. Their equilibrium constants are, therefore, independent of the solvent polarity, as is interestingly also observed for the oxygen exciplex which formally belongs to the charge-separation type. The p-benzoquinone exciplex dissociates in acetonitrile as has been found also by other authors.

Photoexcited zink tetraphenylporphyrin (ZnTPP) reacts with arene diazonium salts via electron transfer according to the oxidation mechanism. This is proved by ESR spectroscopy of ZnTPP+ formed and the fact that N2 and ZnTPP+ are formed in a molar ratio. Due to very different life-times of1(ZnTPP)* and 3(ZnTPP)* it is possible to differentiate between singlet and triplet electron transfer reactions using different diazonium salt concentrations. In this way, the respective quenching constants are determined by means of flash spectroscopy. Due to electron back transfer the singlet reaction at high concentrations of diazonium salts (0.1M) is inefficient (quantum yield 0.1), whereas back electron transfer is symmetry-forbidden in the triplet reaction which, therefore, proceeds with high quantum yields, mearly reaching the ISC quantum yield. From differences between the triplet quenching constants determined by flash spectroscopy and from product quantum yields, respectively, and from corresponding kinetic models it is concluded that the triplet reaction proceeds via a reversibly formed triplet exciplex. Complexes of meso tetraphenyl porphyrin containing Pb(II), Sn(IV), Mn(II), Ni(II), Cu(II) and Fe(III), respectively, have lower sensitization activities decreasing in the order, given in the text.

Monolayers containing solely porphyrins with or without aliphatic chains or porphyrins mixed with phospholipids are studied on water on solid surfaces. The systems are manipulated on the water surface and characterized by film balance techniques, fluorescence microscopy, fluorescence and absorption spectroscopy and, after transfer onto solid supports, by optical and electron microscopy techniques. The data presented contain information on the interrelation between molecular and monolayer structure and on porphyrin-porphyrin and porphyrin-lipid interactions. Homogeneous monolayers can be formed only for porphyrins containing aliphatic chains or in dilution with lipids in the fluid phase. An ordered structure is obtained for zinc 3,8-bis(1'-heptadecenyl)deuteroporphyrin dimethylester (ZnHDPDME) that exhibits two aliphatic chains attached to one edge and two (hydrophilic) ester groups to the opposite edge of the porphyrin moiety. If these groups are bound to the same edge, a disordered structure with little tendency to aggregate formation is obtained. None of the porphyrins are soluble in the solid phase of phospholipids. As this is presumably due to the high packing density given by the area per hydrocarbon chain this is suggested to hold also for other aliphatic matrices including fatty acids. A strong decrease in fluorescence yield with increasing molecular density is observed for ZnHDPDME diluted in phospholipids. This suggests a change in the coordination of the central zinc atom of the porphyrin. As the environment can be changed in a defined and continuous way these systems offer the possibility of studying the relation between the microscopic surroundings and the optical properties.

The effect on rancidity of heated residues of the four commercial types of baking powder was measured in artificial aqueous fat systems. The powders inhibited rancidity in such systems in the following order: combination, tartrate, monocalcium phosphate, and pyrophosphate—the combination being least effective and the pyrophosphate very much more effective than any other type.

A number of phenolic inhibitors were tested in pure dry hard lard and in the same lard in contact with an aqueous solution at pH 7.5. In dry lard, at a concentration of .005%, the order of effectiveness of the antioxidants tested was NDGA (best), BHA, propyl gallate, lauryl gallate, and alpha-tocopherol. In contact with aqueous solutions at pH 7.5 NDGA was much less effective, and BHA was the best antioxidant tried. Of a group of synergistic antioxidants in aqueous solution in contact either with plain lard or with lard containing .005% of the phenolic inhibitors mentioned above, hexametaphosphate and Maddrell’s salt were the most effective. Ascorbate generally accelerated rancidity with all of the primary antioxidants except NDGA. Polyphosphates counteracted the accelerating effect of ascorbate. Combinations of polyphosphate with ascorbate and primary inhibitors gave prolonged protection.