Early growth studies and properties of BP

Boron monophosphide was grown by the chemical vapor deposition reaction of phosphine and diborane. Studies of the early growth show a three dimensional nucleation and coalescing of islands. The index of refraction of the film was determined as a function of film thickness. For thick films, a value of 2.3 was measured for the index of refraction.     

Olfactory discrimination, reversal learning, and stimulus control in rats.

Conducted 3 experiments with a total of 21 Wistar rats. In Exp I Ss were trained to discriminate lights, tones, or odors and then given a series of discrimination reversals. Only Ss trained with odors showed positive transfer on the first reversal and acquisition of a reversal set. Other experiments demonstrated that (a) Ss preferentially attended to odors when presented in compound with lights or tones; (b) odors exerted more discriminative control than tones in tests using compound stimuli of competing sign; and (c) after pretraining on the positive stimulus, acquisition of an odor but not a light discrimination occurred with virtually no errors. These results demonstrate the importance of stimulus modality in the establishment of stimulus control and the need for more careful analysis of stimulus factors in cross-species comparisons of learning ability. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conformation of the molecules in drawn polypropylene revealed by neutron scattering studies

It has not been possible previously to do a complete study of drawn polyolefins using SANS techniques because of void scattering. In the case of polypropylene this can be reduced sufficiently to permit measurements with the Q-vector perpendicular and parallel to the draw direction. A complete analysis has been carried out with a draw ratio 8:1 in which the PPD molecules of narrow molecular weight distribution and molecular weights in the range 390 000 to 50 000 are molecularly dispersed in a drawable PPH matrix. The dimensional changes on drawing are to extend the molecule by a factor of 2 with a corresponding reduction in diameter to a maximum of 40%. We have interpreted the data at high Q on the basis that the molecule is not uniformly distributed but the majority is folded into sub-units and the number of these is proportional to the molecular weight of the polymer. A further feature of the sub-units structure is that its length is approximately two lamellae thick, this dimension is similar to the SANS scattering length (I_n) identified in the study of isotropic material. The double stems belonging to the same molecule have been concentrated by the drawing process some 16 times and a consequence of this is to markedly change the Kratky curves from the isotropic case. Notwithstanding, this increase in the packing of the molecule, the stems are still, on average, some 40 Å apart and surrounded by many stems belonging to other macromolecules. Similarly, each sub-unit is surrounded by sub-units belonging to neighbouring molecules.     

Small-angle neutron scattering study of amorphous polycarbonate

Experiments have been performed on deuterated polycarbonate chains with five different molecular weights, randomly dispersed in a protonated polycarbonate matrix. There is evidence for some ester interchange in the melt. This requires that the values of M_w obtained from the SANS data be used. The measured radii of gyration were found to follow the relationship: R_w = βM^a_w, with β = 0.457(9) and α = 0.5. The high value for β compared with that for polystyrene (β = 0.27) is a reflection of the stiffer backbone in polycarbonate.     

Constraints in meeting food safety and quality requirements in the Turkish dairy industry: a case study of Izmir province

Recent global developments concerning food quality and food safety have influenced and stimulated food legislation in Turkey in accordance with internal and international trade and agreements. In this study, the way in which the dairy industry conforms to this legislation was analyzed through a case study of Izmir province, which generally has all the structural characteristics of the dairy sector in Turkey. A survey in which dairy plant managers responded to a special questionnaire was used to collect data from 86 dairy plants chosen on the basis of proportional sampling. According to the results of this study, (i) there are many dairy processors in the region, (ii) most managers have a limited education concerning their positions, (iii) most firms handle small volumes of milk and have little control over the raw milk supply, (iv) resources are too limited in these firms, limiting their ability to adopt most regulations, and (v) few processors apply the regulatory practices imposed by governmental agencies. Thus, food legislation is not enough to ensure food safety in the dairy industry in Turkey. Technical and educational support should be given to farmers and the staff of dairy firms by the Ministry of Agriculture to form an appropriate food safety infrastructure in Turkey for the milk and processed dairy products industry.     

Raman spectra of proteinaceous materials used in paintings: a multivariate analytical approach for classification and identification

This work presents Raman spectra obtained from thin films of protein materials which are commonly used as binding media in painted works of art. Spectra were recorded over the spectral range of 3250-250 cm(-1), using an excitation wavelength of 785 nm, and several bands have been identified in the fingerprint region that correspond to the various proteins examined. Differences in the C-H vibrations located between 3200 and 2700 cm(-1) can be accounted for with reference to the amino acid composition of the protein-based binding media as well as the presence of fatty acid esters, in the case of egg yolk. In addition, the discrimination of different proteins on the basis of variations in spectra between 3200 and 2700 cm(-1) can be achieved following multivariate analysis of a large data set of spectra, providing a novel and nondestructive alternative based on Raman spectroscopy to other methods commonly used for the analysis of proteins.     

Computational Properties of Two Exact Algorithms for Bayesian Networks

This paper studies computational properties of two exact inference algorithms for Bayesian networks, namely the clique tree propagation algorithm (CTP)¹ and the variable elimination algorithm (VE). VE permits pruning of nodes irrelevant to a query while CTP facilitates sharing of computations among different queries. Experiments have been conducted to empirically compare VE and CTP. We found that, contrary to common beliefs, VE is often more efficient than CTP, especially in complex networks.     

Modified single crystals for high-power underwater projectors

Underwater electroacoustic projectors using single crystals based on the lead magnesium niobate-lead titanate (PMNT) composition were investigated. The large electromechanical coupling coefficient (k(33) > 0.90) and piezoelectric coefficient (d(33) > 1500 pC/N) of PMNT have been demonstrated to improve transducer bandwidth and source level relative to conventional piezoelectric ceramics. The low mechanical quality factor (Q(M) < 200) and low temperature stability (T(RT) < 95°C) of PMNT, however, limit its utility in high-power, high-duty-cycle applications. Use of modified single crystals was shown to result in transducers which exhibit up to 5 dB improvement in source level over PMNT when operated at resonance. Compared with a PZT4 transducer, these modified crystals offer similar source level and power handling capability at resonance, but the available bandwidth is doubled and a 6 dB improvement in maximum source level is achieved when driven off resonance.