Controlled release of 2‐heptanone using starch gel and polycaprolactone matrices and polymeric films

Varroa jacobsoni is a parasitic mite that is threatening the honeybee industry in many parts of the world. 2‐Heptanone, a natural product made by honeybees at low concentrations, is effective at elevated concentrations in controlling mite populations in honeybee colonies, especially when released over a 42 day period. An extrusion process was used to encapsulate 14, 18, and 25% 2‐heptanone in a polycaprolactone (PCL) matrix. Less than 18% of the 2‐heptanone was encapsulated in the PCL matrix. The high vapor permeability of PCL to 2‐heptanone resulted in a high flux rate and limited the usefulness of PCL as an encapsulation matrix for controlled‐release devices. A starch gel containing three times its weight in 2‐heptanone was prepared from starch‐based microcellular foam (MCF). The gel had compressive, tensile, and flexural strength values in the range of 0.56 to 1.9 MPa. 2‐Heptanone quickly evaporated from non‐laminated gels. However, when the gel was laminated with different polymeric films, a wide range of flux rates was obtained. The T₅₀ for gels laminated or coated with poly(vinyl alcohol) (PVAL, 99% hydrolyzed) and ethylene‐vinyl alcohol copolymer (EVAL) was 72 and 1030 days, respectively. The most promising film was a starch/glycerol film that released 50% of the 2‐heptanone (T₅₀) in approximately 13 days. Copyright © 2007 John Wiley & Sons, Ltd.     

Fluorescence enhancement of trans-4-aminostilbene by N-phenyl substitutions: the "amino conjugation effect"

The synthesis, structure, and photochemical behavior of the trans isomers of 4-(N-phenylamino)stilbene (1c), 4-(N-methyl-N-phenylamino)stilbene (1d), 4-(N,N-diphenylamino)stilbene (1e), and 4-(N-(2,6-dimethylphenyl)amino)stilbene (1f) are reported and compared to that of 4-aminostilbene (1a) and 4-N,N-dimethylaminostilbene (1b). Results for the corresponding 3-styrylpyridine (2) and 2-styrylnaphthalene analogues (3) are also included. The introduction of N-phenyl substituents to 4-aminostilbenes leads to a more planar ground-state geometry about the nitrogen atom, a red shift of the absorption and fluorescence spectra, and a less distorted structure with a larger charge-transfer character for the fluorescent excited state. Consequently, the N-phenyl derivatives 1c-e have low photoisomerization quantum yields and high fluorescence quantum yields at room temperature, in contrast to the behavior of 1a, 1b, and most unconstrained monosubstituted trans-stilbenes. The isomerization of 1c and 1d is a singlet-state process, whereas it is a triplet-state process for 1e, presumably due to a relatively higher singlet-state torsional barrier. The excited-state behavior of 1f resembles 1a and 1b instead of 1c-e as a consequence of the less planar amine geometry and weaker orbital interactions between the N-phenyl and the aminostilbene groups. Such an N-phenyl substituent effect is also found for 2 and 3 and thus appears to be general for stilbenoid systems. The nature of this effect can be described as an "amino conjugation effect".     

Mechanistic aspects of the bromination of 10-substituted phenothiazines

The addition of 1 and 2 molar equivalents of bromine to a series of 10-alkylphenothiazines, 1a-d (methyl, ethyl, n-propyl, and isopropyl, respectively), yields the corresponding 3-bromo- and 3,7-dibromo-10-alkylphenothiazines ( 11a-d and 12a-d , respectively). Evidence which supports the typical clectrophilic aromatic substitution mechanism is presented. Radical cations ( 12a-d^.+ ) arc produced when 12a-d are treated with 1 or 2 molar equivalents of bromine. Upon boiling in acetic acid these radical cations are converted predominantly to 1,3,7,9-lelrabromophenothiazine ( 5 ) and the parent 3,7-dibromo-10-alkylphenothiazine ( 12a-d ) with the evolution of hydrogen bromide. The 10-methyl radical ( 12a ) gives, in addition, 1,3,7-tribromo-10-methylphenothiazine ( 15 ). A mechanism if proposed for these reactions in which initial dealkylution of 12b-d^.+ to 3.7-dibromophenothiazine radical cation ( 13 ) occurs followed by reduction of 13^.+ by bromide ion to parent 3,7-dibromophenothiazine ( 13 ). Subsequent bromination of 13 by molecular bromine produced in the previous redox reaction yields 1,3,7-tribromo-( 14 ) and 1,3,7,9-tetra-bromo-( 5 ) phenothiazines. The small size of the methyl group allows 12a to be brominated at the 1-position prior to dealkylation. In addition to undergoing bromination at the 3- and 7-position, 10-isopropylphenothiazine ( 1d ) is oxidized to the radical cation 12e^.+ when treated with bromine. 10-Benzylphenothiazine ( 1e ), however, undergoes oxidation to radical cation 1e^.+ exclusively. This radical cation debenzylates readily at room temperature and is converted finally into phenothiazine.     

Reaction products with internal energy beyond the kinematic limit result from trajectories far from the minimum energy path: an example from H + HBr --> H2 + Br

The importance of reactive trajectories straying far from the minimum energy path is demonstrated for the bimolecular reaction H + HBr --> H2(v', j') + Br at 53 kcal/mol collision energy. Product quantum state distributions are measured and calculated using the quasi-classical trajectory technique, and the calculations indicate that highly internally excited H2 products result from indirect reactive trajectories with bent transition states. A general argument is made suggesting that reaction products with internal energy exceeding a kinematic constraint can, in general, be attributed to reactive collisions straying far from the minimum energy path.     

Separation of double-stranded DNA fragments by capillary electrophoresis: Impacts of poly(ethylene oxide), gold nanoparticles, ethidium bromide, and pH

The separation of DNA by capillary electrophoresis using poly(ethylene oxide) (PEO) containing gold nanoparticles (GNPs) is presented. The impacts of PEO, GNPs, ethidium bromide (EtBr), and pH on the separation of double-stranded DNA have been carefully explored. Using a capillary dynamically coated with 5.0% poly(vinylpyrrolidone) and filled with 0.2% PEO containing 0.3 x GNPs (the viscosity less than 15 cP), we have demonstrated the separation of DNA markers V and VI within 5 min at pH 8.0 and 9.0. In terms of resolution and reproducibility, GNPs have a greater impact on the separation of DNA at pH 9.0. Resolution improvements for large DNA fragments (> 300 base pairs, bp) are greater than those for small ones in the presence of GNPs. It is important to point out that reproducibility is excellent (relative standard deviations for the migration times less than 0.5%) and thus no further dynamic coating is required in at least 20 consecutive runs in the presence of GNPs. Using 0.2% PEO (pH 9.0) containing 0.3 x GNPs, the separation of DNA fragments ranging in size from 21 to 23,130 bp was accomplished in 7 min. The results presented in this study show the advantage of PEO containing GNPs for DNA separation, including rapidity, high resolving power, excellent reproducibility, and ease of filling capillaries.     

Development of a finite element solution module for the analysis of the dynamic behavior and balancing effects of an induction motor system

The study developed a multipurpose finite element solution module with the theoretical groundwork originated from principles of rotordynamics. This module is capable of solving many of the related rotating machine problems such as of the high speed gas bearing spindles and the electric machines. The goal of this paper is to utilize the developed solution module in investigating various aspects of the vibration behavior of an induction motor system for solving its failure problem of the shaft. Some of the crucial factors to the quality and performance of the motor, such as the vibration amplitude as resulted from the bearing wear, damping effects, mass unbalance, and the passing of system resonance critical speeds, are all investigated in the study. An efficient dual-rotor model is verified to have excellent accuracy when comparing the calculated frequency response function (FRF) with that from modal testing. The results of the transient orbit analysis indicate that the bearing stiffness and damping dominates the vibration amplitude remarkably. The effects both from the bearing damping as well as from the clamping–damping between the silicon steel core and the rotating shaft are all examined. It is noticed that the bearing damping plays the major role in the restraint of the vibration amplitudes of the rotor. For the analysis of vibration suppression with different eccentricities of the unbalanced masses, it is found that the adding of balance masses will normally suppress the vibration amplitude effectively until the point where an optimum amount that causes the minimum balanced vibration amplitudes is observed. Both the qualitative and quantitative analyses for the effectiveness of the balance mass added with different eccentricity ratios are studied. Thus, the critical adding mass ratio (i.e. the adding mass ratio at the minimum balanced amplitude factor) can also be predicted through its linear relationship with the eccentricity ratio. Based on all the findings through the study, it is concluded that the approach not only can solve the realistic shaft vibration failure problems of a motor and the demonstrated processes are also believed to be able to help the designers to have better command of motor performance at the system design stage.     

Optical biopsy of liver fibrosis by use of multiphoton microscopy

We demonstrate the application of multiphoton microscopy in diagnosing toxin- (CCl4-) induced liver fibrosis in mice. Although hepatocyte autofluorescence does not vary significantly, different degrees of necrosis and stellate cell proliferation at necrotic sites in livers with fibrosis (ex vivo) can be detected easily from multiphoton-induced autofluorescence images by use of 780-nm excitation. Our result suggests that multiphoton microscopy can be developed into an effective technique for the detection and diagnosis of liver fibrosis in vivo.     

Photoacoustic flow measurements by use of laser-induced shape transitions of gold nanorods

A quantitative technique for flow measurements based on a wash-in analysis is proposed. The technique makes use of the shape dependence of the optical absorption of gold nanorods and the transitions in their shape induced by pulsed laser irradiation. The photon-induced shape transition of gold nanorods involves mainly a rod-to-sphere conversion and a shift in the peak optical absorption wavelength. The application of a series of laser pulses will induce shape changes in gold nanorods as they flow through a region of interest, with quantitative flow information being derived from the photoacoustic signals from the irradiated gold nanorods measured as a function of time. To demonstrate the feasibility of the technique, a Nd:YAG laser operating at 1064 nm was used for irradiation and a 1 MHz ultrasonic transducer was used for acoustic detection. The flow velocity ranged from 0.35 to 2.83 mm/s. Excellent agreement between the measured velocities and the actual velocities was demonstrated, with a linear regression correlation coefficient of 0.93. This study is a pioneer work on wash-in flow estimation in photoacoustic imaging.     

SF6 ground-based infrared solar absorption measurements: long-term trend, pollution events, and a search for SF5CF3 absorption

Infrared solar spectra recorded with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak (31.9°N latitude, 111.6°W, altitude), southwest of Tucson, Arizona, have been analyzed to retrieve average SF₆ tropospheric mixing ratios over a two-decade time span. The analysis is based primarily on spectral fits to absorption by the intense, unresolved ν₃ band Q branch at . A best fit to measurements recorded with SF₆ near typical background concentrations yields a SF₆ increase in the average tropospheric mixing ratio from (10⁻¹² per unit volume) in March 1982 to in March 2002. The long-term increase by a factor of 3.34 over the time span is consistent with the rapid growth of surface mixing ratios measured in situ at Northern Hemisphere remote stations, though the infrared measurements show a large scatter. Average tropospheric mixing ratio enhancements above background by 2-3 orders of magnitude have been identified in spectra recorded on 5 days between November 1988 and April 1997. These spectra were individually analyzed in an attempt to detect the strongest 8- band of SF₅CF₃, a molecule recently identified with an atmospheric growth that has closely paralleled the rise in SF₆ during the past three decades. Absorption by the strongest SF₅CF₃ band was predicted to be above the noise level in the Kitt Peak spectrum with the highest average mean tropospheric SF₆ mixing ratio, assuming the reported atmospheric SF₅CF₃/SF₆ ratio and a room temperature absorption cross sections reported for the SF₅CF₃ 903-cm⁻¹ band. An upper limit of 8×10¹⁵ for the SF₅CF₃ total column was estimated for this case. We hypothesize that the highly elevated SF₆ levels above Kitt Peak resulted from a local release experiment rather than production via electrochemical fluoridation of intermediate products, the proposed source of atmospheric SF₅CF₃. The absence of the SF₅CF₃ feature in the spectra with elevated SF₆ is consistent with the absence of SF₅CF₃ reported in a pure SF₆ sample.