Action du N-bromosuccinimide sur les dioxolannes. Intermediaires réactionnels

1,3-Dioxolan-2-ylium ion intermediates formed by reaction of bromine or NBS on 4-syn-aryl-3,5-dioxa-tricyclo [5.2.1.0^2.6] décanes have been isolated. 2-Succinimido-1,3-dioxolanes have been prepared for the first time.     

The vibrational dynamics of carbon monoxide in a confined space-CO in zeolites

Based on theoretical calculations, and a survey of infrared spectra of CO adsorbed on different cation exchanged zeolites, a model is proposed to explain the influence of the zeolite framework on the vibrational behaviour of CO confined into small void spaces (zeolite channels and cavities). The concepts developed should help to understand a number of details relevant to both, precise interpretation of IR spectra and a better understanding of the vibrational dynamics of small molecules in a confined space.     

Characterization of pp/regenerated tire-rubber blends using proton spin-lattice relaxation time

Proton spin-lattice relaxation time (T₁H) in the solid state was used to determine the molecular mobility of PP/regenerated tire-rubber blends (PP/RgR), employing low-field NMR. The blends were prepared with different quantities of regenerated rubber (5, 10, 15 and 20 wt%). The addition of 5 wt% maleic anhydride functionalized polypropylene (PP-g-MAH) was carried out to evaluate the processing behavior of the reclaimed material. Important differences were observed concerning the molecular mobility according to the content of regenerated rubber. A decrease in the relaxation time of the blends with an increase in PP-g-MAH content indicates that enhanced mobility of PP/regenerated tire-rubber blends was obtained and, thus, PP-g-MAH acts as a plasticizer and/or impact modified.     

Change in echolocation signals with hearing loss in a false killer whale (Pseudorca crassidens)

The echolocation signals of a false killer whale (Pseudorca crassidens) were collected during a wall thickness discrimination task and compared to clicks recorded during an identical experiment in 1992. During the sixteen year time period, the subject demonstrated a loss of high frequency hearing of about 70 kHz. Clicks between the two experiments were compared to investigate the effect of hearing loss on echolocation signals. There was a significant reduction in the peak frequency, center frequency and source level of clicks between the two time periods. Additionally, the subject currently produces more signals with low frequency peaks and fewer signals with high frequency peaks than she did in 1992. These results indicate the subject changed its echolocation signals to match its range of best hearing.     

Hearing sensitivity during target presence and absence while a whale echolocates

Hearing sensitivity was measured in a false killer whale during echolocation. Sensitivity was measured using probe stimuli as sinusoidally amplitude modulated signals with a 22.5-kHz carrier frequency and recording auditory evoked potentials as envelope-following responses. The probes were presented and responses were recorded during short 2-s periods when the animal echolocated to detect the presence or absence of a target in a go/no-go paradigm. In the target-absent trials, a hearing threshold of 90.4 dB re 1 muPa was found; in the target-present trials, the threshold was 109.8 dB. Thus, a 19.4-dB difference was found between thresholds in the target-present and target-absent trials. To check the possibility that this difference was the result of different masking degree of the probe by the emitted sonar clicks, click statistics were investigated in similar trials. No indication was found that the energy of the emitted clicks was higher in the target-present than in target-absent trials; on the contrary, mean click level, mean number of clicks per train, and overall train energy was slightly higher in the target-absent trials. Thus the data indicate that the hearing sensitivity of the whale varied depending on target presence or absence.     

Landau analog levels for dipoles in non-commutative space and phase space

We investigate the analog of Landau quantization, for a neutral polarized particle in the presence of homogeneous electric and magnetic external fields, in the context of non-commutative quantum mechanics. This particle, possessing electric and magnetic dipole moments, interacts with the fields via the Aharonov–Casher and He–McKellar–Wilkens effects. For this model we obtain the Landau energy spectrum and the radial eigenfunctions of the non-commutative space coordinates and non-commutative phase space coordinates. Also we show that the case of non-commutative phase space can be treated as a special case of the usual non-commutative space coordinates.     

Identification of diphenhydramine metabolites in human urine by capillary electrophoresis-ion trap-mass spectrometry

The identification of diphenhydramine (DH) metabolites that are frequently observed in the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) analyses of alkaline liquid/liquid and solid-phase extracts of patient urines is demonstrated. Having standards for DH and diphenhydramine-N-oxide (DHNO), the presence of these two compounds could be confirmed in urines that were collected overnight after administration of 25 mg DH chloride. Using CZE coupled to ion-trap mass spectrometry (CE-MS(n)) with positive electrospray ionization and an acetate buffer at pH 5.6, the [M+H](+) ions of DH (m/z = 256), DHNO (m/z = 272), and nordiphenhydramine (NDH, m/z = 242) and their fragmentation to a common m/z 167 product ion (diphenylcarbinol moiety) was monitored. The data indicate that all three compounds are cations in an acidic environment, the migration order being NDH, DH, and DHNO. Data obtained under negative electrospray ionization conditions suggest the presence of diphenylmethoxyacetic acid-glycine amide ([M-H](-) ion of m/z 298 and fragmentation to m/z 254, loss of CO(2)), a metabolite that could tentatively be assigned to a characteristic peak observed in the MEKC electropherogram at alkaline pH. The data presented in this paper illustrate the value of using CE-MS(n) for identification of urinary drug metabolites for which no standards are available.     

A Trudinger–Moser inequality in a weighted Sobolev space and applications

We establish a Trudinger–Moser type inequality in a weighted Sobolev space. The inequality is applied in the study of the elliptic equation where , f has exponential critical growth and h belongs to the dual of an appropriate function space. We prove that the problem has at least two weak solutions provided is small.     

Chiral Ligands Derived from Monoterpenes: Application in the Synthesis of Optically Pure Secondary Alcohols via Asymmetric Catalysis

The preparation of optically pure secondary alcohols in the presence of catalysts based on chiral ligands derived from monoterpenes, such as pinenes, limonenes and carenes, is reviewed. A wide variety of these ligands has been synthesized and used in several catalytic reactions, including hydrogen transfer, C?C bond formation via addition of organozinc compounds to aldehydes, hydrosilylation, and oxazaborolidine reduction, leading to high activities and enantioselectivities.     

Detection of organic gunshot residues from human hands using direct sample analysis-time of flight-mass spectrometry

The organic gunshot residues (OGSRs), specifically methyl centralite (MC; 1,3-dimethyl-1,3-diphenylurea), ethyl centralite (EC; 1,3-diethyl-1,3-diphenylurea), 2,4-DNT (2,4-dinitrotoluene), and TNT (trinitrotoluene), are characteristic compounds for which forensic analysts test determining if a person has discharged a firearm. A set of 200 samples from 50 shooters were collected as part of the validation study. Pistol 9 mm and special revolver .38 were fired at indoor and outdoor shooting ranges. The development of a methodology based on direct analysis of samples-time of flight-mass spectrometry (DSA-TOF-MS) made it possible to identify the main components of organic shot residues, which gave the possibility to introduce a new method of analysis of shot residues in the Chilean supply area. The DSA-TOF-MS provided extensive information on the composition of the shot residues: MC, EC, 2,4-DNT, and TNT. Samples taken from the trigger hands required minimal sample preparation that reduced analyses time. With the implementation of new alternative analytical methodologies, a great step would be taken in the analysis of OGSRs, because now there is no such technique for its analysis in Chile, and the results would also complement the existing inorganic elemental analyses generated during a gunshot.