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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4647-4651 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Anodic dissolution of a structure composed of the chemically vapor deposited amorphous SiC film and silicon wafer results in the formation of a system of hexagonally ordered pore colonies. This intriguing effect takes place when the structure SiC/Si is subjected to a short-time (several seconds) anodization in 48% HF/ethylene glycol solution. As a result of this procedure the SiC layer is converted into a porous one with diameters of the pores not exceeding 30–50 nm. Continuing the anodization process beyond the complete conversion of SiC layer into a porous one results in porous structure formation in an underlying Si wafer. It appears that pores in silicon form colonies arranged in hexagonal order. Characteristic distance between neighboring colonies increases with the anodic current density applied during the electrochemical process. It is assumed that the effect of self-ordered pore colonies growth is due to the accumulation of mechanical stress at SiC/Si interface due to a lattice mismatch and dynamic pressure developed in the pores during the anodic dissolution reaction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography A 392 (1987), S. 426-434 
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography A 249 (1982), S. 385-392 
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography A 258 (1983), S. 244-251 
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of porous materials 7 (2000), S. 97-101 
    ISSN: 1573-4854
    Keywords: AC impedance ; porous silicon ; residual moisture ; aging effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The present work aims to study the AC impedance of porous silicon films left in the contact with the anodizing bath after their growth is over. It is shown that the layers grown at p-type silicon experience noticeable changes of their impedance behavior resulting in the gradual growth of electrical resistance of the p-PS layer. This change is assumed to be related with the deposition of a passive layer at the pore bottoms associated with reabsorption of dissolved Si-containing material from the electrolyte. The layers formed at n-Si also show changes of the electrical impedance, although they are much more complicated than in the previous case (dependence of the kinetics of changes on the polarization current and polarization time, presence of the inductive loops at the impedance spectra, etc.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-0662
    Keywords: Atmospheric multiphase system ; atmospheric acidity ; cloud chemistry ; cloud acidity ; phase-partitioning ; Kleiner Feldberg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The chemistry of cloud multiphase systems was studied within the Kleiner Feldberg Cloud Experiment 1990. The clouds encountered during this experimental campaign could be divided into two categories according to the origin of air masses in which the clouds formed. From the chemical point of view, clouds passing the sampling site during the first period of the campaign (26 October-4 November) were characterized by lower pollutant loading and higher pH, as compared to clouds during the final period of the experimental campaign (10–13 November). The study of multiphase partitioning of the main chemical constituents of the cloud systems and of atmospheric acidity within the multiphase systems themselves (gas + interstitial aerosol + liquid droplets) are presented in this paper. A general lack of gaseous NH3 was found in these cloud systems, which caused a lack of buffer capacity toward acid addition. Evidence supports the hypothesis that the higher acidity of the cloud systems during this final period of the campaign was due to input of HNO3. Our measurements, however, could not determine whether the observed input was due to scavenging of gaseous HNO3 from the air feeding into the cloud, or to heterogeneous HNO3 formation via NO2 oxidation by O3 to NO3 and N2O5. Sulfate in cloud droplets mainly originated from aerosol SO 4 2− scavenging, since S(IV) to S(VI) liquid phase conversion was inhibited due to both lack of H2O2 and low pH of cloud droplets, which made O3 and metal catalyzed S(IV) oxidation inefficient.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two rigid sorbents with identical nominal hydrophobic functions (Butyl-Toyopearl and poly(N-butylacrylamide)-coated porous glass (Butyl-WPG)) were compared upon chromatographic purification of lectin from Bacillus subtilis. Hydrophobic-interaction chromatography on the Butyl-WPG promotes the better resolution of nonactive contaminants from the active lectin. There were found optimal conditions for HPLC-analysis of purified lectin preparations. One step of chromatography on the butyl-WPG provided a considerable purification of lectin (98% of contaminants were removed), which retained 62,5% of its initial hemagglutinating activity.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1590-3478
    Keywords: Cerebral SPECT ; Filtered backprojection ; Conjugate gradients with modified matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario L'obiettivo dello studio è stato di valutare le immagini cerebrali SPECT con Tc-99m HMPAO, ottenute con il metodo di ricostruzione convenzionale “filtered backprojection (FBP)” versus il nuovo metodo di ricostruzione del gradients coniugato con matrice modificata (CGMM). I due metodi sono stati impiegati per generare immagini SPECT di uno studio perfusionale cerebrate in un uomo di 41 anni che aveva subito embolizzazione multipla dell'emisfero destro. Le immagini sono state acquisite con una gamma camera dedicates agli studi cerebrali the consists di una cristallo anulare di NaI(T1) (CERASPECT). Net metodo CGMM un (retro-) proiettore modella accuratamente la geometria dell'acquisizione dei dati e tiene in debito conto le effettive prestazioni del complesso cristallo-collimatore per la specifica gamma camera usata. Un algoritmo iterativo usa il (retro-) proiettore per stimare la distribuzione del tracciante in un insieme di dati. Il (retro-) proiettore definisce i coefficienti di un enorme insieme di equazioni lineari che legano la distribuzione del tracciante all'interno del campo di vista delta gamma camera ad i conti fotonici misurati, e l'algoritmo iterativo fornisce una valutazione filtrata della soluzione di quell'insieme di equazioni. Sono stati calcolati i dati effettivi della risposta specifica del complesso cristallo-collimators ad una sorgente lineare posizionata alla periferia del campo di vista, i quali sono poi stati usati per calcolare i fattori di misura del (retro-) proiettore. Net metodo CGMM il numero delle iterazioni effettuate svolge quindi una ruolo simile al parametro di frequenza “cut-off” nella ricostruzione FBP. Un notevole miglioramento della risoluzione spaziale é stato ottenuto con il metodo CGMM rispetto a quello FBP; questo ha aiutato considerevolmente a definire le strutture cerebrali grigie dalle strutture bianche a basses captazione sia nelle arse cerebrali normali the nell'emisfero colpito dall'ictus. Sebbene i tempi relativamente lunghi ancora necessari per la procedure CGMM possano essere considerati oggi un limits significativo, con la rapida diffusions dei più moderni sistemi informatici il metodo CGMM può essere proposto come valida alternativa alla tecnica FBP standard allo scopo di ottenere un migliore riconoscimento delle aree cerebrali a differente captazione.
    Notes: Abstract In the present study, we compared Tc-99m HMPAO single photon emission computed tomography (SPECT) brain images obtained using the conventional filtered backprojection (FBP) reconstruction method with the new reconstruction method of conjugate gradients with modified matrix (CGMM). The two methods were employed to generate SPECT images of a brain perfusion study in a 41-year-old patient who had suffered from multiple embolisation of the right hemisphere. Marked improvement in spatial resolution was achieved by CGMM reconstruction as compared to FBP reconstruction; this considerably helped in defining grey matter structures and low-uptake white-matter areas, both in the normal cerebral areas and in the hemisphere that had been affected by stroke. Although the relatively long time still required by the CGMM procedure might be considered as a significant drawback to date, with the increasing diffusion of the new computer facilities the CGMM method can be proposed as a valuable alternative to the standard FBP technique in order to better recognise cerebral areas with different tracer uptake.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Neurological sciences 19 (1998), S. 367-372 
    ISSN: 1590-3478
    Keywords: Regional cerebral blood flow ; Electroencephalogram ; Boxers ; Judoka
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Il fusso ematico regionale cerebrale (rCBF; metodo inalatorio con xenon-133) è stato valutato in due gruppi di pugilatori (24 dilettanti e 20 professionisti) ed in un gruppo di 10 judoka. I risultaoi sono stati confrontati con quelli ottenuti in un gruppo di volontari sani di pari età e sesso. Diciotto pugilatori (9 professionisti e 9 dilettanti) e tutti i judoka eseguirono anche un elettroencefalogramma (EEG). I valori medi di rCBF non differivano da quelli dei soggetti normali sia nei pugilatori dilettanti the nei judoka, mentre i valori dei pugili professionisti erano significativamente ridotti (p〈.001) in tutto il cervello ma soprattutto nelle regioni frontocentrali bilateralmente. La distribuzione dei valori globali di CBF (media delle 32 sonde) era simile nei controlli normali, nei judoka e nei pugilatori dilettanti, sebbene tra quest'ultimi il 12,5% presentava valori significativamente più bassi dei normali. I pugili professionisti presentavano nel 25% dei casi valori globali di CBF significativamente più bassi; negli altri casi il CBF globaae era più basso della media dei controlli, anche se in maniera non significativa. I valori globali di fusso non erano correlati nei due gruppi di pugilatori al numero dei combattimenti ufficiali. Ipoperfusioni regionali, localizzate soprattutto nelle regioni frontocentrali di entrambi gli emisferi, furono trovate nel 35% dei pugili professionistei e nel 29% dei dilettanti ma mai nei judoka. L'EEG è risultato normale nei judoka e nei pugili dilettanti, ma alterato in 3 pugili professionisti. Lo studio ha mostrato l'importanza dell'esplorazione neurofisiologica in atleti ingaggiati in sports in cui la violenza può essere causa di lesioni cerebrali anche importanti. Da questo punto di vista i pugilatori, specialmente i professionisti, risultano compromessi rispetto ai soggetti normali, a differenza dei judoka. Nei pugilatori, la mancata correlázione tra valori perfusionali e numero di incontri indica piuttosto la difficolta di tenere conto di variabili difficilmente quantificabili, quali la quantità e l'asprezza degli incontri fatti durante gli allenamenti.
    Notes: Abstract Regional cerebral blood flow (rCBF) was measured by 133-xenon inhalation in 24 amateur and 20 professional boxers, and in 10 judoka. Results were compared with those from age- and sex-matched healthy controls. Eighteen boxers (9 amateurs and 9 professionals) and all judoka also underwent electroencephalography (EEG). Mean rCBF values did not differ between either amateur boxers or judoka and controls, whereas in professional boxers rCBF was significantly (p〈.001) reduced in the whole brain, especially in the frontocentral regions. Healthy subjects, judoka, and amateur boxers showed a similar distribution of global CBF (gCBF, the mean of 32 probes) values, although 12.5% of amateurs had a significantly lower gCBF than controls. Among professional boxers, 25% showed a significantly low gCBF value; in the remaining 75%, gCBF was below the mean value of controls but did not reach statistical significance. Regional hypoperfusion, mainly in the frontocentral regions of both sides, was found in 35% of professional and in 29% of amateur boxers. A correlation between gCBF values and number of official matches was not found in boxers. EEG was normal in all judoka and amateur boxers, but it was abnormal in 3 professionals. This study shows the relevance of the neurophysiological assessment of athletes engaged in violent sports which can cause brain impairment. In fact, while professional boxers may show brain functional impairment in comparison to normal subjects, judoka do not. The lack of correlation between CBF values in boxers and the number of official matches points to the difficulty of taking into account variables, such as the number and the severity of matches during training.
    Type of Medium: Electronic Resource
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