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1.
A highly sensitive method for infrared radiation detection based on thermal resonance in an active bolometer is set forth. An active bolometer is a self-oscillating system consisting of an IR-sensitive cell in a feedback circuit of an adjustable proportional controller. The analysis of an active bolometer autonomous (dark) dynamics reveals that with a generalized gain factor A variation the system evolves from relaxation type towards oscillating and self-oscillating type. When A=Ac, where Ac is a critical value of the generalized gain factor A, the steady state loses stability through self-excited thermal oscillations. The resonance in a system weakly perturbed by IR radiation modulated at self-oscillation frequency q0[1+exp(iωct)] is considered. It is shown that in a small precritical vicinity =(A−Ac)/Ac of the gain factor the amplitude of forced thermal oscillations is proportional to q0/Ac. The D* calculation reveals that the detection power of a passive (A=0) bolometer increases with feedback introduction by a factor of 1/||. The detection powers of feasible versions of an active bolometer are compared. 相似文献
2.
H. Nowotny F. Benesovsky E. Rudy A. Wittmann 《Monatshefte für Chemie / Chemical Monthly》1960,91(5):975-990
Zusammenfassung Der Aufbau des Dreistoffes Niob-Bor-Silicium wird bei 1600° C mit Hilfe röntgenographischer und mikroskopischer Methoden ermittelt. Die T 2-Phase sowie die ternäre D 88-Phase besitzen einen ausgedehnten homogenen Bereich. Während Silicium in T 2 durch Bor bis annähernd Nb5SiB2 substituiert wird, besteht beim D 88-Typ eine Gitterauffüllung gemäß Nb5Si3B. Oxydationsversuche im Bereich von 400 bis 1200° C zeigen vor allem die Selektivität, indem Nb–Mk bzw. die Nb-Boride bevorzugt in Pentoxyd übergehen. Silicium übt einen stabilisierenden Einfluß auch auf das Bestehen von -Nb2O5 aus. -Nb2O5 tritt als Mischphase mit Anionendefekt auf, wodurch die sogenannte scharfe und diffuse Form erklärt wird. Die Umwandlungstemperatur - wird teilweise erheblich oberhalb der vonGoldschmidt angegebenen beobachtet. Die -Form wird als M-Modifikation nachBrauer identifiziert und relativ häufig nachgewiesen. Die -Form erweist sich alsBrauersche H-Modifikation und entsteht offensichtlich stufenweise (fast kontinuierlich) aus -Nb-Oxyd. Auf die Anionendefekt-Bildung wird nachdrücklich hingewiesen.Mit 3 Abbildungen 相似文献
3.
During nitroxide-mediated polymerization (NMP) in the presence of a nitroxide R2(R1)NO*, the reversible formation of N-alkoxyamines [P-ON(R1)R2] reduces significantly the concentration of polymer radicals (P*) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the C-ON(R1)R2 bond. In this study, theoretical BDEs of a large series of model N-alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (T(c)), and the dissociation rate constant (k(d)), of the N-alkoxyamines are established. The homolytic cleavage of the N-OC bond is also investigated at the B3P86/6-311++G(d,p)//B3LYP/6-31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N-alkoxyamines with a O-C-ON(R1)R2 fragment, and the strengthening of their C-ON(R1)R2 bond is interpreted in terms of stabilizing anomeric interactions. 相似文献
4.
The thermodynamic treatment of double-pseudobinary solutions of the type (A
xBy)
r
o(M
uNv)
s
o presented in a preceding publication was extended to include the conditions defining the critical points for the asymmetric case (r
os
o) and approximations for the spinodal and binodal surface near the critical solution point.Closed solutions for the coordinates of the critical points were obtained only for systems with ideal mixing behavior, and the isothermal binodal and spinodal near the critical solution point in such systems are adequately approximated by circles and ellipses, respectively. An axes ratio of
is nearly independent of the relative sublattice abundance and the major effect of changes in the ratios
o/r
o is a rotation of the binodal by an angle tg
.The principal features of nonideal regular systems for temperatures close to the critical solution point are described by expressions derived from small term expansions of the conditional equations, but generalizations are not possible to the same extent as for the case with ideal boundary systems. The results are discussed and the application of the equations demonstrated on model examples.Mit 6 Abbildungen 相似文献
5.
6.
Guan F Uboh CE Soma LR Luo Y Li R Birks EK Teleis D Rudy JA Tsang DS 《Rapid communications in mass spectrometry : RCM》2002,16(17):1642-1651
Clenbuterol (CBL) is a potent beta(2)-adrenoceptor agonist used for the management of respiratory disorders in the horse. The detection and quantification of CBL can pose a problem due to its potency, the relatively low dose administered to the horse, its slow clearance and low plasma concentrations. Thus, a sensitive method for the quantification and confirmation of CBL in racehorses is required to study its distribution and elimination. A sensitive and fast method was developed for quantification and confirmation of the presence of CBL in equine plasma, urine and tissue samples. The method involved liquid-liquid extraction (LLE), separation by liquid chromatography (LC) on a short cyano column, and pseudo multiple reaction monitoring (pseudo-MRM) by electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS). At very low concentrations (picograms of CBL/mL), LLE produced better extraction efficiency and calibration curves than solid-phase extraction (SPE). The operating parameters for electrospray QTOF and yield of the product ion in MRM were optimized to enhance sensitivity for the detection and quantification of CBL. The quantification range of the method was 0.013-10 ng of CBL/mL plasma, 0.05-20 ng/0.1 mL of urine, and 0.025-10 ng/g tissue. The detection limit of the method was 13 pg/mL of plasma, 50 pg/0.1 mL of urine, and 25 pg/g of tissue. The method was successfully applied to the analysis of CBL in plasma, urine and various tissue samples, and in pharmacokinetic (PK) studies of CBL in the horse. CBL was quantified for 96 h in plasma and 288 h in urine post-administration of CLB (1.6 micro g/kg, 2 x daily x 7 days). This method is useful for the detection and quantification of very low concentrations of CBL in urine, plasma and tissue samples. 相似文献
7.
Peter Rogl Subhash K. Naik Erwin Rudy 《Monatshefte für Chemie / Chemical Monthly》1977,108(5):1189-1211
The system TiC?HfC?WC was investigated by means of melting point, differential thermoanalytical, X-ray diffraction and metallographic techniques on hot pressed and heat treated as well as melted alloy specimens and a complete constitutional diagram from 1500°C through the melting range established. According to the peritectic melting of hexagonal WC both isopleths, TiC?WC as well as HfC?WC show a class II reaction at 2760°C in Ti?W?C and at 2730°C in Hf?W?C. The phase behaviour within the TiC?HfC?WC system is characterized by the presence of a (binary) miscibility gap within TiC?HfC [T c=1780°C, (TiC)0.55(HfC)0.45] which extends into the ternary forming a closed ternary miscibility gap at higher temperatures with an isolated ternary critical point:T c=1800°C, (TiC)0.55(HfC)0.45(WC)0.05. Interaction of the solvus (boundary of the cubic-B 1 monocarbide solid solution) and the ternary miscibility gap was established at 1540°C and (TiC)0.27(HfC)0.41(WC)0.32: Alloys of this composition enter a decomposition reaction on cooling into two isotypic cubic B 1 phases and hexagonal WC. Isothermal sections were calculated assuming regular solutions. 相似文献
8.
Albert-J. Bulterman Jolan J. Vreuls Rudy T. Ghijsen Udo A. Th. Brinkman 《Journal of separation science》1993,16(7):397-403
Liquid chromatographic (LC) type trace enrichment is coupled online with capillary gas chromatography (GC) with mass spectrometric (MS) detection for the analysis of aqueous samples. A volume of 1–10 ml of an aqueous sample is preconcentrated on a trace-enrichment column packed with a polymeric stationary phase. After cleanup with HPLC-grade water the precolumn is dried with nitrogen and subsequently desorbed with ethyl acetate. A fraction of 60 μl is introduced on-line into a diphenyltetramethyldisilazane-deactivated retention gap under partially concurrent solvent evaporation conditions and using an early solvent vapor exit. The analytes are separated and detected by means of GC–MS. The potential of the LC–GC–MS system for monitoring organic pollutants in river and drinking water is studied. Target analysis is carried out with atrazine and simazine as model compounds; the detection limits achieved under full-scan and multiple ion detection conditions are 30 pg and 5 pg, respectively. Identification of unknown compounds (non-target analysis), is demonstrated using a river water sample spiked with 168 pollutants varying in polarity and volatility. 相似文献
9.
Longbo Li Andy T. Tek Rudy J. Wojtecki Rebecca Braslau 《Journal of polymer science. Part A, Polymer chemistry》2019,57(17):1821-1835
Internal plasticization of polyvinyl chloride (PVC) using thermal azide‐alkyne Huisgen dipolar cycloaddition between azidized PVC and electron‐poor acetylenediamides incorporating a branched glutamic acid linker resulted in incorporation of four plasticizing moieties per attachment point on the polymer chain. A systematic study incorporating either alkyl or polyethylene glycol esters provided materials with varying degrees of plasticization, with depressed Tg values ranging from ?1 °C to 62 °C. Three interesting trends were observed. First, Tg values of PVC bearing various internal plasticizers were shown to decrease with increasing chain length of the plasticizing ester. Second, branched internal plasticizers bearing triethylene glycol chains had lower Tg values compared to those with similar length long‐chain alkyl groups. Finally, thermogravimetric analysis of these internally plasticized PVC samples revealed that these branched internal plasticizers bearing alkyl chains are more thermally stable than similarity branched plasticizers bearing triethylene glycol units. These internal tetra‐plasticizers were synthesized and attached to PVC‐azide in three simple synthetic steps. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1821–1835 相似文献
10.
Geometriae Dedicata - We prove a criterion for Benjamini-Schramm convergence of periodic orbits of Lie groups. This general observation is then applied to homogeneous spaces and the space of... 相似文献