Kinetic data for the crosslinking reaction of polycarboxylic acids with cellulose

Kinetic data (rate constant, Arrhenius activation energy, frequency factor) of the esterification of polycarboxylic acids (butane-1, 2, 3, 4-tetracarboxylic acid, citric acid and pyromellitic acid) have been determined by means of isocratic HPLC measuring the portion of polycarboxylic acid that does not react with cellulosic material. The order of activation energy is as follows: citric acid > butane-1, 2, 3, 4-tetracarboxylic acid > pyromellitic acid.     

The promoter-proximal, unstable IB region of the atp mRNA of Escherichia coli: an independently degraded region that can act as a destabilizing element

Non-invasive methods for routine monitoring of reproductive states and reproduction control in large colonies of captive Callithrix jacchus have been developed. Immunoactive urinary oestrone-3-conjugates (E1C) were measured during non-conception cycles (n = 5) and pregnancy (n = 7). Using plasma progesterone levels to time ovulation, ovulation was quantitatively estimated by a) calculating the first E1C rise and b) by establishing an E1C threshold. Ovulation was thus defined as taking place 4 days preceding a) the first rise of E1C above follicular-phase levels, or b) a concentration > or = 4.5 micrograms E1C/mg creatinine. Early pregnancy could be determined after day 20 by continued luteal-phase levels of E1C. Secondly, the luteolytic effect of cloprostenol, injected over a wide range of doses and between days 1 and 64 after ovulation/conception, was analysed. Luteolysis was achieved when cloprostenol was administered after day 5 post-ovulation; the luteolytic effect was found not to be dose-dependent. The success of cloprostenol treatment was 87% as confirmed by endocrine monitoring. The methods described are effective and minimize intervention, and are therefore suitable for long-term applications, particularly in combination with behavioural studies.     

Metabotropic glutamate receptors modulate synaptic transmission in the perforant path: pharmacology and localization of two distinct receptors

Metabotropic glutamate receptors (mGluRs) have emerged as an interesting family of eight different receptor subtypes that can be divided into three groups according to their pharmacology and sequence similarity. In the present study, the specific mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD) and L(+)-2-amino-4-phosphonobutyric acid (L-AP4) depressed field excitatory postsynaptic potentials (fEPSPs) in the rat dentate gyrus evoked by perforant path stimulation in a concentration-dependent, rapid and reversible manner (EC50: L-AP4 5.9 +/- 1.6 microM, (1S,3R)-ACPD 80 +/- 34 microM). In a 'paired-pulse' stimulation protocol, the first fEPSP showed a stronger reduction, resulting in 'paired-pulse' facilitation. The effects of L-AP4 but not of (1S,3R)-ACPD could be antagonized by the group III mGluR antagonists (S)-2-amino-2-methyl-4-phosphonobutanoic acid (MAP4) and (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG). Moreover, (1S,3R)-ACPD was still potently depressing fEPSPs after preperfusion of near saturating concentrations of L-AP4. Together, the results suggest that both substances act on different mGluRs. The effects of (1S,3R)-ACPD could not be further differentiated by selective group I or group II mGluR agonists. Although (2S,1'S,2'S)-2-carboxycyclopropylglycine (L-CCG-I) blocked fEPSPs at concentrations > 1 microM, these effects, as well as L-AP4 effects, were potently antagonized by MAP4. This suggests that mGluR8 might be responsible for the actions of L-AP4 and L-CCG-I. The two different mGluRs showed a distinct distribution when fEPSPs were recorded simultaneously in the outer and middle molecular layer (OML/MML): The L-AP4 sensitive receptor, possibly mGluR8, seems to be located in the OML while (1S,3R)-ACPD showed its main effect in the MML.     

Bestimmung von 5-Methoxypsoralen in Sonnenschutzmitteln

Zusammenfassung Es wird eine Methode zur Bestimmung von 5-Methoxypsoralen in Sonnenschutzmitteln beschrieben. Nach säulenchromatographischer Reinigung wird der Extrakt mittels zweidimensionaler Dünnschichtchromatographie untersucht. Bei positiven Befunden wird das 5-Methoxypsoralen capillar-gaschromatographisch unter Verwendung von 5--Cholestan als innerem Standard quantitativ bestimmt. Die Ergebnisse werden durch Gaschromatographie-Massenspektrometrie (GC-MS) abgesichert. Die Wiederfindungsrate beträgt bei Kosmetika vom Emulsionstyp 70% und bei Sonnenölpräparaten 90%. Die Nachweisgrenze liegt je nach Probenart, zwischen 0,1 und 0,5 mg/kg.Mit dieser Methode wurden in 6 von 21 untersuchten Sonnenschutzmitteln bis zu 28 mg 5-Methoxypsoralen/kg nachgewiesen.

---

Determination of 5-methoxypsoralene in suntan-cosmetics

Summary A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5--cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type.By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.

     

SOME PROPERTIES OF GLAZE SLIPS1

Data are presented for a fritted glaze and a raw porcelain glaze giving the relation The influence of grinding between viscosity and specific gravity and Ph of glaze slip. The influence of grinding on the properties of the slip and of the fired glaze is also discussed.     

Berechnung der Wärmeverluste eines kreiszylindrischen Rohres in einer ebenen Wand

Zusammenfassung Die W?rmeverluste eines in einer ebenen Wand eingebetteten kreiszylindrischen Rohres lassen sich berechnen. Ausgehend von den bekannten Gleichungen für die W?rmeleitung und den W?rmeübergang wird das zu l?sende Randwertproblem formuliert und mittels Reihenentwicklungen integriert. Für die W?rmeverluste ergibt sich so eine gut konvergierende Folge von N?herungswerten. Für den praktischen Gebrauch erleichtert ein Rechenschema die Anwendung. Diese Berechnungen wurden im Rahmen eines dem Battelle-Institut eV., Frankfurt/Main, von der Firma Hackethal, Draht- und Kabelwerke AG, Hannover, erteilten Forschungsauftrages vorgenommen. Der Verfasser dankt dieser Firma für ihre freundliche Genehmigung zur Ver?ffentliehung der Ergebnisse.     

GLOST KILN REFRACTORIES*

Saggers for glost placing must give good life and avoid harmful secondary effects on the ware. Low thermal expansion is the most necessary property but, if carried too far, may cause the fault known as pin chipping. This defect, however, is compensated by low expansion in the pin itself. The system sagger-pin-ware should be adjusted to minimize tensile stresses in cooling.     

Versatile four-probe ac conductivity measurement system

The design of a four-probe ac conductivity measurement system is described. The system is capable of making precision conductance measurements from 10(-8) to 10(-5) S at 20 to 200 Hz. Driven coaxial shields and a controlled current source are utilized to eliminate phase shift/attenuation errors, and make the measurement of conductances on a variety of materials a routine procedure requiring a minimum of operator intervention.