GEODESICS IN LORENTZIAN MANIFOLDS

We present an extension of Geodesics in Lorentzian Manifolds (Semi-Riemannian Manifolds or pseudo-Riemannian Manifolds ). A geodesic on a Riemannian manifold is, locally, a length minimizing curve. On the other hand, geodesics in Lorentzian manifolds can be viewed as a distance between ``events\u27\u27. They are no longer distance minimizing (instead, some are distance maximizing) and our goal is to illustrate over what time parameter geodesics in Lorentzian manifolds are defined. If all geodesics in timelike or spacelike or lightlike are defined for infinite time, then the manifold is called ``geodesically complete\u27\u27, or simply, ``complete\u27\u27. It is easy to show that the magnitude of a geodesic is constant, so one can characterize geodesics in terms of their causal character: if this magnitude is negative, the geodesic is called timelike. If this magnitude is positive, then it is spacelike. If this magnitude is 0, then it is called lightlike or null. Geodesic completeness can be considered by only considering one causal character to produce the notions of spacelike complete, timelike complete, and null or lightlike complete. We illustrate that some of the notions are inequivalent

Praziquantel: its use in control of schistosomiasis in sub-Saharan Africa and current research needs

Treatment with praziquantel (PZQ) has become virtually the sole basis of schistosomiasis control in sub-Saharan Africa and elsewhere, and the drug is reviewed here in the context of the increasing rate that it is being used for this purpose. Attention is drawn to our relative lack of knowledge about the mechanisms of action of PZQ at the molecular level, the need for more work to be done on schistosome isolates that have been collected recently from endemic areas rather than those maintained in laboratory conditions for long periods, and our reliance for experimental work mainly on Schistosoma mansoni, little work having been done on S. haematobium. There is no evidence that resistance to PZQ has been induced in African schistosomes as a result of its large-scale use on that continent to date, but there is also no assurance that PZQ and/or schistosomes are in any way unique and that resistant organisms will not be selected as a result of widespread drug usage. The failure of PZQ to produce complete cures in populations given a routine treatment should therefore solicit considerable concern. With few alternatives to PZQ currently available and/or on the horizon, methods to monitor drug-susceptibility in African schistosomes need to be devised and used to help ensure that this drug remains effective for as long a time as possibl

Die Fruchtbarkeit des Dorsches (Gadus morhua L.) in der westlichen Ostsee und den westnorwegischen Gewässern

An 71 weiblichen Dorschen aus der Kieler Bucht mit Längen von 40-95 cm und 49 Kabeljau aus den Gewässern bei Bergen mit Längen von 61-100 cm wurden Eizählungen durchgeführt. Die Eizahlen werden zu Länge und Gewicht der Fische in Beziehung gesetzt und die Ergebnisse in Diagrammen, Mittelwerten von 10-cm-Gruppen und Regressionsgleichungen dargestellt. Beim Ostseedorsch wurden Eizahlen von 0,2-7 Mill., beim norwegischen Kabeljau von 0,9 bis 8,5 Mill. ermittelt. Bei gleicher Länge und Gewicht kann die Fruchtbarkeit um das 2-3fache variieren. Um die beste mathematische Formulierung für die Beziehungen zwischen Eizahl, Länge und Gewicht zu finden, werden lineare und Exponentialgleichungen berechnet. Dabei ergibt sich, daß ihre Regressionslinien im Hauptuntersuchungsbereich dicht benachbart verlaufen und erst bei den höchsten Werten, die nur durch wenige Beobachtungen belegt sind, stärker divergieren. Als bester Ausdruck der Fruchtbarkeit wurde die Relation Eizahl/Gewicht gefunden. Die Eiproduktion setzt in der Norwegischen See bei den Erstlaichern (im Alter von 4 Jahren) mit 728 000/kg ein und steigt mit zunehmender Größe und Alter auf 850 000/kg. Bei den Erstlaichern in der westlichen Ostsee (im Alter von 3 Jahren) beginnt sie mit 512 000/kg und erhöht sich auf 790000/kg. Die Fruchtbarkeit des Kabeljau in beiden Meeren ist, bezogen auf die Fischlänge, etwa ebenso groß wie die des Schellfisches in der Nordsee

Role of Fungal Biomass in N-Hexane Biofiltration

The biofiltration of n-hexane is studied to optimize determinants factors of hydrophobic VOC filtration efficiency. Four trickle-bed air biofilters (TBABs) were employed; two of which were supplied with nutrients buffered at a neutral pH, while another two at an acidic pH of 4 to induce and enhance fungal growth. The loading rate of n-hexane was kept constant in all TBABs at 13 g/m3/h. At each pH levels studied, the biomass of the TBABs was pre-acclimated using different ratios of n-hexane and methanol. The fungal biomass responsible for the degradation of n-hexane was then examined and quantified. Dichloran Rose Bengal Chloramphenicol agar was used for fungi quantification, and optical microscopy for classification. Effluent biomass was validated by measuring volatile suspended solids. Fungal counts resulting from n-hexane biodegradation were related to nitrate and carbon consumption. It was found that n-hexane elimination capacity closely followed biomass growth, and reached a steady-state at an optimum biomass density of roughly 3000 cfu/ml. Major shifts in fungal species were observed in all TBABs. Dominant fungal species grew slowly to become the most numerous, and were found to provide maximum elimination capacity, although TBABs pre-acclimated to higher methanol concentrations took less time to reach this steady-state. It was concluded, therefore, that steady and monitored growth of TBAB biomass is an essential factor in maximizing fungi’s ability to metabolize VOCs and that a new ecological biofiltration model may be the most effective at VOC purification

Study of the role of IL-17F gene polymorphism in the development of immune thrombocytopenia among the Egyptian children

Background: Interleukin 17F (IL-17F) is a pro-inflammatory cytokine that is recently proved to have a crucial role in the emergence of autoimmune diseases; it induces the expression of various cytokines, chemokines, and adhesion molecules. IL-17F polymorphism is subsequently related to enhanced IL-17F expression and activity; which may result in susceptibility to many autoimmune diseases including primary immune thrombocytopenia (PIT).Aim of the study: This case-control study aimed to investigate the possible association between IL and 17F gene single nucleotide polymorphism (SNP) at rs 7488A/G and PIT susceptibility in Egyptian pediatric patients.Subjects and methods: A total of 50 children with PIT with a mean age of 7 years, together with 50 age and sexmatched healthy controls were enrolled in the study for evaluation. Polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) was used for detection of IL-17F polymorphism at rs7488A/G.Results: Regarding the genotypes distribution, the frequencies of the AA, AG and GG genotypes were 96, 2, and 2% in PIT patients and 90, 10 and 0% in the control group respectively. The A and G allele frequencies were 97 and 3% in the patients’ group versus 95 and 5% in the control group. There was no significant difference in either genotypes or allelic distribution between PIT patients and the controls.Conclusion: Our study suggests that IL17F gene polymorphism at rs7488A/G may not contribute to the susceptibility in development of primary immune thrombocytopenia in the Egyptian children.Keywords: Interleukin 17F (IL-17F), Primary immune thrombocytopenia (PIT), Single nucleotide polymorphism (SNP), Polymerase chain reaction-restriction, fragment polymorphism (PCR-RFLP

The kinetics and acoustics of fingering and note transitions on the flute

Motion of the keys was measured in a transverse flute while beginner, amateur and professional flutists played a range of exercises. The time taken for a key to open or close is typically 10 ms when pushed by a finger or 16 ms when moved by a spring. Delays between the motion of the fingers were typically tens of ms, with longer delays as more fingers are involved. Because the opening and closing of keys will never be exactly simultaneous, transitions between notes that involve the movement of multiple fingers can occur via several possible pathways with different intermediate fingerings. A transition is classified as `safe' if it is possible to be slurred from the initial to final note with little perceptible change in pitch or volume. Some transitions are `unsafe' and possibly involve a transient change in pitch or a decrease in volume. In transitions with multiple fingers, players, on average, used safe transitions more frequently than unsafe transitions. Professionals exhibited smaller average delays between the motion of fingers than did amateurs

Oligorotaxane radicals under orders

A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components-namely oligoviologens-in which different numbers of 4,4'-bipyridinium (BIPY(2+)) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT(4+)) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY(\u2022+) radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne-azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers