8 research outputs found
Rhodiosin and herbacetin in Rhodiola rosea preparations: additional markers for quality control?
Context: Rhodiola rosea L. (Crassulaceae) is well-known to contain flavonoids such as the herbacetin derivative rhodiosin. However, flavonoids are not typically used in quality control.
Objective: This study analyses two flavonoids of R. rosea rhizomes and roots for their potential as analytical markers.
Materials and methods: Two constituents were isolated from ethanolic extracts via HPLC, identified via NMR and quantified via RP-HPLC. Presence and content variation was investigated according to extraction (solvent and repetitions), drying (temperature and duration) and sample origin (homogenously cultivated plants of different provenance, commercial samples).
Results: Rhodiosin was identified as a main flavonoid, accompanied by 10-fold lower concentrated herbacetin. Both compounds were best extracted with 70–90% ethanol, but were also detectable in more aqueous extracts. Different drying conditions had no effect on the flavonoid content. These two flavonoids were consistently identified in rhizome and root extracts of over 100 R. rosea samples. Rhizomes tend to contain less flavonoids, with average ratios of rosavins to flavonoids of 1.4 (rhizomes) and 0.4 (roots). Provenance differences were detected in the range (rhodiosin plus herbacetin) of 760–6300 µg/mL extract corresponding to a maximum of approximately 0.5–4.2% (w/w) in the dry drug.
Conclusions: For the first time, two main flavonoids present in R. rosea were quantified systematically. Rhodiosin and herbacetin can be detected simultaneously to phenylpropenoids or salidroside in authentic samples, influenced by the plant part examined and the plant origin. Rhodiosin and herbacetin may serve as additional marker to guarantee a consistent content of R. rosea products
Testing the Power-Law Hypothesis of the Inter-Conflict Interval
The severity of war, measured by battle deaths, follows a power-law
distribution. Here, we demonstrate that power law also holds in the temporal
aspects of interstate conflicts. A critical quantity is the inter-conflict
interval (ICI), the interval between the end of a conflict in a dyad and the
start of the subsequent conflict in the same dyad. Using elaborate statistical
tests, we confirmed that the ICI samples compiled from the history of
interstate conflicts from 1816 to 2014 followed a power-law distribution. We
propose an information-theoretic model to account for the power-law properties
of ICIs. The model predicts that a series of ICIs in each dyad is independently
generated from an identical power-law distribution. This was confirmed by
statistical examination of the autocorrelation of the ICI series. Our findings
help us understand the nature of wars between normal states, the significance
of which has increased since the Russian invasion of Ukraine in 2022
Mobility and interaction patterns in social networks
The question of analyzing the predictability of human behavior has been widely studied
in literature, to unveil how individuals move, how they can be mobilized and, more
philosophically, to understand to what extent our decisions are random or whether we
are free to choose. As a consequence of humans relate to each other, we also tend to
live in groups at different hierarchies in a social way so it is interesting to analyze how
individual features and choices affect the global structure of a society.
In this work, we explore the limits of human predictability in terms of shopping behavior,
observing that, even when we are constrained to a limited set of possible places where we
can make a purchase, predicting where the next purchase will happen is not accurately
possible to do by only observing the past. The next question is to study how individual
decisions affect emergent phenomena such as the economy or information diffusion across a country. We analyze the contents, temporal and mobility patterns extracted from
users’ social media publications to build a profile of the geographical regions that allow
to predict the unemployment rate. Finally, we also use a mobile phone call dataset
to test whether the dynamics at the urban level, how people create and destroy links
within a city, affect the inter-urban diffusion of diseases, virus or rumors. Our results
suggest that inter-regional structure is robust and does not vary significantly on time so
diffusion processes can be well modeled in terms of static properties of the inter-urban
network.Programa Oficial de Doctorado en IngenierÃa MatemáticaPresidente: Javier Borge Holthoefer.- Secretario: Rubén Cuevas RumÃn.- Vocal: Josep Perelló Palo
Volume 119-20: 1954-55
Annals of the Congregation of the Mission, or collection of edifying letters