Archetypal Analysis: Mining Weather and Climate Extremes

Conventional analysis methods in weather and climate science (e.g., EOF analysis) exhibit a number of drawbacks including scaling and mixing. These methods focus mostly on the bulk of the probability distribution of the system in state space and overlook its tail. This paper explores a different method, the archetypal analysis (AA), which focuses precisely on the extremes. AA seeks to approximate the convex hull of the data in state space by finding “corners” that represent “pure” types or archetypes through computing mixture weight matrices. The method is quite new in climate science, although it has been around for about two decades in pattern recognition. It encompasses, in particular, the virtues of EOFs and clustering. The method is presented along with a new manifold-based optimization algorithm that optimizes for the weights simultaneously, unlike the conventional multistep algorithm based on the alternating constrained least squares. The paper discusses the numerical solution and then applies it to the monthly sea surface temperature (SST) from HadISST and to the Asian summer monsoon (ASM) using sea level pressure (SLP) from ERA-40 over the Asian monsoon region. The application to SST reveals, in particular, three archetypes, namely, El Niño, La Niña, and a third pattern representing the western boundary currents. The latter archetype shows a particular trend in the last few decades. The application to the ASM SLP anomalies yields archetypes that are consistent with the ASM regimes found in the literature. Merits and weaknesses of the method along with possible future development are also discussed

Impedance spectroscopy, electrical relaxation and Ac conductivity studies of organic-inorganic hybrid compound: NH3(C6H4)2NH3HgCl4

Organic–inorganic hybrid sample NH3(C6H4)2NH3HgCl4 was characterized by differential scanning calorimetry (DSC), TGA analysis and electrical impedance spectroscopy. DSC studies indicated the presence of a one-phase transition at 391 K. As for the ac conductivity of the compound NH3(C6H4)2NH3HgCl4, it has been measured in the temperature range of 358 - 413K and the frequency range of 209 Hz–5 MHz. Concerning the Z’ and Z’’ versus frequency plots, they were well-fitted to an equivalent circuit model. The equivalent circuit is composed of a series of combination of two parallel (R//CPE) circuits. Besides, the frequency dependence of the conductivity was interpreted in terms of Jonscher's law σ(ω) = σdc +A ωn.  As regards the conductivity, it follows the Arrhenius relation. The variation of the value of the conductivity with temperatures confirmed the availability of the phase transition at 391K detected by DSC and electrical measurements

Effect of Thiourea on Yield and Quality of Potato (Solanum tuberosum L.)

A field experiment was carried out to study the effect of five concentrations (0, 250, 500, 750 and 1000 mM) of thiourea application on mother tubers on yield and quality attributes of harvested potato, variety Spunta in the region of Chott-Mariem in Tunisia. Treated tubers (Ш = 50 mm) were planted in field after breaking dormancy at a spacing of 80 cm x 30 cm according to completely randomized design (CRD) in three replications. Quality attributes of potato tubers especially fresh matter and dry matter of plant, total reducing sugars in leaves, tuber yield, number and diameter of tubers per plant and number of sprouts per tuber was measured. Soluble proteins and starch content in potato tubers were also quantified.In general we noted that application of thiourea showed significant influence on yield and on quality of tubers comparing to control. Maximum tuber yield per plant, maximum number of tubers per plant and maximum starch content was recorded with 250 mM of thiourea. Moreover, highest dry matter of potato plant was found also at this concentration. While increasing dose of thiourea thereafter it showed slight significant improvement and do not affect significantly the diameter of tubers comparing to control

PHYSIOLOGICAL MECHANISMS FOR POTATO DORMANCY RELEASE AND SPROUTING: A REVIEW

Potato ( Solanum tuberosum \ua0L.) tubers undergo a period of dormancy, during which visible bud growth is inhibited. The length of the dormancy is determined by environmental, physiological and hormonal control mechanisms. Dormancy is the final stage of tuber life, which serves to preserve tubers as organs of vegetative reproduction under unfavourable growth conditions. Since the duration of potato tuber dormancy and sprouting time bear significant economic importance, this review considers the regulation of dormancy and sprouting of potato by phytohormones and reactive oxygen species. Two phytohormones, ABA and ethylene suppress tuber sprouting; however, the exact role of ethylene remains to be elucidated. Cytokinins and gibberellins are required for bud breaking and sprout growth, respectively. The auxin seems to play a role in vascular development. Thus, tuber dormancy and sprouting can be controlled in potato by manipulation of Reactive Oxygen Species (ROS), especially H2O2\ua0metabolism via the inhibition of catalase (CAT) activity.The possible mechanisms by which CAT inhibitors or H2O2\ua0overcome dormancy and promote sprouting in the potato tuber are discussed.La pomme de terre ( Solanum tuberosum \ua0L.) conna\ueet une p\ue9riode de dormance durant laquelle la germination des bourgeons visibles est inhib\ue9e. La dur\ue9e de dormance est d\ue9termin\ue9e par des m\ue9canismes de contr\uf4le environnemental, physiologique and hormonal. La dormance est le stade final de la vie des tubercules servant \ue0 pr\ue9server les tubercules comme organes de reproduction v\ue9g\ue9tative sous condition de germination d\ue9favorables. Etant donn\ue9 que la dur\ue9e de la dormance des tubercules de la pomme de terre et le temps de rejet rev\ueatent une importance \ue9conomique significative, cette revue consid\ue8re la r\ue9gulation de la dormance et le rejet de la pomme de terre par des hormones et d\u2019esp\ue8ces r\ue9actives d\u2019oxyg\ue8ne (ROS). Deux phytohormones\ua0; ABA et \ue9thyl\ue8ne emp\ueachent le rejet des tubercules\ua0; par ailleurs, le r\uf4le extractif de l\u2019\ue9thyl\ue8ne reste \ue0 \ue9lucider. Les cytokinines and les gibb\ue9rellines sont n\ue9cessaires dans l\u2019\ue9limination des bourgeons et la croissance des rejets, respectivement. L\u2019auxine semble jouer un r\uf4le dans le d\ue9veloppement vasculaire. Ainsi, la dormance et les rejets des tubercules peuvent \ueatre contr\uf4l\ue9s par manipulation d\u2019esp\ue8ces r\ue9actives d\u2019oxyg\ue8ne (ROS), sp\ue9cialement le m\ue9tabolisme du H2O2\ua0\ue0 travers l\u2019inhibition de l\u2019activit\ue9 de la catalase (CAT). Les m\ue9canismes possibles par lesquels les inhibiteurs du CAT ou H2O2\ua0 surmontent la dormance et facilitent le rejet de la pomme de terre sont discut\ue9s

KARSTOLOGIE EN ZONE ARIDE : FORMATIONS KARSTIFIEES DU SUD EST ALGERIEN. METHODES ET OUTILS.

Un karst est un espace ouvert sur l’extérieur permettant l’introduction dans une roche compacte peu soluble, de traceurs des événements climatiques d’une période donnée. Un karst est donc un conservatoire, mémoire de l’histoire d’une région, d’un pays, d’un continent, voire d’un espace plus vaste encore. Comme dans tout le Bassin méditerranéen, en Algérie subsistent des formations karstiques. Celles-ci ont été étudiées par quelques auteurs et non des moindres tels : Durozoy G., Collignon B., Coiffait P.E., Quinif Y., Maire R. et plus récemment Abdessalem M., Kardache R. etc. Toutes les informations recueillies, du reste aussi importantes les unes que les autres, ne suffisent toujours pas à cerner la karstologie du SE algérien. Beaucoup de travail reste à accomplir tan t la répartition de ces formations en surface est importante, s’étendant jusqu’au piémont du Sahara algérien. Un seul chercheur ne peut y suffire.A cet effet, il nous semble important de tenter une reconstitution des événements qui ont atteint ces formations.En première approche, les karsts du SE de l’Algérie, s’inscrivant dans un milieu aride où règnent une pluviosité extrêmement irrégulière et de très longuespériodes sèches, sont cités comme exemple.L’étude, en l’absence du recours aux techniques de mesures isotopiques, s’est principalement basée sur l’histoire géologique de la région en insistant davantage sur la paléosédimentologie, les phases tectoniques, les épisodes d’érosion, d’émersion et d’accumulation des corps sédimentaires, le paléoclimat enfin

Elements Discrimination in the Study of Super-Heavy Elements using an Ionization Chamber

Dedicated ionization chamber was built and installed to measure the energy loss of very heavy nuclei at 2.7 MeV/u produced in fusion reactions in inverse kinematics (beam of 208Pb). After going through the ionization chamber, products of reactions on 12C, 18O targets are implanted in a Si detector. Their identification through their alpha decay chain is ambiguous when their half-life is short. After calibration with Pb and Th nuclei, the ionization chamber signal allowed us to resolve these ambiguities. In the search for rare super-heavy nuclei produced in fusion reactions in inverse or symmetric kinematics, such a chamber will provide direct information on the nuclear charge of each implanted nucleus.Comment: submitted to NIMA, 10 pages+4 figures, Latex, uses elsart.cls and grahpic

Unlocking hidden mineral resources: Characterization and potential of bitterns as alternative sources of critical raw materials

Mineral extraction from seawater brines has emerged as a viable solution to reduce Europe's reliance on imported Critical Raw Materials (CRM). However, the economic viability of this approach hinges on the local demand for sodium chloride, the primary product of such extraction processes. This study investigates the potential of residual brines, commonly known as "bitterns," generated during solar sea-salt extraction in traditional saltworks, as an alternative source of minerals. The Mediterranean region, encompassing South-European, NorthAfrican, Near East coasts, and parts of the Atlantic regions, is particularly conducive to exploring this prospect due to its extensive solar sea salt industry. Saltworks in the region, adopting various operational strategies based on feed quality or local climate conditions, produce different types of bitterns, each holding a latent resource potential that has remained largely unexplored. Within the framework of the EU-funded SEArcularMINE project, it was conducted an extensive analytical campaign to characterize bitterns collected from a diverse saltworks network. The analysis revealed the presence of sodium, potassium, magnesium, chloride, sulfate, and bromide in concentrations ranging from g/ kg, while boron, calcium, lithium, rubidium, and strontium were found in the mg/kg range. Additionally, trace elements (TEs) such as cobalt, cesium, gallium, and germanium were detected at concentrations in the order of mu g/kg. Detailed results on the composition of bitterns are presented, emphasizing the distinct characteristics observed at different sites. The estimated potential for mineral recovery from these bitterns is approximately 190 euro/m3, considering the production capacity of about 9 Mm3 per year in the Mediterranean area. This finding underscores the significant contribution that mineral recovery from bitterns could make in securing access to CRMs for the European Union

Relative spins and excitation energies of superdeformed bands in 190Hg: Further evidence for octupole vibration

An experiment using the Eurogam Phase II gamma-ray spectrometer confirms the existence of an excited superdeformed (SD) band in 190Hg and its very unusual decay into the lowest SD band over 3-4 transitions. The energies and dipole character of the transitions linking the two SD bands have been firmly established. Comparisons with RPA calculations indicate that the excited SD band can be interpreted as an octupole-vibrational structure.Comment: 12 pages, latex, 4 figures available via WWW at http://www.phy.anl.gov/bgo/bc/hg190_nucl_ex.htm

Multi-decadal modulations in the Aleutian-Icelandic Low seesaw and the axial symmetry of the Arctic Oscillation signature, as revealed in the 20th century reanalysis

Seesaw relationship in intensity between the surface Aleutian and Icelandic Lows (AIS) is a manifestation of atmospheric teleconnection that bridges the interannual variability over the Pacific and Atlantic in particular winter months. Analysis of the 20th Century Reanalysis data reveals that the strength and timing of AIS have undergone multi-decadal modulations in conjunction with those in structure of the Arctic Oscillation (AO) signature, extracted in the leading mode of interannual sea-level pressure (SLP) variability over the extratropical Northern Hemisphere. Specifically, events of what may be called ‘pure AO’, in which SLP anomalies exhibit a high degree of axial symmetry in association with in-phase SLP variability between the midlatitude Atlantic and Pacific, tended to occur during multi-decadal periods in which the inter-basin teleconnection through AIS was active under the enhanced interannual variability of the Aleutian Low. In contrast, the axial symmetry of the AO pattern was apparently reduced during a multi-decadal period in which the AIS teleconnection was inactive under the weakened interannual variability of the Aleutian Low. In this period, the leading mode of interannual SLP variability represented a meridional seesaw between the Atlantic and Arctic, which resembles SLP anomaly pattern associated with the cold-ocean/warm-land (COWL) temperature pattern. These multi-decadal modulations in interannual AIS signal and the axial symmetry of the interannual AO pattern occurred under multi-decadal changes in the background state that also represented the polarity changes of the COWL-like anomaly pattern

Excitation energies of superdeformed states in 196Pb: towards a systematic study of the second well in Pb isotopes

The excitation energy of the lowest-energy superdeformed band in 196Pb is established using the techniques of time-correlated γ-ray spectroscopy. Together with previous measurements on 192Pb and 194Pb, this result allows superdeformed excitation energies, binding energies, and two-proton and two-neutron separation energies to be studied systematically, providing stringent tests for current nuclear models. The results are examined for evidence of a “superdeformed shell gap.