415 research outputs found
Rigidity versus flexibility of the ligand upon the porosity degree of new metal-organic polymeric materials
No full textIn the context of the adsorption gas property, four metal-organic polymeric materials based on cobalt(II), palladium(II), nickel(II) and zinc(II) with the rigid 4,4'-bipyrazole (labeled as Co-bpz, Pd-bpz, Ni-bpz and Zn-bpz), and four polymeric materials based on cobalt(II) nitrate, cobalt(II) acetate, nickel(II) nitrate and copper(II) acetate with the flexible bis(1,2,4-triazolyl)methane (labeled as Co1-btm, Co2-btm, Ni-btm and Cu-btm) have been investigated toward N-2 adsorption at 77 K. Their porous nature is manifested by the following values of the Langmuir surface area: 1057 m(2)/g, 1035 m(2)/g, 962 m(2)/g and 866 m(2)/g for Co-bpz, Pd-bpz, Ni-bpz and Zn-bpz, respectively, whereas the values of the surface area for the btm-based materials are all null. These results show that the rigid 4,4'-bipyrazolyl ligand induces the formation of porous polymeric structures, whereas the flexible bis(1,2,4-triazolyl)methane ligand induces the formation of nonporous structures
Nickel(II) and copper(I,II)-based metal-organic frameworks incorporating an extended tris-pyrazolate linker
No full textSolvothermal reactions between the tritopic pyrazole-based ligand 1,3,5-tris((1H-pyrazol-4-yl)phenyl)benzene (H3BTPP) and nickel(ii) perchlorate or copper(ii) nitrate afforded two new metal-organic frameworks, Ni3(BTPP)2·solvent (Ni-BTPP) and CuI4CuII2(OH)2(BTPP)2·solvent (Cu-BTPP). Powder diffraction structure determination methods were employed to determine the crystal and molecular structure of the copper(i,ii) derivative: triangular [Cu3N6(μ3-OH)] nodes are connected to six nearby ones by the pyrazolate ligands, thus constructing flat two-dimensional layers that stack to form slit-like one-dimensional channels. Thermogravimetric analyses highlighted both the thermal stability and the permanent porosity of these two materials. Porosity was confirmed by N2 adsorption at 77 K, yielding Langmuir specific surface areas of 1923(3) m2 g-1 and 874(8) m2 g-1 for Ni-BTPP and Cu-BTPP, respectively. Additionally, Ni-BTPP adsorbed 1.73 mmol g-1 (7.6 wt%) of CO2 at the mild conditions of 298 K and 1 bar
THE SPECIES CONCEPT, THEMATIC SUBJECT IN NATURAL SCIENCES – THE SCIENTIFIC APPROACHES OF EMIL G. RACOVITZA AND NICOLAE BOTNARIUC
No full textSpecies concepts represent one of the “hot” topics of the current evolutionary biology. The Romanian natural scientists EMIL G. RACOVITZA and NICOLAE BOTNARIUC defined animal species in different ways:
EMIL G. RACOVITZA supported a Genealogic species concept, expressed as “a colony of isolated consanguines”. The RACOVITZA’s concept considers species as homogenous
lineages of organisms which evolve during their history. Description of such entities requires the recognition of primitive and derived states of the morphologic traits. Hence EMIL G. RACOVITZA’s ideas preceded the principles of phylogenetic systematics of WILLY HENNIG and his followers. Geographic isolation is viewed by RACOVITZA as one of the main drivers of the speciation process.
NICOLAE BOTNARIUC developed an innovative Systems-species concept where quasiindependent organisms through their relationships within populations build a supraindividual system. The integrative properties of the population offer the necessary
traits allowing the identification of species. Evolution is the emergent property of species (represented by populations) within the context of ecosystems and within the interpopulation relationships of a biocoenosis (the next level of the organizational
hierarchy of the living matter). NICOLAE BOTNARIUC applied his concept to interbreeding and agamous populations. In this latter case the exchange of genetic information is realised through the self-reproducing individuals changing, under selection pressure, the clonal genetic structure of the population. The systems-species concept of BOTNARIUC applies to populations living within a wide spectrum of ecological conditions and existing during various time-frames; it offers a different perspective as compared to the narrow ecological species-concept of VAN VALEN.
Recent research offers additional confirmation of the views of the two Romanian biologists. It is argued that the species-concepts discussed should be used within a pluralistic cultural framework of the evolutionary systems biology. Finally, it is emphasized that the ideas of EMIL G. RACOVITZA and NICOLAE BOTNARIUC should represent stimulating arguments for new innovative research projects
EMILE G. RACOVITZA (1868–1947): HIS VIEWS ON THE ADVANCEMENT OF BIOSPELEOLOGY ARE STILL USEFUL TODAY
No full textThe views of EMILE G. RACOVITZA proposed in his Essay on biospeleological problems (1907) represent a scientific revolution. The major contribution of RACOVITZA to the development of biospeleology, as modern research, is exemplified through excerpts from his publications dealing with various aspects of taxonomy and systematics of cave fauna. We show that RACOVITZA considered taxonomy an important factor for the advancement of biospeleological research. The present contribution documents the long-term effort of RACOVITZA to establish robust taxonomic methods which support the development of new directions in biospeleology, related to the origin and evolution of those organisms. This essay offers a snapshot of the original ideas of RACOVITZA and in this way contributes to keep alive the legacy of a remarkable scientist
IN MEMORY OF EMIL G. RACOVITZA (1868–1947) – HIS IDEAS REVERBERATE IN OUR SCIENTIFIC RESEARCH
No full textThe ideas of E. G. Racovitza which led to the development of biospelaeology (biospeology, is the term used by Racovitza and adopted here) are reviewed. We emphasize the important research programme named Biospeologica which allowed to implement practical investigations on the subterranean animals due to enthusiastic cooperative work of many scientists. It leads to the exploration of many caves and other hypogean habitats. It is stressed out that the aim of Racovitza’s efforts was to stimulate
scientists to contribute with their research to the development of an encyclopedic view of the “Natural History of the Subterranean Domain”. Examples from our own research reflect such ideas. We adopted Racovitza’s views on the phylogenetic systematics,
on the way to identify the relict aspect displayed by many subterranean animal groups. Also it is pointed out the importance of Racovitza’s ideas for reconstruction of the dynamic dispersion of homogeneous phylogenetic animal lineages in time and space. Such ideas help us to develop biogeographic scenarios which are important for understanding earth’s history. It is confirmed this
way that the ambitious programme of Racovitza, became during the time a real research tradition that merits being pursued by young naturalists interested in solving exciting problems related to the origin and evolution of the subterranean domain and its ecosystems
Beiträge zur Kenntnis der cavernicolen Antroleucosomiden (Diplopoda, Ascospermophora)
No full textThe family of the Antroleucosomidae is known from the Mediterranean region. In this paper the author describes the new genus Dacosoma with the species D. motasi of caves of the southern Carpathians together with two new species of Bulgarosoma, B. Ocellatum n. sp. of the caves of Mount Banat and B. meridionalis of the cave on Rhodope mountains. A new and complete description is also given for Antroleucosoma banaticum Verh. 1899 and B. bureschi Verh. 1926 based on the study of material coming from the type localities
What we don´t measure about human resources: towards a conceptual framework for analysing the role of soft variables in human resources management modelling
No full textLow retention of valuable employees and difficulties in finding qualified candidates for recruitmentare two issues managers face in Romania, but are a growing concern around the world (Deloitte,2004; Holton & Naquin, 2004). High turnover of specialists disrupts organizational continuity(Lum, et al,1998) and the current policies don’t seem to have the expected results, according to thefield study of the author. We suspect that the cause of inefficient policies lies in a misperception ofdynamics, ignorance of feedback loops and of intangible stocks, like the job satisfaction ofemployees. Although well documented in psychology literature (Lichenstein, 1998), the influence ofjob satisfaction on turnover seems to be ignored by the policy makers. We test policies that accountfor the determinants of job satisfaction and show that the outcome of such policies is better thanthe current ones. Implications for HR policy design and directions for future research are indicated
Sur la remarquable conformation des apophyses g\ue9nitales m\ue2les chez an polydesmide n\ue9otropical
No full textVolume: 169Start Page: 67End Page: 7
Contribution à l’étude des Spelaeonethini (Isopoda, Oniscidea, Trichoniscidae)
No full textFollowing a brief review of the classification of the family Trichoniscidae Sars, 1899, problems related to the definition of the tribe Spelaeonethini Schmőlzer, 1965 are emphasised. Obvious conflicts between the diagnosis of several genera of the tribe Spelaeonethini are pointed ou
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