15 research outputs found
Retail trade-area delineation techniques for central place cities under 20,000 population
Call number: LD2668 .P7 1974 C5
The twisted arc model for chiral molecules
We present a simple model for chiral molecules which yields the
frequency-dependent multipole-multipole polarizabilities required for
calculating the dispersive van der Waals constants in a simple, closed, and
consistent form. The model consists of a single effective charge confined to a
one-dimensional wire formed by two circular arcs, which are twisted with
respect to each other by an angle characterizing the chirality. The resulting
polarizabilities show a simple functional dependence on the model parameters,
and they serve to mimic the chiral properties of small molecules, such as H2S2,
in a reasonably realistic way.Comment: 21 pages, 4 figure
Adrenal myelolipoma: a comprehensive review
INTRODUCTION: Adrenal myelolipoma is an invariably benign neoplasm of the adrenal gland that is the second most common primary adrenal incidentaloma following adrenocortical adenomas. It is composed of elements of adipose tissue and extramedullary hematopoiesis. Hypotheses on stem cells and hormonal factors have been formulated regarding its pathogenesis that is still obscure. Despite its benign behavior, adrenal myelolipoma is clinically relevant as it might cause significant difficulties in the differential diagnosis of adrenal tumors. METHODS: We have reviewed 420 cases reported between 1957 and 2017 on adrenal myelolipoma retrieved from PubMed and Scopus databases and also 20 of our case series to provide a comprehensive analysis of their pathology, epidemiological and clinical features. RESULTS AND CONCLUSIONS: The average age for its diagnosis was 51 years, and no gender difference was observed. The average size of tumors was 10.2 cm. Congenital adrenal hyperplasia was associated to 10% of all cases analyzed, while other adrenal hypersecretory disorders (cortisol, aldosterone) were found in 7.5% of cases. Computed tomography and magnetic resonance imaging can be reliably used for its differential diagnosis. If the diagnosis of an adrenal myelolipoma is unambiguous, and no associated symptoms or hormonal activity are established, surgical intervention is usually not necessary
Reductive Elimination from Sterically Encumbered Ni–Polypyridine Complexes
Herein we disclose the synthesis of sterically encumbered
dialkylnickel(II)
complexes bearing 2,9-dimethyl-1,10-phenanthroline ligands. A comparison
with their unsubstituted analogues by both X-ray crystallography and
theoretical calculations revealed significant distortions in their
molecular structures. Eyring plots along with stoichiometric and photoexcitation
studies revealed that sterically encumbered dialkylnickel(II) complexes
enable facile C(sp3)–C(sp3) reductive elimination, thus offering an
improved understanding of Ni catalysis
Reductive Elimination from Sterically Encumbered Ni–Polypyridine Complexes
Herein we disclose the synthesis of sterically encumbered
dialkylnickel(II)
complexes bearing 2,9-dimethyl-1,10-phenanthroline ligands. A comparison
with their unsubstituted analogues by both X-ray crystallography and
theoretical calculations revealed significant distortions in their
molecular structures. Eyring plots along with stoichiometric and photoexcitation
studies revealed that sterically encumbered dialkylnickel(II) complexes
enable facile C(sp3)–C(sp3) reductive elimination, thus offering an
improved understanding of Ni catalysis
Reductive Elimination from Sterically Encumbered Ni–Polypyridine Complexes
Herein we disclose the synthesis of sterically encumbered
dialkylnickel(II)
complexes bearing 2,9-dimethyl-1,10-phenanthroline ligands. A comparison
with their unsubstituted analogues by both X-ray crystallography and
theoretical calculations revealed significant distortions in their
molecular structures. Eyring plots along with stoichiometric and photoexcitation
studies revealed that sterically encumbered dialkylnickel(II) complexes
enable facile C(sp3)–C(sp3) reductive elimination, thus offering an
improved understanding of Ni catalysis
Room-Temperature-Stable Magnesium Electride via Ni(II) Reduction
Herein, we report the synthesis of highly reduced bipyridyl magnesium complexes and the first example of a stable
organic magnesium electride supported by quantum mechanical computations and X-ray diffraction. These complexes serve as
unconventional homogeneous reductants due to their high solubility, modular redox potentials, and formation of insoluble, noncoordinating byproducts. The applicability of these reductants is showcased by accessing low-valent (bipy)2Ni(0) species that are
challenging to access otherwise