On the isotropic constant of non-symmetric convex bodies

We estimate the isotropic constant of non-symmetric convex bodies and discrete sets in ℝ ⁿ .     

Lifetime of the second excited state in157Gd

The mean life of the 131.5 keV, 7/2^? state in¹⁵⁷Gd was measured using a modified version of the microwave method. The result obtained is \(\tau = 137 \pm 7ps.\) .The deduced magnetic parametersg _K, g_R are discussed and compared with theory.     

Ultraviolet Radiation Exposure and its Impacts on Cutaneous Phosphorylation Signaling in Carcinogenesis: Focusing on Protein Tyrosine Phosphatases†

Sunlight exposure is a significant risk factor for UV-induced deteriorating transformations of epidermal homeostasis leading to skin carcinogenesis. The ability of UVB radiation to cause melanoma, as well as basal and squamous cell carcinomas, makes UVB the most harmful among the three known UV ranges. UVB-induced DNA mutations and dysregulation of signaling pathways contribute to skin cancer formation. Among various signaling pathways modulated by UVB, tyrosine phosphorylation signaling which is mediated by the action of protein tyrosine kinases (PTKs) on specific tyrosine residues is highly implicated in photocarcinogenesis. Following UVB irradiation, PTKs get activated and their downstream signaling pathways contribute to photocarcinogenesis by promoting the survival of damaged keratinocytes and increasing cell proliferation. While UVB activates oncogenic signaling pathways, it can also activate tumor suppressive signaling pathways as initial protective mechanisms to maintain epidermal homeostasis. Tyrosine dephosphorylation is one of the protective mechanisms and is mediated by the action of protein tyrosine phosphatases (PTPs). PTP can counteract UVB-mediated PTK activation and downregulate oncogenic signaling pathways. However, PTPs have not been studied extensively in photocarcinogenesis with previous studies regarding their inactivation induced by UVB. This current review will summarize the recent progress in the protective function of PTPs in epidermal photocarcinogenesis.     

Nature and Strength of Weak O⋅⋅⋅O Interactions in Nitryl Halide Dimers

The use of real space functions and molecular graphs has pushed some chemists to wonder: Are interactions between negatively charged oxygen atoms possible? In this contribution we analyze whether there is a real interaction between oxygen atoms in nitryl halide dimers (XNO₂)₂ (X=F, Cl, Br and I) and in tetranitromethane and derivatives. Based on ab-initio and density functional theories (DFT) methods, we show these complexes are weakly stabilized. Energy decomposition analyses based on local molecular orbitals (LMOEDA) and interacting quantum atoms (IQA) reveal both dispersion and exchange play a crucial role in the stabilization of these complexes. Electron charge density and IQA analyses indicate that the oxygen atoms are connected by privileged exchange channels. In addition, electrostatic interactions between O and N atoms are also vital for the stabilization of the complexes. Finally, a reasonable explanation is given for the dynamic behavior of nitryl groups in tetranitromethane and derivatives.     

Temperature Ramp Strategy for Regulating Oxygen Vacancies in NiCo2O4 Nanoneedles Towards Enhanced Electrocatalytic Water Splitting

Oxide-based systems often suffer from higher overpotentials compared to transition metal sulfides and phosphides for the electrochemical hydrogen evolution reaction (HER). Interestingly, the generation of oxygen vacancy/defect has been seen as the strategy for further activating transition metal oxides (NiCo₂O₄ as a model system) for an electrochemical water-splitting process. Herein, we employ the temperature ramp strategy (ambient air calcination) for the generation of oxygen vacancies in NiCo₂O₄ (NCO) towards the tuning of electrocatalytic enhancements. The NiCo₂O₄ synthesized at temperature ramp rates of 2 °C/min (NCO-2), 5 °C/min (NCO-5), and 10 °C/ min (NCO-10) depicts contrasting structural features and varying Ni : Co : O surface composition. The decrease in the crystallite size and converse trend in the particle strain were observed from NCO-2 to NCO-10. Interestingly, the surface Ni : Co : O ratios of 1 : 0.78 : 3.6, 1 : 0.81 : 3.3, and 1 : 0.69 : 2.8 for NCO-2, NCO-5, and NCO-10, respectively, were observed. The reduced relative oxygen ratio in the latter implies the generation of an ample amount of oxygen vacancy defects. HER performance depicts a consistent trend with enhanced oxygen defect concentration with the overpotential requirement of 700, 647, and 597 mV for NCO-2, NCO-5, and NCO-10, respectively, for the generation of a cathodic current of 25 mA cm⁻². The same trend in an electrocatalytic enhancement is observed for other cathodic currents.     

Peptide Bond Formation in the Protonated Serine Dimer Following Vacuum UV Photon-Induced Excitation

Possible routes for intra-cluster bond formation (ICBF) in protonated serine dimers have been studied. We found no evidence of ICBF following low energy collision-induced dissociation (in correspondence with previous works), however, we do observe clear evidence for ICBF following photon absorption in the 4.6–14 eV range. Moreover, the comparison of photon-induced dissociation measurements of the protonated serine dimer to those of a protonated serine dipeptide provides evidence that ICBF, in this case, involves peptide bond formation (PBF). The experimental results are supported by ab initio molecular dynamics and exploration of several excited state potential energy surfaces, unraveling a pathway for PBF following photon absorption. The combination of experiments and theory provides insight into the PBF mechanisms in clusters of amino acids, and reveals the importance of electronic excited states reached upon UV/VUV light excitation.     

Competitive formation of condensed azines and dihydropyridines in the reaction of ethyl 3,3-diaminoacrylate with <Emphasis Type="Italic">o</Emphasis>-halo carbaldehydes

The reaction of ethyl 3,3-diaminoacrylate with quinoline-3-carbaldehydes and 3-nitrobenzaldehydes to give a dihydropyridine and condensed azine has been studied with respect to the number and reactivity of the halogen atoms in an ortho position to the formyl groups. For the series of quinoline-3-carbaldehydes it was found that the reaction course is determined by the number of chlorine atoms. 2-and 4-Chloroquinoline-3-carbaldehydes give dihydropyridines and a benzo[c][2,7-]naphthyridine is formed in the reaction with 2,4-dichloroquinoline-3-carbaldehyde. The main products in the case of nitrobenzaldehydes are dihydropyridines which points the deciding influence of the low electrophilicity of aromatic ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 567–577, April, 2008.     

Applications of Carbohydrate‐Gold Nanoparticles for Volumetric Flow Measurements Using an Opto‐Acoustic Technique

Gold nanoparticles with carbohydrate ligands attached on their surface have been synthesized and characterized with various techniques. The new nanoparticle conjugates have shown great potentials as a contrast agent for opto‐acoustic imaging. Hemocompatibility measurements of human blood for the carbohydrate‐gold nanoparticles have shown that the conjugates are feasible for in vivo testing. Preliminary quantitative flow measurements using the conjugates were also studied in this work based on the indicator‐dilution theory. In vitro phantom experiments were designed and conducted, and results were discussed.     

Citric acid-coated gold nanoparticles for visual colorimetric recognition of pesticide dimethoate

Journal of Nanoparticle Research - Highly fluorescent nanoparticles, or quantum dots, have multiple applications in biology and biomedicine; however, in most cases, it is necessary to functionalize...