An intermediate in a new synthesis approach to β‐substituted β‐hydroxy­aspartame

The crystal and molecular structure of 1‐tert‐butyl 4‐ethyl (2′R,3′R,5′R,2S,3S)‐3‐bromo­methyl‐3‐hydroxy‐2‐[(2′‐hydroxy‐2′,6′,6′‐tri­methyl­bi­cyclo­[3.1.1]­hept‐3′‐yl­idene)­amino]­succinate, C₂₁H₃₄BrNO₆, is presented. This compound is an intermediate in the new synthetic route to β‐substituted β‐hydroxy­aspartates, which are blockers of glutamate transport.     

World First for Diamond in Synchrotron-Based IR Photothermal Nanospectroscopy

For the first time, infrared spectra on the sub-wavelength scale have been delivered by a synchrotron-radiation-induced thermal expansion technique [1 P.M. Donaldson, Optics Express 24(3), 1852–1864 (2016).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]. The novel experimental result was achieved by coupling an atomic force microscope (AFM) to an infrared (IR) beamline at the UK's national synchrotron facility, Diamond Light Source. Via broadband synchrotron illumination and an AFM sub-micron tip, molecular IR spectra were obtained by detecting a resonance-enhanced (RE) photothermal signal with spatial resolution beyond the diffraction limit. Together with results on synchrotron IR nanoscopy in scattering mode from the IR beamline at the Advanced Light Source two years ago, the Diamond photothermal nanoprobe approach moves vibrational analysis beyond the diffraction limit and into nanoscale absorption spectroscopy.     

Approach to Synthesis of γ-Aminobutyric Acid (GABA) Analogues with Rigid Conformations - Convenient One Pot Synthesis of Functionalized Bisnaphthalenes

Silica gel supported cerium (IV) ammonium nitrate has been successfully employed to achieve functionalized C-C-linked bisnaphthalenes. The study demonstrates the utility of silica gel support for controlling over oxidation in cerium (IV) based oxidants and is of significance to prepare GABA analogues with restricted conformation required for studying GABAergic processes in neurochemical investigations.     

Stabilisation frontière indirecte du système de Timoshenko

In this Note, we study the indirect boundary stabilization of the Timoshenko system with only one dissipation law. Under the equal speed wave propagation condition, we establish the exponential stability of the system. On the contrary, we show that the decay rate is polynomial.     

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga+ and C 60 + projectiles

This article investigates the influence of the organic film thickness on the characteristic and molecular ion yields of polystyrene (PS), in combination with two different substrates (Si, Au) or gold condensation (MetA-SIMS), and for atomic (Ga⁺) and polyatomic (C ₆₀ ⁺ ) projectile bombardment. PS oligomer (m/z ～ 2000 Da) layers were prepared with various thicknesses ranging from 1 up to 45 nm on both substrates. Pristine samples on Si were also metallized by evaporating gold with three different thicknesses (0.5, 2, and 6 nm). Secondary ion mass spectrometry was performed using 12 keV atomic Ga⁺ and C ₆₀ ⁺ projectiles. The results show that upon Ga⁺ bombardment, the yield of the fingerprint fragment C₇H ₇ ⁺ increases as the PS coverage increases and reaches its maximum for a thickness that corresponds to a complete monolayer (～3.5 nm). Beyond the maximum, the yields decrease strongly and become constant for layers thicker than 12 nm. In contrast, upon C ₆₀ ⁺ bombardment, the C₇H ₇ ⁺ yields increase up to the monolayer coverage and they remain constant for higher thicknesses. A strong yield enhancement is confirmed upon Ga⁺ analysis of gold-metallized layers but yields decrease continuously with the gold coverage for C ₆₀ ⁺ bombardment. Upon Ga⁺ bombardment, the maximum PS fingerprint ion yields are obtained using a monolayer spin-coated on gold, whereas for C ₆₀ ⁺ , the best results are obtained with at least one monolayer, irrespective of the substrate and without any other treatment. The different behaviors are tentatively explained by arguments involving the different energy deposition mechanisms of both projectiles.     

Isolating stem cells in the inter-follicular epidermis employing synchrotron radiation-based Fourier-transform infrared microspectroscopy and focal plane array imaging

Normal function and physiology of the epidermis is maintained by the regenerative capacity of this tissue via adult stem cells (SCs). However, definitive identifying markers for SCs remain elusive. Infrared (IR) spectroscopy exploits the ability of cellular biomolecules to absorb in the mid-IR region (λ?=?2.5–25?μm), detecting vibrational transitions of chemical bonds. In this study, we exploited the cell’s inherent biochemical composition to discriminate SCs of the inter-follicular skin epidermis based on IR-derived markers. Paraffin-embedded samples of human scalp skin (n?=?4) were obtained, and 10-μm thick sections were mounted for IR spectroscopy. Samples were interrogated in transmission mode using synchrotron radiation-based Fourier-transform IR (FTIR) microspectroscopy (15?×?15?μm) and also imaged employing globar-source FTIR focal plane array (FPA) imaging (5.4?×?5.4?μm). Dependent on the location of derived spectra, wavenumber–absorbance/intensity relationships were examined using unsupervised principal component analysis. This approach showed clear separation and spectral differences dependent on cell type. Spectral biomarkers concurrently associated with segregation of SCs, transit-amplifying cells and terminally-differentiated cells of epidermis were primarily PO ₂ ^? vibrational modes (1,225 and 1,080?cm^?1), related to DNA conformational alterations. FPA imaging coupled with hierarchical cluster analysis also indicated the presence of specific basal layer cells potentially originating from the follicular bulge, suggested by co-clustering of spectra. This study highlights PO ₂ ^? vibrational modes as potential putative SC markers.

Synthesis of O-spiro-C-aryl glycosides using organocatalysis

An organocatalysis strategy has been developed toward the synthesis of O-spiro-C-aryl glycosides with different configurations in the sugar part. This strategy has been extended to the synthesis of the Papulacandin class of compounds.     

Observabilité et contrôlabilité exacte indirecte interne par un contrôle localement distribué de systèmes d'équations couplées

We study the observability and the exact controllability of a weakly coupled system with an internal locally control acting on only one equation. We show that, for sufficiently large time, the observation of the velocity of the first component of the solution on a neighborhood of a part of the boundary allows us to get back a weakened energy of initial data of the second component, this if the coupling parameter is sufficiently small, but non-vanishing. This result leads to a uniqueness theorem and, by the HUM method, we prove that the total system is exactly controllable.     

Non performance estimation of a microwave communication link due to rain during the monsoon months of 2006 over Kolkata

The non performance of a microwave communication link located over Kolkata due to heavy rain in the monsoon months of 2006 has been investigated by monitoring the amplitude variation of signal on twenty hour basis. It has been seen that the link did not serve any purpose for 4% during the monsoon period of 2006 while the signal level was less than −78 dBm. Infact the study revealed that the link performance started deteriorating when the signal was of the order of −73 dBm.