Sulfamic acid: An efficient and recyclable catalyst for the regioselective hydrothiolation of terminal alkenes and alkynes with thiols

Herein, we described a new method for the preparation of thioethers through hydrothiolation of alkenes and alkynes, using sulfamic acid as a reusable catalyst. Generally, this new methodology afforded the desired products in very good yields, under metal and solvent-free conditions. Furthermore, the catalyst was easily recovered and reused for further catalytic reactions without loss of activity.     

Electronic Wave-Packets in Integer Quantum Hall Edge Channels: Relaxation and Dissipative Effects

We theoretically investigate the evolution of the peak height of energy-resolved electronic wave-packets ballistically propagating along integer quantum Hall edge channels at filling factor equal to two. This is ultimately related to the elastic scattering amplitude for the fermionic excitations evaluated at different injection energies. We investigate this quantity assuming a short-range capacitive coupling between the edges. Moreover, we also phenomenologically take into account the possibility of energy dissipation towards additional degrees of freedom—both linear and quadratic—in the injection energy. Through a comparison with recent experimental data, we rule out the non-dissipative case as well as a quadratic dependence of the dissipation, indicating a linear energy loss rate as the best candidate for describing the behavior of the quasi-particle peak at short enough propagation lengths.     

Existence and non-existence results for strong external difference families

We consider strong external difference families (SEDFs); these are external difference families satisfying additional conditions on the patterns of external differences that occur, and were first defined in the context of classifying optimal strong algebraic manipulation detection codes. We establish new necessary conditions for the existence of $(n,m,k,\lambda )$-SEDFs; in particular giving a near-complete treatment of the $\lambda =2$ case. For the case $m=2$, we obtain a structural characterization for partition type SEDFs (of maximum possible $k$ and $\lambda$), showing that these correspond to Paley partial difference sets. We also prove a version of our main result for generalized SEDFs, establishing non-trivial necessary conditions for their existence.     

High-temperature failure of GaN LEDs related with passivation

This paper analyses the thermally-activated failure mechanisms of GaN LED test-structures related with the presence of a hydrogen rich SiN passivation layer, by comparing the electrical and optical behaviour of samples with and without passivation during thermal stress. The analysis was carried out by means of electroluminescence, cathodoluminescence, emission microscopy and current–voltage measurements. Thermal treatment induced degradation only on the samples with passivation: identified degradation modes were an efficiency decrease exponential in time, emission crowding, and a forward voltage increase. On the other side, thermal treatment did not change the behaviour of the LEDs without passivation. An interpretation for the degradation of the passivated samples is the following: as a consequence of passivation deposition, a considerable amount of hydrogen is incorporated in the passivation layer. Heating at 250 C allows this hydrogen to interact with the LED surface, thus worsening the transport properties of p-GaN and of the p-ohmic contact, and then the current and emission distribution, inducing the observed degradation and emission crowding. The activation energy of the degradation process was found to be equal to 1.3 eV. Comparison between spectral electroluminescence and cathodoluminescence measurements shows how the mechanism mentioned above is not the only ageing cause and the thermal worsening of QW confinement and/or the creation of nonradiative centers possibly contribute to the LED damage.     

Hofmeister series: the hydrolytic activity of Aspergillus niger lipase depends on specific anion effects

The specific activity of lipase A (Aspergillus niger) toward the hydrolysis of p-nitrophenyl acetate (p-NPA) is shown to increase as a result of sodium salt addition according to specific ion effects of the Hofmeister series. This shows explicitly that the Hofmeister effect is due to the different specific interactions between anions and the enzymatic surface.     

Counting statistics of non-Markovian quantum stochastic processes

We derive a general expression for the cumulant generating function (CGF) of non-Markovian quantum stochastic transport processes. The long-time limit of the CGF is determined by a single dominating pole of the resolvent of the memory kernel from which we extract the zero-frequency cumulants of the current using a recursive scheme. The finite-frequency noise is expressed not only in terms of the resolvent, but also initial system-environment correlations. As an illustrative example we consider electron transport through a dissipative double quantum dot for which we study the effects of dissipation on the zero-frequency cumulants of high orders and the finite-frequency noise.     

Previous infection with Staphylococcus aureus strains attenuated experimental encephalomyelitis

Background

Bacterial superantigens are potent T cell activators that can activate T cells with specificity for antigens of the central nervous system (CNS). In this study, we compared the effect of two S. aureus strains on experimental autoimmune encephalomyelitis (EAE) development. C57BL/6 female mice were infected with S. aureus ATCC 51650, which produces toxic shock syndrome toxin 1 (TSST-1+) or S. aureus ATCC 43300, which does not produce toxins (TOX-). Three days later, the animals were subjected to EAE induction by immunization with myelin oligodendrocyte glycoprotein (MOG). The weight variation, disease incidence and clinical score were recorded daily. Cytokines and Foxp3+ regulatory T cells in the brain were evaluated during the acute disease phase. Cytokines and Foxp3+ regulatory T cells in the spleen and histopathological analysis of the CNS were assessed during the chronic stage.

Results

Previous infection with both strains similarly decreased the clinical score; however, only the TSST-1+ strain clearly diminished inflammation in the CNS. The infections also modulated cytokine production in the spleen and CNS. Reduced production of IL-5 and IL-10 was detected in MOG-stimulated spleen cultures in the TOX- and TSST-1+ infected groups, respectively. In S. aureus stimulated cultures, there was an increased production of IFN-γ and IL-10 in both infected groups and an increased level of IL-5 in the TSST-1+ group. CNS infiltrating cell cultures from previously infected mice produced less IL-17 in response to MOG and more IFN-γ in response to S. aureus stimulation.

Conclusions

These results indicated that both strains attenuated clinical EAE manifestations, but only TSST-1 clearly decreased CNS inflammation.     

Control of spin in quantum dots with non-Fermi-liquid correlations

Spin effects in the transport properties of a quantum dot with spin-charge separation are investigated. It is found that the nonlinear transport spectra are dominated by spin dynamics. Strong spin polarization effects are observed in a magnetic field. They can be controlled by varying gate and bias voltages. Complete polarization is stable against interactions. When polarization is not complete it is power law enhanced by non-Fermi-liquid effects.     

Covariation among vowel height effects on acoustic measures

Covariation among vowel height effects on vowel intrinsic fundamental frequency (IF(0)), voice onset time (VOT), and voiceless interval duration (VID) is analyzed to assess the plausibility of a common physiological mechanism underlying variation in these measures. Phrases spoken by 20 young adults, containing words composed of initial voiceless stops or /s/ and high or low vowels, were produced in habitual and voluntarily increased F(0) conditions. High vowels were associated with increased IF(0) and longer VIDs. VOT and VID exhibited significant covariation with IF(0) only for males at habitual F(0). The lack of covariation for females and at increased F(0) is discussed.     

L-α-Aminoadipic Acid from L-Glutamic Acid

A convenient procedure for the preparation of L-α-aminoadipic acid from L-glutamic acid is described.