Effects of heavy colored Higgs scalars on SU(5) predictions

We show that the inclusion in the renormalization group equations of heavy colored Higgs scalars present in the grand unified model of SU(5) can affect the predictions of the model. If only the $\text{24}$ and $\text{5}$ of Higgs are present, the effects on the predictions are small. However, if a $\text{45}$ of Higgs were present, it will lead to large uncertainties in the values of sin²θ_W and the lifetime of the proton due to unknown parameters in the Higgs potential; the uncertaity in the latter due to colored Higgs is a factor of 60. The effect on the b-quark mass prediction is also discussed.     

Noise in phototransistor optical isolators

Noise measurements were performed on several commercially available phototransistor optical isolators in order to examine the signal detection limits of typical devices. It was found that, in general, phototransistor optical isolators are very noisy devices exhibiting all of the common types of noise usually found in bipolar junction transistors. A large number of devices exhibited burst noise which dominated their low-frequency noise performance. The noise performance of devices without burst noise was dominated by 1/f noise or flicker noise at low frequencies and by shot noise at high frequencies. Experimental data indicates that in most cases the electrical noise contribution of the LED is negligible and that the dominant source of noise is the phototransistor.     

Manipulating the fragmentation patterns of phosphopeptides via gas-phase boron derivatization: Determining phosphorylation sites in peptides with multiple serines

Trivalent boron species readily react with protonated phosphopeptides to give addition products with the loss of boron ligands. In the present study, trimethoxyborane (TMB), diisopropoxymethylborane (DIPM), and diethylmethoxyborane (DEMB) were allowed to react with four phosphopeptides, VsSF, LSsF, LsGASA, and VSGAsA (lower-case s indicates phosphoserine). Each of the phosphopeptides contains one serine that is phosphorylated and one that is not. Under collision-activated dissociation (CAD) conditions, the boron-derivatized peptides give fragmentation patterns that differ significantly from that of the protonated phosphopeptide. The patterns vary, depending on the number of labile (i.e., alkoxy) ligands on the boron. In general, boron derivatization increases the yield of phosphate-containing sequence ions, but dramatic effects are only seen with certain reagent/peptide combinations. However, the suite of reagents provides a means of altering and increasing the information content of phosphopeptide CAD spectra.