Amino Acid Profiling by Reactive Desorption Electrospray Ionization Tandem Mass Spectrometry (DESI-MS/MS)

Desorption electrospray ionization mass spectrometry (DESI MS) has gained significant recognition over the past few years because of its simplicity and rapid throughput capabilities, allowing for the direct analysis of samples with a wide variety of sizes, shapes, and chemistries. Addition of various reagents into the DESI spray solvent enables atmospheric pressure ion molecule reactions between these reagents in the charged micro droplets and analyte molecules on the sample surface affording improved selectivity and sensitivity in some cases. Presented is a rapid screening method for amino acids (aas) based on reactive DESI. Amino acids have been shown to play key roles in the regulation of cellular processes. They are also particularly vital in the determination of metabolic disorders such as phenylketonurea, homocystinuria, and tyrosinemia. The most specific and reliable methods for diagnosing these disorders are based on the determination of aas in body fluids using methodologies such as gas/liquid chromatography, tandem MS, and various combinations thereof. However, these methods are usually time-consuming, increasing the time physicians wait before administering treatment or regulating the diet of diseased infants. The reactive DESI approach presented here is based on the formation of stable noncovalent complexes between alpha-cyclodextrin (dissolved in the spray solvent) and amino acids present in the sample affording a selective method for their detection. However, the selectivity and sensitivity of screening for aas was improved by performing the MS analysis in the multiple reaction monitoring mode when using a quadrupole ion trap or by the precursor ion scan when using a triple quadrupole MS instrument, affording an average twenty-five times sensitivity improvement compared to analysis in full scan mode. The observation of similar complexes with various carboxylic acids including formic acid and acetic acid, and evidence from tandem MS experiments indicate that amino acid:alpha-cyclodextrin complexation reactions occur by hydrogen bonding interaction with carboxyl group of the aas. The specificity and sensitivity provided by this approach seems very promising for applications in the rapid screening of aas directly from body fluids including urine and plasma for amino acid disorders in a clinical setting.Facundo Fernandez - Faculty Mentor ; Julia Kubanek - Committee Member/Second Reade

Gauge Boson - Gauge Boson Scattering in Theories with Large Extra Dimensions

We consider the scattering amplitudes of the form V_1 V_2 -> V_3 V_4, where V_i=\gamma, Z, W or g(=gluon) are the Standard Model gauge bosons, due to graviton exchange in Kaluza-Klein theories with large extra dimensions. This leads to a number of experimentally viable signatures at high energy leptonic and hadronic colliders. We discuss the observability or future limits on the scale of the gravitational interactions (m_D), that may be obtained at an e+e- Next Linear Collider (NLC) and at the LHC, by studying some of these type of gauge boson scattering processes. We find that the attainable limits through these type of processes are: m_D > 3 TeV at the NLC and m_D > 6 TeV at the LHC.Comment: 27 pages, plain latex, 7 figures embadded in the text using epsfi

Multiple episodes of sand injection leading to accumulation and leakage of hydrocarbons along the San Andreas/San Gregorio fault system, California

Acknowledgements We acknowledge the reviews of three anonymous referees and are also very grateful to Andrew Hurst and David Iacopini for their critical comments of an earlier version of the paper. We also wish to thank Denis Bureau and Antonella Gatto for their support in the field.Peer reviewedPostprin

Dijet Production at Hadron Colliders in Theories with Large Extra Dimensions

We consider the production of high invariant mass jet pairs at hadron colliders as a test for TeV scale gravitational effects. We find that this signal can probe effective Planck masses of about 10 TeV at the LHC with center of mass energy of 14 TeV and 1.5 TeV at the Tevatron with center of mass energy of 2 TeV. These results are compared to analogous scattering processes at leptonic colliders.Comment: 15 pages with 3 figure

Graviton Production By Two Photon and Electron-Photon Processes In Kaluza-Klein Theories With Large Extra Dimensions

We consider the production of gravitons via two photon and electron-photon fusion in Kaluza-Klein theories which allow TeV scale gravitational interactions. We show that at electron-positron colliders, the processes l+l- -> l+ l- graviton, with l=e, mu, can lead to a new signal of low energy gravity of the form l+l- -> l+l- + missing energy which is well above the Standard Model background. For example, with two extra dimensions at the Next Linear Collider with a center of mass energy of 500 or 1000 GeV, hundreds to thousands such l+ l- graviton events may be produced if the scale of the gravitational interactions, M_D, is around a few TeV. At a gamma-electron collider, more stringent bounds may be placed on M_D via the related reaction e^-\gamma -> e^- graviton. For instance, if a 1TeV electron positron collider is converted to an electron-photon collider, a bound of ~10TeV may be placed on the scale M_D if the number of extra dimensions delta=2 while a bound of ~4TeV may be placed if delta=4.Comment: 25 pages 6 figures, minor changes made in the text and changes in reference

The Diboson Excess: Experimental Situation and Classification of Explanations; A Les Houches Pre-Proceeding

We examine the `diboson' excess at $\sim 2$ TeV seen by the LHC experiments in various channels. We provide a comparison of the excess significances as a function of the mass of the tentative resonance and give the signal cross sections needed to explain the excesses. We also present a survey of available theoretical explanations of the resonance, classified in three main approaches. Beyond that, we discuss methods to verify the anomaly, determining the major properties of the various surpluses and exploring how different models can be discriminated. Finally, we give a tabular summary of the numerous explanations, presenting their main phenomenological features.Comment: 37 pages, 9 Figures, 1 Tabl

Non-linear susceptibilities of spherical models

The static and dynamic susceptibilities for a general class of mean field random orthogonal spherical spin glass models are studied. We show how the static and dynamical properties of the linear and nonlinear susceptibilities depend on the behaviour of the density of states of the two body interaction matrix in the neighbourhood of the largest eigenvalue. Our results are compared with experimental results and also with those of the droplet theory of spin glasses.Comment: 20 pages, 2 fig

Influence of carbon partitioning kinetics on final Austenite fraction during quenching and partitioning

The quenching and partitioning (Q&P) process is a two-stage heat-treatment procedure proposed for producing steel microstructures that contain carbon-enriched retained austenite. In Q&P processing, austenite stabilization is accomplished by carbon partitioning from supersaturated martensite. A quench temperature selection methodology was developed to predict an optimum process quench temperature; extension of this methodology to include carbon partitioning kinetics is developed here. Final austenite fraction is less sensitive to quench temperature than previously predicted, in agreement with experimental results

Supplemental Ascorbate Diminishes DNA Damage Yet Depletes Glutathione and Increases Acute Liver Failure in a Mouse Model of Hepatic Antioxidant System Disruption

Cellular oxidants are primarily managed by the thioredoxin reductase-1 (TrxR1)- and glutathione reductase (Gsr)-driven antioxidant systems. In mice having hepatocyte-specific codisruption of TrxR1 and Gsr (TrxR1/Gsr-null livers), methionine catabolism sustains hepatic levels of reduced glutathione (GSH). Although most mice with TrxR1/Gsr-null livers exhibit long-term survival, ~25% die from spontaneous liver failure between 4- and 7-weeks of age. Here we tested whether liver failure was ameliorated by ascorbate supplementation. Following ascorbate, dehydroascorbate, or mock treatment, we assessed survival, liver histology, or hepatic redox markers including GSH and GSSG, redox enzyme activities, and oxidative damage markers. Unexpectedly, rather than providing protection, ascorbate (5 mg/mL, drinking water) increased the death-rate to 43%. In adults, ascorbate (4 mg/g × 3 days i.p.) caused hepatocyte necrosis and loss of hepatic GSH in TrxR1/Gsr-null livers but not in wildtype controls. Dehydroascorbate (0.3 mg/g i.p.) also depleted hepatic GSH in TrxR1/Gsr-null livers, whereas GSH levels were not significantly affected by either treatment in wildtype livers. Curiously, however, despite depleting GSH, ascorbate treatment diminished basal DNA damage and oxidative stress markers in TrxR1/Gsr-null livers. This suggests that, although ascorbate supplementation can prevent oxidative damage, it also can deplete GSH and compromise already stressed livers