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Articles 1 - 30 of 142
Full-Text Articles in Physics
Single-Stage Few-Cycle Pulse Amplification, Sagnik Ghosh, Nathan G. Drouillard, Tj Hammond
Single-Stage Few-Cycle Pulse Amplification, Sagnik Ghosh, Nathan G. Drouillard, Tj Hammond
Physics Publications
Kerr instability can be exploited to amplify visible, near-infrared, and midinfrared ultrashort pulses. We use the results of Kerr instability amplification theory to inform our simulations amplifying few-cycle pulses. We show that the amplification angle dependence is simplified to the phase-matching condition of four-wave mixing when the intense pump is considered. Seeding with few-cycle pulses near the pump leads to broadband amplification without spatial chirp, while longer pulses undergo compression through amplification. Pumping in the midinfrared leads to multioctave spanning amplified pulses with single-cycle duration not previously predicted. We discuss limitations of the amplification process and optimizing pump and seed …
Spectral Broadening For Pulse Compression Using Liquid Alcohols, Jacob A. Stephen, Chathurangani J. Arachchige, Tj Hammond
Spectral Broadening For Pulse Compression Using Liquid Alcohols, Jacob A. Stephen, Chathurangani J. Arachchige, Tj Hammond
Physics Publications
Although gases, and more recently solids, have been used to create few-cycle pulses, we explore using liquid alcohols for spectral broadening and femtosecond pulse compression. By using a series of 1 cm cuvettes filled with 1-decanol, we have compressed a pulse from 83.6 fs down to 31.3 fs with a spectrum capable of supporting 25 fs pulses without filamentation.We measure the nonlinear index of refraction for various liquids, measuring n2 = (6.8 ± 0.5) × 10−20 m2 W−1 for 1-decanol.We demonstrate liquids to be a compact, simple, versatile, and cost-effective material to obtain broad spectra.
Measurement Of Dispersion And Index Of Refraction Of 1-Decanol With Spectrally Resolved White Light Interferometry, Nathan G. Drouillard, Tj Hammond
Measurement Of Dispersion And Index Of Refraction Of 1-Decanol With Spectrally Resolved White Light Interferometry, Nathan G. Drouillard, Tj Hammond
Physics Publications
The high density, high nonlinearity, and stability of liquids make them an attractive medium for spectral broadening and supercontinuum generation in ultrafast experiments. To understand ultrashort pulse propagation in these media, their indices of refraction and dispersions must be characterized. We employ a Mach-Zehnder interferometer to generate a series of interferograms, which we refer to as a spectrogram, to develop a new method of using spectrally resolved white light interferometry to determine the refractive indices of materials. We determine the indices of refraction of BK7, sapphire, ethanol, and 1-decanol at 24°C across the visible and near infrared. To our knowledge, …
A Simple And Efficient Centrifugation Filtration Method For Bacterial Concentration And Isolation Prior To Testing Liquid Specimens With Laser-Induced Breakdown Spectroscopy, Dylan J. Malenfanta, Alexandra E. Paulick, Steven J. Rehse
A Simple And Efficient Centrifugation Filtration Method For Bacterial Concentration And Isolation Prior To Testing Liquid Specimens With Laser-Induced Breakdown Spectroscopy, Dylan J. Malenfanta, Alexandra E. Paulick, Steven J. Rehse
Physics Publications
An inexpensive filtration device was designed and constructed to rapidly concentrate bacteria in a liquid suspension on the surface of a disposable filter medium while at the same time separating the bacterial cells from larger contaminants in the suspension on the basis of their size. The device consists of a two-stage insert that is held rigidly in a standard tube during bacterial suspension centrifugation. The filters can be easily removed from the insert for subsequent testing with laser-induced breakdown spectroscopy in a process that takes only three minutes. Filter media of 0.45 micron pore size was found to capture approximately …
Concentration Of Bacterial Specimens During Centrifugation Prior To Laser-Induced Breakdown Spectroscopy Analysis, Alexandra E. Paulicka, Dylan J. Malenfanta, Steven J. Rehse
Concentration Of Bacterial Specimens During Centrifugation Prior To Laser-Induced Breakdown Spectroscopy Analysis, Alexandra E. Paulicka, Dylan J. Malenfanta, Steven J. Rehse
Physics Publications
A metal cone device has been designed and fabricated for use with a custom centrifuge tube insert to allow the simple and rapid concentration of bacterial cells in a circular area with a diameter of 1 mm. The device concentrates cells suspended in up to 1 mL of liquid at the center of a highly flat disposable filter medium which can be easily removed from the centrifuge tube insert for subsequent testing with laser-induced breakdown spectroscopy. Two-dimensional elemental mapping of the filter evidenced a high concentration of bacteria on the filter under the location of the cone hole, as well …
A Review Of The Use Of Laser-Induced Breakdown Spectroscopy For Bacterial Classification, Quantification, And Identification, Steven J. Rehse
A Review Of The Use Of Laser-Induced Breakdown Spectroscopy For Bacterial Classification, Quantification, And Identification, Steven J. Rehse
Physics Publications
The use of laser-induced breakdown spectroscopy to determine the elemental composition of bacterial cells has been described in the peer-reviewed literature since 2003. Fifteen years on, significant accomplishments have been reported that have served to clarify and underscore the areas of bacteriological investigation that LIBS is well-suited for as well as the challenges that yet remain to be faced. This review will attempt to summarize the state of the field by surveying the available body of knowledge. The early days of these experiments, roughly from 2003 to 2007, in which many of the most fundamental experiments were initially conducted will …
Helium Tune-Out Wavelength: Gauge Invariance And Retardation Corrections, Gordon W. F. Drake, Jacob Gabriel Manalo, Pei-Pei Zhang, Kenneth George Herbert Baldwin
Helium Tune-Out Wavelength: Gauge Invariance And Retardation Corrections, Gordon W. F. Drake, Jacob Gabriel Manalo, Pei-Pei Zhang, Kenneth George Herbert Baldwin
Physics Publications
The problem of calculating the tune-out wavelength for an atom interacting with a plane electromagnetic wave is formulated as a zero in the Rayleigh scattering cross section, rather than a zero in the dynamic polarizability. Retardation (finite wavelength) corrections are discussed in the velocity gauge, and possible gauge transformations to a length form are investigated. For the special case of S-states, it is shown that a pure length form exists for the leading pxz retardation correction, even though one does not exist in general. The results of high-precision calculations in Hylleraas coordinates are presented for the tune-out wavelength of …
N (2p) Production In Electron-N2 Collisions, Wladyslaw Kedzierski, Jeff Dech, J. W. Mcconkey
N (2p) Production In Electron-N2 Collisions, Wladyslaw Kedzierski, Jeff Dech, J. W. Mcconkey
Physics Publications
A unique detector which is selectively sensitive to low energy metastable atoms, has been used to study the production of ground state N (2P) atoms following collisions of low energy (0-200 eV) electrons with molecular nitrogen. TOF techniques have revealed the existence of at least two distinct mechanisms yielding this dissociation product. Released kinetic energies in the dissociation have allowed positioning of the parent molecular states in the Franck-Condon region. This has allowed probable parent states, such as B' 3Σu¯, b' 1Σu+ and C' 3Πu, to be identified making use of recent theoretical calculations. Both direct and predissociation processes are …
Determination Of The Zinc Concentration In Human Fingernails By Laser-Induced Breakdown Spectroscopy, Steven J. Rehse, Vlora A. Riberdy, Christopher J. Frederickson
Determination Of The Zinc Concentration In Human Fingernails By Laser-Induced Breakdown Spectroscopy, Steven J. Rehse, Vlora A. Riberdy, Christopher J. Frederickson
Physics Publications
The absolute concentration of zinc in human fingernail clippings tested ex vivo was determined by 1064 nm laser-induced breakdown spectroscopy and confirmed by speciated isotope dilution mass spectrometry. A nail testing protocol that sampled across the nail (perpendicular to the direction of growth) was developed and validated by scanning electron microscopy energy dispersive x-ray spectroscopy. Using this protocol, a partial least squares regression model predicted the zinc concentration in five subjects’ fingernails to within 7 ppm on average. The variation of the zinc concentration with depth into the nail as determined by laser-induced breakdown spectroscopy was studied and found to …
Use Of Solid N2 Surfaces In Metastable Particle Detection, Wladyslaw Kedzierski, J. W. Mcconkey
Use Of Solid N2 Surfaces In Metastable Particle Detection, Wladyslaw Kedzierski, J. W. Mcconkey
Physics Publications
A novel detector is described in which solid nitrogen at 17 K is used as the most significant element. Metastable particles impinge on this element and immediately transfer their internal energy to the solid nitrogen producing photons, via excimer formation or otherwise, whose wavelength depends on the metastable being detected and the energy transfer process. The performance of the instrument for the detection of atomic oxygen and molecular nitrogen metastables is discussed.
Selective Detection Of Singlet Gerade Metastable States Of N-2, Wladyslaw Kedzierski, J. W. Mcconkey
Selective Detection Of Singlet Gerade Metastable States Of N-2, Wladyslaw Kedzierski, J. W. Mcconkey
Physics Publications
Metastable N-2 molecules produced by electron impact on N2 are detected using a unique solid nitrogen matrix detector. The time-of-flight system is shown to be selectively sensitive to a(1)Pi(g) and (1)Sigma(+)(g) or (1)Gamma(g) metastable species. The latter species had been identified theoretically previously but was detected experimentally for the first time in the present investigation. Their identification and excitation as a function of electron energy from threshold to 300 eV are presented. Comparison is made with the data obtained by other techniques. Published by AIP Publishing.
Vuv Study Of Electron Impact Dissociative Excitation Of Thymine, C. J. Tiessen, J. A. Trocchi, J. D. Hein, J. Dech, Wladyslaw Kedzierski, J. W. Mcconkey
Vuv Study Of Electron Impact Dissociative Excitation Of Thymine, C. J. Tiessen, J. A. Trocchi, J. D. Hein, J. Dech, Wladyslaw Kedzierski, J. W. Mcconkey
Physics Publications
Dissociative excitation of thymine following electron impact was studied in the energy range up to 430 eV. Emissions in the vacuum ultra-violet spectral region below 150 nm were studied and found to be dominated by the hydrogen Lyman series. Emission cross section data reveal that Lyman-α excitation displays a broad maximum at an electron impact energy of 160 eV. The probability of extracting other excited atoms from the parent molecule is found to be insignificant. Possible excitation and dissociation mechanisms in the parent molecule are discussed.
Advances In Atomic, Molecular, And Optical Physics, J. W. Mcconkey, Wladyslaw Kedzierski
Advances In Atomic, Molecular, And Optical Physics, J. W. Mcconkey, Wladyslaw Kedzierski
Physics Publications
The use of rare gas matrices for the detection of a variety of low-energy metastable species, particularly those from atoms with an np4 outer electron configuration, is discussed in detail. The historical development of the detector is outlined and its performance as a function of rare gas, matrix temperature, and metastable species is discussed. Examples of its use are given for electron impact dissociation of a wide variety of oxygen and sulfur containing targets.
Production Of O(1d) Following Electron Impact On Co2, Wladyslaw Kedzierski, J. D. Hein, C. J. Tiessen, D. Lukic, J. A. Trocchi, T. Z. Mlinaric, J. W. Mcconkey
Production Of O(1d) Following Electron Impact On Co2, Wladyslaw Kedzierski, J. D. Hein, C. J. Tiessen, D. Lukic, J. A. Trocchi, T. Z. Mlinaric, J. W. Mcconkey
Physics Publications
We have studied the excitation of metastable O(1D) following dissociative excitation of CO2 in the electron impact energy range from threshold to 400 eV. A solid Ne matrix at ∼20 K forms the heart of the detector. This is sensitive to the metastable species through the formation of excited excimers (NeO*), The resultant excimer radiation is readily detected, providing a means of measuring the production of the metastables. Using a pulsed electron beam and time-of-flight techniques, we have measured the O(1D) kinetic energy spectrum and its relative production cross sections as a function of electron …
Sensitive And Specific Discrimination Of Pathogenic And Nonpathogenic Escherichia Coli Using Raman Spectroscopy - A Comparison Of Two Multivariate Analysis Techniques, Steven Rehse, Khozima Hamasha, Qassem I. Mohaidat, Russell A. Putnam, Ryan C. Woodman, Sunil Palchaudhuri
Sensitive And Specific Discrimination Of Pathogenic And Nonpathogenic Escherichia Coli Using Raman Spectroscopy - A Comparison Of Two Multivariate Analysis Techniques, Steven Rehse, Khozima Hamasha, Qassem I. Mohaidat, Russell A. Putnam, Ryan C. Woodman, Sunil Palchaudhuri
Physics Publications
The determination of bacterial identity at the strain level is still a complex and time-consuming endeavor. In this study, visible wavelength spontaneous Raman spectroscopy has been used for the discrimination of four closely related Escherichia coli strains: pathogenic enterohemorrhagic E. coli O157:H7 and non-pathogenic E. coli C, E. coli Hfr K-12, and E. coli HF4714. Raman spectra from 600 to 2000 cm-1 were analyzed with two multivariate chemometric techniques, principal component-discriminant function analysis and partial least squares-discriminant analysis, to determine optimal parameters for the discrimination of pathogenic E. coli from the non-pathogenic strains. Spectral preprocessing techniques such as smoothing with …
A Comparison Of Multivariate Analysis Techniques And Variable Selection Strategies In A Laser-Induced Breakdown Spectroscopy Bacterial Classification, Russell Putnam, Q.I. Mohaidat, Andrew Daabous, Steven Rehse
A Comparison Of Multivariate Analysis Techniques And Variable Selection Strategies In A Laser-Induced Breakdown Spectroscopy Bacterial Classification, Russell Putnam, Q.I. Mohaidat, Andrew Daabous, Steven Rehse
Physics Publications
Laser-induced breakdown spectroscopy has been used to obtain spectral fingerprints from live bacterial specimens from thirteen distinct taxonomic bacterial classes representative of five bacterial genera. By taking sums, ratios, and complex ratios of measured atomic emission line intensities three unique sets of independent variables (models) were constructed to determine which choice of independent variables provided optimal genuslevel classification of unknown specimens utilizing a discriminant function analysis. A model composed of 80 independent variables constructed from simple and complex ratios of the measured emission line intensities was found to provide the greatest sensitivity and specificity. This model was then used in …
Pathogen Identification With Laser-Induced Breakdown Spectroscopy: The Effect Of Bacterial And Biofluid Specimen Contamination, Q.I. Mohaidat, K. Sheikh, S. Palchaudhuri, Steven J. Rehse
Pathogen Identification With Laser-Induced Breakdown Spectroscopy: The Effect Of Bacterial And Biofluid Specimen Contamination, Q.I. Mohaidat, K. Sheikh, S. Palchaudhuri, Steven J. Rehse
Physics Publications
In this paper, the potential use of laser-induced breakdown spectroscopy (LIBS) for the rapid discrimination and identification of bacterial pathogens in realistic clinical specimens is investigated. Specifically, the common problem of sample contamination was studied by creating mixed samples to investigate the effect that the presence of a second contaminant bacterium in the specimen had on the LIBS-based identification of the primary pathogen. Two closely related bacterial specimens, Escherichia coli strain ATCC 25922 and Enterobacter cloacae strain ATCC 13047, were mixed together in mixing fractions of 10:1, 100:1, and 1000:1. LIBS spectra from the three mixtures were reliably classified as …
Spin-Forbidden Helium I Transition Rates, D. C. Morton, Gordon W. F. Drake
Spin-Forbidden Helium I Transition Rates, D. C. Morton, Gordon W. F. Drake
Physics Publications
We have calculated spin-forbidden transition rates in neutral helium using the spin-orbit and spin-other-orbit Breit-Pauli operators.
Variational Energies And The Fermi Contact Term For The Low-Lying States Of Lithium: Basis-Set Completeness, L. M. Lang, Z. C. Yan, H. X. Qiao, Gordon W. F. Drake
Variational Energies And The Fermi Contact Term For The Low-Lying States Of Lithium: Basis-Set Completeness, L. M. Lang, Z. C. Yan, H. X. Qiao, Gordon W. F. Drake
Physics Publications
Nonrelativistic energies for the low-lying states of lithium are calculated using the variational method in Hylleraas coordinates. Variational eigenvalues for the infinite nuclear mass case with up to 34020 terms are -7.478060323910147(1) a.u. for 1s22s2S, -7.35409842144437(1) a.u. for 1s23s2S, -7.31853084599891(1) a.u. for 1s24s2S, -7.41015653265241(4) a.u. for 1s22p2P, and -7.335523543524688(3) a.u. for 1s23d2D. The selection of the minimum set of angular momentum configurations is discussed, with the 2P and 3D states as examples to demonstrate the impact of various configurations on the variational energies. It is shown by numerical example that the second spin function (i.e., coupled to form a triplet …
Quantum Theory Of Longitudinal Momentum Transfer In Above-Threshold Ionization, A. S. Titi, Gordon W. F. Drake
Quantum Theory Of Longitudinal Momentum Transfer In Above-Threshold Ionization, A. S. Titi, Gordon W. F. Drake
Physics Publications
In the ionization process, longitudinal momentum along the direction of propagation is transferred to the photoelectrons due to the action of the magnetic component of Lorentz force. In a recent experiment by Smeenk, such a transfer is observed in the ionization of argon and neon atoms by circularly polarized light at 800 and 1400 nm in the intensity range of 1014-1015W/cm2. They accounted for the results by a purely classical model. We present a fully quantum-mechanical calculation of the transfer of longitudinal momentum to the photoelectrons. The results are in agreement with the observations of Smeenk at high intensities, but …
The Effect Of Bacterial Environmental And Metabolic Stresses On A Laser-Induced Breakdown Spectroscopy (Libs) Based Identification Of Escherichia Coli And Streptococcus Viridans, Q. Mohaidat, S. Palchaudhuri, Steven J. Rehse
The Effect Of Bacterial Environmental And Metabolic Stresses On A Laser-Induced Breakdown Spectroscopy (Libs) Based Identification Of Escherichia Coli And Streptococcus Viridans, Q. Mohaidat, S. Palchaudhuri, Steven J. Rehse
Physics Publications
In this paper we investigate the effect that adverse environmental and metabolic stresses have on the laser-induced breakdown spectroscopy (LIBS) identification of bacterial specimens. Single-pulse LIBS spectra were acquired from a non-pathogenic strain of Escherichia coli cultured in two different nutrient media: a trypticase soy agar and a MacConkey agar with a 0.01% concentration of deoxycholate. A chemometric discriminant function analysis showed that the LIBS spectra acquired from bacteria grown in these two media were indistinguishable and easily discriminated from spectra acquired from two other non-pathogenic E. coli strains. LIBS spectra were obtained from specimens of a nonpathogenic E. coli …
Critical Comparison Of Diffuse Reflectance Spectroscopy And Colorimetry As Dermatological Diagnostic Tools For Acanthosis Nigricans: A Chemometric Approach, S. Devpura, B. Pattamadilok, Z.U. Syed, Steven Rehse, P. Vemulapalli
Critical Comparison Of Diffuse Reflectance Spectroscopy And Colorimetry As Dermatological Diagnostic Tools For Acanthosis Nigricans: A Chemometric Approach, S. Devpura, B. Pattamadilok, Z.U. Syed, Steven Rehse, P. Vemulapalli
Physics Publications
Quantification of skin changes due to acanthosis nigricans (AN), a disorder common among insulin-resistant diabetic and obese individuals, was investigated using two optical techniques: diffuse reflectance spectroscopy (DRS) and colorimetry. Measurements were obtained from AN lesions on the neck and two control sites of eight AN patients. A principal component/discriminant function analysis successfully differentiated between AN lesion and normal skin with 87.7% sensitivity and 94.8% specificity in DRS measurements and 97.2% sensitivity and 96.4% specificity in colorimetry measurements. © 2011 Optical Society of America.
Variational Upper Bounds For Low-Lying States Of Lithium, L. M. Wang, Z. C. Yan, H. X. Qiao, Gordon W. F. Drake
Variational Upper Bounds For Low-Lying States Of Lithium, L. M. Wang, Z. C. Yan, H. X. Qiao, Gordon W. F. Drake
Physics Publications
We present improved calculations of variational energy eigenvalues for the 1s22s2S, 1s23s2S, and 1s22p2P states of lithium using basis sets with up to 30 224 terms in Hylleraas coordinates. The nonrelativistic energies for infinite nuclear mass are -7.4780603239101437(45) a.u. for 1s22s2S, -7. 3540984214443164(32) a.u. for 1s23s2S, and -7.4101565326516(5) a.u. for 1s22p2P, which represent the most accurate variational upper bounds to date. An important advantage of the basis sets with multiple distance scales is their exceptional numerical stability. © 2011 American Physical Society.
Isotope-Shift Measurements Of Stable And Short-Lived Lithium Isotopes For Nuclear-Charge-Radii Determination, W. Nortershauser, R. Sanchez, G. Ewald, Gordon W. F. Drake
Isotope-Shift Measurements Of Stable And Short-Lived Lithium Isotopes For Nuclear-Charge-Radii Determination, W. Nortershauser, R. Sanchez, G. Ewald, Gordon W. F. Drake
Physics Publications
Changes in the mean square nuclear charge radii along the lithium isotopic chain were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. Nuclear charge radii of light elements are of high interest due to the appearance of the nuclear halo phenomenon in this region of the nuclear chart. During the past years we have developed a laser spectroscopic approach to determine the charge radii of lithium isotopes which combines high sensitivity, speed, and accuracy to measure the extremely small field shift of an 8-ms-lifetime isotope with production rates on the order of only 10 …
Spin-Forbidden Radiative Decay Rates From The 3′,3p 1,2 And 3′,1p 1 States Of Helium, D. C. Morton, Gordon W. F. Drake
Spin-Forbidden Radiative Decay Rates From The 3′,3p 1,2 And 3′,1p 1 States Of Helium, D. C. Morton, Gordon W. F. Drake
Physics Publications
We have calculated atomic helium spontaneous decay rates and absorption oscillator strengths for the spin-forbidden transitions from 3′,3P 1,2 and 3′,1P 1 to all lower 1S 0 and 3S 1 states. In particular we found A 10=44.33(4)′, s -1 for the E1 transition 3′,3P 1-1′,1S 0 and 0.1147(1) s -1 for the M2 transition 3′,3P 2-1′,1S 0. © 2011 American Physical Society.
Electron Impact Dissociation Of N2o And Co2 With Single Particle Detection Of O(1d2), Wladyslaw Kedzierski, E Blejdea, Aldo Dicarlo, J. W. Mcconkey
Electron Impact Dissociation Of N2o And Co2 With Single Particle Detection Of O(1d2), Wladyslaw Kedzierski, E Blejdea, Aldo Dicarlo, J. W. Mcconkey
Physics Publications
Production of metastable O(1D2) atoms following controlled electron impact on N2O and CO2 targets has been studied using a neon rare gas matrix detector operating at a temperature of <20 K. A 100 eV pulsed electron beam was used in conjunction with time-of-flight (TOF) techniques to establish O-atom fragment kinetic energies. Probable dissociation channels are discussed.
Metastable Oxygen Atom Detection Using Rare Gas Matrices, Wladyslaw Kedzierski, E Blejdea, Aldo Dicarlo, J. W. Mcconkey
Metastable Oxygen Atom Detection Using Rare Gas Matrices, Wladyslaw Kedzierski, E Blejdea, Aldo Dicarlo, J. W. Mcconkey
Physics Publications
The use of solid rare gas matrices as detectors of metastable oxygen atoms is investigated. A 100 eV electron beam colliding with N2O target gas is used as the source of O(1S). The parameters considered are surface temperature, time delay of excimer emission and spectral response to O(1S). In all cases, detector sensitivity maximized at temperatures ≤20 K. Krypton was found to provide the most sensitive surface and neon the least.
Theoretical Proposal For A Biosensing Approach Based On A Linear Array Of Immobilized Gold Nanoparticles, S.M.H. Rafsanjani, T. Cheng, S. Mittler, Chitra Rangan
Theoretical Proposal For A Biosensing Approach Based On A Linear Array Of Immobilized Gold Nanoparticles, S.M.H. Rafsanjani, T. Cheng, S. Mittler, Chitra Rangan
Physics Publications
We propose a sensing mechanism for detection of analytes that can specifically recognized. The sensor is based on closely-spaced chains of functionalized gold nanoparticles (NPs) immobilized on a waveguide surface, with the signal detected by evanescent waveguide absorption spectroscopy. The localized surface plasmon spectrum of a linear array of closely-spaced, hemispherical gold NPs is calculated using the discrete dipole approximation. The plasmon band is found to broaden to a nanowirelike spectrum when a dielectric coating is put on the particles, and the light polarization is along the NP chain. The origin of this broadening is shown to be the polarization-dependent …
Regulation Of Polar Peptidoglycan Biosynthesis By Wag31 Phosphorylation In Mycobacteria, C. Jani, H. Eoh, J.J. Lee, K. Hamasha
Regulation Of Polar Peptidoglycan Biosynthesis By Wag31 Phosphorylation In Mycobacteria, C. Jani, H. Eoh, J.J. Lee, K. Hamasha
Physics Publications
Background. Sensing and responding to environmental changes is a central aspect of cell division regulation. Mycobacterium tuberculosis contains eleven Ser/Thr kinases, two of which, PknA and PknB, are key signaling molecules that regulate cell division/morphology. One substrate of these kinases is Wag31, and we previously showed that partial depletion of Wag31 caused morphological changes indicative of cell wall defects, and that the phosphorylation state of Wag31 affected cell growth in mycobacteria. In the present study, we further characterized the role of the Wag31 phosphorylation in polar peptidoglycan biosynthesis. Results. We demonstrate that the differential growth among cells expressing different wag31 …
Towards The Clinical Application Of Laser-Induced Breakdown Spectroscopy For Rapid Pathogen Diagnosis: The Effect Of Mixed Cultures And Sample Dilution On Bacterial Identification, Steven J. Rehse, Q.I. Mohaidat, S. Palchaudhuri
Towards The Clinical Application Of Laser-Induced Breakdown Spectroscopy For Rapid Pathogen Diagnosis: The Effect Of Mixed Cultures And Sample Dilution On Bacterial Identification, Steven J. Rehse, Q.I. Mohaidat, S. Palchaudhuri
Physics Publications
Laser-induced breakdown spectroscopy has been utilized to classify and identify bacterial specimens on the basis of their atomic composition. We have characterized the effect that the presence of a second bacterial species in the ablated specimen had on the identification of the majority species. Specimens with a reduced number of bacterial cells (approximately 2500) were identified with 100% accuracy when compared to undiluted specimens. In addition, a linear dependence of the total spectral power as a function of cell number was determined. Lastly, a high selectivity was obtained for a LIBS-based analysis of nine separate bacterial strains from four genera.