High-Resolution Infrared-Vacuum Ultraviolet Photoion and Pulsed Field Ionization-Photoelectron Methods for Spectroscopic Studies of Neutrals and Cations

We show that by scanning the frequency of a single mode infrared (IR) optical parametric oscillator (IR-OPO) laser to excite the molecular species of interest and fixing the frequency of a vacuum ultraviolet (VUV) laser to photoionize the IR excited species, high-resolution IR spectra of polyatomic neutrals can be obtained with high sensitivity. The fact that this IR-VUV-photoion (IR-VUV-PI) method is based on VUV photoionization probe, and thus, allows the identification of the neutral IR absorber, makes it applicable for IR spectroscopy measurements of isotopemers, radicals, and clusters, which usually exist as impure samples. The highly resolved IR-VUV-PI measurements achieved using the single mode IR-OPO laser have made possible the selection of single rovibrational states of CH3X (X=Br and I), C2H4, and C3H4 for VUV-pulsed field ionization-photoelectron (VUV-PFI-PE) measurements, resulting in rovibrationally resolved photoelectron spectra for these polyatomic molecules. These experiments show that the signal-to-noise ratios of the IR-VUV-PI and IR-VUV-PFI-PE spectra obtained by employing the high-resolution IR-OPO laser are significantly higher than those observed in previous IR-VUV-PI and IR-VUV-PFI-PE studies using a low-resolution IR-OPO laser. Further improvement in sensitivity of IR-VUV-PI and IR-VUV-PFI-PE measurements by using the collinear arrangement of IR-VUV lasers and molecular beam is discussed.     

Rheo-optical studies of concentrated polystyrene solutions subjected to transient simple shear flow

Concentrated polystyrene solutions were investigated on the inception and cessation of simple shear flow by means of the technique of two-color flow birefringence. Both monodisperse solutions of various molecular weights and bimodal mixtures were studied. The molecular weight affected both the amount of overshoot in the birefringence and the response time on the inception of shear flow. Large overshoots in birefringence, up to 250%, and undershoot in the orientation angle were observed. The shear stress and the first normal stress difference were calculated by using the stress–optical rule. The amount of strain at the peaks in the stress growth curves are presented along with the steady-state viscosity and primary normal stress coefficient. The experimental results are compared qualitatively with theoretical predictions of various molecular models.     

Photochemical functionalization of hydrogen-terminated diamond surfaces: a structural and mechanistic study

Hydrogen-terminated diamond surfaces can be covalently modified with molecules bearing a terminal vinyl (C=C) group via a photochemical process using sub-band-gap light at 254 nm. We have investigated the photochemical modification of hydrogen-terminated surfaces of nanocrystalline and single-crystal diamond (111) to help understand the structure of the films and the underlying mechanism of photochemical functionalization. A comparison of the rates of photochemical modification of single-crystal diamond and nanocrystalline diamond films shows no significant difference in reactivity, demonstrating that the modification process is not controlled by grain boundaries or other structures unique to polycrystalline films. We find that both single-crystal and polycrystalline hydrogen-terminated diamond samples exhibit negative electron affinity and are functionalized at comparable rates, while oxidized surfaces with positive electron affinity undergo no detectable reaction. Gas chromatography-mass spectrometry (GC-MS) analysis shows the formation of new chemical products in the liquid phase that are formed only when the alkenes are illuminated in direct contact with H-terminated diamond, while control experiments with other surfaces and in the dark show no reaction. Our results show that the functionalization is a surface-mediated photochemical reaction and suggest that modification is initiated by the photoejection of electrons from the diamond surfaces into the liquid phase.     

Effects of synaptic noise and filtering on the frequency response of spiking neurons

Noise can have a significant impact on the response dynamics of a nonlinear system. For neurons, the primary source of noise comes from background synaptic input activity. If this is approximated as white noise, the amplitude of the modulation of the firing rate in response to an input current oscillating at frequency omega decreases as 1/square root[omega] and lags the input by 45 degrees in phase. However, if filtering due to realistic synaptic dynamics is included, the firing rate is modulated by a finite amount even in the limit omega-->infinity and the phase lag is eliminated. Thus, through its effect on noise inputs, realistic synaptic dynamics can ensure unlagged neuronal responses to high-frequency inputs.     

Directed flow of lambda hyperons in (2-6 )A GeV Au+Au collisions

Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.     

Thermodynamic Cost of Reliability and Low Temperatures: Tightening Landauer's Principle and the Second Law

Landauer's principle states that the erasure of one bit of information requires thefree energy kT ln 2. We argue that the reliability of the bit erasure process isbounded by the accuracy inherent in the statistical state of the energy source(the resources) driving the process. We develop a general framework describingthe thermodynamic worth of the resources with respect to reliable bit erasureor good cooling. This worth turns out to be given by the distinguishability of theresource's state from its equilibrium state in the sense of a statistical inferenceproblem. Accordingly, Kullback—Leibler relative information is a decisivequantity for the worth of the resource's state. Due to the asymmetry of relativeinformation, the reliability of the erasure process is bounded rather by the relativeinformation of the equilibrium state with respect to the actual state than by therelative information of the actual state with respect to the equilibrium state (whichis the free energy up to constants).     

Some Connections between Frames,Mutually Unbiased Bases,and POVM’s in Quantum Information Theory

This paper gives a very brief overview of some aspects of quantum information theory, then explains the relationship between a positive operator valued measure (POVM) and a frame. Some special types of POVM’s are defined and conjectures about them shown to be essentially conjectures about the existence of special types of frames. Finally, some connections with quantum channels and separable states are discussed.     

Sequential and localized grafting on aliphatic polyester diblock copolymers using alkyne deprotection and click cycloaddition

Diblock copolymers, in which both blocks are composed of aliphatic polyesters, were synthesized from two different alkyne‐functionalized δ‐valerolactone monomers by ring opening polymerization and subsequent click cycloaddition. Trimethylsilyl protection of the alkyne functionality of one block was instrumental to the success of the synthesis. These novel aliphatic polyester diblock copolymers were characterized by ¹H and ¹³C NMR spectroscopy, gel permeation chromatography (GPC), and infrared (IR) spectroscopy. Sequential functionalization of the diblock copolymers with hydrophobic groups on one block, and hydrophilic groups on the other block, provides access to amphiphilic structures. Micellar structures generated from these polyester amphiphiles were characterized by fluorescence spectroscopy and transition electron microscopy (TEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009