Atomic Ring Research Articles

ISAACS– interactive structure analysis of amorphous and crystalline systems

ISAACS(interactive structure analysis of amorphous and crystalline systems) is a cross-platform program developed to analyze the structural characteristics of three-dimensional structure models built by computer simulations. The models may have any degree of periodicity (i.e.crystallinity) and local symmetry. The following structural information is computed from the models: total and partial radial distribution functions and structure factors for X-ray or neutron scattering, coordination numbers, bond-angle and near atomic neighbor distributions, bond-valence sums, ring statistics, and spherical harmonics invariants. The information may be visualized conveniently and stored for further use.

E. L. Doctorow's Vicious Eroticism: Dangerous Affect in <em>The Book of Daniel</em>

E. L. Doctorow’s Vicious Eroticism: Dangerous Affect in The Book of Daniel Eric Dean Rasmussen (bio) Oh, baby, you know it now. We done played enough games for you, ain’t we. You a smart lil fucker. You know where it’s at now, don’ you big daddy. You got the picture. This is the story of a fucking, right? You pullin’ out yo lit-er-ary map, mutha? You know where we goin’, right muthafuck? —E. L. Doctorow (1971, 22–23) E. L. Doctorow’s The Book of Daniel is saturated with a negative affect that I will refer to as vicious eroticism. I borrow the phrase from Daniel Isaacson Lewin, the novel’s narrator, who uses it to describe the predatory aura exuding from Selig Mindish, whose testimony condemned Daniel’s biological parents, Rochelle and Paul Isaacson, to death: “There was about him some vicious eroticism. He was always looking at Rochelle’s tits or ass, a fact which she didn’t seem to notice. He was always treating Paul with his clumsy humor like a ridiculous child, with shards of envy perhaps for Paul’s mind or youth, or energy” (104). In Daniel’s damning portrait of his parents’ friend and family dentist, Mindish’s “vicious eroticism” manifests itself in observable behaviors: his lecherous gazing at Rochelle, patronizing treatment of Paul, opportunistic conversational tendencies and generally wolfish habitus. When Paul and Rochelle are tried as atomic spies, Mindish’s vicious eroticism provides the basis for their failed defense. Their attorney argues that Selig’s unsatiated lust for Rochelle prompted Mindish to betray the couple by falsely accusing them of participating in an atomic spy ring. Doctorow doesn’t disclose whether the Isaacsons actually spied for the Soviet Union, but the fact of this matter is less relevant than the link made between sexual desire and a political betrayal of deathly consequence. Broadly speaking, vicious eroticism connotes the sadism infusing characters’ sexual and political desires. Insofar as vicious eroticism pervades Daniel’s violently sexualized narrative, it acts as the text’s “global or organizing affect,” the predominant “feeling [End Page 189] tone” that establishes the book’s “affective bearing” toward the world (Ngai 28–29).1 Coming to terms with how this “objectified emotion” organizes Daniel’s often explicit and frequently sadistic sexual content is crucial to understanding this political novel, particularly Doctorow’s deployment of what, since the novel’s publication in 1971, has become a predominant postmodern trope: the fantasy of a directly transmissible experience. Taking seriously two of Daniel’s schizoid rhetorical interjections (a fragmentary formulation, “the novel as a sequence of analyses” (281) and the Ebonics-inflected taunt cited in the epigraph), this essay analyzes Daniel’s book as “the story of a fucking” (23)—a narrative that imagines sexual sadism, defined broadly to encompass a range of eroticized practices, to be an exceptionally affective and meaningful mode of communication. It provides an account of the dialectic between affect and meaning in Daniel’s fragmentary book, elucidating Doctorow’s avowed commitment to literature’s ability to convey the “truth of the felt life” (2003, 52) while observing how The Book of Daniel stages some of the dangers involved in conflating a truthful representation of an event with the experience of reliving the event’s affective force.2 This account focuses on three aspects of the book’s vicious eroticism: epistemological: the desire to know that motivates it; rhetorical: the tone of the erotically charged rhetoric and the reasons why various characters, all of whom Daniel depicts as victims, deploy sexualized figures to denote sociopolitical oppression; and technological: the fantasy that sexual violence, as a mode of “extreme and dangerous affective communication (30), can function as an affective technology for the “artful transfer of knowledge” (71) and be deployed pedagogically for political purposes. Throughout The Book of Daniel, epistemology is eroticized. Daniel’s desire for verifiable knowledge regarding the Isaacsons’ alleged spying and the nature of their involvement with Mindish and other Communist Party members gets conflated with his sexual desires. He fantasizes that the transmission of this impossible knowledge can be effected affectively and sexually, with human bodies serving as the primary conduit...

Structural Analysis of Some Alkali Diborate Glasses

This manuscript presents a theoretical analysis of the correlation between the computed bulk modulus and the structure of a series of multicomponent sodium diborate based glasses in terms of the bond compression model. The main parameters in the analysis were the computed elastic moduli, the average stretching force constant and the average atomic ring size. These parameters were calculated for every glass series and for every glass composition. The results showed that the average force constant and the elastic moduli of these glasses are sensitive to the decrease in the sodium diborate content. This behaviour was attributed to the increase in the molar volume, and to the role of the dierent modifiers.

Photoelectron angular distributions from strong-field coherent electronic excitation

Photoelectron Angular Distributions (PADs) resulting from nonperturbative excitation of potassium atoms using shaped femtosecond laser pulses are presented. We study control exerted by (1) the polarization of an unshaped, i.e., a bandwidth-limited light pulse, (2) shaped linearly polarized light, and (3) a combination of both degrees of freedom, i.e., polarization-shaped laser pulses. A theoretical approach to describe PADs from nonperturbative Resonance Enhanced Multi-Photon Ionization (REMPI) with ultrashort polarization-shaped laser pulses is presented and compared to experimental results. Applications of this technique to the generation and observation of atomic ring currents are discussed.

Non-linear stability analyses of optical pattern formation in an atomic sodium vapour ring cavity

The development of spontaneous stationary equilibrium patterns induced by the injection of a laser pump field into a purely absorptive two-level atomic sodium vapour ring cavity is investigated by means of various weakly non-linear stability analyses applied to the appropriate governing evolution equation for this optical phenomenon. In the quasi-equilibrium limit for its atomic variables, the mathematical system modelling that phenomenon can be reduced to a single modified Swift-Hohenberg non-linear partial differential time-evolution equation describing the intracavity field on an unbounded 2D spatial domain. Diffraction of radiation can induce transverse patterns consisting of stripes, squares and hexagonal arrays of bright spots or honeycombs in an initially uniform plane-wave configuration. Then, these theoretical predictions are compared with both relevant experimental evidence and existing numerical simulations from some recent non-linear optical pattern formation studies.

The price of atomic selfish ring routing

We study selfish routing in ring networks with respect to minimizing the maximum latency. Our main result is an establishment of constant bounds on the price of stability (PoS) for routing unsplittable flows with linear latency. We show that the PoS is at most 6.83, which reduces to 4.57 when the linear latency functions are homogeneous. We also show the existence of a (54,1)-approximate Nash equilibrium. Additionally we address some algorithmic issues for computing an approximate Nash equilibrium.

Elastic and structural properties of vanadium–lithium–borate glasses

The ternary xV2O5–(40 − x)Li2O–60B2O3 glass system, where x = 1, 2, 3, 4 and 6 mol%, was prepared by normal quenching. Ultrasonic velocities and attenuation were measured at room temperature using a pulse-echo technique. Various parameters, such as elastic moduli, micro-hardness, Poisson's ratio and Debye temperature, were determined from the measured densities and velocities. The composition dependence of these parameters, in addition to the glass-transition temperature, suggested that vanadium ions were incorporated into these glasses as a network modifier, resulting in the reconversion of BO4 tetrahedra to BO3 triangles by the breaking of B–O–B linkages and the formation of nonbridging oxygens (NBOs). The outcome was a reduction in network connectivity and rigidity with increasing V2O5 content. The results are explained quantitatively in terms of fractal bond connectivity, average atomic volume, network dimensionality, packing density, number of network bonds per unit volume, cross-link density and atomic ring size. The Makishima and Mackenzie model appears to be valid for the studied glasses when the fate of BO4 tetrahedra and creation of NBOs are taken into account.

Structural analysis of 30RO–30Al2O3–40B2O3 ( R = Mg, Ca or Sr) glasses

Bond-compression and ring-deformation models are used to quantitatively analyze the acoustical properties (elastic moduli, Poisson's ratio, Debye temperature and longitudinal attenuation) of 30RO–30Al2O3–40B2O3 glasses (in wt%), where R = Mg, Ca or Sr. The network structure of the glass is quantified in terms of the four-fold coordinated formers, atomic ring size, cross-link density, first-order stretching force constant and bulk modulus. It is found that network strength increases in the order Mg > Ca > Sr. Structural changes of the glasses are deduced by relating the elastic moduli, the ratio of bond compression to experimental bulk modulus and ultrasonic attenuation to structural parameters and oxygen density.

Structural Analysis of Borotellurite Glass

The average cross-link density, number of the network bonds per unit volume, average stretching force constant, atomic ring size and the ratio Kbc/Ke have been calculated and discussed according to bond compression model for borotellurite glass. The result showed that the connectivity and rigidity of the borotellurite glasses increases with TeO2 content due to the transformation of BO3 units to BO4 and TeO3 units to TeO4. Comparison between theoretical calculated and experimental elastic moduli and Poisson's ratio has been carried out. The results showed good agreement between experimental and theoretical calculated elastic moduli.

Ultrasonic characterization of heavy metal TeO 2–WO 3–PbO glasses below room temperature

The longitudinal ultrasonic attenuation measurements have been made using pulse echo method at fundamental frequencies of 2, 4, 6 and 8 MHz in 20WO 3–(80− x) TeO 2– xPbO ternary tellurite glasses ( x=10, 12.5, 15, 17.5 and 20 mol%) in the temperature range 160–280 K. The results showed the presence of a broad peak which shifts to higher temperature with increasing frequency. The ultrasonic attenuation peaks suggest that the experimental behavior is controlled by thermally activated structural relaxations. The internal friction, acoustic activation energy, deformation potential, relaxation strength, number of loss centers and density of state have been calculated both as a function of temperature and PbO content. The acoustic activation energy was found to decrease from 0.156 to 0.135 eV with the increase of PbO content. The results showed that both the number of loss centers and their activation energy decrease with the atomic ring size. An increase in the density of state is observed with addition of PbO content at the same frequency in the whole range of temperature which is associated with structural units formed when PbO is added.

Structure–activity relationships in nitrothiophenes

The structure and electronic properties of a series of biologically active 2-nitrothiophenes (1) have been calculated using both semi-empirical and ab initio molecular orbital methods. Multi-linear regression analysis suggests that there is a reasonable correlation between the experimental activity of the derivatives against either Escherichia coli or Micrococcus luteus and calculated properties such as the HOMO energies, the total atomic charges and ring angles at the heterocyclic sulfur atom, but there is no correlation with the calculated solvation energies or dipole moments. The presence or absence of an additional nitro group at the 3-position of the ring also has a significant effect on the activity. From the derived QSAR equations, the 2-chloro- or 2-bromo-3,5-dinitrothiophenes (1a and 1c) are predicted to show the highest activity against both bacteria, while 2-nitrothiophene (1n) is predicted to be the least active, in line with the experimental results.

Generation of microscale current loops, atom rings, and cubic clusters using twisted optical molasses

We propose a scheme for a viable and highly flexible all-optical atomic cooling and trapping using twisted light. In particular, we explain how one-dimensional twisted optical molasses should lead to a microscale atomic ring or a picoampere ionic current. Two-dimensional and three-dimensional molasses lead, respectively, to the creation of atom or ion loops and discrete atom clusters positioned at the eight corners of a microcube. These features at the microscale should find applications in physics and in quantum information processing using optically trapped atoms and ions.

Quantitative analysis of ultrasonic attenuation in TiO 2-doped CaO–Al 2O 3–B 2O 3 glasses

A comprehensive quantitative analysis of the composition dependence of ultrasonic attenuation in TiO 2-doped 30CaO–30Al 2O 3–40B 2O 3 glasses was achieved according to the central force theory and ring deformation model. Empirical formulas relating ultrasonic attenuation at room temperature and 4 MHz frequency with a number of physical and structural parameters, such as the bulk modulus, oxygen density, average first order stretching force constant and atomic ring size of the network, number of loss centers, i.e. double-well systems (oxygen atoms vibrating in asymmetric double-well potentials) and the barrier height of the asymmetric double-well potential are reported. The good agreement between the observed and theoretically calculated values of bulk modulus evidences the validity of the derived empirical equations for the studied glasses.

Modeling the amorphous-to-crystalline phase transformation in network materials

We have developed a computationally efficient rate equation model to study transformations between amorphous and crystalline phases of network forming materials. Amorphous and crystalline phases are treated in terms of their atomic ring distributions. The transformation between the two phases is considered to be driven by the conversion of one set of rings into another, following the Wooten-Winer-Weaire bond-switching algorithm. Our rate equation model describes both the generation and collapse of amorphous regions in thin crystalline films, the processes crucial for phase-change data storage materials. It is found that the amorphous spot collapse is assisted by the motion of certain crystal facets.

Structural interpretations of aluminosilicate glasses

This manuscript presents a theoretical analysis of the correlation between the bulk moduli and the structure of a series of multicomponent aluminosilicate glasses in terms of the bond compression model. The main parameters in the analysis were the computed elastic moduli, the average stretching-force constant and the average atomic ring size. These parameters were calculated for every glass series and for every glass composition. The results showed that the average force constant of these glasses increases and the elastic moduli decrease with the increase in the SiO 2 content (pure covalent bonds). This behaviour was attributed to the decrease in the molar volume, and the role of both CaO and Al 2O 3. The average atomic ring size of the studied glasses are about two-thirds of pure SiO 2, whilst the elastic moduli of pure SiO 2 glass are about two thirds of these glasses.

Ultrasonic study and physical properties of some borate glasses

The structure of the glass system (75− x)B 2O 3– xBi 2O 3–25Li 2O, where x=5, 10, 15, and 20 mol% was investigated by using pulse-echo technique. Elastic properties of the glass system have been calculated together with Poisson’s ratio and Debye temperature from the measured densities as well as longitudinal and shear ultrasonic velocities at room temperature. Ultrasonic velocity measurements were taken at 4 MHz. Estimated parameters based on Makishima–Mackenzie theory and bond compression model were calculated in order to analyse the experimental elastic moduli. Addition effect of Bi 2O 3 on the elastic moduli was investigated in terms of the number of network bonds and the mean cross-link density of the glass systems. The average atomic ring size of the network was also calculated and it was found that it depends on the concentration of the modifiers. Composition dependence of the elastic moduli and Poisson’s ratio from one hand and the trend of both the ring diameter and the packing density from the other hand showed structural change at x=15 mol%.

Structural analysis of alkali borate glasses

This paper reports on the elastic properties of alkali borate glass systems (R 2O–B 2O 3, R=K, Rb, Cs). The elastic moduli were calculated in terms of Makishima–Mackenzie model and a model by Bridge et al. The average cross-link density, number of network bonds per unit volume, average stretching force constant, atomic ring size, and the ratio K bc/ K e, have been calculated and discussed according to bond compression model to analyze the borate anomaly. Young's modulus, packing density and Poisson's ratio have been calculated and analyzed according to Makishima–Mackenzie model. Debye temperature has been calculated and discussed in terms of the cross-link density of these glasses. The borate anomaly was discussed in terms of experimentally derived Debye temperature and theoretically calculated elastic moduli. The results showed good agreement between experimental and theoretical data for the borate anomaly representation.

Quantitative analysis of elastic moduli and structure of B 2O 3–SiO 2 and Na 2O–B 2O 3–SiO 2 glasses

The average cross-link density n ̄ c , number of network bonds per unit volume n b, average stretching force constant F ̄ and atomic ring size ℓ have been calculated for the binary B 2O 3–SiO 2 and ternary Na 2O–B 2O 3–SiO 2 glass systems. These data have been used to calculate the bond compression bulk modulus K bc and Poisson's ratio σ cal for each glass sample. The variation of these parameters and the ratio K bc/ K e with composition were discussed quantitatively in terms of the change in structure of the glass network. The result showed that the connectivity and hence the rigidity of the B 2O 3–SiO 2 glasses decreases with increasing B 2O 3 concentration. Whereas increasing of Na 2O modifier in Na 2O–B 2O 3–SiO 2 glasses increase the cross-link density due to the transformation of three-fold-coordinated boron atoms into four-fold-coordinated ones. This in turn raises the resistance of the network to deformation and increases the observed density and elastic moduli of this glass system. Moreover, the theoretical elastic moduli have been obtained for each glass sample and compared with the corresponding experimental values. The results showed excellent agreement for the majority of the samples examined.

Bond compression bulk modulus and Poisson’s ratio of the polycomponent silicate glasses

Abstract The theoretical bulk modulus and Poisson’s ratio of the 65SiO 2 –15PbO–5CaO–(15− X )K 2 O– X Na 2 O glass system ( X =0–15 mol%) have been calculated using the bond compression model. The atomic ring size of the network has been also obtained for each sample according to the ring deformation model. These parameters have been interpreted quantitatively in terms of the most important structure factors. The composition dependence of these parameters showed that the elasticity and hence the response of this glass system is influenced by the chemical nature of the modifying oxides. Moreover, variation of the estimated atomic ring size with the ratio of bond compression ( K bc ) to experimental ( K e ) bulk modulus was studied to obtain more information about the structure of these glasses. The results showed that the small values of K bc / K e are attributed to the very close (small-ringed) three-dimensional network of these glasses.

Ultrasonic studies on ternary TeO 2–V 2O 5–Sm 2O 3 glasses

Longitudinal and shear wave velocities were measured in different compositions of the ternary glass system; 65TeO 2–(35 − x)V 2O 5– xSm 2O 3 at room temperature and at 4 MHz frequency using pulse echo technique. The densities of the glasses were measured by the displacement method using toluene as immersion liquid. The elastic moduli, Debye temperature, softening temperature, and micro-hardness were then calculated and have been used to obtain quantitative details about the structure of these glasses. The effect of adding Sm 2O 3, on the expense of V 2O 5, was investigated in terms of the number of network bonds of the glass. The average atomic ring size of the network was also calculated and it was found that it depends on the concentration of the modifier. The results obtained showed that these glasses become more stable and compact when modified with the rare earth oxide Sm 2O 3. This in turn increases the number of network bonds per unit volume and decrease the average atomic ring size of the network and consequently increases the elastic properties of these glasses.