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Thesis
Peer Reviewed

My thesis describes the study of nanoscale physics using infrared spectroscopy and nanoscopy methods. The first phase of my research was the development of new methods for tuning metamaterials, which possess custom tailored optical properties not easily found in nature. Working together with Tom Driscoll, I co-invented a simple yet effective method for tuning the magnetic permeability of a Split Ring Resonator based metamaterial. This is the topic of Chapter 1. My subsequent research dealt with near field optics, in particular the application of the infrared imaging method of scattering Scanning Nearfield Optical Microscopy to ultrathin materials such as single layer Graphene and 2nm thin SiO₂ layers on Silicon. On both of these materials we demon- strated incredible sensitivity to ̲< 10 x 10 x 1nm³ volumes (Chapter 3). Thanks to the incredibly large momenta of the evanescent light utilized in sSNOM, we also discovered a rich array of previously unobserved physics in Graphene. In particular, we were able to observe the resonance enhancement of the SiO₂ phonon by the presence of plasmon oscillations in Graphene (Chapter 2). Lastly, a large part of my thesis work also involved building the first cryogenic sSNOM with which we were able to directly image the metal to insulator transition in the correlated oxide: V₂O₃, shown in the last chapter

Cover page: Application of infrared nanooptics to ultrathin materials

Article

Design Studies of Nb3Sn High-Gradient Quadrupole Models for LARP

Andreev, Nikolai

LBL Publications (2008)

Cover page: Design Studies of Nb3Sn High-Gradient Quadrupole Models for LARP

Article
Peer Reviewed

Efficient proton acceleration from laser-driven cryogenic hydrogen target of various shapes

LBL Publications (2017)

We theoretically investigate high energy, collimated proton beam with three dimensional particle in cell simulations of ultrashort petawatt laser interaction with cryogenic hydrogen target of various shapes. Here we show that under appropriate conditions between the laser and target parameters, the protons are accelerated to high energies mainly due to collisionless shock acceleration mechanism combined with TNSA. The dependence of the protonic energy on the laser field, target shape and thickness is reported. It is demonstrated that the irradiation of intense laser (20fs, 2PW) with cryogenic hydrogen target at optimal thickness allows the efficient generation of high energy proton beam (100 MeV) of small divergence. Our results also indicate that diffracted laser field strongly affects the collimation of ions as it passes beside the mass limited target. This approach predicts a possible pathway to control laser driven ion sources.

Cover page: Efficient proton acceleration from laser-driven cryogenic hydrogen target of various shapes

Article

Secular Cycles and Millennial Trends

Cliodynamics, Volume 7, Issue 2 (2016)

In the current paper we investigate the relation between secular cycles and millennial trends. The tests we have performed suggest that the structure of millennial trends cannot be adequately understood without secular cycles being taken into consideration. At a certain level of analysis millennial trends turn out to be a virtual byproduct of the demographic cycle mechanisms, which turn out to incorporate certain trend-creating mechanisms. Demographic-political cycle models can serve as a basis for the development and testing of models accounting not only for cycles but also for secular trends. In order to do this, we suggest to alter the basic assumptions of the earlier generations of demographic cycle models (that both the carrying capacity of land and the polity size are constant). The variables such as carrying capacity of land, cultural complexity, and empire sizes are actually not constant, but rather experience long-term trend dynamics in the rise, and the new generation of models needs to account for this fact.

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Cover page: Secular Cycles and Millennial Trends

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Article

Average age at death in infancy and infant mortality level: reconsidering the Coale-Demeny formulas at current levels of low mortality.

CEDA Papers (2015)

The longterm historical decline in infant mortality has been accompanied by increasing concentration of infant deaths at the earliest stages of infancy. The influence of prenatal and neonatal conditions has become increasingly dominant relative to postnatal conditions as external causes of death such as infectious disease have been diminished. In the mid-1960s Coale and Demeny developed formulas describing the dependency of the average age of death in infancy on the level of infant mortality from data obtained up to that time.

Almost at the same time as Coale and Demeny’s analysis, as shown in this paper, in the more developed countries a steady rise in average age of infant death began. This paper demonstrates this phenomenon with several different data sources, including the linked individual birth and infant death datasets available from the US National Center for Health Statistics and the Human Mortality Database. A possible explanation for the increase in average age of death in infancy is proposed, and modifications of the Coale-Demeny formulas for practical application to contemporary low levels of mortality are offered.

Cover page: Average age at death in infancy and infant mortality level: reconsidering the Coale-Demeny formulas at current levels of low mortality.

Article
Peer Reviewed

Circumscription Theory of the Origins of the State: A Cross-Cultural Re-Analysis

Cliodynamics, Volume 7, Issue 2 (2016)

In the paper we express some doubts about one of the assumptions of Robert Carneiro’s model on state (and chiefdom) formation, namely the role of circumscription. In our opinion, the main flaw of Carneiro’s original theory of state formation is that it implicitly assumes that every community dreamt to conquer its neighboring communities. We test the presence of various types of warfare (such as conquest warfare, land acquisition warfare, and plunder warfare) in societies with different degrees of political centralization. Quantitative cross-cultural tests reveal a rather strong correlation between political complexity and the presence of conquest warfare suggesting that conquest warfare was virtually absent among independent communities. Newer works by Carneiro propose a model explaining how simple chiefdoms could appear in the absence of conquest warfare. This model also includes circumscription, but our analysis suggests that it is unnecessary.

Cover page: Circumscription Theory of the Origins of the State: A Cross-Cultural Re-Analysis

Article
Peer Reviewed

Modification of Salmonella Lipopolysaccharides Prevents the Outer Membrane Penetration of Novobiocin

UC Berkeley Previously Published Works (2015)

Small hydrophilic antibiotics traverse the outer membrane of Gram-negative bacteria through porin channels. Large lipophilic agents traverse the outer membrane through its bilayer, containing a majority of lipopolysaccharides in its outer leaflet. Genes controlled by the two-component regulatory system PhoPQ modify lipopolysaccharides. We isolate lipopolysaccharides from isogenic mutants of Salmonella sp., one lacking the modification, the other fully modified. These lipopolysaccharides were reconstituted as monolayers at the air-water interface, and their properties, as well as their interaction with a large lipophilic drug, novobiocin, was studied. X-ray reflectivity showed that the drug penetrated the monolayer of the unmodified lipopolysaccharides reaching the hydrophobic region, but was prevented from this penetration into the modified lipopolysaccharides. Results correlate with behavior of bacterial cells, which become resistant to antibiotics after PhoPQ-regulated modifications. Grazing incidence x-ray diffraction showed that novobiocin produced a striking increase in crystalline coherence length, and the size of the near-crystalline domains.

Cover page: Modification of Salmonella Lipopolysaccharides Prevents the Outer Membrane Penetration of Novobiocin

Article

Critical Current and Instability Threshold Measurement of Nb3Sn Cables for High Field Accelerator Magnets

LBL Publications (2004)

Article
Peer Reviewed

Gel phase formation in dilute triblock copolyelectrolyte complexes

UCLA Previously Published Works (2017)

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

Cover page: Gel phase formation in dilute triblock copolyelectrolyte complexes

Article

LARP Long Nb3Sn Quadrupole Design

LBL Publications (2008)