S. Roth

Bio: S. Roth is an academic researcher from Max Planck Society. The author has contributed to research in topics: Carbon nanotube & Polyacetylene. The author has an hindex of 44, co-authored 281 publications receiving 25195 citations.

Cytotoxic benzylidene hydrazides of terephthalic acid and related compounds.

Abstract: The present investigation involved the synthesis of a number of novel benzylidene hydrazides as candidate cytotoxic agents. The preparation of these compounds from terephthalic acid and isophthalic acid proceeded satisfactorily. However, the reaction of phthalic acid hydrazide with various aryl aldehydes was unsuccessful in general. Some of the unexpected products were identified. The shapes and also the distances between the centers of the aryl rings designated B and C of three representative compounds 1b, 2b and 3b were determined. The compounds designated 1a-e, 2a-e and 3b were screened against human HCT116 and HT29 colon cancer cells as well as human CRL1790 non-malignant colon cells which revealed the tumor-selective toxicity displayed by these compounds.

Polarization Dependence of Recombination Kinetics in Stretch-Oriented trans-Polyacetylene

Abstract: The transient photoconductivity of fully oriented Durham-Graz trans-polyacetylene has been investigated. In this paper we report on a detailed series of measurements on the polarization dependence of the transient photocurrent. The influence of the external field, of the intensity and wavelength of the incident light, and of the temperature on the measured anisotropy has been studied. The results suggest interchain charge creation is the predominant mechanism of photoexcitation of carriers.

A time resolved study of electrolummescence in fullerene crystals

Abstract: Summary form only given. Earlier work has shown the ability of fullerene crystals to electroluminesce under DC conditions with a highly nonlinear current-intensity characteristic above a certain threshold voltage [1]. This is similar to the nonlinear phenomena found in the highly excited luminescence and photoconductivity, that are discussed in terms of many body effects [2]. To develop this theoretical model and to investigate the temporal behaviour of electron-hole recombination, measurements of the electroluminescent response of a silver-C60-silver device to triangle and rectangular voltage pulses of different frequencies were performed in the present case. The experiments show the occurence of a phase shift between the voltage pulse and the luminescence signal. This phase shift approaches asymptotically the value of /spl pi//2 with increasing frequency, corresponding to a time delay of about 100 /spl mu/s. In addition an accompanying drop of the luminescence intensity is observable. A theoretical analysis of these processes is proposed, taking into account the dependence of the accumulation and recombination time on the charge carrier concentration.

Transient Photoconductivity in Oriented Conjugated Polymers

Abstract: A powerful technique for probing the underlying physics in a material is the investigation of the behaviour of photoexcited states, which are produced by absorption of light. Electroactive conjugated polymers exhibit a wide variety of photoexcitations, such as solitons, polarons, bipolarons, and excitons1.

The rise of graphene

Abstract: Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The electronic properties of graphene

Abstract: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Abstract: We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

Graphene: Status and Prospects

Abstract: Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temperature. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop experiment. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.