Brad W. Zeiger

Bio: Brad W. Zeiger is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Sonochemistry & Viscosity. The author has an hindex of 4, co-authored 7 publications receiving 932 citations. Previous affiliations of Brad W. Zeiger include Urbana University.

Sonochemical synthesis of nanomaterials

Abstract: High intensity ultrasound can be used for the production of novel materials and provides an unusual route to known materials without bulk high temperatures, high pressures, or long reaction times. Several phenomena are responsible for sonochemistry and specifically the production or modification of nanomaterials during ultrasonic irradiation. The most notable effects are consequences of acoustic cavitation (the formation, growth, and implosive collapse of bubbles), and can be categorized as primary sonochemistry (gas-phase chemistry occurring inside collapsing bubbles), secondary sonochemistry (solution-phase chemistry occurring outside the bubbles), and physical modifications (caused by high-speed jets or shock waves derived from bubble collapse). This tutorial review provides examples of how the chemical and physical effects of high intensity ultrasound can be exploited for the preparation or modification of a wide range of nanostructured materials.

Sonofragmentation of Molecular Crystals

Abstract: Possible mechanisms for the breakage of molecular crystals under high-intensity ultrasound were investigated using acetylsalicylic acid (aspirin) crystals as a model compound for active pharmaceutical ingredients. Surprisingly, kinetics experiments ruled out particle–particle collisions as a viable mechanism for sonofragmentation. Two other possible mechanisms (particle–horn and particle–wall collisions) were dismissed on the basis of decoupling experiments. Direct particle–shock wave interactions are therefore indicated as the primary mechanism of sonofragmentation of molecular crystals.

Mathematical modelling of the evolution of the particle size distribution during ultrasound-induced breakage of aspirin crystals

Abstract: While the effects of ultrasound on crystals have been heavily investigated experimentally, population balance models that describe the effects of all physical parameters such as solution viscosity and applied power on the crystal size distribution have been lacking. This article presents one of the first population balance models for describing the crystal breakage that results from ultrasound. Aspirin crystals dispersed in various solvents, dodecane and silicon oils of known viscosity, were subjected to ultrasound to study this sonofragmentation that occurs due to cavitation when bubbles violently collapse, creating extreme conditions in the immediate vicinity of the bubbles. Population balance models are developed with three models for binary breakage events and cavitation rate proportional to the applied power and exponentially related to solvent viscosity. The resulting population balance models provide reasonable agreement with the experimental data over the ranges of applied power and solvent viscosity investigated, with nearly overlapping crystal size distributions for applied power between 10 and 40 W. The statistical analysis supports the breakage model in which cavitation bubbles cause the aspirin crystals to break into two equal-sized particles.

Sonofragmentation of molecular crystals: Observations and Modeling

Abstract: The need for new production methods of active pharmaceutical ingredients (APIs) with a specific crystal size distribution is acute for improved drug delivery by aerosolization, injection or ingestion, for control of bioavailability, and for economy of preparation. "Sonocrystallization" (i.e., the use of ultrasound for the crystallization of APIs) is under very active investigation for its ability to influence particle size and size distribution, reduce metastable zone-width, induction time, and supersaturation levels required for nucleation, improve reproducibility of crystallization, control of polymorphism, and reduce or eliminate the need for seed crystals or other foreign materials. We will review the potential mechanisms for the breakage of molecular crystals under high-intensity ultrasound and relate our experimental and modeling studies of the sonocrystallization and fragmentation of acetylsalicylic acid (aspirin) crystals as a model API. Surprisingly, kinetics experiments rule out particle-particle collisions as a viable mechanism for sonofragmentation. Direct particle-shockwave interactions are the primary mechanism of sonofragmentation of molecular crystals.

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。

Sonochemical synthesis of nanomaterials

Abstract: High intensity ultrasound can be used for the production of novel materials and provides an unusual route to known materials without bulk high temperatures, high pressures, or long reaction times. Several phenomena are responsible for sonochemistry and specifically the production or modification of nanomaterials during ultrasonic irradiation. The most notable effects are consequences of acoustic cavitation (the formation, growth, and implosive collapse of bubbles), and can be categorized as primary sonochemistry (gas-phase chemistry occurring inside collapsing bubbles), secondary sonochemistry (solution-phase chemistry occurring outside the bubbles), and physical modifications (caused by high-speed jets or shock waves derived from bubble collapse). This tutorial review provides examples of how the chemical and physical effects of high intensity ultrasound can be exploited for the preparation or modification of a wide range of nanostructured materials.