Coherent spin dynamics of electrons and holes in CsPbBr3_3 perovskite crystals

The lead halide perovskites demonstrate huge potential for optoelectronic applications, high energy radiation detectors, light emitting devices and solar energy harvesting. Those materials exhibit strong spin-orbit coupling enabling efficient optical orientation of carrier spins in perovskite-based devices with performance controlled by a magnetic field. Perovskites are promising for spintronics due to substantial bulk and structure inversion asymmetry, however, their spin properties are not studied in detail. Here we show that elaborated time-resolved spectroscopy involving strong magnetic fields can be successfully used for perovskites. We perform a comprehensive study of high-quality CsPbBr$_3$ crystals by measuring the exciton and charge carrier $g$-factors, spin relaxation times and hyperfine interaction of carrier and nuclear spins by means of coherent spin dynamics. Owing to their "inverted" band structure, perovskites represent appealing model systems for semiconductor spintronics exploiting the valence band hole spins, while in conventional semiconductors the conduction band electrons are considered for spin functionality.Comment: 8 pages, 3 figures + supplementary informatio

Coupling qualitative and quantitative analyses of pharmaceutical materials enabled by second harmonic generation microscopy

The detection and characterization of crystallinity is critical throughout the drug development process. From the initial establishment of an active pharmaceutical ingredient’s (API) crystal structure to stability testing and quality control, the phase of an API affects the solubility, bioavailability, stability, and efficacy of a drug product. Second harmonic generation (SHG) microscopy has recently been developed as a selective and rapid method for imaging crystallinity in drug formulations. While SHG microscopy can enable the high signal-to-noise (SNR) detection of crystallinity, the intrinsic chemical information content within SHG images is relatively low. In cases of trace crystallinity and/ or small crystal volumes, new tools capable of rapid, qualitative crystal characterization are needed to fill this measurement gap. Several strategies for increasing the chemical information content of SHG microscopy were developed. Following combined computational and experimental studies to help determine the body of crystalline API structures amenable to imaging by SHG microscopy, measurements by confocal Raman spectroscopy and synchrotron X-ray diffraction were performed on regions of interest (ROI) identified by SHG. In both cases, spatial restriction of the spectroscopic technique to these regions of interest lowered the detection limits of Raman and synchrotron X-ray diffraction by several orders of magnitude. To further expand the capabilities of SHG microscopy, nonlinear optical Stokes ellipsometric (NOSE) microscopy was developed to assess crystal structure characteristics through the polarization dependence of SHG. Rapid (8 MHz) polarization modulation enabled NOSE microscopies at video rates (up to 15 Hz). Following development and validation, NOSE microscopy was used in conjunction with an iterative, nonlinear least-squares fitting algorithm to discriminate polymorphic crystal forms of the small molecule D-mannitol. Finally, to extend the linear dynamic range of photon counting measurements as described here-in, a novel digital filter derived from linear discriminant analysis (LDA) was developed and validated via theoretical and experimental nonlinear optical (NLO) measurements

Formal semantics for LIPS (Language for Implementing Parallel/distributed Systems)

This thesis presents operational semantics and an abstract machine for a point-to-point asynchronous message passing language called LIPS (Language for Implementing Parallel/ distributed Systems). One of the distinctive features of LIPS is its capability to handle computation and communication independently. Taking advantage of this capability, a two steps strategy has been adopted to define the operational semantics. The two steps are as follows: • A big-step semantics with single-step re-writes is used to relate the expressions and their evaluated results (computational part of LIPS). • The developed big-step semantics has been extended with Structural Operational Semantics (SOS) to describe the asynchronous message passing of LIPS (communication part of LIPS). The communication in LIPS has been implemented using Asynchronous Message Passing System (AMPS). It makes use of very simple data structures and avoids the use of buffers. While operational semantics is used to specify the meaning of programs, abstract machines are used to provide intermediate representation of the language's implementation. LIPS Abstract Machine (LAM) is defined to execute LIPS programs. The correctness of the execution of the LIPS program/expression written using the operational semantics is verified by comparing it with its equivalent code generated using the abstract machine. Specification of Asynchronous Communicating Systems (SACS) is a process algebra developed to specify the communication in LIPS programs. It is an asynchronous variant of Synchronous Calculus of Communicating Systems (SCCS). This research presents the SOS for SACS and looks at the bisimulation equivalence properties for SACS which can be used to verify the behaviour of a specified process. An implementation is said to be complete when it is equivalent to its specifications. SACS has been used for the high level specification of the communication part of LIPS programs and is implemented using AMPS. This research proves that SACS and AMPS are equivalent by defining a weak bisimulation equivalence relation between the SOS of both SACS and AMPS

INVESTIGATING INVASION IN DUCTAL CARCINOMA IN SITU WITH TOPOGRAPHICAL SINGLE CELL GENOME SEQUENCING

Synchronous Ductal Carcinoma in situ (DCIS-IDC) is an early stage breast cancer invasion in which it is possible to delineate genomic evolution during invasion because of the presence of both in situ and invasive regions within the same sample. While laser capture microdissection studies of DCIS-IDC examined the relationship between the paired in situ (DCIS) and invasive (IDC) regions, these studies were either confounded by bulk tissue or limited to a small set of genes or markers. To overcome these challenges, we developed Topographic Single Cell Sequencing (TSCS), which combines laser-catapulting with single cell DNA sequencing to measure genomic copy number profiles from single tumor cells while preserving their spatial context. We applied TSCS to sequence 1,293 single cells from 10 synchronous DCIS patients. We also applied deep-exome sequencing to the in situ, invasive and normal tissues for the DCIS-IDC patients. Previous bulk tissue studies had produced several conflicting models of tumor evolution. Our data support a multiclonal invasion model, in which genome evolution occurs within the ducts and gives rise to multiple subclones that escape the ducts into the adjacent tissues to establish the invasive carcinomas. In summary, we have developed a novel method for single cell DNA sequencing, which preserves spatial context, and applied this method to understand clonal evolution during the transition between carcinoma in situ to invasive ductal carcinoma

Lipid nanoparticles for topical and transdermal application for alopecia treatment

Tese de mestrado integrado. Bioengenharia. Faculdade de Engenharia. Universidade do Porto. 201

PList-based Divide and Conquer Parallel Programming

This paper details an extension of a Java parallel programming framework – JPLF. The JPLF framework is a programming framework that helps programmers build parallel programs using existing building blocks. The framework is based on {em PowerLists} and PList Theories and it naturally supports multi-way Divide and Conquer. By using this framework, the programmer is exempted from dealing with all the complexities of writing parallel programs from scratch. This extension to the JPLF framework adds PLists support to the framework and so, it enlarges the applicability of the framework to a larger set of parallel solvable problems. Using this extension, we may apply more flexible data division strategies. In addition, the length of the input lists no longer has to be a power of two – as required by the PowerLists theory. In this paper we unveil new applications that emphasize the new class of computations that can be executed within the JPLF framework. We also give a detailed description of the data structures and functions involved in the PLists extension of the JPLF, and extended performance experiments are described and analyzed