'Backroom Boys’: Occupational Dynamics in Crime Scene Examination

publication-status: Publishedtypes: ArticleDespite a sustained preoccupation with crime scene investigation in policing and instructional literatures, government reviews and media accounts, the crime scene examiner has received scant sociological attention. Focusing on scientific support personnel in an English police force, this article analyses how embedded actors who routinely facilitate the provision of crime scene examination reflect on their role and position in the investigative process. The analysis draws on data collected in a small number of semi-structured interviews with stakeholders at different levels of seniority, in order to map an understanding of the inter and intra-professional interactions, exchanges, dependencies and negotiations employed by those working at the coalface of investigative practice. Hoping to illuminate some of the sense-making practices behind the enactment of forensic activities, the discussion examines the articulation of professional identities and the conclusion reflects more broadly on the processes of professionalisation and discourses of professionalism that accompany standardised forensic accomplishments

MISNIS: an intelligent platform for Twitter topic mining

Twitter has become a major tool for spreading news, for dissemination of positions and ideas, and for the commenting and analysis of current world events. However, with more than 500 million tweets flowing per day, it is necessary to find efficient ways of collecting, storing, managing, mining and visualizing all this information. This is especially relevant if one considers that Twitter has no ways of indexing tweet contents, and that the only available categorization “mechanism” is the #hashtag, which is totally dependent of a user's will to use it. This paper presents an intelligent platform and framework, named MISNIS - Intelligent Mining of Public Social Networks’ Influence in Society - that facilitates these issues and allows a non-technical user to easily mine a given topic from a very large tweet's corpus and obtain relevant contents and indicators such as user influence or sentiment analysis. When compared to other existent similar platforms, MISNIS is an expert system that includes specifically developed intelligent techniques that: (1) Circumvent the Twitter API restrictions that limit access to 1% of all flowing tweets. The platform has been able to collect more than 80% of all flowing portuguese language tweets in Portugal when online; (2) Intelligently retrieve most tweets related to a given topic even when the tweets do not contain the topic #hashtag or user indicated keywords. A 40% increase in the number of retrieved relevant tweets has been reported in real world case studies. The platform is currently focused on Portuguese language tweets posted in Portugal. However, most developed technologies are language independent (e.g. intelligent retrieval, sentiment analysis, etc.), and technically MISNIS can be easily expanded to cover other languages and locations

Establishing the digital chain of evidence in biometric systems

Traditionally, a chain of evidence or chain of custody refers to the chronological documentation, or paper trail, showing the seizure, custody, control, transfer, analysis, and disposition of evidence, physical or electronic. Whether in the criminal justice system, military applications, or natural disasters, ensuring the accuracy and integrity of such chains is of paramount importance. Intentional or unintentional alteration, tampering, or fabrication of digital evidence can lead to undesirable effects. We find despite the consequences at stake, historically, no unique protocol or standardized procedure exists for establishing such chains. Current practices rely on traditional paper trails and handwritten signatures as the foundation of chains of evidence.;Copying, fabricating or deleting electronic data is easier than ever and establishing equivalent digital chains of evidence has become both necessary and desirable. We propose to consider a chain of digital evidence as a multi-component validation problem. It ensures the security of access control, confidentiality, integrity, and non-repudiation of origin. Our framework, includes techniques from cryptography, keystroke analysis, digital watermarking, and hardware source identification. The work offers contributions to many of the fields used in the formation of the framework. Related to biometric watermarking, we provide a means for watermarking iris images without significantly impacting biometric performance. Specific to hardware fingerprinting, we establish the ability to verify the source of an image captured by biometric sensing devices such as fingerprint sensors and iris cameras. Related to keystroke dynamics, we establish that user stimulus familiarity is a driver of classification performance. Finally, example applications of the framework are demonstrated with data collected in crime scene investigations, people screening activities at port of entries, naval maritime interdiction operations, and mass fatality incident disaster responses

Multiexcitons in semiconductor quantum dots

In spite of about 25 years of intense research efforts, the semiconductor quantum dots remain to attract a relevant scientific interest and continue to surprise with new and interesting physical properties. Great part of this research has been devoted to optical studies of single objects, which also hold for the subject of this work. It is perhaps surprising, though the main body of optical studies of single quantum dots has been so far focused on emission spectroscopy (photoluminescence) and has been largely related to the recombination of rather simple electron-hole complexes such as excitons (neutral and charged) and biexcitons. Strongly con ned quantum dots, such as those studied in this work, may, however, accommodate a large number of (photo-excited) carriers. The studies of energy levels and of recombination processes of single quantum dots, optically filled with up to four electron-hole pairs are the subject of this work. The dots used in the present experiments, formed out of the Ga(Al)As matrix, represent relatively strongly con ned zero-dimensional systems, and display several, atomic-like s-, p-,. . . shells. The studied dots are fairly bright, their optical response is within a suitable spectral range covered by efficient CCD detectors and accessible with the Ti:Sapphire laser. Single dots can be easily selected in our structures as they exhibit an extremely low surface density (∼10 6 cm −2 ). Experimental techniques applied in this work include the methods of single dot spectroscopy, polarization (when necessary linear or circular) resolved techniques, application of (high, up to 28 T) magnetic fields and photon correlation measurements. Distinct, below- and above-dot-barrier laser excitation has been used for photoluminescence experiments. Importantly, the photoluminescence excitations experiments (in magnetic fields) have been carried out, as well. Depending on excitation conditions (power and wavelength of laser), the investigated dots show a multitude of relatively sharp lines, each dot displaying the same, characteristic pattern of lines, grouped into distinct clusters corresponding to subsequent atomic-like shells. Spectral range covering the s- and p-shells region has been explored in the present studies. The assignment of spectral lines (identification of electron-hole complexes, carriers number and levels occupation, involved in the initial- and final-state of the recombination process) has been at large provided by the results of polarization (linear) resolved micro-photoluminescence and photon correlation experiments. Those experiments depict three distinct families of emission lines, each related to recombination of, correspondingly, neutral, positively charged and negatively charged electron-hole (excitonic) complexes. The emission lines observed within a four step cascade of a neutral quadexciton down to the recombination of a neutral exciton and two step cascades of positively charged biexcitons down to the recombination of a singlet and triplet state of positively charged excitons have been studied in details. The fine structure, induced by exchange interactions and preliminarily seen in (linear) polarization resolved emission experiment at zero magnetic field, has been studied for various emission lines (related to s- and p- shells). The evolution of this splitting has been then investigated as a function of the magnetic field. The results are interpreted in terms of the shape anisotropy of dots and an interplay between spin- and orbital-mediated effects, characteristic of different recombination processes. A significant portion of this work has aimed to compare the emission spectra measured at a relatively high excitation power (which include the recombination processes of up to quadexciton complexes) with photoluminescence excitation spectra (which probe the excited states of a single exciton). Such experiments have been also carried out as a function of the magnetic field. As expected the emission spectra of high order excitonic complexes are indeed greatly affected by Coulomb interactions between carriers and in consequence are in general very different from the photoluminescence excitation spectra (quasi absorption) of a neutral and charged exciton. Two types of the magnetic field evolution of detected absorption lines (resonant peaks), the s- and p-shell related, have been measured. The s-shell like resonant peaks were attributed to the transition between the excited hole levels in the valence band and the ground s-shell level in the conduction band. Nevertheless, there exists an emission line which is observed within the p-shell cluster, and which coincides with the absorption line. That "coinciding resonance" is concluded to be an excited excitonic state which recombines radiatively due to efficient blocking of its relaxation towards the ground state.Pomimo około 25 lat intensywnych prac badawczych, półprzewodnikowe kropki kwantowe wciąż cieszą sią szerokim zainteresowaniem naukowym i nadal zaskakują nowymi oraz ciekawymi właściwościami fizycznymi. Duża część przeprowadzonych na nich do tej pory badań została poświęcona pomiarom optycznym pojedynczych obiektów, które są również tematem tej pracy. Zdumiewające jest w pewnym stopniu to, że główny nurt badań optycznych pojedynczych kropek kwantowych był dotychczas skoncentrowany na spektroskopii emisyjnej (fotoluminescencji) i opierał się w dużej mierze na rekombinacji prostych kompleksów elektron-dziura, takich jak ekscyton (neutralny i naładowany) oraz biekscyton. Kropki kwantowe z silnym uwięzieniem kwantowym, takie jak te, którymi zajmowano się w ramach niniejszej pracy, mogą jednak pomieści¢ dużą liczbę (fotowzbudzonych) nośników. Badania poziomów energetycznych i procesów rekombinacji pojedynczych kropek kwantowych, wypełnionych optycznie maksymalnie czterema parami elektron-dziura są tematem bieżącej pracy. Będące przedmiotem rozważań kropki, wytworzone w matrycy GaAlAs, stanowią systemy zerowymiarowe o stosunkowo silnym potencjale wiążącym i ukazują kilka kwazi-atomowych powłok: s, p, d. Są one dość jasnymi obiektami, a ich emisja optyczna przypada na obszar widma promieniowania elektromagnetycznego, który pokrywa się z zakresem czułości wydajnych detektorów CCD oraz jest dostępny przy użyciu lasera tytan-szafir. Poszczególne kropki można łatwo wybrać w analizowanej strukturze, ze względu na ich bardzo niską gęstość powierzchniową (∼10 6 cm −2 ). Stosowane w tej pracy techniki eksperymentalne obejmują metody spektroskopii pojedynczych kropek kwantowych wykorzystujące rozdzielczość polaryzacyjną (liniową lub w razie potrzeby kołową), zewnętrzne pola magnetyczne, w tym wysokie - do 28 T oraz pomiary korelacji fotonów. Wyróżnione są dwa obszary energii lasera pobudzającego kropki, poniżej oraz powyżej bariery, które mają wpływ na wyniki eksperymentów fotoluminescencyjnych. Istotne są również przeprowadzone badania pobudzania fotoluminescencji (w polu magnetycznym). W zależności od warunków pobudzania (mocy lasera i długości fali), w widmach badanych kropek pojawia się wiele ostrych linii, przy czym każda kropka ma bardzo charakterystyczny, identyczny układ linii, pogrupowanych w różne serie, odpowiadające kolejnym kwazi-atomowym powłokom. Prezentowane w niniejszej pracy badania obejmują zakres widmowy, który zawiera w sobie region powłok s i p. Przypisanie linii widmowych (identyfikacja kompleksów elektron-dziura, liczby nośników oraz obsadzonych poziomów energetycznych, odpowiadających za stan początkowy oraz końcowy w procesie rekombinacji) zostało głównej mierze oparte na wynikach pomiarów mikroluminescencji przeprowadzonych z rozdzielczością polaryzacyjną (liniową) oraz eksperymencie korelacji pojedynczych fotonów. Wyniki tych badań ukazują trzy różne rodziny linii emisyjnych z których każda związana jest z rekombinacją odpowiednio: neutralnych, naładowanych dodatnio i naładowanych ujemnie kompleksów ekscytonowych (elektron-dziura). Szczegółowo badane są w tej pracy linie emisyjne, obserwowane w ramach czerostopniowej kaskady rekombinacji neutralnego kwadryekscytonu do neutralnego ekscytonu oraz w ramach dwuetapowych kaskad rekombinacji dodatnio naładowanych biekscytonów do stanu singletowego i trypletowego dodatnio naładowanego ekscytonu. Wynikająca z oddziaływania wymiennego struktura subtelna, która w eksperymencie ujawnia się jako (liniowo) spolaryzowana emisja w zerowym polu magnetycznym, jest analizowana dla różnych linii emisyjnych (związanych z powłoką s i p). Badaniom poddany jest również wpływ pola magnetycznego na to rozszczepienie. Interpretacja wyników uwzględnia anizotropię kształtu kropek oraz oddziaływania związane z charakterystycznymi dla różnych procesów rekombinacji efektami spinowymi i orbitalnymi. Znaczna część pracy jest poświęcona porównaniu widm emisyjnych mierzonych przy stosunkowo dużej mocy pobudzania (które obejmują procesy rekombinacji aż z kompleksu kwadryekscytonowego) z widmami pobudzania fotoluminescencji (które próbkują stany wzbudzone pojedynczych ekscytonów). Tego rodzaju eksperymenty zostały przeprowadzone także w funkcji pola magnetycznego. Zgodnie z oczekiwaniami, widma emisyjne kompleksów wieloekscytonowych są modyfikowane przez oddziaływane kulombowskie między nośnikami, w związku z czym na ogół znacznie różnią się od widm pobudzania fotoluminescencji (kwazi-absorcji) neutralnego oraz naładowanego ekscytonu. Dwa rodzaje dyspersji linii absorpcyjnych (rezonansów) w polu magnetycznym, charakterystyczne dla powłoki s i p, zostały zaobserwowane. Rezonanse o dyspersji powłoki s są przypisane przejściom między wzbudzonymi stanami dziurowymi w paśmie walencyjnym a podstawowym poziomem powłoki s w paśmie przewodnictwa. Tym niemniej istnieje linii emisyjna, która jest obserwowana w zakresie emisji z powłoki p i która pokrywa się z linią absorpcyjną. Ten „pokrywający się rezonans” jest identyfikowany jako wzbudzony stan ekscytonowy, który rekombinuje promieniście ze względu na efektywną blokadę jego relaksacji do poziomu podstawowego

Written evidence submitted by Northumbria University Centre for Forensic Science (FSS 70)

Published as part of House of Commons Science and Technology Select Committee: The Forensic Science Service Session 2010-12, , Volume II, Additional written evidenc

Leveraging Metadata for Extracting Robust Multi-Variate Temporal Features

abstract: In recent years, there are increasing numbers of applications that use multi-variate time series data where multiple uni-variate time series coexist. However, there is a lack of systematic of multi-variate time series. This thesis focuses on (a) defining a simplified inter-related multi-variate time series (IMTS) model and (b) developing robust multi-variate temporal (RMT) feature extraction algorithm that can be used for locating, filtering, and describing salient features in multi-variate time series data sets. The proposed RMT feature can also be used for supporting multiple analysis tasks, such as visualization, segmentation, and searching / retrieving based on multi-variate time series similarities. Experiments confirm that the proposed feature extraction algorithm is highly efficient and effective in identifying robust multi-scale temporal features of multi-variate time series.Dissertation/ThesisM.S. Computer Science 201

Microplastics in the Rhine River – from the Swiss catchment towards the North Sea

The threat of plastic waste in the environment has evoked rising concern over the past decades. While these versatile and incredibly popular polymer materials undoubtedly fulfil unprecedented services, their extreme durability and alleged toxicity represent major downsides, once in the environment. As plastics break down into smaller microplastics (MP) they evidently pollute almost every thinkable habitat on the globe today. While an estimated 5–12 million tons of plastic end up in the oceans every year, rivers are important pathways, carrying an annual freight of 0.41–4 million tons downstream. The Rhine River, one of Europe’s main streams and one of the World’s busiest waterways, reportedly holds substantial amounts of MP in its near-surface waters and sediments. However, little is known about potential MP sources, seasonal dynamics and the MP pollution of benthic sediments of this major river. In my dissertation I address three pivotal knowledge gaps about MP in the Rhine River and investigate a new type of method to safely and efficiently separate MP from surrounding environmental sample matrices. The surface water MP pollution of the Rhine River was earlier characterised by the distinct appearance of vast amounts (~60%) of rigid polystyrene microbeads of unknown origin and former purpose. In a sustained investigation of a defined river stretch in the Lower Rhine downstream Cologne, we managed to narrow down the entry region of these pollutants and close-to-certainly unveil the particle’s former purpose as ion-exchange resin beads used in diverse fluid purification applications. As more data on MP in rivers emerges, an interesting gap opens: empirical field studies tend to generate temporally restricted snapshot data while modellers, laudably seeking the bigger picture, are confronted with enormous uncertainties in their results. In a bid to reduce this void we embarked on a quadruplicate surface water MP observation in the Rhine catchment during 2016–2017. The investigation included three nival discharge regime tributaries and the Rhine in Switzerland as well as a pluvial Rhine River section towards the German-Dutch border. It became evident that despite a coherent increasing MP concentration gradient downstream, reflecting average discharge and catchment size, overall variability in environmental MP data was large. This hampers clear-cut estimations about concentration fluctuations but at the same time reinforces the theory of high MP seasonal pollution fluxes in the European winter months, when Rhine discharge is highest. Seeking to contribute to the very scarce knowledge of MP and benthic sediment interaction in large dynamic rivers, we took a diving bell and a dredging vessel to the riverbed at two previously identified surface MP hotspots at the German Middle and Lower Rhine. Due to expected water turbulence and flow velocity, substantial settling of MP in such stretches is not necessarily anticipated. Interestingly, it showed that even the Rhine riverbed is not spared from vast MP pollution. The applied research technology allowed for reliable detection of MP down to particle sizes of 11 μm and yielded strongly varying concentrations of 260–11,000 MP kg^–1, with a strongly skewed size class distribution towards the smallest MP particles. Experience showed us that environmental sample preparation for MP research can be a tedious and resource-intensive enterprise – including health and environmental hazards. Instead of attacking the unwanted portions in a sample (e.g. biogenic residue to isolate MP), a more efficient approach is to select the MP specifically. We refined a proposed lipophilicity-based separation technique and broadened its scope by successfully testing it to four different types of environmental matrices. This one-for-all approach may present a promising means for quicker, cheap, safe and efficient MP data compilation. The method was successfully applied for the seasonal surface MP investigation presented in this dissertation

Pattern Recognition

A wealth of advanced pattern recognition algorithms are emerging from the interdiscipline between technologies of effective visual features and the human-brain cognition process. Effective visual features are made possible through the rapid developments in appropriate sensor equipments, novel filter designs, and viable information processing architectures. While the understanding of human-brain cognition process broadens the way in which the computer can perform pattern recognition tasks. The present book is intended to collect representative researches around the globe focusing on low-level vision, filter design, features and image descriptors, data mining and analysis, and biologically inspired algorithms. The 27 chapters coved in this book disclose recent advances and new ideas in promoting the techniques, technology and applications of pattern recognition