A microscope for Fermi gases

Diese Dissertation berichtet über ein neuartiges Quantengasmikroskop, mit dem Vielteilchensysteme von fermionischen Atomen in optischen Gittern untersucht werden. Die einzelplatzaufgelöste Abbildung ultrakalter Gase im Gitter hat mächtige Experimente an bosonischen Vielteilchensystemen ermöglicht. Die Erweiterung dieser Fähigkeit auf Fermigase bietet neue Aussichten, komplexe Phänomene stark korrelierter Systeme zu erforschen, für die numerische Simulationen oft nicht möglich sind. Mit Standardtechniken der Laserkühlung, optischen Fallen und Verdampfungskühlung werden ultrakalte Fermigase von 6Li präpariert und in ein 2D optisches Gitter mit flexibler Geometrie geladen. Die Atomverteilung wird mithilfe eines zweiten, kurzskaligen Gitters eingefroren. Durch Raman-Seitenbandkühlung wird an jedem Atom Fluoreszenz induziert, während seine Position festgehalten wird. Zusammen mit hochauflösender Abbildung erlaubt die Fluoreszenz die Rekonstruktion der ursprünglichen Verteilung mit Einzelplatzauflösung und hoher Genauigkeit. Mithilfe von magnetisch angetriebener Verdampfungskühlung produzieren wir entartete Fermigase mit fast einheitlicher Füllung im ersten Gitter. Dies ermöglicht die ersten mikroskopischen Untersuchungen an einem ultrakalten Gas mit klaren Anzeichen von Fermi-Statistik. Durch die Präparation eines Ensembles spinpolarisierter Fermigase detektieren wir eine Abflachung im Dichteprofil im Zentrum der Wolke, ein Charakteristikum bandisolierender Zustände. In einem Satz von Experimenten weisen wir nach, dass Verluste von Atompaaren an einem Gitterplatz, bedingt durch lichtinduzierte Stöße, umgangen werden. Die Überabtastung des zweiten Gitters erlaubt eine deterministische Trennung der Atompaare in unterschiedliche Gitterplätze. Die Kompression einer dichten Wolke in der Falle vor dem Laden ins Gitter führt zu vielen Doppelbesetzungen von Atomen in unterschiedlichen Bändern, die wir ohne Anzeichen von paarweisen Verlusten abbilden können. Somit erhalten wir die wahre Besetzungsstatistik an jedem Gitterplatz. Mithilfe dieser Besonderheit werten wir die lokale Besetzungsstatistik an einem Ensemble bandisolierenderWolken aus. Im Zentrum bei hoher Füllung sind die Atomzahlfluktuationen um eine Größenordnung unterdrückt, verglichen mit klassischen Gasen, eine Manifestation des Pauliverbots. Die Besetzungswahrscheinlichkeiten werden verwendet, um die lokale Entropie an jedem Gitterplatz zu messen. Eine niedrige Entropie pro Atom bis 0.34kB wird im Zentrum des Bandisolators gefunden. Die Erweiterung der Quantengasmikroskopie auf entartete Fermigase eröffnet neue Möglichkeiten der Quantensimulation stark korrelierter Vielteilchensysteme und kann einzigartige Erkenntnisse über fermionische Systeme im und außerhalb vom Gleichgewicht, Quantenmagnetismus und verschiedene Phasen des Fermi-Hubbard-Modells ergeben.This thesis reports on a novel quantum gas microscope to investigate many-body systems of fermionic atoms in optical lattices. Single-site resolved imaging of ultracold lattice gases has enabled powerful studies of bosonic quantum many-body systems. The extension of this capability to Fermi gases offers new prospects to studying complex phenomena of strongly correlated systems, for which numerical simulations are often out of reach. Using standard techniques of laser cooling, optical trapping, and evaporative cooling, ultracold Fermi gases of 6Li are prepared and loaded into a large-scale 2D optical lattice of flexible geometry. The atomic distribution is frozen using a second, short-scaled lattice, where we perform Raman sideband cooling to induce fluorescence on each atom while maintaining its position. Together with high-resolution imaging, the fluorescence signals allow for reconstructing the initial atom distribution with single-site sensitivity and high fidelity. Magnetically driven evaporative cooling in the plane allows for producing degenerate Fermi gases with almost unity filling in the initial lattice, allowing for the first microscopic studies of ultracold gases with clear signatures of Fermi statistics. By preparing an ensemble of spin-polarised Fermi gases, we detect a flattening of the density profile towards the centre of the cloud, which is a characteristic of a band-insulating state. In one set of experiments, we demonstrate that losses of atom pairs on a single lattice site due to light-assisted collisions are circumvented. The oversampling of the second lattice allows for deterministic separation of the atom pairs into different sites. Compressing a high-density sample in a trap before loading into the lattice leads to many double occupancies of atoms populating different bands, which we can image with no evidence for pairwise losses. We therefore gain direct access to the true number statistics on each lattice site. Using this feature, we can evaluate the local number statistics on an ensemble of band-insulating clouds. In the central region of high filling, the atom number fluctuations are suppressed by an order of magnitude compared to classical gases, which is a manifestation of Pauli blocking. Occupation probabilities are used to measure the local entropy on each individual site. The entropy per atom is found to be as low as 0.34kB in the band-insulating core. The extension of quantum gas microscopy to degenerate Fermi gases opens up new avenues in quantum simulation of strongly correlated many-body systems and can yield unprecedented insight into fermionic systems in and out of equilibrium, quantum magnetism and different phases of the Fermi-Hubbard model

The Influence of Knowledge and Skills of Employees Toward Human Resource Information System Performance in Transportation Firm: A Case Study of Aramex Company of Egypt

This study was to find out whether there is a relationship between knowledge, skill and Human Resource Information System (HRIS) Performance. This study examined the relationship between performances of HRIS in Aramex Company of Egypt. This study is designed to provide the benefit for practitioners, especially for employees and management position in Aramex Company. The study found that there are positive relationship between knowledge, skill and HRIS performance in Aramex Company

Blended Learning Using Virtual Reality Environments

Immersive virtual reality isn’t just for gaming. It’s poised to have a big impact on education as well, giving students an opportunity to interact with content in three-dimensional learning environments. Blended learning, according to the Inn sight Institute is "a formal education program in which a student learns at least inpart through online delivery of content and instruction with some element of student' control over time, place, path and/orpace". On the other hand, there are many disadvantage found in blended learning such as the learners with low motivation or bad study habits may fall behind, and many others. So, there is an essential need to improve and develop the theory of the blended learning by using virtual reality environments and get rid of these disadvantages to develop the faceto-face learning to add a lot of features such as excitement and make it more efficient. As well as affirms clarity of the scientific content of the lecture that the student may be miss them by absent or even mentally, so student can live atmosphere the lecture again and overcome the difficulties resulting from the using blended learning or traditional learning. Firstly, this approach is applied by building a specialized website application that allow using virtual reality feature in order to measure the effectiveness of this study on students, and then a questionnaires was designed and the information result of these questionnaires impact was gathered. It is found that, the most of students were excited, active and they understand the lecture in an easy way with a high Likert Scale (4.74), but they found difficulties in using VR tools which has a low Likert scale (2.66)

Poly Methyl Methacrylate Denture Base Filled With Nitrile Butadiene Rubber And Ceramic Particles

Poly (methyl methacrylate) (PMMA) resin is the most common and suitable material for fabrication of denture base application. However, PMMA denture base material is poor in impact strength (IS) and fracture toughness (KIC) due to its brittleness. In this study, the properties of PMMA denture base composite was enhanced by incorporation of ceramic fillers (Al2O3 and yttrium stabilized zirconia (YSZ) powders) as toughening particles together with nitrile butadiene rubber (NBR) particles as impact modifier. The PMMA powder was mixed with liquid monomer and stabilized with 0.0025% hydroquinone. Benzoyl peroxide (BPO) and ethylene glycol dimethacrylate (EGDMA) were used as initiator and cross-linking agent, respectively. This study was divided into four different stages. The first stage, different ratios of NBR particles (5, 7.5 and 10 wt.%) was mixed with ceramic fillers fixed at 5 wt..% (Al2O3 and YSZ). In this stage, the effects of both untreated and treated ceramic fillers by silane (γ-MPS) were determined through their impact strength (IS), fracture toughness (KIC) and microstructure morphology examination. It was found that the optimum ratio was 7.5 wt.% of NBR particles when ceramic fillers fixed at 5 wt.% (for both untreated and treated by silane). In the second stage, the optimum ratio of ceramic fillers (Al2O3 and YSZ fillers) (fixed at 5 wt.%) together with 7.5 wt.% NBR (optimum ratio obtained from first stage) was investigated. The optimum ratio of second stage was 2.5 wt.% Al2O3 and 2.5 wt.% YSZ as mixtures particles. Third stage was used to study the effect of filler loading in the PMMA matrix. It is noticed that for 1 to 5 wt.% of filler loading, the IS and KIC values were increased compared to PMMA matrix and commercial PMMA. Final stage, the optimum ratio of filler loading (5 wt.%) was evaluated for both surface roughness (Ra) and residual MMA monomer. The result of Ra of reinforced PMMA denture base by the conventional laboratory polishing system (lathe polishing) showed smoother surfaces compared to threshold level (0.2 μm) from 2.11 μm to 0.19 μm. While the amount of residual MMA monomer of reinforced PMMA denture base (1.016%) was reduced when compared to commercial PMMA (1.916%) and PMMA matrix (1.080%)

Shortest Path Routing Using Heuristic Search

Shortest Path problems are inevitable in road network applications such as city emergency handling and drive guiding system, in where the optimal routing have to be found. To achieve the best path, there are many algorithms which are more or less effective, depending on the particular case. Efficiency depends not only on the time needed for calculation, but also on the reliability of the result. A* algorithm is able to return the best path (if it exists) between two nodes, according to accessibility/ orientation and, of course, cost of arcs. In this project A* algorithm was used, to suggest shortest path model between two selected points to find the fastest and shortest route on Malaysia map. This prototype then guides the users according to their interest and work

50% failure rate in final year medical exams; Whose fault is it?

To The Editor: Having read Dr Benamer’s views on medical teaching, we remembered our days as medical students [1]. We share Dr Benamer’s and other’s views that teaching in Libyan medical schools should shift from being subject focused to being learning focused [1,2].We remember one incident when our professor showed us an ECG and asked about the diagnosis. He was so furious when none of us was able to make the diagnosis to the extent that he left the lecture room without completing the teaching session. This is just one example among many that illustrates the lack of teaching skills so common in our medical institutions and the poor state of the Teacher-Student relationship.Therefore, it is not surprising that many students prefer not to attend lectures. In our view and from our experience, the formats of the lectures were organised around information designed for students to be memorised rather than learnt (spoon feeding) Which is one of the reasons why many students have found the teaching sessions simply boring and useless.In their attempts to overcome this problem, students tried to find ways to learn; acquiring knowledge through the organisation of discussion groups and seeking the help of senior students when necessary. These discussion groups mimic what has been recently introduced as Problem Based Learning (PBL) [3]. Even though these discussion groups may have lacked direction, they were perceived to be an important factor in the success of many students.Given the poor attendance rates to the lectures, the teachers failed to investigate the reasons behind this and take proactive steps to correct the problem. Because of the lack of teacher analysis and reflection it comes as no surprise that the format and quality of teaching has continued along the same traditional lines with the same problems being continually encountered.The point here is that many of these students went on to become highly successful physicians and surgeons in their working life amongst more modern teaching systems and approaches in the west. So it is logical to conclude that should the methods of teaching and teaching skills improve, the success rate among final year medical students will undoubtedly follow suit.It is our recommendation that in order to improve the success rate amongst students, a more modern way of teaching is urgently required [3]. Teachers first need to recognise that problems exist, and then act proactively to address them [4]. One way is the provision of ‘Train The Trainer’ and other similar courses to increase teaching skills, coupled with more discussion groups, clinical clerks, case presentations, increased student involvement during medical rounds and within lectures, and increased attendance at common procedures. All of the above will surely result in increasing the success rate beyond the current 50% passing rate for final year students

EVALUATION OF THE PROTECTIVE EFFECT OF NIGELLA SATIVA (BLACK CUMIN) OIL AGAINST VANCOMYCIN-INDUCED NEPHROTOXICITY IN RATS

Objective: The study was designed to investigate a possible protective effect of Nigella sativa (NS) against vancomycin (VAN)-induced nephrotoxicity in rats. Methods: Twenty-eight adult male Albino rats were randomly divided into four groups; seven rats in each. Group I (control): The animals were treated with normal saline (2 ml/kg/day) given orally and intraperitoneally (IP); Group II: VAN was given at a dose of 400 mg/kg/day for 7 days IP and normal saline orally; Group III: NS oil was given at a dose of 2 ml/kg/day for seven days orally and normal saline IP; and Group IV: VAN 400 mg/kg/day IP in combination with NS oil 2 ml/kg/day orally for 7 days. Twenty-four hours after the last dose, the animals were sacrificed, and serum was collected to estimate urea and creatinine. Then, both kidneys were excised, one for homogenate preparation to estimate renal tissue malondialdehyde (MDA), glutathione (GSH) and neutrophil gelatinase-associated lipocalin (NGAL) and the other for histopathological examination. Results: NS significantly decreased serum urea and creatinine compared to VAN treated group, p<0.001. NS significantly increased renal tissue GSH compared to VAN treated group p<0.001. NS lowered MDA and NGAL levels in the homogenate of renal tissues compared to their elevated levels in rats treated with VAN, but this did not achieve statistical significance. NS also ameliorated renal histopathological changes induced by VAN. Conclusion: NS has a protective effect against VAN-induced nephrotoxicity

The Effects of Molecular Chaperones on Tau Fibril Assembly

The accumulation of microtubule-associated protein tau into fibrillar aggregates is the hallmark of Alzheimer’s disease and other neurodegenerative disorders, collectively referred to as tauopathies. Fibrils can propagate from one cell to the next and spread throughout the brain. However, a study shows that only small aggregates can be taken up by cultured neuronal cells. The mechanisms that lead to the breakage of fibrils into smaller fragments remain unknown. In yeast, the AAA+ chaperone HSP104 processes the reactivation of protein aggregates and is responsible for fragmentation of fibrils. This study focused on investigating the effects of molecular chaperones on tau fibrils and using HSP104 as a model system to test whether we can monitor fibril fracturing. The assays used to detect the chaperone’s actions on tau utilized acrylodan fluorescence, thioflavin T fluorescence, and sedimentation. Tau fibrils were either formed with a cofactor, heparin, to accelerate assembly or without a cofactor. In the process of investigating the effects of HSP104 on tau fibrils, this study established an assay to determine the effects of breakage on the seeding properties of tau fibrils. Our findings demonstrated that the sonication of tau fibrils produces smaller fragments (seeds) that accelerate the conversion of monomeric tau into fibrils. The use of this assay with HSP104 provided evidence that HSP104 inhibits the elongation of tau fibrils. Indeed, HSP104 inhibits the aggregation of soluble tau into aggregates. However, tau fibril breakage and dissociation were not observed with HSP104, either alone or in combination with co-chaperones (HSP70 and HSP40). Our findings provide insights into the seeding properties of tau fibrils, and suggest that fragmentation is a critical part of tau assembly. This knowledge should be valuable for understanding tau fibril aggregation and propagation in the brain, which is necessary to identify new treatments for neurodegenerative diseases