An Audit of 6 years of Oral and Maxillofacial Surgical Conditions admitted for Interventional Treatment at Muhimbili National Hospital, Dar es Salaam – Tanzania

Background: The world wide pattern of OMFS conditions has been rarely reported despite its significance in the head and neck medicine; maxillofacial trauma and tumors. The main objective of this study was to audit oral and maxillofacial surgical (OMFS) conditions admitted for interventional treatment at Muhimbili National Hospital. Methods: Patients presenting to the OMFS unit with oral and maxillofacial pathological conditions between January 2003 - January 2009 were studied prospectively. Data for analysis were obtained from the daily operation list and includes age, sex, location, diagnosis of the pathological lesion, surgical procedure and date of procedure. Results: During the study period, the unit offered specialized services to 454 patients. Among them, 222 were males and 232 females. The mean age of the patients was 31.7 and the range was 79 years. Patient aged 21-30 years were mostly affected. Of the pathological lesions attended, benign tumors were the most common 255(56.2%) followed by fractures 58(12.8%), cysts 46(10.1%), malignant tumors 36(7.9%) and chronic infections 17(3.7%). Of the 255 cases of benign tumors 155(60.8%) were located on the mandible and 64 (25.1%) on the maxilla. Malignant tumors were 36 cases in which 11(30.6%) were located on the mandible. Maxillofacial fractures accounted 58 cases in which 31(53.4%) cases were located on the mandible. Cysts were 46 cases of which 17(37%) were located on the floor of the mouth, 10(21.7%) on the mandible and 7(15.2%) on the maxilla. Tumor excision was the commonest procedure performed 119(26.2%), followed by Tumor excision + reconstruction 89(19.6%), ORIF+IMF 51(11.2%), Fistulectomy 45(9.9%), Tumor enucleation 45(9.9%), Wide surgical excision 27(5.9%), Sinusectomy 16(3.5%) and Sequestrectomy 15(3.3%). Conclusion: There is a significant burden of OMFS conditions attended at MNH. We suggest that the government enhance the state of medical infrastructure in the local hospitals in terms of manpower and facilities for the diagnosis and treatment of simpler OMFS disease as well as timely referral on to regional center for the more complex issues. This will reduce the burden of OMF conditions experienced by this hospital and improve OMF services country wide

Bio-self-healing of cementitious mortar incubated within clay soil

The use of bacteria-based self-healing concrete for sub-structures in ground conditions is an area of increasing interest for enhancing the durability and longevity of infrastructure. In line with this objective, the present study investigates the bio-self-healing performance when a cementitious material is embedded in clay soil with varying chemical exposures and water-saturation regimes. Laboratory experiments were conducted on pre-cracked mortar specimens with Bacillus Subtilis encapsulated in perlite. The specimens were then incubated in the soil with different pH and sulphate levels, representing three exposure classes (based on Eurocodes). The crack healing ratio was evaluated through visual inspection and capillary-water absorption - before and after soil incubation. Findings showed that all inoculated specimens exhibited healing ratios noticeably larger than the control specimens, which mainly experienced small autogenous healing. Of note, the best healing performance was observed when the soil was fully-saturated and pH-neutral. From the design perspective of bio-concrete, this study emphasises the consideration of groundwater regime as well as acidity and sulphate of the ground. This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers

Monitoring the bio-self-healing performance of cement mortar incubated within soil and water using electrical resistivity

In research on self-healing concrete, the restorative performance can be evaluated by a wide range of techniques. However, most of these techniques can be challenging to apply to concrete samples embedded in soil without causing a significant disturbance to the test (as they require removing the samples from the soil, washing off any residue, and examining and returning them). To provide a solution to this issue, we investigated the potential application of an in-situ, non-destructive method utilising electrical resistivity (embedded electrodes). The study was conducted on bio-mortar specimens incubated within saturated soil and water for 11 weeks. The bio-specimens were cast by adding expanded perlite impregnated with Bacillus subtilis and nutrients to the fresh mix. Standard cement mortar (without bacterial agents) was also tested to serve as control specimens. Additional testing (capillary rise and absolute porosity) was conducted under typical conditions to provide context for interpreting the changes in electrical resistivity in relation to the healing process. The bio-mortar showed greater improvements in electrical resistivity (accompanied by a reduction in crack area, water absorption and absolute porosity) than the control mortar. The study demonstrated that the electrical resistivity technique could potentially monitor the self-healing performance of concrete embedded in soil without disturbing the concrete-soil system

Certified algorithms for equilibrium states of local quantum Hamiltonians

We design algorithms for computing expectation values of observables in the equilibrium states of local quantum Hamiltonians, both at zero and positive temperature. The algorithms are based on hierarchies of convex relaxations over the positive semidefinite cone and the matrix relative entropy cone, and give certified and converging upper and lower bounds on the desired expectation value. In the thermodynamic limit of infinite lattices, this shows that expectation values of local observables can be approximated in finite time, which contrasts with recent undecidability results about properties of infinite quantum lattice systems. In addition, when the Hamiltonian is commuting on a 2-dimensional lattice, we prove fast convergence of the hierarchy at high temperature leading to a runtime guarantee for the algorithm that is polynomial in the desired error.Comment: 24 pages, 2 figures, comments welcom

Segregation and precipitation of Er in Ge

Although Er-doped Genanomaterials are attractive for photonic applications, very little is known about the basic properties of Er in Ge. Here, the authors study the annealing behavior of Geimplanted with keV Er ions to doses resulting in ≲1at.% of Er. Large redistribution of Er, with segregation at the amorphous/crystalline interface, starts at ≳500°C, while lower temperatures are required for material recrystallization. However, even at 400°C, Er forms precipitates. The concentration of Er trapped in the bulk after recrystallization decreases with increasing temperature but is independent of the initial bulk Er concentration for the range of ion doses studied here.Work at the ANU was supported by the ARC

A Subpolynomial-Time Algorithm for the Free Energy of One-Dimensional Quantum Systems in the Thermodynamic Limit

We introduce a classical algorithm to approximate the free energy of local, translation-invariant, one-dimensional quantum systems in the thermodynamic limit of infinite chain size. While the ground state problem (i.e., the free energy at temperature T = 0) for these systems is expected to be computationally hard even for quantum computers, our algorithm runs for any fixed temperature T > 0 in subpolynomial time, i.e., in time O((1/?)^c) for any constant c > 0 where ? is the additive approximation error. Previously, the best known algorithm had a runtime that is polynomial in 1/? where the degree of the polynomial is exponential in the inverse temperature 1/T. Our algorithm is also particularly simple as it reduces to the computation of the spectral radius of a linear map. This linear map has an interpretation as a noncommutative transfer matrix and has been studied previously to prove results on the analyticity of the free energy and the decay of correlations. We also show that the corresponding eigenvector of this map gives an approximation of the marginal of the Gibbs state and thereby allows for the computation of various thermodynamic properties of the quantum system

Bio-protection of cementitious materials below ground: The significance of natural soil environments

This study explores the potential impact of natural soil on concrete crack self-healing in sub-surface structures. Three types of pre-cracked cement mortar samples were prepared for laboratory experiments, with some samples inoculated with bacterial healing agents, others supplemented with nutrients to attract indigenous soil bacteria, and plain mortar served as controls. The samples were placed within saturated soil under two conditions: slightly organic natural soil and sterilised soil. After 100 days, crack closure was evaluated through microscopic inspection, water absorption tests, and SEM-EDX scanning. The results indicated calcite precipitation on crack surfaces across all samples, but with varying ratios of crack closure (16%–81%). Notably, most samples incubated in natural soil exhibited an overall increase (up to 59.4%) in healing ratio compared to those in sterilised soil, highlighting the potential of indigenous soil microorganisms and their microbial activity in enhancing the biogenic mineral precipitation and thus protecting sub-surface concrete structures

Dose Reference Levels in Radiography for the Most Common Examinations in Sudan

Background: The aim of this study was to establish national diagnostic reference levels (DRLs) for the first time in Sudan. This is done through evaluation of entrance surface dose (ESD) to patients undergoing selected X-ray examinations.Materials and Methods: ESD per examination was estimated from X-ray tube output parameters in 15 hospitals comprising 20 rooms and a sample of 8 most common X-ray examinations with 11 basic views and a total of 1490 projections. Third quartile was calculated from the resultant distributed mean ESDs in each hospital surveyed.Results: The results obtained in mGy were, 1.9 for PA skull, 1.2 for lateral Skull, 0.539 for PA chest, 3 for abdomen and pelvis, 4.9 for AP lumbosacral spine, 18.5 for lateral lumbosacral spine, 1.35 for AP cervical spine, 1.67 for lateral cervical spine 0.4 for AP knee joint and 1.4 for AP shoulder. With exception of PA chest in all hospitals, mean ESDs were found to be within the international reference dose the major drawback is the large variations in hospitals for the same procedure.Conclusions: The results are valuable for establishing a solid base for national ESDs and can provide a data base for future dose measurements

Adaptive proportional resonant controller for single-phase grid-connected PV inverter based on grid impedance estimation technique

Ph. D ThesisPhotovoltaic PV systems have shown a significant growth in recent years driven by the increased efficiency and reductions in the cost of PV modules. Today, distribution generation based PV systems have a major contribution to the total electricity production worldwide. However, in areas with high penetration of PV system connected to the grid, interaction may arise between the grid and PV system. This research focuses on the effect of grid operating conditions on the performance of grid-connected PV inverter systems. A simulation model of the system under investigation has been developed to evaluate the impact of frequency deviation, grid voltage distortion and grid impedance variation on the harmonic performance of the injected current as well as the voltage at the point of the common coupler. Proportional resonance PR controller is employed to regulate the current produced from the PV inverter due to its reputation in tracking sinusoidal signals. The obtained simulation results demonstrate that the harmonic performance of the grid current and PCC voltage can be significantly influenced by the change of grid operating conditions. In particular, grid impedance variation can result in a shift in the system resonance frequency leading to distortion in network current and voltage. To adapt the PR controller to the grid impedance variation, a novel adaptive PR controller which takes into account the change in grid impedance is proposed. The adaptive consists of a high-order digital band-pass filter and chain of statistical signal processing technique. Simulation results show that the harmonic performance of grid current and PCC voltage can be enhanced and the proposed APR controller is robust against impedance variation. Finally, the proposed control method is experimentally implemented and the obtained results validate the effectiveness of the proposed control structure.Libyan Ministry of Higher Education and Scientific Research, and the general electricity company of Libya (GECOL