318 research outputs found

    Performance of Mud Mortar Walls Under Seismic Loading

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    The inherently brittle nature of unreinforced masonry structures results in poor performance during earthquakes, presenting major hazards to communities. Many of these structures found in Nepal were severely damaged or destroyed during two earthquakes in 2015. The purpose of this project is to test the effect on seismic response of several modifications to stone and mud mortar structures. These structures are common in many areas of Nepal. Two T-shaped stone and mud mortar masonry walls are constructed. The first wall has no modifications and represents current building practices. The second wall uses steel wire mesh as external reinforcement. Each wall is subjected to simulated strong ground motions of increasing intensity until failure. The results are expected to indicate better toughness during an earthquake as a result of the steel reinforcement. Therefore, these results can be applied in regions like Nepal in an effort to avoid a repeat of the catastrophic damage seen in 2015

    The effect of Auger heating on intraband carrier relaxation in semiconductor quantumrods

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    The rate at which excited charge carriers relax to their equilibrium state affects many aspects of the performance of nanoscale devices, including switching speed, carrier mobility and luminescent efficiency. Better understanding of the processes that govern carrier relaxation therefore has important technological implications. A significant increase in carrier-carrier interactions caused by strong spatial confinement of electronic excitations in semiconductor nanostructures leads to a considerable enhancement of Auger effects, which can further result in unusual, Auger-process-controlled recombination and energy-relaxation regimes. Here, we report the first experimental observation of efficient Auger heating in CdSe quantum rods at high pump intensities, leading to a strong reduction of carrier cooling rates. In this regime, the carrier temperature is determined by the balance between energy outflow through phonon emission and energy inflow because of Auger heating. This equilibrium results in peculiar carrier cooling dynamics that closely correlate with recombination dynamics, an effect never before seen in bulk or nanoscale semiconductors.Comment: 7 pages, 4 figure

    Secondary breast lymphoma diagnosed by vacuum-assisted breast biopsy: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>Breast lymphoma, either as a manifestation of primary extranodal disease or as secondary involvement, is a rare malignancy, and its diagnosis, prognosis, and treatment have not been clearly defined. On the other hand, Vacuum-assisted breast biopsy (VABB) is a minimally invasive technique with ever-growing use for the diagnosis of mammographically detected, non-palpable breast lesions.</p> <p>Case presentation</p> <p>A symptom-free, 56-year-old woman presented with a non-palpable BI-RADS 4B lesion without microcalcifications. She had a positive family history for breast cancer and a history of atypical ductal hyperplasia in the ipsilateral breast four years ago. She reported having been treated for non-Hodgkin lymphoma 12 years ago. With the suspicion of breast cancer, mammographically guided VABB with 11-gauge probe (on the stereotactic Fisher's table) was performed. VABB made the diagnosis of a non-Hodgkin, grade II, B-cell germinal-center lymphoma. VABB yielded enough tissue for immunohistochemistry/WHO classification.</p> <p>Conclusion</p> <p>This is the first case in the literature demonstrating the successful diagnosis of breast lymphoma by VABB, irrespectively of the level of clinical suspicion. It should be stressed that VABB was able to yield enough tissue for WHO classification. In general, lymphoma should never be omitted in the differential diagnosis, since no pathognomonic radiologic findings exist for its diagnosis.</p

    Growth of few-wall carbon nanotubes with narrow diameter distribution over Fe-Mo-MgO catalyst by methane/acetylene catalytic decomposition

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    Few-wall carbon nanotubes were synthesized by methane/acetylene decomposition over bimetallic Fe-Mo catalyst with MgO (1:8:40) support at the temperature of 900°C. No calcinations and reduction pretreatments were applied to the catalytic powder. The transmission electron microscopy investigation showed that the synthesized carbon nanotubes [CNTs] have high purity and narrow diameter distribution. Raman spectrum showed that the ratio of G to D band line intensities of IG/ID is approximately 10, and the peaks in the low frequency range were attributed to the radial breathing mode corresponding to the nanotubes of small diameters. Thermogravimetric analysis data indicated no amorphous carbon phases. Experiments conducted at higher gas pressures showed the increase of CNT yield up to 83%. Mössbauer spectroscopy, magnetization measurements, X-ray diffraction, high-resolution transmission electron microscopy, and electron diffraction were employed to evaluate the nature of catalyst particles

    Borderline breast core needle histology: predictive values for malignancy in lesions of uncertain malignant potential (B3)

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    Breast core needle biopsy (CNB) is an accurate test but may result in borderline histology (lesions of uncertain malignant potential or B3). This is an evaluation of the largest series (to date) of B3 histology, which focusses on estimating positive predictive values (PPV) for malignancy. We identified all B3 CNBs over a 10-year period in a single institution (N=372) from a series of 4035 consecutive needle biopsies. We describe the imaging findings, and report excision histology outcomes (N=279) and category-specific PPV for B3 lesions using two approaches including estimates based on subjects who had either excision or follow-up (N=328). B3 represented 9.2% of all CNB results. Excision histology was benign in 181 (64.9%) and malignant in 98 (35.1%) subjects (61 ductal carcinoma in situ, 37 invasive carcinoma). Positive predictive value for malignancy (based on excision histology) was 35.1% (95% CI: 29.5–40.7) and PPV (based on excision or review) was 29.9% (95% CI: 24.9–34.8). Lesion-specific PPV (estimates in parentheses for excision or follow-up) was atypical ductal hyperplasia 44.7% (40.6%); lobular intraepithelial neoplasia 60.9% (58.3%); papillary lesion 22.7% (15.9%); radial scar 16.7% (12.3%); phyllodes tumour 12.5% (12.5%); and B3 not specified 20.0%. Approximately one-third of CNB results classified as B3 are malignant on excision, and the likelihood of malignancy varies substantially between specific lesion groups. Whereas cases may be selectively managed without surgery, the majority warrant excision biopsy based on our estimates. Research is needed to improve differentiation between malignant and benign diseases in B3 lesions using diagnostic or predictive methods

    Herlyn-werner-wunderlich syndrome: MRI findings, radiological guide (two cases and literature review), and differential diagnosis

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    <p>Abstract</p> <p>Background</p> <p>Herlyn-Werner-Wunderlich (HWW) syndrome is a very rare congenital anomaly of the urogenital tract involving Müllerian ducts and Wolffian structures, and it is characterized by the triad of didelphys uterus, obstructed hemivagina and ipsilateral renal agenesis. It generally occurs at puberty and exhibits non-specific and variable symptoms with acute or pelvic pain shortly following menarche, causing a delay in the diagnosis. Moreover, the diagnosis is complicated by the infrequency of this syndrome, because Müllerian duct anomalies (MDA) are infrequently encountered in a routine clinical setting.</p> <p>Cases presentation</p> <p>two cases of HWW syndrome in adolescents and a differential diagnosis for one case of a different MDA, and the impact of magnetic resonance (MR) imaging technology to achieve the correct diagnosis.</p> <p>Conclusions</p> <p>MR imaging is a very suitable diagnostic tool in order to perform the correct diagnosis of HWW syndrome.</p

    Cutaneous Head and Neck Squamous Cell Carcinoma with Regional Metastases: The Prognostic Importance of Soft Tissue Metastases and Extranodal Spread

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    Extranodal spread (ENS) is an established adverse prognostic factor in metastatic cutaneous squamous cell carcinoma (cSCC); however, the clinical significance of soft tissue metastases (STM) is unknown. The aim of this study was to evaluate the prognosis of patients with STM from head and neck cSCC, and to compare this with that of node metastases with and without ENS. Patients with cSCC metastatic to the parotid and/or neck treated by primary surgical resection between 1987 and 2007 were included. Metastatic nodes > 3 cm in size were an exclusion criterion. A Cox proportional hazard model was used to determine the effect of STM adjusting for other relevant prognostic factors. The population included 164 patients with a median follow-up of 26 months. There were 8 distant and 37 regional recurrences. There were 22 were cancer-specific deaths, and 29 patients died. STM was a significant predictor of reduced overall (hazard ratio 3.3; 95% confidence interval 1.6-6.4; P = 0.001) and disease-free survival (hazard ratio 2.4; 95% confidence interval 1.4-4.1; P = 0.001) when compared to patients with node disease with or without ENS. After adjusting for covariates, STM and number of involved nodes were significant independent predictors of overall and disease-free survival. In metastatic cSCC of the head and neck, the presence of STM is an independent predictor of reduced survival and is associated with a greater adverse effect than ENS alone

    Effect of Correlated tRNA Abundances on Translation Errors and Evolution of Codon Usage Bias

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    Despite the fact that tRNA abundances are thought to play a major role in determining translation error rates, their distribution across the genetic code and the resulting implications have received little attention. In general, studies of codon usage bias (CUB) assume that codons with higher tRNA abundance have lower missense error rates. Using a model of protein translation based on tRNA competition and intra-ribosomal kinetics, we show that this assumption can be violated when tRNA abundances are positively correlated across the genetic code. Examining the distribution of tRNA abundances across 73 bacterial genomes from 20 different genera, we find a consistent positive correlation between tRNA abundances across the genetic code. This work challenges one of the fundamental assumptions made in over 30 years of research on CUB that codons with higher tRNA abundances have lower missense error rates and that missense errors are the primary selective force responsible for CUB
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