Electron diffraction characterization of nanocrystalline materials using a Rietveld-based approach. Part I. Methodology.

Transmission electron microscopy is a powerful experimental tool, very effective for the complete characterization of nanocrystalline materials by employing a combination of imaging, spectroscopy and diffraction techniques. Electron powder diffraction (EPD) pattern fingerprinting in association with chemical information from spectroscopy can be used to deduce the identity of the crystalline phases. Furthermore, EPD has similar potential to X-ray powder diffraction (XRPD) for extracting additional information regarding material specimens, such as microstructural features and defect structures. The aim of this paper is to extend a full-pattern fitting procedure, broadly used for analysing XRPD patterns, to EPD. The interest of this approach is twofold: in the first place, the relatively short times involved with data acquisition allow one to speed up the characterization procedures. This is a particularly interesting aspect in the case of metastable structures or kinetics studies. Moreover, the reduced sampling volumes involved with electron diffraction analyses can better reveal surface alteration layers in the analysed specimen which might be completely overlooked by conventional bulk techniques. The first step forward to have an effective application of the proposed methodology concerns establishing a reliable calibration protocol to take into correct account the instrumental effects and thus separate them from those determined by the structure, microstructure and texture of the analysed samples. In this paper, the methodology for determining the instrumental broadening of the diffraction lines is demonstrated through a full quantitative analysis based on the Rietveld refinement of the EPD. In this regard, a CeO2 nanopowder reference specimen has been used. The results provide indications also on the specific features that a good calibration standard should have.

Solving Bilevel Optimization Problems Using Kriging Approximations.

Bilevel optimization involves two levels of optimization, where one optimization problem is nested within the other. The structure of the problem often requires solving a large number of inner optimization problems that make these kinds of optimization problems expensive to solve. The reaction set mapping and the lower level optimal value function mapping are often used to reduce bilevel optimization problems to a single level; however, the mappings are not known a priori, and the need is to be estimated. Though there exist a few studies that rely on the estimation of these mappings, they are often applied to problems where one of these mappings has a known form, that is, piecewise linear, convex, etc. In this article, we utilize both these mappings together to solve general bilevel optimization problems without any assumptions on the structure of these mappings. Kriging approximations are created during the generations of an evolutionary algorithm, where the population members serve as the samples for creating the approximations. One of the important features of the proposed algorithm is the creation of an auxiliary optimization problem using the Kriging-based metamodel of the lower level optimal value function that solves an approximate relaxation of the bilevel optimization problem. The auxiliary problem when used for local search is able to accelerate the evolutionary algorithm toward the bilevel optimal solution. We perform experiments on two sets of test problems and a problem from the domain of control theory. Our experiments suggest that the approach is quite promising and can lead to substantial savings when solving bilevel optimization problems. The approach is able to outperform state-of-the-art methods that are available for solving bilevel problems, in particular, the savings in function evaluations for the lower level problem are substantial with the proposed approach.

A new sample preparation protocol for SEM and TEM particulate matter analysis.

A new methodology has been developed to prepare electron microscopy, both SEM and TEM, specimens starting from particulate matter collected using environmental sampling systems. The approach is based on the extraction of the particles to be analyzed from the harvesting substrates. The extracted particles can be directly observed in an SEM, possibly in low-vacuum mode to prevent electrical charging. In order to prepare electron transparent samples, TEM observations require a further step, consisting in embedding the particles in an electron transparent carbon film deposited before dissolving the acetate extracting substrate. The protocol has been tested by analyzing particles collected during bench tests on brake pads and discs, carried out on a dynamometer equipped with a particulate matter sampling apparatus. The main advantages of the approach are: the complete extraction of the particulate matter specimens from the original substrates, that in this way do not interfere with the analyses; the extracted samples retain the topological information of the collection in the specimens prepared for SEM; possibility to be applied to any kind of particulate matter harvesting substrates.

Growth rules for the repair of Asynchronous Irregular neuronal networks after peripheral lesions.

Several homeostatic mechanisms enable the brain to maintain desired levels of neuronal activity. One of these, homeostatic structural plasticity, has been reported to restore activity in networks disrupted by peripheral lesions by altering their neuronal connectivity. While multiple lesion experiments have studied the changes in neurite morphology that underlie modifications of synapses in these networks, the underlying mechanisms that drive these changes are yet to be explained. Evidence suggests that neuronal activity modulates neurite morphology and may stimulate neurites to selective sprout or retract to restore network activity levels. We developed a new spiking network model of peripheral lesioning and accurately reproduced the characteristics of network repair after deafferentation that are reported in experiments to study the activity dependent growth regimes of neurites. To ensure that our simulations closely resemble the behaviour of networks in the brain, we model deafferentation in a biologically realistic balanced network model that exhibits low frequency Asynchronous Irregular (AI) activity as observed in cerebral cortex. Our simulation results indicate that the re-establishment of activity in neurons both within and outside the deprived region, the Lesion Projection Zone (LPZ), requires opposite activity dependent growth rules for excitatory and inhibitory post-synaptic elements. Analysis of these growth regimes indicates that they also contribute to the maintenance of activity levels in individual neurons. Furthermore, in our model, the directional formation of synapses that is observed in experiments requires that pre-synaptic excitatory and inhibitory elements also follow opposite growth rules. Lastly, we observe that our proposed structural plasticity growth rules and the inhibitory synaptic plasticity mechanism that also balances our AI network both contribute to the restoration of the network to pre-deafferentation stable activity levels.

Life-Threatening Hemoptysis.

Life-threatening hemoptysis (LTH) is any amount of hemoptysis that causes significant hemodynamic decompensation or respiratory distress which may lead to death if left untreated. While the amount of hemoptysis that qualifies as massive hemoptysis has continued to be debated, any amount between 100 to 1,000 mL/day is considered significant. Up to 15% cases of hemoptysis are LTH and need urgent life-saving intervention. Understanding of pulmonary vascular anatomy is of paramount importance to manage LTH. The goal of treatment lies in airway protection, appropriate oxygenation, and prevention of exsanguination. Once the airway is stabilized, a quick diagnosis and control of bleeding site is targeted. This chapter highlights current practices and approach to LTH including medical management, bronchoscopic approach, and advanced therapies such as bronchial artery embolization and surgical resection. We review situations, such as bronchiectasis, vascular malformation, diffuse alveolar hemorrhage, and tracheostomy bleed and specific approach to management of these conditions in a systematic and evidence-based manner.

Subacute Aspergillosis "Fungal Balls" Complicating COVID-19.

Severe acute respiratory syndrome coronavirus-2 infection (SARS-CoV-2), commonly known as COVID-19 (coronavirus disease-2019), began in the Wuhan District of Hubei Province, China. It is regarded as one of the worst pandemics, which has consumed both human lives and the world economy. COVID-19 infection mainly affects the lungs triggering severe hypoxemic respiratory failure, also providing a nidus for superimposed bacterial and fungal infections. We report the case of a 73-year-old male who presented with progressive dyspnea; diagnosed with SARS-CoV-2-related severe acute respiratory distress syndrome and complicated with lung cavitations growing Aspergillus sp. COVID-19, to our knowledge, has rarely been associated with subacute invasive pulmonary aspergillosis with aspergillomas. Subacute invasive pulmonary aspergillosis as a superimposed infection in patients with SARS-CoV-2 is a rare entity. By reporting this case, we would like to make the readers aware of this association.

Losartan-induced Severe Hepatic Injury: A Case Report and Literature Review.

Medications have been known to cause adverse drug reactions that affect various organs; these are mostly reversible reactions that improve with the cessation of the culprit medication. Losartan is an angiotensin-one receptor blocker which has been approved by the Food and Drug Administration (FDA) for the treatment of arterial hypertension. Fatigue, anemia, weakness, and cough are some of the common adverse effects of losartan. Acute hepatic injury has rarely been reported as an adverse effect of losartan. We report a case of a 61-year-old female with severe hepatic injury secondary to losartan use. None of the cases reported so far had such a high elevation of liver enzymes as seen in our patient.

An Intensive Care Unit Outbreak of Acute Respiratory Distress Syndrome due to Human Metapneumo Virus Infection.

Human metapneumo virus is an emerging cause of upper and lower respiratory tract illness with increasing reports of a varied spectrum of disease over all age groups. We report an outbreak of 6 cases of human metapneumo virus infection in the intensive care unit of a metropolitan tertiary care center over 6 weeks, leading to severe acute respiratory distress syndrome. We report the subsequent favorable outcomes due to the institution of extracorporeal membrane oxygenation.

Electrocardiogram Changes with Acute Alcohol Intoxication: A Systematic Review.

BACKGROUND: Acute alcohol intoxication has been associated with cardiac arrhythmias but the electrocardiogram (ECG) changes associated with acute alcohol intoxication are not well defined in the literature. OBJECTIVE: Highlight the best evidence regarding the ECG changes associated with acute alcohol intoxication in otherwise healthy patients and the pathophysiology of the changes. METHODS: A literature search was carried out; 4 studies relating to ECG changes with acute alcohol intoxication were included in this review. RESULTS: Of the total 141 patients included in the review, 90 (63.8%) patients had P-wave prolongation, 80 (56%) patients had QTc prolongation, 19 (13.5%) patients developed T-wave abnormalities, 10 (7%) patients had QRS complex prolongation, 3 (2.12%) patients developed ST-segment depressions. CONCLUSION: The most common ECG changes associated with acute alcohol intoxication are (in decreasing order of frequency) P-wave and QTc prolongation, followed by T-wave abnormalities and QRS complex prolongation. Mostly, these changes are completely reversible.

Severe Pulmonary Hypertension Due to Adult-Onset Still's Disease.

A 29-year-old female with adult-onset Still's disease (AOSD) presented with progressive shortness of breath both on rest and on exertion, increased abdominal girth, and swelling in both legs. She was on oral prednisone and was recently started on canakinumab (interleukin-1 antagonist) for joint pain and rash of AOSD. Echocardiogram showed severely dilated right ventricle, dilated pulmonary artery, moderately reduced right ventricular systolic function, but with normal left ventricular systolic function. Computed tomography with contrast ruled out pulmonary embolism. Blood tests ruled out other rheumatologic diseases. The patient was diagnosed with right-sided heart failure likely secondary to AOSD. Right heart catheterization was needed but could not be performed because of severely dilated pulmonary artery. The patient was transferred to a higher center for further management and possible cardiopulmonary transplant.

Type II Renal Tubular Acidosis Secondary to Topiramate: A Review.

Topiramate (TMP) is a broad-spectrum anticonvulsant drug used to treat a wide variety of seizure disorders, for migraine prophylaxis, and for many other indications. An important side effect of TMP is metabolic acidosis, which is mediated by renal tubular defects. TMP inhibits carbonic anhydrase, an enzyme that is necessary for acid handling in the proximal renal tubule. Patients can present with asymptomatic serum electrolyte derangements, acute change in mental status, hyperventilation, cardiac arrhythmias, or other sequelae of metabolic acidosis and associated respiratory compensation. If taken chronically, TMP can cause renal stone formation, bone mineralization defects, and several other effects secondary to changes in serum and urine pH and electrolytes. There is no well-studied way to prevent metabolic acidosis in patients taking TMP, but physicians should be vigilant when prescribing this drug to patients with the history of renal diseases and other comorbidities, and aware of this potential etiology of metabolic acidosis. We present a literature review of the underlying mechanisms involved in the development of renal tubular acidosis secondary to TMP and its clinical consequences.

Rare Case of Spinal Cord Compression as Initial Presentation of Thymic Carcinoma.

Thymic carcinomas are rare aggressive cancers with limited clinical trial data. Its usual treatment is surgical resection with variable response to chemotherapy and radiation. It usually presents as anterior mediastinal mass with late sequela of metastases to the lymph nodes, pleura and bones. We present of thymic carcinoma with a rare initial presentation of vertebral metastases causing spinal cord compression.