Avalanches in Breakdown and Fracture Processes

We investigate the breakdown of disordered networks under the action of an increasing external---mechanical or electrical---force. We perform a mean-field analysis and estimate scaling exponents for the approach to the instability. By simulating two-dimensional models of electric breakdown and fracture we observe that the breakdown is preceded by avalanche events. The avalanches can be described by scaling laws, and the estimated values of the exponents are consistent with those found in mean-field theory. The breakdown point is characterized by a discontinuity in the macroscopic properties of the material, such as conductivity or elasticity, indicative of a first order transition. The scaling laws suggest an analogy with the behavior expected in spinodal nucleation.Comment: 15 pages, 12 figures, submitted to Phys. Rev. E, corrected typo in authors name, no changes to the pape

Partnerships in African crop biotech

Even in sub-Saharan Africa's most progressive nations, agbiotech partnerships are still often poorly oriented to end users, fragmented in scope and of limited impact in achieving the United Nation's Millennium Development Goals

Not Every Snoring Is Obstructive Sleep Apnea (OSA): Plasma Cell Neoplasm Masquerading as OSA

Introduction: Obstructive sleep apnea is a common condition characterized by recurrent upper airway obstruction during sleep, inducing hypoxia and sleep fragmentation. Plasma cell neoplasms are a group of commodities characterized by the neoplastic expansion of clonal plasma cells, which can be present as a single lesion (solitary plasmacytoma) or numerous lesions (multiple myeloma). We present an intriguing case of plasma cell neoplasm causing tracheal compression simulating OSA. Case Description: A 39-year-old morbidly obese male with no past medical history presented with excessive fatigue, heavy snoring, and pauses in breathing during sleep. He denied shortness of breath, wheezing, and orthopnea. On physical exam, his neck circumference was 45 cm. On screening with the STOP-BANG questionnaire, he had a high risk of OSA with a score of 6 points. The patient underwent a home sleep study showing moderate sleep apnea with an Apnea Hypopnea Index (AHI) of 23.2, followed by a CPAP titration study with a recommended pressure of 13 cm H2O. However, even after three months, the patient\u27s symptoms did not improve. Moreover, he started complaining of worsening shortness of breath and exercise intolerance. A pulmonary function test (PFT) demonstrated a combined moderately severe obstructive and restrictive defect with no significant bronchodilator response and normal DLCO. Echocardiogram was normal with EF of 65%. A chest CT scan showed multiple polypoid lesions in the upper trachea, left lower lobe bronchus, and right bronchus intermedius. The patient underwent diagnostic bronchoscopy with endobronchial biopsies with tumor debulking. The biopsy showed diffuse plasma cell infiltrate with mature features with immunohistochemistry positive for CD138+ plasma cells with kappa light chain restriction, features suggestive of plasma cell neoplasm. Discussion: OSA is a common sleep-related disorder with a prevalence of up to 15 to 30% in the United States. Common risk factors include age, male sex, obesity, upper airway, and craniofacial abnormalities. The patient usually presents with daytime somnolence, loud snoring, gasping, choking, or pauses in breathing while sleeping. The diagnosis is confirmed with polysomnography, and treatment includes positive airway pressure therapy. However, numerous organic causes that can compress mimic OSA secondary to compression of the airways, like the plasma cell neoplasm compressing the trachea in our case. Therefore, other differentials should also be considered in some instances, especially if the symptoms are not improved or worsened despite the treatment of OSA