Stops and MET: the shape of things to come

LHC experiments have placed strong bounds on the production of supersymmetric colored particles (squarks and gluinos), under the assumption that all flavors of squarks are nearly degenerate. However, the current experimental constraints on stop squarks are much weaker, due to the smaller production cross section and difficult backgrounds. While light stops are motivated by naturalness arguments, it has been suggested that such particles become nearly impossible to detect near the limit where their mass is degenerate with the sum of the masses of their decay products. We show that this is not the case, and that searches based on missing transverse energy (MET) have significant reach for stop masses above 175 GeV, even in the degenerate limit. We consider direct pair production of stops, decaying to invisible LSPs and tops with either hadronic or semi-leptonic final states. Modest intrinsic differences in MET are magnified by boosted kinematics and by shape analyses of MET or suitably-chosen observables related to MET. For these observables we show that the distributions of the relevant backgrounds and signals are well-described by simple analytic functions, in the kinematic regime where signal is enhanced. Shape analyses of MET-related distributions will allow the LHC experiments to place significantly improved bounds on stop squarks, even in scenarios where the stop-LSP mass difference is degenerate with the top mass. Assuming 20/fb of luminosity at 8 TeV, we conservatively estimate that experiments can exclude or discover degenerate stops with mass as large as ~ 360 GeV and 560 GeV for massless LSPs.Comment: Version submitted to journal with improved analysis and small fixes, 27 pages, 11 figures, 2 table

Osteomyelitis of the ribs in children: a rare and potentially challenging diagnosis

Background Rib osteomyelitis is rare in children and can mimic other pathologies. Imaging has a major role in the diagnosing rib osteomyelitis. Objective To evaluate clinical presentation and imaging findings in children with rib osteomyelitis. Materials and methods We performed a retrospective (2009–2018) study on children with rib osteomyelitis verified by either positive culture or pathology. We excluded children with multifocal osteomyelitis or empyema necessitans. We reviewed medical charts for clinical, laboratory and pathology data, and treatment. All imaging modalities for rib abnormalities were evaluated for presence and location of osteomyelitis and abscess. We calculated descriptive statistics to compare patient demographics, clinical presentation and imaging findings. Results The study group included 10 children (6 boys, 4 girls), with an average age of 7.3 years (range, 3 months to 15.9 years). The most common clinical presentations were fever (n=8) and pain (n=5). Eight children had elevated inflammatory indices (leukocytosis, erythrocyte sedimentation rate [ESR], C-reactive protein [CRP]). Localized chest wall swelling was found initially in six children and later in two more children. Rib osteomyelitis was suspected on presentation in only two children. All children had chest radiographs. Rib lytic changes were found on only one chest radiograph, in two of the four ultrasound studies, and in four of eight CTs. Bone marrow signal abnormalities were seen in all eight MRIs. In nine children the osteomyelitis involved the costochondral junction. Six children had an associated abscess. Staphylococcus aureus was cultured in eight children. Osteomyelitis was diagnosed based on pathology in one child with negative cultures. Conclusion While rib osteomyelitis is rare, imaging findings of lytic changes at the costochondral junction combined with a history of fever, elevated inflammatory markers or localized soft-tissue swelling in the chest should raise suspicion for this disease

High Resolution ³He Pulmonary MRI

Hyperpolarized gas MRI of the mouse lung is of great interest due to the urgent need for novel biomarkers for the assessment of respiratory-disease progression and development of new therapies. Small animal 3He lung MRI requires high-spatial-resolution imaging (<500 μm) to obtain acceptable images for visualization of all branches of lung microstructure from the mouse trachea to lung parenchyma. The use of conventional fast-gradient-recalled echo (FGRE) pulse sequences for high-spatial-resolution mouse lung imaging is challenging due to the signal loss caused by significant diffusion-weighting by the imaging gradients, particularly in larger airways where 3He diffusion is maximized. In this chapter, a modified FGRE approach called X-Centric is described for acquiring 3He mouse lung MRI. X-Centric is a center-out technique, allowing high-spatial-resolution, and high signal-to-noise ratio density-weighted imaging, as it is a short-TE method minimizing diffusion decay. Here, we also take advantage of a high-performance insertable-gradient-set interfaced with a clinical MRI system and a custom-built constant-volume ventilator to get the maximum benefits of X-Centric. High-spatial-resolution 3He X-Centric imaging was performed in a phantom and mouse lungs, yielding a nominal resolution of 39 μm and 78 μm respectively. We also demonstrate the feasibility of 129Xe/19F X-Centric MRI in a phantom and in rat lungs

A biophysical Raman spectroscopic model for noninvasive screening of skin cancer

Raman spectroscopy (RS) is sensitive to the molecular composition of biological tissues. Raman optical fiber- based probes have demonstrated efficacy in noninvasive cancer screening of the skin, breast, stomach, cervical, lung and brain. Currently, statistical algorithms such as principle component analysis (PCA) are the standard approaches for describing the spectral variance of the RS data and providing tissue classification. However, a PCA-based analysis does not allow for an examination of the biophysical basis of disease, such as microstructural organization of proteins and lipids. Understanding those biophysical parameters is essential to interpret the diagnostic result similar to that a pathologist is familiar reading, and develop diagnostic algorithms for fast and accurate cancer screening. Please click Additional Files below to see the full abstract

The net cost of incorporating resistance testing into HIV/AIDS treatment in South Africa: a Markov model with primary data

<p>Abstract</p> <p>Background</p> <p>Current guidelines for providing antiretroviral therapy (ART) in South Africa's public sector programme call for switching patients from first-line to second-line treatment upon virologic failure as indicated by two consecutive viral loads above 5000 copies/ml, but without laboratory evidence of viral resistance. We modelled the net cost of adding resistance testing for patients with virological failure and retaining patients without resistance on first-line therapy, rather than switching all failures to second-line therapy.</p> <p>Methods</p> <p>Costs were estimated for three scenarios: routine maintenance (standard care without resistance testing, switch all failures to second line); resistance testing (resistance test for patients with failure, switch those with resistance); and limited testing (resistance test for patients with failure in the first three years, switch those with resistance). A Markov model was used to estimate the cost of each arm over five years after first line initiation. Rates of treatment failure, viral resistance and treatment costs were estimated with primary data from a large HIV treatment cohort at a public facility in Johannesburg. Future costs were discounted at 3%.</p> <p>Results</p> <p>Virological failure rates over five years were 19.8% in routine maintenance and 20.2% in resistance testing and limited testing; 16.8% and 11.4% of failures in routine and limited testing, respectively, did not have any resistance mutations, resulting in 3.1% and 2.0% fewer patients switching to second-line ART by the end of five years. Treatment costs were estimated at US$526 and$1268 per patient per year on first-line and second-line therapy, respectively; a resistance test cost $242. The total average cost per patient over five years was$2780 in routine maintenance; $2775 in resistance testing; and$2763 in limited testing.</p> <p>Conclusions</p> <p>Incorporating resistance testing into treatment guidelines in South Africa is potentially cost-neutral and can identify other reasons for failure, conserve treatment options, and generate information about emerging resistance patterns.</p

Chronic cigarette smoking is linked with structural alterations in brain regions showing acute nicotinic drug-induced functional modulations

Background Whereas acute nicotine administration alters brain function which may, in turn, contribute to enhanced attention and performance, chronic cigarette smoking is linked with regional brain atrophy and poorer cognition. However, results from structural magnetic resonance imaging (MRI) studies comparing smokers versus nonsmokers have been inconsistent and measures of gray matter possess limited ability to inform functional relations or behavioral implications. The purpose of this study was to address these interpretational challenges through meta-analytic techniques in the service of clarifying the impact of chronic smoking on gray matter integrity and more fully contextualizing such structural alterations. Methods We first conducted a coordinate-based meta-analysis of structural MRI studies to identify consistent structural alterations associated with chronic smoking. Subsequently, we conducted two additional meta-analytic assessments to enhance insight into potential functional and behavioral relations. Specifically, we performed a multimodal meta-analytic assessment to test the structural?functional hypothesis that smoking-related structural alterations overlapped those same regions showing acute nicotinic drug-induced functional modulations. Finally, we employed database driven tools to identify pairs of structurally impacted regions that were also functionally related via meta-analytic connectivity modeling, and then delineated behavioral phenomena associated with such functional interactions via behavioral decoding. Results Across studies, smoking was associated with convergent structural decreases in the left insula, right cerebellum, parahippocampus, multiple prefrontal cortex (PFC) regions, and the thalamus. Indicating a structural?functional relation, we observed that smoking-related gray matter decreases overlapped with the acute functional effects of nicotinic agonist administration in the left insula, ventromedial PFC, and mediodorsal thalamus. Suggesting structural-behavioral implications, we observed that the left insula?s task-based, functional interactions with multiple other structurally impacted regions were linked with pain perception, the right cerebellum?s interactions with other regions were associated with overt body movements, interactions between the parahippocampus and thalamus were linked with memory processes, and interactions between medial PFC regions were associated with face processing. Conclusions Collectively, these findings emphasize brain regions (e.g., ventromedial PFC, insula, thalamus) critically linked with cigarette smoking, suggest neuroimaging paradigms warranting additional consideration among smokers (e.g., pain processing), and highlight regions in need of further elucidation in addiction (e.g., cerebellum). Electronic supplementary material The online version of this article (doi:10.1186/s12993-016-0100-5) contains supplementary material, which is available to authorized users