Detecting a Light Stop from Top Decays at the Tevatron

We study the possibility of discovering or excluding a light top squark (stop) based on top quark decays in the t-tbar events produced at the Fermilab Tevatron. In particular, we consider the Minimal Supersymmetric Standard Model with the sparticle spectrum m_{chi^+_1}+m_b, M_W+m_{chi^0_1}+m_b > m_{stop} > m_{chi^0_1}+m_c, where chi^0_1 is the lightest neutralino and chi^+_1 is the lightest chargino, so that t -> stop chi^0_1 and stop -> c chi^0_1. All other sparticle masses are assumed to be heavier than m_t. Such a spectrum seeks to explain the experimental values of alpha_s(M_Z^2), R_b and A_{LR} obtained from LEP/SLC data. We find that the prospect to observe a light stop via this channel at the Tevatron is very promising.Comment: 12 pages with 1 Postscript figure using psfig.sty. Postscript file available at http://sgi2.hep.anl.gov:8001/index.htm

Clinical and brain imaging findings in a child with vitamin B12 deficiency

Vitamin B12 (Vit-B12) deficiency is a rare and treatable cause of failure to thrive and delayed development in infants who are exclusively breastfed. Apart from genetic causes, it can be related to a malabsorption syndrome or when the mother follows a strict vegetarian or vegan diet, causing a low hepatic storage of Vit-B12 in the infant at birth. As the neurological symptoms are nonspecific, a brain magnetic resonance imaging (MRI) exam is usually performed to rule out primary causes of neurodevelopmental delay. Findings related to brain atrophy are usually observed. A favorable response is achieved with Vit-B12 therapy, and neurological symptoms dramatically improve within a few days after the treatment. We present the case of an infant with severe Vit-B12 deficiency, exclusively breastfed by his young vegan mother, and whose clinical symptoms together with MRI findings improved after treatment. Brain atrophy recovery after Vit-B12 therapy has been seldom documented

Anomalous t-c-g coupling: The connection between single top production and top decay

Continuing earlier work, we examine the constraint on an anomalous t-c-g coupling from top quark decay. We find that from current CDF measurements of the branching ratio $t \rightarrow W b$, the minimum scale at which new physics can strongly modify the t-c-g coupling is \Ltcg $\geq$ about 950 GeV. At the upgraded Tevatron, single top production can constrain \Ltcg $\geq$ 4.5 TeV. The connection between t-c production and the decay $t \rightarrow c g$ is examined, showing how constraints on one lead to a constraint on the other.Comment: 5 pages. Requires epsf.sty to process .eps formatted figure

Evaluation of demarcation line after epithelium-off iontophoresis corneal collagen cross-linking for progressive keratoconus

The aim of the study was to visualize and evaluate the characteristics and depth of the demarcation line with anterior segment optical coherence tomography (AS-OCT) after epithelium-off iontophoresis corneal collagen cross-linking (epi-off I-CXL). In this prospective, consecutive, single center study 18 eyes of 18 patients with keratoconus were involved. One month after epi-off I-CXL, all the patients underwent an AS-OCT scan to search for a demarcation line and its characteristics. The corneal stromal demarcation line was identified in all the eyes. Mean depth of the corneal stromal demarcation line was 261.8 ± 46.7 μm (range: 184 to 362 μm), at 56.7 ± 12% corneal depth. In conclusion, epi-off I-CXL determines a demarcation line that can be visualized with AS-OCT, which seems clearly distinguishable and similar to that created in standard CXL

Malignancy course of pituitary adenoma in MEN1 syndrome: Clinical-Neuroradiological signs

Pituitary carcinomas (PCa) are extremely rare, indistinguishable from pituitary adenomas on histopathological grounds and have a poor prognosis. Most PCa start as PRL or ACTH secreting tumors in males, with relapsing invasive behaviour, refractoriness to medical and radiotherapy and increasing hormonal levels. The presence of distant metastases is still required for the diagnosis of PCa. The association with genetic endocrine diseases must be taken into account, since it adds further risk of evolution towards malignancy. Intradural spinal metastases have also been reported, so a complete craniospinal MR evaluation is recommended, when clinically indicated. We report a case of PCa, associated with MEN1 syndrome, with evidence of meningeal spread to the tentorium cerebelli, clival dura and spinal drop metastases mimicking spinal nerves schwannomas

Simulation and implementation of a piezoelectric sensor for harmonic in-situ strain monitoring

To monitor the strain in a multilayer steel/adhesive/ceramic beam structure, a 9-µmthick piezoelectric PVDF film is inserted in the adhesive joint. Two 2D finite element models of the structure with and without the film were developed using a sub-structuring procedure to reduce computational time and to refine the mesh in the thickness of the film. The models provide the harmonic displacement of the beam and the voltage across the film which is related to the strain. A prototype of the analyzed structure has been developed as well. Simulation and experimental analysis was performed and obtained results were compared. It was demonstrated that the influence of the presence of the film on the stress distribution is negligible, thus the implementation of an embedded PVDF film is a well-suited technique to monitor the strain transfer in a bonded assembl

Supersymmetric QCD flavor changing top quark decay

We present a detailed and complete calculation of the gluino and scalar quarks contribution to the flavour-changing top quark decay into a charm quark and a photon, gluon, or a Z boson within the minimal supersymmetric standard model including flavour changing gluino-quarks-scalar quarks couplings in the right-handed sector. We compare the results with the ones presented in an earlier paper where we considered flavour changing couplings only in the left-handed sector. We show that these new couplings have important consequences leading to a large enhancement when the mixing of the scalar partners of the left- and right-handed top quark is included. Furthermore CP violation in the flavour changing top quark decay will occur when a SUSY phase is taken into account.Comment: 14 pages, latex, 3 figure

Surgical treatment of primary tracheal tumors in children and adolescents

Pediatric primary tracheal tumors (PTTs) are rare entities, with an estimated incidence of 0.2% among all neoplasms in children and adolescents. Benign lesions and malignancies are rather equally represented, with subglottic hemangioma, granular cell tumor, carcinoid tumor, and low-grade mucoepidermoid carcinoma being the most common histotypes. Guidelines on management and treatment of pediatric PTTs are not available, and only a few reviews, case reports, and single surgeon/institute experiences have been published. A literature search was carried out focusing on the surgical approaches utilized in the most recent publications to manage pediatric PTTs, thus including case reports, single institute experiences, and reviews on surgical techniques. Moreover, we divided the available intervention modalities based on an anatomical classification, distinguishing between laryngotracheal, cervical tracheal, lower tracheal, and carinal scenarios. Endoscopic treatment is still underused, even for benign lesions: this is mainly due to the difficulties that surgeons may experience during airway management, appropriate tumor visualization, and its safe removal with adequate prevention/management of intraoperative complications. Considering open surgery, simple tumorectomy via median thyrotomy is the treatment of choice whenever possible (mainly for benign tumors), whereas in case of wider excisions, laryngotracheal resection and reconstruction with cartilage graft, end-to-end anastomosis, or neo-carinal reconstruction represent the most widely used procedures. All these techniques are similar to what described in adults. Strict cooperation with an experienced team of pediatric anesthesiologists and intensivists is of paramount importance for the adequate management of PTTs in young children. We are far from establishing a common guideline for treatment of PTTs. Mini-invasive procedures should be encouraged and developed since the majority of pediatric histotypes are benign or low-grade cancers. Moreover, patients should be addressed to specialized pediatric centers in order to improve and refine the existing techniques, laying the groundwork for the proposal of new procedures.

Radiation-induced sarcoma of the head and neck: A review of the literature

In the last decades, radiotherapy (RT) has become one of the cornerstones in the treatment of head and neck (HN) malignancies and has paralleled an increase in long-term patient survival. This lead to a concomitant increase in the incidence of radiation-induced sarcomas (RIS) of the irradiated field, with an annual rate up to 0.17%. The new techniques of irradiation do not seem to influence the risk of RIS of the HN (RISHN), which mainly develop within the middle-dose field. The median latency of RISHN after RT is 10-12 years and osteosarcoma is the most represented histotype, even though there is a high variability in time of occurrence and histological features observed. There is no clear evidence of predisposing factors for RISHN, and genetic findings so far have not revealed any common mutation. Early clinical diagnosis of RISHN is challenging, since it usually occurs within fibrotic and hardened tissues, while radiological findings are not pathognomonic and able to differentiate them from other neoplastic entities. Given the highly aggressive behavior of RISHN and its poor sensitivity to chemotherapy, radical surgery is the most important prognostic factor and the only curative option at present. Nevertheless, the anatomy of the HN district and the infiltrative nature of RIS do not always allow radical intervention. Therefore, a wise integration with systemic therapy and, when feasible, re-irradiation should be performed. Future findings in the genomic features of RISHN will be crucial to identify a possible sensitivity to specific drugs in order to optimize a multimodal treatment that will be ideally complementary to surgery and reirradiation