Assessment of the probability of contaminating Mars

New methodology is proposed to assess the probability that the planet Mars will by biologically contaminated by terrestrial microorganisms aboard a spacecraft. Present NASA methods are based on the Sagan-Coleman formula, which states that the probability of contamination is the product of the expected microbial release and a probability of growth. The proposed new methodology extends the Sagan-Coleman approach to permit utilization of detailed information on microbial characteristics, the lethality of release and transport mechanisms, and of other information about the Martian environment. Three different types of microbial release are distinguished in the model for assessing the probability of contamination. The number of viable microbes released by each mechanism depends on the bio-burden in various locations on the spacecraft and on whether the spacecraft landing is accomplished according to plan. For each of the three release mechanisms a probability of growth is computed, using a model for transport into an environment suited to microbial growth

New methodology for assessing the probability of contaminating Mars

Methodology is proposed to assess the probability that the planet Mars will be contaminated by terrestrial microorganisms aboard a spacecraft. The present NASA methods are extended to permit utilization of detailed information on microbial characteristics, the lethality of release and transport mechanisms, and of other information about the Martian environment. Different types of microbial release are distinguished, and for each release mechanism a probability of growth is computed. Using this new methodology, an assessment was carried out for the 1975 Viking landings on Mars. The resulting probability of contamination for each Viking lander is 6 x 10 to the -6 power, and is amenable to revision as additional information becomes available

Arterial calcification on preoperative computed tomography imaging as a risk factor for pharyngocutaneous fistula formation after total laryngectomy

BACKGROUND: Research in esophageal surgery showed that computed tomography (CT) assessed arterial calcification (AC) is associated with postoperative complications. We investigated the association between AC and pharyngocutaneous fistula (PCF) formation after laryngectomy. METHODS: This was a retrospective cohort study of patients undergoing laryngectomy. AC was scored at 10 different anatomical locations on CT imaging, blinded for PCF occurrence. Association with PCF was investigated using logistic regression. RESULTS: The 224 patients were included; 62 (27.7%) developed a PCF. Moderate to severe AC was widespread in patients undergoing TL; 7.1% of patients had at most mild AC, of whom 1 experienced a PCF (p = 0.05). A higher cumulative calcification score was associated with PCF in univariable (OR 1.11, p = 0.04) and multivariable analysis (OR 1.14, p = 0.05). CONCLUSION: AC is widespread in patients undergoing laryngectomy and its burden is associated with PCF. Extensive AC on preoperative imaging may be considered a risk factor for PCF

Institutional investors and corporate governance

We provide a comprehensive overview of the role of institutional investors in corporate governance with three main components. First, we establish new stylized facts documenting the evolution and importance of institutional ownership. Second, we provide a detailed characterization of key aspects of the legal and regulatory setting within which institutional investors govern portfolio firms. Third, we synthesize the evolving response of the recent theoretical and empirical academic literature in finance to the emergence of institutional investors in corporate governance. We highlight how the defining aspect of institutional investors – the fact that they are financial intermediaries – differentiates them in their governance role from standard principal blockholders. Further, not all institutional investors are identical, and we pay close attention to heterogeneity amongst institutional investors as blockholders

Trismus following radiotherapy to the head and neck is likely to have distinct genotype dependent cause

OBJECTIVES: Trismus frequently occurs as a consequence of radiotherapy or chemo-radiotherapy to the head and neck, with a loss of function that can reduce the overall quality of life. Radiation can trigger an intense fibrosis within the masticatory muscles and transforming growth factor beta 1 (TGF β1) is involved in this process. As in other tissues the degree of fibrosis may be related to a single nucleotide polymorphism; C-T at position -509 in the TGF β1 gene. MATERIALS AND METHODS: Trismus was measured in 62 patients before and after radiotherapy or chemoradiotherapy, blood was taken for DNA extraction, and genotype analysis of the TGF β1 gene. Trismus was analysed against, patient age, sex, tumour site and stage, radiotherapy, and chemotherapy. RESULTS AND CONCLUSIONS: After radiotherapy or chemo-radiotherapy the reduction in mouth opening was shown to be significantly related to the presence of the T allele (p<0.001), with patients homozygous the most likely to be severely affected. No other patient, tumour or treatment factors were significant. Hence the TGF β1 genotype is likely to be an important predictor of the degree of post radiotherapy or chemo-radiotherapy trismus

Time interval between primary radiotherapy and salvage laryngectomy: a predictor of pharyngocutaneous fistula formation

Salvage laryngectomy (SL) is associated with high levels of morbidity. Rates of pharyngocutaneous fistulae (PCF) are as high as 35 % in some series. Patients at highest risk of such complications may be candidates for altered surgical management in terms of additional tissue transfer, or delayed tracheoesophageal puncture. This study investigates the relationship between the time from primary radiotherapy (RT) to salvage surgery and the development of PCF. 26 consecutive patients who underwent SL between 2000 and 2010 were identified from our institutional database. Demographic, staging, treatment and complication data were collected. Subgroup analysis was performed using the Student's t test or Mann-Whitney U test for continuous variables and either Chi-squared test or Fisher's Exact test for categorical variables. 26 patients underwent SL between October 2003 and July 2010. Of these, 15 (58 %) developed a PCF. On analysis of the time between pre-operative RT and surgery, a significant difference was seen, with a mean time of 19.5 months in those who developed a PCF versus 47.0 months in those who did not (p = 0.02). Patient characteristics, treatment, and pathology results were comparable between the two groups. There was no significant difference in distribution of the other covariates between the PCF and non-PCF groups. We reported a high rate of PCF and identified an association between PCF and a short time from primary treatment to salvage surgery. Identifying factors associated with higher rates of post-operative morbidity allows surgeons to adapt surgical planning in an attempt to minimize rates of PCF

NiTiBOND, eine optimierte Steigbügelprothese zur chirurgischen Behandlung der Otosklerose

Compared to traditional stapes prostheses, self-crimping prostheses have been shown to result in similar, if not better, closure of the air bone gap in patients undergoing stapedotomy for otosclerosis. To achieve self-crimping, nitinol, a shape memory alloy, has been used for several years but concerns have been raised regarding possible damage to the incus and its muco-periosteum. We investigate these concerns with regard to the newer NiTiBOND stapes prosthesis in an observational multi-centre study.In a multicentre, prospective observational study, 76 patients undergoing stapedotomy with the NiTiBond prosthesis across 4 centres were compared to 75 -retrospectively selected control SMart patients. Complications, intra-operative user-friendliness and audiological results at 3 months were documented.Audiological improvement and the rate of complications were similar in both groups. Non inferiority was shown at all frequencies and in the pure-tone average. The NiTiBOND prosthesis was described as very user-friendly.By eliminating manual crimping, stapedotomy using the NiTiBOND prosthesis can be facilitated and standardized. Furthermore, intraoperative handling characteristics of the prosthesis are very good which may further reduce operative risk. Importantly, we show that these benefits are not to the detriment of audiological outcome. Larger and longer-term studies are required to further evaluate results

Should elective neck dissection be routinely performed in patients undergoing salvage total laryngectomy?

AbstractBackground:The prevalence of occult neck metastasis in patients undergoing salvage total laryngectomy remains unclear, and there is controversy regarding whether elective neck dissection should routinely be performed.Method:A retrospective case note review of 32 consecutive patients undergoing salvage total laryngectomy in a tertiary centre was performed, in order to correlate pre-operative radiological staging with histopathological staging.Results:The median patient age was 61 years (range, 43–84 years). With regard to lymph node metastasis, 28 patients were pre-operatively clinically staged (following primary radiotherapy or chemoradiotherapy) as node-negative, 1 patient was staged as N1, two patients as N2c and one patient as N3. Fifty-two elective and seven therapeutic neck dissections were performed. Pathological analysis up-staged two patients from clinically node-negative (following primary radiotherapy or chemoradiotherapy) to pathologically node-positive (post-surgery). No clinically node-positive patients were down-staged. More than half of the patients suffered a post-operative fistula.Conclusion:Pre-operative neck staging had a negative predictive value of 96 per cent. Given the increased complications associated with neck dissection in the salvage setting, consideration should be given to conservative management of the neck in clinically node-negative patients (staged following primary radiotherapy or chemoradiotherapy).</jats:sec

Sentinel Lymph Node Biopsy for T1/T2 Oral Cavity Squamous Cell Carcinoma-A Prospective Case Series

BACKGROUND: Sentinel lymph node biopsy (SLNB) is an established technique in breast and melanoma surgery and is gaining acceptance in the management of oral cavity squamous cell carcinoma. We report a single institution's experience of SLNB between 2006 and 2010. METHODS: Prospective consecutive cohort study of 59 patients recruited between 2006 and 2010. All patients underwent SLNB with preoperative lymphoscintigraphy, intraoperative blue dye, and handheld gamma probe. Sentinel nodes were evaluated with step-serial sectioning and immunohistochemistry. Endpoints included: overall survival (OS), disease-specific survival (DSS), local recurrence-free survival (LRFS), and regional recurrence-free survival (RRFS). RESULTS: A total of 59 patients (36 male and 23 female) were operated on. Of these, 42 patients (71%) were pT1 and 17 patients (29%) were pT2. In two patients the sentinel node was not identified and proceeded to elective neck dissection. A total of 150 nodes were harvested from the remaining 57 patients of which 21 nodes were positive in 17 patients; three patients had positive contralateral nodes. The 2-year OS, DSS, LRFS, and RRFS for the SLNB negative patients were 97.5, 100, 95.8, and 95.8% and for the SLNB positive patients 68.2, 81.8, 83.9, and 100% respectively. Only OS and DSS approached statistical significance with P values of 0.07 and 0.06. CONCLUSIONS: SLNB is a safe and accurate diagnostic technique for staging the neck with a negative predictive value in our series of 97.5%. Furthermore, in our series three patients (5%) had positive contralateral neck drainage that would have been missed by conventional ipsilateral neck dissection