Shifted Landau levels in curved graphene sheets

We study the Landau levels in curved graphene sheets by measuring the discrete energy spectrum in the presence of a magnetic field. We observe that in rippled graphene sheets, the Landau energy levels satisfy the same square root dependence on the energy quantum number as in flat sheets, $E_n \sim \sqrt{n}$. Though, we find that the Landau levels in curved sheets are shifted towards lower energies by an amount proportional to the average spatial deformation of the sheet. Our findings are relevant for the quantum Hall effect in curved graphene sheets, which is directly related to Landau quantization. For the purpose of this study, we develop a new numerical method, based on the quantum lattice Boltzmann method, to solve the Dirac equation on curved manifolds, describing the low-energetic states in strained graphene sheets

Time-resolved oxygen production by PSII: chasing chemical intermediates

AbstractPhotosystem II (PSII) produces dioxygen from water in a four-stepped process, which is driven by four quanta of light and catalysed by a Mn-cluster and tyrosine Z. Oxygen is liberated during one step, coined S3⇒S0. Chemical intermediates on the way from reversibly bound water to dioxygen have not yet been tracked, however, a break in the Arrhenius plot of the oxygen-evolving step has been taken as evidence for its existence.We scrutinised the temperature dependence of (i) UV-absorption transients attributable to the reduction of the Mn-cluster and tyrosine Z by water, and (ii) polarographic transients attributable to the release of dioxygen. Using a centrifugatable and kinetically competent Pt-electrode, we observed no deviation from a linear Arrhenius plot of oxygen release in the temperature range from −2 to 32 °C, and hence no evidence, by this approach, for a sufficiently long-lived chemical intermediate. The half-rise times of oxygen release differed between Synechocystis WT* (at 20 °C: 1.35 ms) and a point mutant (D1–D61N: 13.1 ms), and the activation energies differed between species (Spinacia oleracea, 30 kJ/mol versus Synechocystis, 41 kJ/mol) and preparations (PSII membranes, 41 kJ/mol versus core complexes, 33 kJ/mol, Synechocystis).Correction for polarographic artefacts revealed, for the first time, a temperature-dependent lag-phase of the polarographic transient (duration at 20 °C: 0.45 ms, activation energy: 31 kJ/mol), which was indicative of a short-lived intermediate. It was, however, not apparent in the UV-transients. Thus the “intermediate” was probably newly formed and transiently bound oxygen

Linear accelerator-based stereotactic radiosurgery in 140 brain metastases from malignant melanoma

Background: To retrospectively access outcome and prognostic parameters of linear accelerator-based stereotactic radiosurgery in brain metastases from malignant melanoma. Methods: Between 1990 and 2011 140 brain metastases in 84 patients with malignant melanoma (median age 56 years) were treated with stereotactic radiosurgery. At initial stereotactic radiosurgery 48 % of patients showed extracerebral control. The median count of brain metastases in a single patient was 1, the median diameter was 12 mm. The median dose applied was 20 Gy/80 % isodose enclosing. Results: The median follow-up was 7 months and the median overall survival 9 months. The 6-, 12- and 24 month overall survival rates were 71 %, 39 % and 25 % respectively. Cerebral follow-up imaging showed complete remission in 20 brain metastases, partial remission in 39 brain metastases, stable disease in 54 brain metastases, progressive disease in 24 brain metastases and pseudo-progression in 3 brain metastases. Median intracerebral control was 5.3 months and the 6- and 12-month intracerebral progression-free survival rates 48 % and 38 %, respectively. Upon univariate analysis, extracerebral control (log-rank, p < 0.001), the response to stereotactic radiosurgery (log-rank, p < 0.001), the number of brain metastases (log-rank, p = 0.007), the recursive partitioning analysis class (log-rank, p = 0.027) and the diagnosis-specific graded prognostic assessment score (log-rank, p = 0.011) were prognostic for overall survival. The most common clinical side effect was headache common toxicity criteria grade I. The most common radiological finding during follow-up was localized edema within the stereotactic radiosurgery high dose region. Conclusion: Stereotactic radiosurgery is a well-tolerated and effective treatment option for brain metastases in malignant melanoma and was able to achieve local remissions in several cases. Furthermore, especially patients with controlled extracerebral disease and a low count of brain metastases seem to benefit from this treatment modality. Prospective trials analysing the effects of combined stereotactic radiosurgery and new systemic agents are warranted

Feasibility and robustness of dynamic F-18-FET PET based tracer kinetic models applied to patients with recurrent high-grade glioma prior to carbon ion irradiation

The aim of this study was to analyze the robustness and diagnostic value of different compartment models for dynamic F-18-FET PET in recurrent high-grade glioma (HGG). Dynamic F-18-FET PET data of patients with recurrent WHO grade III (n:7) and WHO grade IV (n: 9) tumors undergoing re-irradiation with carbon ions were analyzed by voxelwise fitting of the time-activity curves with a simplified and an extended one-tissue compartment model (1TCM) and a two-tissue compartment model (2TCM), respectively. A simulation study was conducted to assess robustness and precision of the 2TCM. Parameter maps showed enhanced detail on tumor substructure. Neglecting the blood volume V-B in the 1TCM yields insufficient results. Parameter K-1 from both 1TCM and 2TCM showed correlation with overall patient survival after carbon ion irradiation (p = 0.043 and 0.036, respectively). The 2TCM yields realistic estimates for tumor blood volume, which was found to be significantly higher in WHO IV compared to WHO III (p = 0.031). Simulations on the 2TCM showed that K1 yields good accuracy and robustness while k(2) showed lowest stability of all parameters. The 1TCM provides the best compromise between parameter stability and model accuracy;however application of the 2TCM is still feasible and provides a more accurate representation of tracer-kinetics at the cost of reduced robustness. Detailed tracer kinetic analysis of F-18-FET PET with compartment models holds valuable information on tumor substructures and provides additional diagnostic and prognostic value

Radiotherapy for Colorectal Cancer: Current Standards and Future Perspectives

Background: Multimodal treatment approaches are indispensable for patients with advanced-stage colorectal cancer. Radiotherapy has been established as essential part of perioperative concepts and was introduced as an option to face challenges such as local relapse or oligometastases. Methods: A literature review was performed to summarize evidence and current standards of radiotherapeutic concepts in the treatment of colorectal cancer. Results: For stage II/III rectal cancer, neoadjuvant radiotherapy is superior to adjuvant treatment. Two preoperative regimens have been established and are commonly used with different objectives: short-course radiotherapy (SC-RT) and long-course chemoradiotherapy (LC-CRT). Both reduce the risk of local relapse. Additionally, LC-CRT aims at downsizing the tumor to potentially reduce radicalness of surgery. There is increasing evidence that not all stage II/III rectal cancer patients need neoadjuvant irradiation but also that in some cases surgery might be omitted. Stereotactic body radiotherapy (SBRT) of the liver shows high rates of local control in oligometastatic patients. Intraoperative and particle radiotherapy extend the spectrum of treatment options for locally recurrent patients. Conclusion: Radiotherapeutic concepts are crucial for the primary management of locally advanced colorectal cancer and can essentially contribute to treatment approaches in locally recurrent, oligometastatic or palliative patients

Re-irradiation in the treatment of patients with cerebral metastases of solid tumors: retrospective analysis

Background: Goal of this retrospective analysis was to evaluate the role of repeat whole brain radiotherapy in the palliative care of patients with brain metastases due to solid tumors. Methods: Data regarding demographic data, primary tumor, metastasis, radiotherapy and symptoms were compiled on 134 patients with cerebral metastases that received repeat whole brain radiotherapy (WBRT) in our clinic between 2002 and 2011. Results: The analyzed group consisted of 63 (47%) women and 71 (53%) men with a median age of 57 at the start of re-irradiation. Most frequent primary site was the lung (87%). Sixty patients with lung cancer received the first WBRT prophylactically. At the time of re-WBRT 81% of all patients suffered from additional extracerebral metastases. Time between first and second WBRT was a median of 13.4 months. Full dose for the first WBRT was 30 Gy in 2.0 Gy single dose, for the second 20 Gy in 2.0 Gy single dose. At the start of the Re-WBRT 81 patients (60.4%) had mild, 32 (23.9%) severe neurological symptoms, 21 patients (15.7%) were asymptomatic. The median Karnofsky performance status was 70%. Overall, re-WBRT was tolerated satisfactorily. Main side effects were fatigue, erythema and focal alopecia, 10% of patients discontinued treatment before reaching the planned dose. Median survival was 2.8 months since the end of the re-WBRT with good performance status at the start of the re-irradiation being a key indicator for longer survival. Fifty-two patients (39%) showed a clinical improvement of neurological symptoms after the therapy, 59 patients (44%) remained stable, 23 patients (17%) showed worse symptoms. Conclusions: From this large patient collective we were able to show that re-WBRT can be an important therapeutic option with low rate of acute side effects for patients in adequate general condition

Prior surgical intervention and tumor size impact clinical outcome after precision radiotherapy for the treatment of optic nerve sheath meningiomas (ONSM)

<p>Abstract</p> <p>Purpose</p> <p>We analyzed our long-term experience with fractionated stereotactic radiotherapy (FSRT) in patients with meningioma of the optic nerve sheath (ONSM).</p> <p>Patients and Methods</p> <p>Between January 1991 and January 2010, 40 patients with ONSM were treated using FSRT. Of these, 19 patients received radiotherapy as primary treatment, and 21 patients were treated after surgical resection. The median target volume was 9.2 ml, median total dose was 54 Gy in median single fractions of 1,8 Gy.</p> <p>Results</p> <p>Local progression-free survival was 100%. Median survival after FSRT was 60 months (range 4-228 months). In all patients overall toleration of FSRT was very good. Acute toxicity was mild. Prior to RT, 29 patients complained about any kind of visual impairment including visual field deficits, diplopia or amaurosis. Prior surgical resection was identified as a negative prognostic factor for visual outcome, whereas patients with larger tumor volumes demonstrated a higher number of patients with improvement of pre-existing visual deficits.</p> <p>Conclusion</p> <p>Long-term outcome after FSRT for ONSM shows improved vision in patients not treated surgically prior to RT; moreover, the best improvement of visual deficits are observed in patients with larger target volumes. The absence of tumor recurrences supports that FSRT is a strong alternative to surgical resection especially in small tumors without extensive compression of normal tissue structures</p

Prognostic factors for survival of women with unstable spinal bone metastases from breast cancer

Background: Bone metastases are an important clinical issue in women with breast cancer. Particularly, unstable spinal bone metastases (SBM) are a major cause of severe morbidity and reduced quality of life (QoL) due to frequent immobilization. Radiotherapy (RT) is the major treatment modality and is capable of promoting re-ossification and improving stability. Since local therapy response is excellent, survival of these patients with unstable SBM is of high clinical importance. We therefore conducted this analysis to assess survival and to determine prognostic factors for bone survival (BS) in women with breast cancer and unstable SBM. Methods: A total population of 92 women with unstable SBM from breast cancer who were treated with RT at our department between January 2000 and January 2012 was retrospectively investigated. We calculated overall survival (OS) and BS (time between first diagnosis of bone metastases until death) with the Kaplan-Meier method and assessed prognostic factors for BS with a Cox regression model. Results: Mean age at first diagnosis of breast cancer was 60.8 years ± SD 12.4 years. OS after 1, 2 and 5 years was 84.8, 66.3 and 50 %, respectively. BS after 1, 2 and 5 years was 62.0, 33.7 and 12 %, respectively. An age &gt; 50 years (p &lt; .001; HR 1.036 [CI 1.015–1.057]), the presence of a single bone metastasis (p = .002; HR 0.469 [CI 0.292–0.753]) and triple negative phenotype (p &lt; .001; HR 1.068 [CI 0.933–1.125]) were identified as independent prognostic factors for BS. Conclusions: Our analysis demonstrated a short survival of women with breast cancer and unstable SBM. Age, presence of a solitary SBM and triple-negative phenotype correlated with survival. Our results may have an impact on therapeutic decisions in the future and offer a rationale for future prospective investigations