RESUMO
INTRODUCTION: The pathogenesis of chronic subdural hematoma (CSDH) has not been completely understood. However, different mechanisms can result in space-occupying subdural fluid collections, one pathway can be the transformation of an original trauma-induced acute subdural hematoma (ASDH) into a CSDH. MATERIALS AND METHODS: All patients with unilateral CSDH, requiring burr hole trephination between 2018 and 2023 were included. The population was distributed into an acute-to-chronic group (group A, n = 41) and into a conventional group (group B, n = 282). Clinical and radiographic parameters were analyzed. In analysis A, changes of parameters after trauma within group A are compared. In analysis B, parameters between the two groups before surgery were correlated. RESULTS: In group A, volume and midline shift increased significantly during the progression from acute-to-chronic (p < 0.001, resp.). Clinical performance (modified Rankin scale, Glasgow Coma Scale) dropped significantly (p = 0.035, p < 0.001, resp.). Median time between trauma with ASDH and surgery for CSDH was 12 days. Patients treated up to the 12th day presented with larger volume of ASDH (p = 0.012). Before burr hole trephination, patients in group A presented with disturbance of consciousness (DOC) more often (p = 0.002), however less commonly with a new motor deficit (p = 0.014). Despite similar midline shift between the groups (p = 0.8), the maximal hematoma width was greater in group B (p < 0.001). CONCLUSION: If ASDH transforms to CSDH, treatment may become mandatory early due to increase in volume and midline shift. Close monitoring of these patients is crucial since DOC and rapid deterioration is common in this type of SDH.
Assuntos
Progressão da Doença , Hematoma Subdural Agudo , Hematoma Subdural Crônico , Humanos , Hematoma Subdural Crônico/cirurgia , Hematoma Subdural Crônico/diagnóstico por imagem , Hematoma Subdural Agudo/cirurgia , Hematoma Subdural Agudo/diagnóstico por imagem , Masculino , Feminino , Idoso , Pessoa de Meia-Idade , Idoso de 80 Anos ou mais , Adulto , Trepanação/métodos , Escala de Coma de Glasgow , Estudos RetrospectivosRESUMO
BACKGROUND: Despite multiple studies on the embolization of the middle meningeal artery, there is limited data on the treatment response of recurrent chronic subdural hematomas (CSDH) to embolization and on the volume change. METHODS: We retrospectively compared the treatment response and volume change of recurrent CSDHs in a conventional group (second surgery) with an embolization group (embolization as stand-alone treatment) during the time-period from August 2019 until June 2022. Different clinical and radiological factors were assessed. Treatment failure was defined as necessity of treatment for second recurrence. Hematoma volumes were determined in the initial CT scan before first surgery, after the first surgery, before retreatment as well as in an early (1 day-2 weeks) and in a late follow-up CT scan (2-8 weeks). RESULTS: Fifty recurrent hematomas after initial surgery were treated either by second surgery (n = 27) or by embolization (n = 23). 8/27 (26,6%) surgically treated and 3/23 (13%) of the hematomas treated by embolization needed to be treated again. This leads to an efficacy in recurrent hematomas of 73,4% in surgically treated and of 87% in embolized hematomas (p = 0.189). In the conventional group, mean volume decreased significantly already in the first follow-up CT scan from 101.7 ml (SD 53.7) to 60.7 ml (SD 40.3) (p = 0.001) and dropped further in the later follow-up scan to 46.6 ml (SD 37.1) (p = 0.001). In the embolization group, the mean volume did decrease insignificantly from 75.1 ml (SD 27.3) to 68 ml (SD 31.4) in the first scan (p = 0.062). However, in the late scan significant volume reduction to 30.8 ml (SD 17.1) could be observed (p = 0.002). CONCLUSIONS: Embolization of the middle meningeal artery is an effective treatment option for recurrent CSDH. Patients with mild symptoms who can tolerate slow volume reduction are suitable for embolization, whereas patients with severe symptoms should be reserved for surgery.
Assuntos
Embolização Terapêutica , Hematoma Subdural Crônico , Humanos , Hematoma Subdural Crônico/diagnóstico por imagem , Hematoma Subdural Crônico/cirurgia , Artérias Meníngeas/diagnóstico por imagem , Artérias Meníngeas/cirurgia , Estudos Retrospectivos , Resultado do TratamentoRESUMO
BACKGROUND: Topical negative pressure wound therapy (TNPWT) is a regularly used method in modern wound treatment with a growing and diverse potential for clinical use. So far positive effects on microcirculation have been observed and examined, although precise statements on the underlying mechanism appear unsatisfying. OBJECTIVE: The aim of our study was to extend the understanding of the effect of TNPWT on tissue perfusion and determine the time frame and the extent to which the tissue perfusion changes due to TNPWT. MATERIAL AND METHODS: TNPWT was applied to the anterior thighs of 40 healthy individuals for 30 min, respectively. Before and up to 90 min after the application, measurements of the amount of regional haemoglobin (rHb), capillary venous oxygen saturation (sO2), blood flow (flow) and velocity were conducted with spectrophotometry (combining white light spectrometry and laser Doppler spectroscopy) within two different depths/skin layers. A superficial measuring probe for depths up to 3 mm and a deep measuring probe for up to 7 mm were used. RESULTS: All parameters show significant changes after the intervention compared to baseline measurements. The greater effect was seen superficially. The superficially measured rHb, sO2 and flow showed a significant increase and stayed above the baseline at the end of the protocol. Whereas deeply measured, the rHb initially showed a decrease. The flow and sO2 showed a significant increase up to 60 min after the intervention. CONCLUSION: The application of TNPWT on healthy tissue shows an increase in capillary-venous oxygen saturation and haemoglobin concentration of at least 90 min after intervention. A possible use in clinical practice for preconditioning to enhance wound healing for high-risk patients to develop wound healing disorder, requires further studies to investigate the actual duration of the effect.
Assuntos
Capilares/fisiologia , Microcirculação , Tratamento de Ferimentos com Pressão Negativa , Pele/irrigação sanguínea , Adulto , Velocidade do Fluxo Sanguíneo , Feminino , Voluntários Saudáveis , Hemoglobinas/metabolismo , Humanos , Fluxometria por Laser-Doppler , Masculino , Oxigênio/sangue , Saturação de Oxigênio , Projetos Piloto , Estudos Prospectivos , Fluxo Sanguíneo Regional , Espectrofotometria , Coxa da Perna , Fatores de Tempo , Adulto JovemRESUMO
BACKGROUND: This observational study was performed to show the impact of complications and interventions during neurocritical care on the outcome after aneurysmal subarachnoid hemorrhage (SAH). METHODS: We analyzed 203 cases treated for ruptured intracranial aneurysms, which were classified regarding clinical outcome after one year according to the modified Rankin Scale (mRS). We reviewed the data with reference to the occurrence of typical complications and interventions in neurocritical care units. RESULTS: Decompressive craniectomy (odds ratio 21.77 / 6.17 ; p < 0.0001 / p = 0.013), sepsis (odds ratio 14.67 / 6.08 ; p = 0.037 / 0.033) and hydrocephalus (odds ratio 3.71 / 6.46 ; p = 0.010 / 0.00095) were significant predictors for poor outcome and death after one year beside "World Federation of Neurosurgical Societies" (WFNS) grade (odds ratio 3.86 / 4.67 ; p < 0.0001 / p < 0.0001) and age (odds ratio 1.06 / 1.10 ; p = 0.0030 / p < 0.0001) in our multivariate analysis (binary logistic regression model). CONCLUSIONS: In summary, decompressive craniectomy, sepsis and hydrocephalus significantly influence the outcome and occurrence of death after aneurysmal SAH.
Assuntos
Craniotomia/métodos , Cuidados Críticos/métodos , Hemorragia Subaracnóidea/complicações , Hemorragia Subaracnóidea/cirurgia , Resultado do Tratamento , Idoso , Craniotomia/mortalidade , Descompressão Cirúrgica/métodos , Descompressão Cirúrgica/mortalidade , Feminino , Humanos , Hidrocefalia/etiologia , Hidrocefalia/mortalidade , Masculino , Pessoa de Meia-Idade , Sepse/etiologia , Sepse/mortalidade , Hemorragia Subaracnóidea/mortalidadeRESUMO
We report a case of an unusual spontaneous obliteration of a spinal dural arteriovenous fistula after diagnosis confirmation through spinal angiography. To our knowledge, there are only two previously documented cases of spontaneous disappearance of non-traumatic spinal dural arteriovenous fistulas.
Assuntos
Fístula Arteriovenosa , Malformações Vasculares do Sistema Nervoso Central , Angiografia , Malformações Vasculares do Sistema Nervoso Central/diagnóstico por imagem , Humanos , Coluna VertebralRESUMO
BACKGROUND: An unsettled controversy over the appropriate surgical approach in cases of cervical radiculopathy caused by degenerative vertebrae and intervertebral discs is still present. The purpose of this study is to examine the efficacy of microsurgical posterior foraminotomy in the treatment of cervical radiculopathy and to find out whether the underlying pathology (soft disc herniation/spondylosis) is of value in predicting long-term outcome after this procedure. METHODS: Patients, who underwent posterior cervical foraminotomy (PCF) at our department between 2006 and 2013 for unilateral mono-segmental lateral soft disc herniation, or spondylosis, or both, were enrolled in this study. Demographic, clinical and surgical data were retrospectively reviewed. The patients were subsequently interviewed by telephone to identify their long-term outcome. The clinical outcomes were evaluated using Odom's criteria. Descriptive statistics were frequencies and percentage of occurrence for categorical variables and mean and range for continuous variables. RESULTS: One hundred eighty-one patients were included in this study, with a median follow-up of 58 months (mean 43 months, range 12-96 months). The overall re-operation rate was 7.2% (13 patients); 11 patients (6%) for recurrent root symptoms due to recurrent disc herniation (six patients, 3.3%) and re-stenosis (five patients, 2.8%), one patient (0.55%) for wound infection and one patient (0.55%) for postoperative haematoma. Among the eleven patients who underwent re-operation for recurrent root symptoms there was one patient who additionally had persistent cerebrospinal fluid leak and superficial posterior wound infection. There was no significant difference between lateral soft disc herniation and spondylosis in term of re-operation rate. At discharge, excellent or good outcome was achieved in 89% of patients; the long-term success rate was 97.2% using Odom's criteria. CONCLUSION: Microsurgical PCF is an effective technique for treating lateral spinal root compression. Proper patient selection is obligatory to achieve the best results.
Assuntos
Vértebras Cervicais/cirurgia , Discotomia/métodos , Microcirurgia/métodos , Radiculopatia/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Seguimentos , Humanos , Degeneração do Disco Intervertebral/cirurgia , Deslocamento do Disco Intervertebral/cirurgia , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/terapia , Recidiva , Reoperação/estatística & dados numéricos , Estudos Retrospectivos , Doenças da Coluna Vertebral/cirurgia , Raízes Nervosas Espinhais/cirurgia , Espondilose/cirurgia , Infecção da Ferida Cirúrgica/epidemiologia , Infecção da Ferida Cirúrgica/terapia , Resultado do Tratamento , Adulto JovemRESUMO
Deep learning-based methods have demonstrated high classification performance in the detection of cardiovascular diseases from electrocardiograms (ECGs). However, their blackbox character and the associated lack of interpretability limit their clinical applicability. To overcome existing limitations, we present a novel deep learning architecture for interpretable ECG analysis (xECGArch). For the first time, short- and long-term features are analyzed by two independent convolutional neural networks (CNNs) and combined into an ensemble, which is extended by methods of explainable artificial intelligence (xAI) to whiten the blackbox. To demonstrate the trustworthiness of xECGArch, perturbation analysis was used to compare 13 different xAI methods. We parameterized xECGArch for atrial fibrillation (AF) detection using four public ECG databases ( n = 9854 ECGs) and achieved an F1 score of 95.43% in AF versus non-AF classification on an unseen ECG test dataset. A systematic comparison of xAI methods showed that deep Taylor decomposition provided the most trustworthy explanations ( + 24 % compared to the second-best approach). xECGArch can account for short- and long-term features corresponding to clinical features of morphology and rhythm, respectively. Further research will focus on the relationship between xECGArch features and clinical features, which may help in medical applications for diagnosis and therapy.
Assuntos
Fibrilação Atrial , Aprendizado Profundo , Eletrocardiografia , Redes Neurais de Computação , Eletrocardiografia/métodos , Humanos , Fibrilação Atrial/diagnóstico , Fibrilação Atrial/fisiopatologia , Bases de Dados Factuais , Inteligência Artificial , AlgoritmosRESUMO
Robotic platforms for chemistry are developing rapidly but most systems are not currently able to adapt to changing circumstances in real-time. We present a dynamically programmable system capable of making, optimizing, and discovering new molecules which utilizes seven sensors that continuously monitor the reaction. By developing a dynamic programming language, we demonstrate the 10-fold scale-up of a highly exothermic oxidation reaction, end point detection, as well as detecting critical hardware failures. We also show how the use of in-line spectroscopy such as HPLC, Raman, and NMR can be used for closed-loop optimization of reactions, exemplified using Van Leusen oxazole synthesis, a four-component Ugi condensation and manganese-catalysed epoxidation reactions, as well as two previously unreported reactions, discovered from a selected chemical space, providing up to 50% yield improvement over 25-50 iterations. Finally, we demonstrate an experimental pipeline to explore a trifluoromethylations reaction space, that discovers new molecules.
RESUMO
The HMG-domain transcription factor Sox10 is expressed throughout oligodendrocyte development and is an important component of the transcriptional regulatory network in these myelin-forming CNS glia. Of the known Sox10 regulatory regions, only the evolutionary conserved U2 enhancer in the distal 5'-flank of the Sox10 gene exhibits oligodendroglial activity. We found that U2 was active in oligodendrocyte precursors, but not in mature oligodendrocytes. U2 activity also did not mediate the initial Sox10 induction after specification arguing that Sox10 expression during oligodendroglial development depends on the activity of multiple regulatory regions. The oligodendroglial bHLH transcription factor Olig2, but not the closely related Olig1 efficiently activated the U2 enhancer. Olig2 bound U2 directly at several sites including a highly conserved one in the U2 core. Inactivation of this site abolished the oligodendroglial activity of U2 in vivo. In contrast to Olig2, the homeodomain transcription factor Nkx6.2 repressed U2 activity. Repression may involve recruitment of Nkx6.2 to U2 and inactivation of Olig2 and other activators by protein-protein interactions. Considering the selective expression of Nkx6.2 at the time of specification and in differentiated oligodendrocytes, Nkx6.2 may be involved in limiting U2 activity to the precursor stage during oligodendrocyte development.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Elementos Facilitadores Genéticos , Células-Tronco Neurais/metabolismo , Oligodendroglia/metabolismo , Fatores de Transcrição SOXE/genética , Animais , Sequência de Bases , Sítios de Ligação , Linhagem Celular Tumoral , Sequência Conservada , Evolução Molecular , Células HEK293 , Proteínas de Homeodomínio/metabolismo , Humanos , Camundongos , Camundongos Transgênicos , Ratos , Proteínas Repressoras/metabolismo , Medula Espinal/citologia , Medula Espinal/embriologia , Medula Espinal/crescimento & desenvolvimento , Fatores de Transcrição/metabolismoRESUMO
Human malignant brain tumors such as gliomas are devastating due to the induction of cerebral edema and neurodegeneration. A major contributor to glioma-induced neurodegeneration has been identified as glutamate. Glutamate promotes cell growth and proliferation in variety of tumor types. Intriguently, glutamate is also an excitatory neurotransmitter and evokes neuronal cell death at high concentrations. Even though glutamate signaling at the receptor and its downstream effectors has been extensively investigated at the molecular level, there has been little insight into how glutamate enters the tumor microenvironment and impacts on metabolic equilibration until recently. Surprisingly, the 12 transmembrane spanning tranporter xCT (SLC7A11) appeared to be a major player in this process, mediating glutamate secretion and ferroptosis. Also, PPARγ is associated with ferroptosis in neurodegeneration, thereby destroying neurons and causing brain swelling. Although these data are intriguing, tumor-associated edema has so far been quoted as of vasogenic origin. Hence, glutamate and PPARγ biology in the process of glioma-induced brain swelling is conceptually challenging. By inhibiting xCT transporter or AMPA receptors in vivo, brain swelling and peritumoral alterations can be mitigated. This review sheds light on the role of glutamate in brain tumors presenting the conceptual challenge that xCT disruption causes ferroptosis activation in malignant brain tumors. Thus, interfering with glutamate takes center stage in forming the basis of a metabolic equilibration approach.
RESUMO
Dihydrofolate reductase (DHFR) is a key enzyme involved in the folate pathway that has been heavily targeted for the development of therapeutics against cancer and bacterial and protozoa infections amongst others. Despite being an essential enzyme for Mycobacterium tuberculosis (Mtb) viability, DHFR remains an underexploited target for tuberculosis (TB) treatment. Herein, we report the preparation and evaluation of a series of compounds against Mtb DHFR (MtbDHFR). The compounds have been designed using a merging strategy of traditional pyrimidine-based antifolates with a previously discovered unique fragment hit against MtbDHFR. In this series, four compounds displayed a high affinity against MtbDHFR, with sub-micromolar affinities. Additionally, we determined the binding mode of six of the best compounds using protein crystallography, which revealed occupation of an underutilised region of the active site.
RESUMO
Co-extrusion is commonly used to produce polymer multilayer products with different materials tailoring the property profiles. Adhesion between the individual layers is crucial to the overall performance of the final structure. Layer adhesion is determined by the compatibility of the polymers at the interface and their interaction forces, causing for example the formation of adhesive or chemical bonds or an interdiffusion layer. Additionally, the processing conditions, such as temperature, residence time, cooling rate, and interfacial shear stress, have a major influence on the interactions and hence resulting layer adhesion. Influences of temperature and residence time are already quite well studied, but influence of shear load on the formation of an adhesion layer is less explored and controversially discussed in existing literature. In this work, we investigated the influence of different processing conditions causing various shear loads on layer adhesion for a two-layer co-extruded polymer sheet using a polypropylene and polypropylene talc compound system. Therefore, we varied the flow rates and the flow geometry of the die. Under specific conditions interfacial flow instabilities are triggered that form micro layers in the transition regime between the two layers causing a major increase in layer adhesion. This structure was analyzed using confocal Raman microscopy. Making use of these interfacial flow instabilities in a controlled way enables completely new opportunities and potentials for multi-layer products.
RESUMO
Study Objective: Application of high concentrations of oxygen to increase oxygen partial pressure (pO2) is the most important treatment for patients with carbon monoxide intoxication or divers with suspected decompression illness. The aim of this study was to evaluate the oxygenation performance of various non-invasive oxygen systems. Methods: The effect of different oxygen systems on arterial pO2, pCO2 and pH and their subjective comfort was evaluated in 30 healthy participants. Eight devices were included: nasal cannula, non-rebreather mask, AirLife Open mask, Flow-Safe II CPAP device, SuperNO2VA nasal PAP device, all operated with 15 L/min constant flow oxygen; nasal high-flow (50 L/min flow, 1.0 FiO2), non-invasive positive pressure ventilation (NPPV, 12 PEEP, 4 ASB, 1.0 FiO2) and a standard diving regulator (operated with pure oxygen). Results: Diving regulator, SuperNO2VA, nasal high-flow and NPPV achieved mean arterial pO2 concentrations between 538 and 556 mm Hg within 5 minutes. The AirLife Open mask, the nasal cannula and the non-rebreather mask achieved concentrations of 348-451 mm Hg and the Flow-Safe II device 270 mm Hg. Except for the AirLife open mask, pCO2 decreased and pH increased with all devices. The highest pH values were observed with NPPV, diving regulator, Flow-Safe II and nasal high-flow but apparent hyperventilation was uncommon. The AirLife Open and the non-rebreather mask were the most comfortable, the SuperNO2VA and the nasal cannula the most uncomfortable devices. Conclusion: A standard diving regulator and the SuperNO2VA device were equally effective in providing highest physiologically possible pO2 as compared to nasal high-flow and NPPV.
RESUMO
Objective. After skin flap transplants, perfusion strength monitoring is essential for the early detection of tissue perfusion disorders and thus to ensure the survival of skin flaps. Camera-based photoplethysmography (cbPPG) is a non-contact measurement method, using video cameras and ambient light, which provides spatially resolved information about tissue perfusion. It has not been researched yet whether the measurement depth of cbPPG, which is limited by the penetration depth of ambient light, is sufficient to reach pulsatile vessels and thus to measure the perfusion strength in regions that are relevant for skin flap transplants.Approach. We applied constant negative pressure (compared to ambient pressure) to the anterior thighs of 40 healthy subjects. Seven measurements (two before and five up to 90 min after the intervention) were acquired using an RGB video camera and photospectrometry simultaneously. We investigated the performance of different algorithmic approaches for perfusion strength assessment, including the signal-to-noise ratio (SNR), its logarithmic components logS and logN, amplitude maps, and the amplitude height of alternating and direct signal components.Main results. We found strong correlations of up tor= 0.694 (p< 0.001) between photospectrometric measurements and all cbPPG parameters except SNR when using the green color channel. The transfer of cbPPG signals to POS, CHROM, and O3C did not lead to systematic improvements. However, for direct signal components, the transformation to O3C led to correlations of up tor= 0.744 (p< 0.001) with photospectrometric measurements.Significance. Our results indicate that a camera-based perfusion strength assessment in tissue with deep-seated pulsatile vessels is possible.
Assuntos
Fotopletismografia , Transplantes , Estatura , Humanos , Perfusão , Coxa da PernaRESUMO
Despite huge potential, automation of synthetic chemistry has only made incremental progress over the past few decades. We present an automatically executable chemical reaction database of 100 molecules representative of the range of reactions found in contemporary organic synthesis. These reactions include transition metal-catalyzed coupling reactions, heterocycle formations, functional group interconversions, and multicomponent reactions. The chemical reaction codes or χDLs for the reactions have been stored in a database for version control, validation, collaboration, and data mining. Of these syntheses, more than 50 entries from the database have been downloaded and robotically run in seven modular chemputers with yields and purities comparable to those achieved by an expert chemist. We also demonstrate the automatic purification of a range of compounds using a chromatography module seamlessly coupled to the platform and programmed with the same language.
RESUMO
The explosion in the use of machine learning for automated chemical reaction optimization is gathering pace. However, the lack of a standard architecture that connects the concept of chemical transformations universally to software and hardware provides a barrier to using the results of these optimizations and could cause the loss of relevant data and prevent reactions from being reproducible or unexpected findings verifiable or explainable. In this Perspective, we describe how the development of the field of digital chemistry or chemputation, that is the universal code-enabled control of chemical reactions using a standard language and ontology, will remove these barriers allowing users to focus on the chemistry and plug in algorithms according to the problem space to be explored or unit function to be optimized. We describe a standard hardware (the chemical processing programming architecture-the ChemPU) to encompass all chemical synthesis, an approach which unifies all chemistry automation strategies, from solid-phase peptide synthesis, to HTE flow chemistry platforms, while at the same time establishing a publication standard so that researchers can exchange chemical code (χDL) to ensure reproducibility and interoperability. Not only can a vast range of different chemistries be plugged into the hardware, but the ever-expanding developments in software and algorithms can also be accommodated. These technologies, when combined will allow chemistry, or chemputation, to follow computation-that is the running of code across many different types of capable hardware to get the same result every time with a low error rate.
RESUMO
Little progress has been made in the long-term management of malignant brain tumors, leaving patients with glioblastoma, unfortunately, with a fatal prognosis. Glioblastoma remains the most aggressive primary brain cancer in adults. Similar to other cancers, glioblastoma undergoes a cellular metabolic reprogramming to form an oxidative tumor microenvironment, thereby fostering proliferation, angiogenesis and tumor cell survival. Latest investigations revealed that micronutrients, such as selenium, may have positive effects in glioblastoma treatment, providing promising chances regarding the current limitations in surgical treatment and radiochemotherapy outcomes. Selenium is an essential micronutrient with anti-oxidative and anti-cancer properties. There is additional evidence of Se deficiency in patients suffering from brain malignancies, which increases its importance as a therapeutic option for glioblastoma therapy. It is well known that selenium, through selenoproteins, modulates metabolic pathways and regulates redox homeostasis. Therefore, selenium impacts on the interaction in the tumor microenvironment between tumor cells, tumor-associated cells and immune cells. In this review we take a closer look at the current knowledge about the potential of selenium on glioblastoma, by focusing on brain edema, glioma-related angiogenesis, and cells in tumor microenvironment such as glioma-associated microglia/macrophages.
RESUMO
Co-extrusion is a widely used processing technique for combining various polymers with different properties into a tailored multilayer product. Individual melt streams are combined in a die to form the desired shape. Under certain conditions, interfacial flow instabilities are observed; however, fundamental knowledge about their onset and about critical conditions in science and industry is scarce. Since reliable identification of interfacial co-extrusion flow instabilities is essential for successful operation, this work presents in situ measurement approaches using a novel co-extrusion demonstrator die, which is fed by two separate melt streams that form a well-controlled two-layer co-extrusion polymer melt flow. An interchangeable cover allows installation of an optical coherence tomography (OCT) sensor and of an ultrasonic (US) measurement system, where the former requires an optical window and the latter good direct coupling with the cover for assessment of the flow situation. The feasibility of both approaches was proven for a material combination that is typically found in multilayer packaging applications. Based on the measurement signals, various parameters are proposed for distinguishing reliably between stable and unstable flow conditions in both measurement systems. The approaches presented are well suited to monitoring for and systematically investigating co-extrusion flow instabilities and, thus, contribute to improving the fundamental knowledge about instability onset and critical conditions.
RESUMO
Medulloblastoma is a common primary brain tumor in children but it is a rare cancer in adult patients. We reviewed the literature, searching PubMed for articles on this rare tumor entity, with a focus on tumor biology, advanced neurosurgical opportunities for safe tumor resection, and multimodal treatment options. Adult medulloblastoma occurs at a rate of 0.6 per one million people per year. There is a slight disparity between male and female patients, and patients with a fair skin tone are more likely to have a medulloblastoma. Patients present with cerebellar signs and signs of elevated intracranial pressure. Diagnostic efforts should consist of cerebral MRI and MRI of the spinal axis. Cerebrospinal fluid should be investigated to look for tumor dissemination. Medulloblastoma tumors can be classified as classic, desmoplastic, anaplastic, and large cell, according to the WHO tumor classification. Molecular subgroups include WNT, SHH, group 3, and group 4 tumors. Further molecular analyses suggest that there are several subgroups within the four existing subgroups, with significant differences in patient age, frequency of metastatic spread, and patient survival. As molecular markers have started to play an increasing role in determining treatment strategies and prognosis, their importance has increased rapidly. Treatment options include microsurgical tumor resection and radiotherapy and, in addition, chemotherapy that respects the tumor biology of individual patients offers targeted therapeutic approaches. For neurosurgeons, intraoperative imaging and tumor fluorescence may improve resection rates. Disseminated disease, residual tumor after surgery, lower radiation dose, and low Karnofsky performance status are all suggestive of a poor outcome. Extraneural spread occurs only in very few cases. The reported 5-year-survival rates range between 60% and 80% for all adult medulloblastoma patients.
Assuntos
Neoplasias Encefálicas/cirurgia , Meduloblastoma/cirurgia , Adulto , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/patologia , Humanos , Meduloblastoma/genética , Meduloblastoma/patologia , PrognósticoRESUMO
BACKGROUND: Test anxiety is a common phenomenon at universities with the potential to impair academic performance and student well-being. This study was conducted to investigate prevalence, characteristics, and development of the test anxiety categories "emotionality", "worry", "interference", and "lack of confidence" among first year medical students. METHODS: Overall, 625 freshman medical students were enrolled. They were recruited from the participants of a first semester anatomy course. The participants were assessed four times with a validated psychological test anxiety questionnaire (Prüfungsangstfragebogen, PAF). The first assessment was conducted at the commencement of the first semester. All further assessments were performed two days prior to each of three mandatory oral anatomy tests in the course of one half year. Prevalence rates as well as mean global and subscale scores of the test anxiety dimensions "emotionality", "worry", "interference" and "lack of confidence" were determined and compared between assessments. RESULTS: Approximately 50% of the study participants showed pronounced test anxiety in at least one dimension over the observation period. Only about 10% were considered test anxiety-positive according to the global PAF scale. Worry showed the highest (up to 48%) and interference the lowest (≈5%) prevalence rates. Emotionality had a stable prevalence of approximately 17%, whereas lack of confidence showed a rising trend over the observation period from 15.2% up to 24.0%. CONCLUSION: Test anxiety is substantially more prevalent among medical students as commonly reported and deserves more detailed, dimension-specific exploration in future. Especially worry and lack of confidence give reason for concern, demanding further investigation.