bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of 3 radiographic scales for the prediction of delayed ischemia and prognosis following subarachnoid hemorrhage
Authors: Kramer Andreas H. , Hehir Michael , Nathan Bart , Gress Darryl , Dumont Aaron S. , Kassell Neal F. , Bleck Thomas P.
Published: July 2008

Object

Delayed cerebral ischemia is a major cause of morbidity and death following aneurysmal subarachnoid hemorrhage and requires timely intervention for a successful outcome to be achieved. In this study the investigators compared the commonly used Fisher scale with 2 newer radiographic scales for the prediction of vasospasm, delayed infarction, and poor outcome.

Methods

This was a single-center, retrospective cohort study involving 271 consecutive patients with a ruptured cerebral aneurysm. Without knowledge of subsequent events, admission CT scans were each assigned scores by using 3 different grading schemes: the Fisher, modified Fisher, and Claassen scales. For each of the scales, the relationship between an increasing score and the risk of later complications was assessed in univariate and multiple logistic regression analyses.

Results

With the Fisher scale, the risk of complications was relatively high when the score was 3, but not for other scores. In contrast, using the other scales, there was a more linear relationship between a rising score and the frequency of complications. This was particularly true for the modified Fisher scale, in which each stepwise increase was associated with an escalating risk of vasospasm, delayed infarction, and poor prognosis. Kappa scores measuring interobserver variability among 4 CT readers were also slightly better with the newer scales.

Conclusions

Although the modified Fisher and Claassen scales have yet to be prospectively validated, the authors' findings suggest that the clinical performance of these systems is superior to that of the Fisher scale.
Bevacizumab and irinotecan therapy in glioblastoma multiforme: a series of 13 cases
Authors: Ali Sheikh A. , McHayleh Wassim M. , Ahmad Asif , Sehgal Rajesh , Braffet Molly , Rahman Mohsin , Bejjani Ghassan , Friedland David M.
Published: July 2008

Object

Endothelial proliferation has been recognized as a marker of high-grade or aggressive glioma. Bevacizumab is a humanized immunoglobulin G1 monoclonal antibody to vascular endothelial growth factor that has been shown to have activity in malignant gliomas when combined with irinotecan. The authors report on a case series of 13 patients with recurrent heavily pretreated malignant glioma that was treated with the combination of bevacizumab and irinotecan.

Methods

Standard therapy with primary resection followed by adjuvant chemotherapy and radiation had failed in all patients. The median number of therapies applied, including initial surgery, was 5 (range 3–7 therapies). Nine patients were started on bevacizumab at a dose of 5 mg/kg every 2 weeks. Four patients received bevacizumab at a dose of 10 mg/kg; irinotecan was given at a dose of 125 mg/kg every week for 3 weeks.

Results

Of the 13 treated patients, 10 (77%) had a radiologically demonstrated partial response and 3 (23%) had stable disease. Six patients (46%) had a clinical response. The median time to disease progression while on treatment was 24 weeks. The median overall survival was 27 weeks. The disease progressed in 8 patients, despite an initial response. Five patients are still responding to therapy. Six of the 8 patients whose disease progressed have died. Bevacizumab was discontinued in 2 patients because of nonfatal intracranial bleeding.

Conclusions

The combination of bevacizumab and irinotecan is safe and has excellent activity even in this relapsed, heavily pretreated population of patients with high-grade malignant glioma, most of whom would not be candidates for clinical trials.
Progressive peritumoral edema defining the optic fibers and resulting in reversible visual loss
Authors: Baggenstos Martin , Chew Emily , Butman John A. , Oldfield Edward H. , Lonser Russell R.
Published: July 2008

Hemangioblastomas are frequently associated with peritumoral edema caused by extravasation of plasma ultrafiltrate through permeable neoplastic vessels. The authors report the clinical and imaging findings in a 62-year-old man with von Hippel–Lindau disease who presented with rapid (within 24 hours) loss of color vision and nearcomplete loss of left eye vision (acuity too poor to test). Serial MR imaging demonstrated a stable vascular tumor in the medioinferior aspect of the left optic nerve, associated with progressive edema extending from the nerve through to the bilateral optic radiations. Complete resection of the lesion was performed via an extended transsphenoidal approach, and histological examination confirmed the lesion was a hemangioblastoma. Postoperatively, the patient recovered color vision and had improvement in visual acuity (20/320). Serial imaging in this unique case captured the progressive extravasation of peritumoral edema that tracked and defined the parallel white matter tracts of first- and second-order neurons of the optic system, causing vision loss. Tumor resection led to resolution of the edema and improvement in visual function.
Craniospinal dissemination in teratocarcinosarcoma
Authors: Tchoyoson Lim C. C. , Thiagarajan Anuradha , Sim Chee Seng , Khoo Mark L. , Shakespeare Thomas P. , Ng Ivan
Published: July 2008

There have been fewer than 60 cases of malignant teratocarcinosarcoma (TCS) described in the literature, usually arising in the nose and paranasal sinuses. The authors report on a patient who presented with neurological symptoms caused by a frontal lobe TCS, and in whom widespread spinal tumor dissemination developed. In rare cases, TCSs can occur with a predominantly cranial and neurological presentation and spread to the spinal canal.
Do Statins Prevent or Promote Cancer?
Authors: Goldstein Mark R. , Mascitelli Luca , Pezzetta Francesca
Published: July 2008

In their commentary, Drs. Takahashi and Nishibori 1 discuss putative antitumour effects of statins. [...]
Successful laparoscopic splenectomy after living-donor liver transplantation for thrombocytopenia caused by antiviral therapy
Authors: Kato Hiroyuki
Published: July 2008

Laparoscopic surgery is the main treatment method for patients with gastrointestinal malignant tumors. Although laparoscopic surgery is minimally invasive, its tool stimulation and pneumoperitoneum pressure often cause strong stress reactions in patients. On the other hand, gastrointestinal surgery can cause stronger pain in patients, compared to other surgeries. Transversus abdominis plane block (TAPB) can effectively inhibit the transmission of nerve impulses caused by surgical stimulation, alleviate patient pain, and thus alleviate stress reactions. Remazolam is an acting, safe, and effective sedative, which has little effect on hemodynamics and is suitable for most patients. TAPB combined with remazolam can reduce the dosage of total anesthetic drugs, reduce adverse reactions, reduce stress reactions, and facilitate the rapid postoperative recovery of patients.
Adaptive actuator/component fault compensation for nonlinear systems
Authors: Zhang Yingwei , Qin S. Joe
Published: July 2008

An active fault compensation control law is developed for a class of nonlinear systems to guarantee closed‐loop stability in the presence of faults, based on a neural network representation of the fault dynamics. Changes in the systems due to faults are modeled as unknown nonlinear functions. The closed‐loop stability of the robust fault compensation scheme is established in the Lyapunov's sense. The nonlinear fault function is represented by a neural network, then an adaptive corrective control law is formulated to ensure system stability. The main contributions presented are the design of the fault compensation and corrective control law of nonlinear systems with unmatched uncertainties and the stability analysis of the closed‐loop systems in the presence of fault modeling errors. Applications of the proposed design indicate that the fault compensation control law is effective for a nonlinear fermentation process. © 2008 American Institute of Chemical Engineers AIChE J, 2008
Optimal design of batch‐storage network under joint uncertainties
Authors: Yi Gyeongbeom
Published: July 2008

This study sought to find analytic solutions to the problem of determining the optimal capacity of a batch‐storage network to meet demand for finished products in a system undergoing joint random variations of operating time and batch quantity. The raw material purchasing flow and final product demand flow are susceptible to joint random variations in the order cycle time and batch size. The production processes also have joint random variations in production cycle time and product quantity. Waste regeneration or disposal processes are included into the network to treat the spoiled materials from failed batches. The objective function of the optimization is minimizing the expected total cost, which is composed of setup and inventory holding costs as well as the capital costs of constructing processes and storage units. A production and inventory method, the PSW (periodic square wave) model, provides a unique graphical method to find the upper/lower bounds and average of random flows, which are used to construct terms of the objective function and constraints of the optimization model. The advantage of this model is that it provides a set of simple analytic solutions while also maintaining a realistic description of the random material flows between processes and storage units; as a consequence of these analytic solutions, the computation burden is significantly reduced. The proposed method has the potential to rapidly provide very useful data on base investment decisions during the early plant design stage. It should be particularly useful when these decisions must be made in a highly uncertain business environment. © 2008 American Institute of Chemical Engineers AIChE J, 2008
Genetic Polymorphisms of IL‐1A, IL‐1B, IL‐1RN, NFKB1, FAS, and FASL, and Risk of Silicosis in a Chinese Occupational Population
Authors: Wu Fen , Xia Zhaolin , Qu Yabin , Tang Yunxia , Cao Duozhi , Sun Pin , Christiani David C.
Published: July 2008

Objective

To test whether polymorphisms in IL‐1, NF‐KB, FAS, and FASL genes are associated with risk of silicosis.

Methods

A case–control study was conducted with 183 silicosis patients and 111 silica‐exposed miners who were frequency‐matched by age, dust exposure duration, work location, and type of work. Genotype analysis was performed on genomic DNA, using a PCR‐RFLP assay.

Results

Individuals carrying the NFKB1 ins/del genotype had a decreased risk of silicosis (adjusted OR = 0.57, 95% CI = 0.32–0.998, P = 0.049) compared with subjects carrying the ins/ins genotype and individuals with the FAS‐1377AA homozygote had a decreased risk of silicosis compared with those with the −1377GG genotype (adjusted OR = 0.42, 95% CI = 0.19–0.93, P = 0.03). The analysis of haplotypes of polymorphisms in FAS showed that there was a 2.71‐fold (OR = 2.71, 95% CI = 1.22–6.03, P = 0.011) increased risk of silicosis for subjects with alleles of FAS‐1377G and FAS‐670G, compared with those carrying alleles of FAS‐1377G and FAS‐670A.

Conclusion

Although the polymorphisms at NFKB1, FAS‐1377, and extended haplotype FAS‐1377G/‐670G may play a role in the development of silicosis in the Chinese population, our findings should be verified by larger studies with >1 case/control ratio. Am. J. Ind. Med. 51:843‐851, 2008. © 2008 Wiley‐Liss, Inc.
Bigger groups have fewer parasites and similar cortisol levels: a multi‐group analysis in red colobus monkeys
Authors: Snaith Tamaini V. , Chapman Colin A. , Rothman Jessica M. , Wasserman Michael D.
Published: July 2008

If stress and disease impose fitness costs, and if those costs vary as a function of group size, then stress and disease should exert selection pressures on group size. We assessed the relationships between group size, stress, and parasite infections across nine groups of red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda. We used fecal cortisol as a measure of physiological stress and examined fecal samples to assess the prevalence and intensity of gastrointestinal helminth infections. We also examined the effect of behaviors that could potentially reduce parasite transmission (e.g., increasing group spread and reducing social interactions). We found that cortisol was not significantly related to group size, but parasite prevalence was negatively related to group size and group spread. The observed increase in group spread could have reduced the rate of parasite transmission in larger groups; however, it is not clear whether this was a density‐dependent behavioral counter‐strategy to infection or a response to food competition that also reduced parasite transmission. The results do not support the suggestion that gastrointestinal parasitism or stress directly imposed group‐size‐related fitness costs, and we cannot conclude that they are among the mechanisms limiting group size in red colobus monkeys. Am. J. Primatol. 70:1072–1080, 2008. © 2008 Wiley–Liss, Inc.
Die asymmetrische Aminokatalyse – Goldrausch in der organischen Chemie
Authors: Melchiorre Paolo , Marigo Mauro , Carlone Armando , Bartoli Giuseppe
Published: July 2008

Die Katalyse mit chiralen sekundären Aminen (asymmetrische Aminokatalyse) ist ein leistungsfähiges Verfahren zur chemo‐ und enantioselektiven Funktionalisierung von Carbonylverbindungen. Allein in den letzten acht Jahren wuchs dieses Feld zu einem eigenständigen Teilgebiet der Synthesechemie heran, dessen Ziel es sein muss, jede beliebige chirale Verbindung effizient, rasch und stereoselektiv herzustellen. Möglich wurde dieser Fortschritt durch hochqualifizierte Forschung und einen eindrucksvollen wissenschaftlichen Wettbewerb. Dieser Aufsatz beschreibt den “Goldrausch der asymmetrischen Aminokatalyse” und weist auf die Meilensteine dieser Entwicklung hin. Wie auf allen Wissenschaftsgebieten gilt letztlich: Der Fortschritt hängt vom Menschen ab.
Removal of o‐xylene from off‐gas by a combination of bioreactor and adsorption
Authors: Li L. , Wang S. B. , Feng Q. C. , Liu J. X.
Published: July 2008

Biofiltration is an effective technology for the treatment of gaseous waste. However, a biofiltration system needs a bioreactor of large volume and it is slow to adapt to fluctuating concentrations in waste gas. To overcome these disadvantages, a bench‐scale system integrating a biofilter and an adsorption unit for the treatment of gases containing o‐xylene was investigated in this study. The adsorption unit was packed with granule active carbon (GAC). The results showed that 90% of o‐xylene could be removed in the biofilter at an inlet concentration below 900 mg/m3. The maximum elimination capacity was 80 g/m3h when the o‐xylene loading rate was less than 100 g/m3h. High o‐xylene concentration in inlet gas resulted in an overload of the biofilter. Using the adsorption unit, the outlet concentration of o‐xylene could be reduced significantly. The surface properties of GAC and the factors affecting the adsorption performance were investigated, and GAC regeneration method was also evaluated. The combination of adsorption and microbial processes not only led to a high and stable efficiency of o‐xylene removal, but also improved the capacity of resisting the shock loads. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Learning to be a doctor while learning anatomy!
Authors: Netterstrøm Ingeborg , Kayser Lars
Published: July 2008

This article presents results from a longitudinal study following a cohort of medical students. Semistructured interviews are conducted every year, in which the students tell about their experiences learning medicine, their daily life, and their social activities in relation to university. The aim of the study is to analyze how medical students develop their professional competencies, values, and attitudes. This article focuses on the medical student's professional development in relation to the process of studying and learning anatomy. We analyze interviews conducted while the students are in their third and fifth semester. Anatomy plays a significant role in the medical student's educational process, on both a cognitive and emotional level. It seems that students in learning the subject matter adapt to fundamental values in the medical profession and are thus transformed into real medical students, sharing a unique experience. The implications for curricular development and professionalism are discussed, and this article argues that the issue of professionalism must be addressed in the educational process in the preclinical years and in relation to the basic sciences. Anat Sci Ed 2008. © 2008 American Association of Anatomists.
Body painting as a tool in clinical anatomy teaching
Authors: McMenamin Paul G.
Published: July 2008

The teaching of human anatomy has had to respond to significant changes in medical curricula, and it behooves anatomists to devise alternative strategies to effectively facilitate learning of the discipline by medical students in an integrated, applied, relevant, and contextual framework. In many medical schools, the lack of cadaver dissection as the primary method of learning is driving changes to more varied and novel learning and teaching methodologies. The present article describes the introduction and evaluation of a range of body painting exercises in a medical curriculum. Body painting was introduced into integrated clinical skills teaching sessions which included clinically important aspects of respiratory system, musculoskeletal system, and topics in regional anatomy including head and neck. Nontoxic body paints, easels, a mixture of brush sizes, and anatomical images were supplied. Students were allowed between 20 and 40 min to complete body painting tasks, in which they were encouraged to alternate between painting and acting as a model. Students were encouraged to use life‐like rendering and coloration where appropriate. Evaluation of these sessions was performed at the end of the semester as part of a larger evaluation process. The kinesthetic nature and active participation together with the powerful visual images of underlying anatomy appear to contribute to the value of body painting as a teaching exercise. In addition, it may have the added bonus of helping break down apprehension regarding peer–peer examination. Some practical advice on introducing this method of teaching in medical curricula based on the outcomes of the evaluation is given. On the basis of our experience and student feedback, we strongly advocate the use of body painting as an adjunct to surface anatomy and clinical skills teaching classes. Anat Sci Ed 2008. © 2008 American Association of Anatomists.
How much anatomy is enough?
Authors: Bergman Esther M. , Prince Katinka J.A.H. , Drukker Jan , van der Vleuten Cees P.M. , Scherpbier Albert J.J.A.
Published: July 2008

Innovations in undergraduate medical education, such as integration of disciplines and problem based learning, have given rise to concerns about students' knowledge of anatomy. This article originated from several studies investigating the knowledge of anatomy of students at the eight Dutch medical schools. The studies showed that undergraduate students uniformly perceived deficiencies in their anatomical knowledge when they started clinical training regardless of their school's didactic approach. A study assessing students' actual knowledge of clinical anatomy revealed no relationship between students' knowledge and the school's didactic approach. Test failure rates based on absolute standards set by different groups of experts were indicative of unsatisfactory levels of anatomical knowledge, although standards differed markedly between the groups of experts. Good test performance by students seems to be related to total teaching time for anatomy, teaching in clinical context, and revisiting anatomy topics in the course of the curriculum. These factors appeared to outweigh the effects of disciplinary integration orwhether the curriculum was problem‐based or traditional. Anat Sci Ed 2008. © 2008 American Association of Anatomists.
Effect of the use of instructional anatomy videos on student performance
Authors: Saxena Varun , Natarajan Pradeep , O'Sullivan Patricia S. , Jain Sharad
Published: July 2008

Medical schools have reduced the time allotted to anatomy instruction. Consequently, schools engage students in more independent settings using information and communication technologies (ICT). There has been limited research in the use of video aids, a type of ICT, to enhance anatomy examination performance. The objective of this study is to describe the design, usage, and effect on examination performance of eight locally developed instructional anatomy videos. First‐year UCSF medical students (n = 141) had access to the videos. They reported their video usage, reason for usage, and satisfaction. The prior year students (n = 141) served as a historical control group. Anatomy and radiology examination performance was compared between groups while controlling for prior performance. The students with and without access to the videos did not differ in examination performance. Sixty‐one (43%) students in the experimental group responded to the survey. Of these, 79% reported using at least one video, viewing an average of 4.75 of the eight videos. They watched 3.27 (SD = 1.57, range 1–5) of the five anatomy videos and 1.48 (SD = 1.35; range 0–3) of the three radiology videos. In a regression analysis controlling for age and MCAT scores, using the anatomy videos at least once improved anatomy examination performance by 3.4% (P‐value = 0.007). There was no relationship between radiology video usage and radiology exam score. Video resource availability did not enhance student performance in anatomy and radiology. However, when analyzing performance for those whom we knew level of video use, there was a statistically different and higher anatomy achievement. Anat Sci Ed, 2008. © 2008 American Association of Anatomists.
Das Angriffspotential sulfatsaurer Böden in Norddeutschland
Authors: Gröger Jens , Hamer Kay , Schulz Horst D.
Published: July 2008

In Norddeutschland treten verbreitet Moor‐ und Marschböden mit hohen Pyritgehalten auf, die bei der Oxidation große Mengen an Säure und Sulfat freisetzen können. Diese relativ jungen Bildungen (< 10.000 Jahre) werden als potentiell sulfatsaure Böden bezeichnet. Diese Böden stellen ein bedeutendes Gefährdungspotential für Betonbauteile dar, die im Kontakt zu diesen Böden stehen und finden in bisherigen Regelungen nur wenig Beachtung. Die Verbreitung ist häufig fleckenhaft und nicht an Gesteinsformationen gebunden, was die Identifizierung und Kartierung dieser Böden erschwert. Die oft niedrige Säureneutralisationskapazität der Böden bei gleichzeitig hohen Pyritgehalten führt bei der Oxidation zu einem kombinierten Säure‐ und Sulfatangriff auf in den Boden eingebrachte Betonteile.
Pilotprojekt der neuen Normengeneration im Kühlturmbau – Die Naturzugkühltürme von BoA 2 & 3 in Neurath
Authors: Wörmann Ralf , Haupt Ralf , Ohlmann Uwe
Published: July 2008

Seit Anfang 2006 errichtet RWE Power am Standort Neurath zwei Braunkohlekraftwerksblöcke mit optimierter Anlagentechnik – kurz BoA. Nach der Inbetriebnahme von BoA1 in Niederaußem im Jahr 2003 werden sie die Blöcke 2 und 3 dieser modernsten Bauart sein. Zu den auffälligsten Bauwerken der neuen Kraftwerksblöcke gehören die beiden 173 m hohen Kühltürme. In diesem Beitrag wird ein Überblick über Planung und Ausführung der beiden Türme gegeben. Dabei erfolgt die Planung erstmals im Kühlturmbau auf Basis der neuen Normengeneration und der neuen Fassung der VGB‐Richtlinie “Bautechnik bei Kühltürmen” aus dem Jahr 2005.
Zum nachträglichen Kürzen und Verankern von glatten Spanngliedern im Verbund
Authors: Novák Balthasar , Sasmal Saptarshi , Röhm Constanze , Schnabel Thomas , Becker Reinhard
Published: July 2008

Die Stuttgarter Straßenbahnen AG (SSB) plant derzeit zusammen mit der Stadt Stuttgart den Einbau eines Aufzugs in einer unterirdischen Straßenbahnhaltestelle. Zur Durchführung dieses Vorhabens wird es erforderlich, vorhandene Spannbetonträger unter einer dreispurigen Straße zu kürzen. Die Besonderheit ist, dass es sich hierbei um glatten Spannstahl mit nachträglichem Verbund handelt, bei dem eine Verankerung über Verbund nicht üblich ist. Hier galt es also, zunächst das Verbundverhalten zu studieren; alternativ wurde eine neue Spanngliedverankerung entwickelt. Neben Laborversuchen zum Verbundverhalten wurde ein Spannglied des bestehenden Tragwerks in Feldmitte durchtrennt, das vorher mit mehreren Dehnmessstreifen (DMS) im Verankerungsbereich versehen wurde. So konnte in einer Langzeitstudie die Entwicklung der Dehnungen sowohl unter laufendem Verkehr als auch unter definierter Belastung (48t‐Kran) verfolgt werden, und es konnte gezeigt werden, dass auch unter nicht vorwiegend ruhender Beanspruchung allein über den Verbund die Einleitung der Vorspannung sichergestellt werden kann. Mit den aus den durchgeführten push‐in Versuchen erzielten Ergebnissen der Verbundeigenschaften konnten die Ergebnisse des Feldversuchs sehr gut prognostiziert werden. Weiterhin wurden Laborversuche für das neue Verankerungselement unter statischer und nicht vorwiegend ruhender Belastung durchgeführt. Mit den Ergebnissen konnte die Tauglichkeit für den geplanten Einsatz nachgewiesen werden. Die Untersuchungen wurden durch numerische Untersuchungen zur Ermittlung der Beanspruchung im Verankerungsbereich abgerundet.
Besonderheiten bei der Beurteilung des Ankündigungsverhaltens von Spannbetonbrücken nach dem Riss‐vor‐Bruch‐Kriterium
Authors: Albertin‐Hummel Ursula , Brandt Bernd
Published: July 2008

Brücken ohne ausreichendes Ankündigungsverhalten hinsichtlich eines Versagens nach dem Riss‐vor‐Bruch‐Kriterium bergen ein Versagensrisiko. Dieses Risiko ist besonders groß, wenn in den betreffenden Brücken ein gefährdeter Spannstahl eingebaut ist, der zur Spannungsrisskorrosion neigt. Auswirkungen aus der Tragkonstruktion und Unwägbarkeiten in der Bauausführung beeinflussen das Ankündigungsverhalten zusätzlich.

Zur Beurteilung des Restrisikos für den Bauherrn werden verschiedene Einflüsse auf die Gesamtkonstruktion anhand numerischer Berechnungen untersucht. Dabei werden sowohl Einflüsse aus Temperaturbeanspruchungen als auch aus Querschnittsversagen mit Schnittgrößenumlagerung näher betrachtet.
Group Sequential and Adaptive Designs – A Review of Basic Concepts and Points of Discussion
Authors: Vandemeulebroecke Marc
Published: July 2008

In recent times, group sequential and adaptive designs for clinical trials have attracted great attention from industry, academia and regulatory authorities. These designs allow analyses onaccumulating data– as opposed to classical, “fixed‐sample” statistics. The rapid development of a great variety of statistical procedures is accompanied by a lively debate on their potential merits and shortcomings. The purpose of this review article is to ease orientation in both respects. First, we provide a concise overview of the essential technical concepts, with special emphasis on their interrelationships. Second, we give a structured review of the current controversial discussion on practical issues, opportunities and challenges of these new designs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Testing for Group Effect in a 2 × k Heteroscedastic ANOVA Model
Authors: Troendle James F.
Published: July 2008

It is natural to want to relax the assumption of homoscedasticity and Gaussian error in ANOVA models. For a two‐way ANOVA model with 2 × k cells, one can derive tests of main effect for the factor with two levels (referred to as group) without assuming homoscedasticity or Gaussian error. Empirical likelihood can be used to derive testing procedures. An approximate empirical likelihood ratio test (AELRT) is derived for the test of group main effect. To approximate the distributions of the test statistics under the null hypothesis, simulation from the approximate empirical maximum likelihood estimate (AEMLE) restricted by the null hypothesis is used. The homoscedastic ANOVA F ‐test and a Box‐type approximation to the distribution of the heteroscedastic ANOVA F ‐test are compared to the AELRT in level and power. The AELRT procedure is shown by simulation to have appropriate type I error control (although possibly conservative) when the distribution of the test statistics are approximated by simulation from the constrained AEMLE. The methodology is motivated and illustrated by an analysis of folate levels in the blood among two alcohol intake groups while accounting for gender. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unbiased Estimation of Selected Treatment Means in Two‐Stage Trials
Authors: Bowden Jack , Glimm Ekkehard
Published: July 2008

Straightforward estimation of a treatment's effect in an adaptive clinical trial can be severely hindered when it has been chosen from a larger group of potential candidates. This is because selection mechanisms that condition on the rank order of treatment statistics introduce bias. Nevertheless, designs of this sort are seen as a practical and efficient way to fast track the most promising compounds in drug development. In this paper we extend the method of Cohen and Sackrowitz (1989) who proposed a two‐stage unbiased estimate for the best performing treatment at interim. This enables their estimate to work for unequal stage one and two sample sizes, and also when the quantity of interest is the best, second best, or j ‐th best treatment out of k. The implications of this new flexibility are explored via simulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Continuous Multi‐Injection Reactor for Multipurpose Production – Part I
Authors: Barthe P. , Guermeur C. , Lobet O. , Moreno M. , Woehl P. , Roberge D. M. , Bieler N. , Zimmermann B.
Published: July 2008

The paper presents an analysis of chemical production requirements in an exclusive synthesis market environment and describes how this analysis guided the development of a modular multi‐injection reactor. Detailed engineering of a reactor in the light of the requirements of an organometallic reaction, as well as characterization of the reactor is reported. This reactor has provided the target chemistry result at Lonza Ltd. as detailed in a companion paper.
Liquid Extraction of Vanillin in Rectangular Microreactors
Authors: Fries D. Maria , Voitl T. , von Rohr P. Rudolf
Published: July 2008

In this paper, the extraction of vanillin dissolved in water with a suitable organic phase using microstructured devices made of PDMS is discussed. Two flow patterns, segmented and stratified flow, were compared. LIF and μ‐PIV measurements showed a laminar profile for stratified flow; whereas for segmented flow, vortices in the slug end were detected. Additionally, for the stratified flow regime, the influence of the channel width and therefore the surface‐to‐volume ratio was investigated. A decrease of the channel cross‐sectional area results in a significant enhancement of mass transfer for the stratified flow regime. A further increase in mass transfer was obtained using segmented flow instead of stratified flow. However, stratified flow may be favored due to the ease of implementation of phase separation on the chip.
Multiscale Modeling Approach for Production of Perfume Microcapsules
Authors: Vásquez R. V. Tona , Jiménez Esteller L. , Bojarski A. D.
Published: July 2008

Microreactors are currently showing great promise as novel tools upon which new chemical technology can be built and for support process intensification in many industrial sectors. In this work, a modeling strategy is presented that integrates process units at multiple scales with microstructured elements to support the synthesis and characterization of perfume‐containing microcapsules. The strategy concerns two interconnected modules: microreactor unit models, where microcapsules are produced (developed in MATLAB®), and normal scale unit operation models (performed in Aspen Plus®). Encapsulation of the microreactor model and integration of flows between micro and normal scale equipments are implemented within Aspen Plus. All former features are successfully presented together in an integrated fashion with other key issues like recovery and reuse of solvents used for the minimization of environmental impacts.
Propane Conversion at Ambient Temperatures C–C and C–H Bond Activation Using Cold Plasma in a Microreactor
Authors: Ağıral A. , Trionfetti C. , Lefferts L. , Seshan K. , (Han) Gardeniers J. G. E.
Published: July 2008

In this work, the oxidative conversion of propane was studied using a dielectric barrier discharge microreactor. This generates a cold microplasma at atmospheric pressure and ambient temperatures. Surprisingly, large amounts of products with molecular weight higher than propane, such as C4 and C4+, were mainly observed due to C–C bond formation, in contrast to what is usually observed for this reaction when it is carried out under thermal activation, which leads to cracking products. A chemical kinetic model was developed to better understand the radical reaction network. Interestingly, the results suggest that (i) at lower level of propane conversion the model can nicely predict the experimental results and (ii) depending on the radical density the product selectivity can be tailored. In particular, at higher radical density, enhanced C–C bond formation was observed.
Dispersion and Holdup in Multiphase Packed Bed Microreactors
Authors: Márquez N. , Castaño P. , Makkee M. , Moulijn J. A. , Kreutzer M. T.
Published: July 2008

Liquid holdup and dispersion are reported for a column of 2 mm internal diameter, filled with 0.1 mm spherical particles, for multiphase flows with hydrocarbon liquid flow rates of 10–100 μL/min and nitrogen gas flow rates of 50–1000 μL/min using different tracers with varying diffusion coefficients and vapor pressures. It was found that the liquid holdup (liquid volume/external void volume) was between 0.65 and 0.85, with variations between different experiments and limited impact of flow rate on the holdup. The dispersion characteristics were very similar to single‐phase dispersion. The particle Peclet number for dispersion was close to 0.2. This value was of the same order of magnitude – just a factor of two to three lower – as the value that was obtained without gas flow. Tracer volatility did cause the tracer to elude earlier, but did not cause significant additional dispersion. The results suggest that the fluid mechanical interaction between the gas and the liquid was very limited.
“Sandwich Reactor” for Heterogeneous Catalytic Processes: N2O Decomposition as a Case Study
Authors: Bromley B. , Hessel V. , Renken A. , Kiwi‐Minsker L.
Published: July 2008

A novel “sandwich” microreactor designed as a thin (∼ 300 μm) porous plate of sintered metal fibers (SMF), sandwiched between metallic plates is reported. The SMF surface was coated by Fe‐ZSM‐5 thin film (< 2 μm) rendering a catalyst highly active in the decomposition of N2O. The 3D open microstructure of SMF plates presents a low pressure drop during the passage of reacting gases. The high thermoconductivity of metallic SMF improves the heat transfer, avoiding hot‐spot formation during exothermic reactions. The temperature measured in the middle and at the outlet of the reactor confirmed the isothermal reactor operation. The sandwich microreactor showed high permeability and a narrow residence time distribution close to an ideal plug‐flow reactor. The kinetics of the N2O decomposition was studied and the reaction was shown not to be limited by mass transfer when conducted in the microreactor.
Microfluidic‐Assisted Synthesis of Polymer Particles
Authors: Serra C. A. , Chang Z.
Published: July 2008

Microfluidic devices have recently emerged as promising tools for the synthesis of polymer particles. Over conventional processes, microfluidic‐assisted processes allow the production of polymer particles with an improved control over their sizes, size distributions, morphologies, and compositions. In this paper, the most common microfluidic devices are reviewed. Both projection photolithography and emulsification processes are reported for the continuous flow synthesis of polymer particles from a stream of polymerizable liquids. For the latter process, two distinct categories of microfluidic devices have been identified: microchannel‐based and capillary‐based microsystems. For each category, the existing geometries are described and the different emulsification methods including the co‐flowing, cross‐flowing, or flow‐focusing of the continuous and dispersed phases are commented upon. Finally, for each microsystem the various polymer particles achieved in such devices including, but not restricted to, janus, core–shell, or porous particles and capsules are reported.
Characterization of a Redispersion Microreactor by Studying its Dispersion Performance
Authors: Rothstock S. , Hessel V. , Löb P. , Werner B.
Published: July 2008

A redispersion microreactor concept developed for liquid‐liquid biphasic reactions was characterized by studying its dispersion performance for the n‐heptane/water system both with and without surfactant. The concept is based on repeated droplet breakage by so‐called redispersion units distributed over the length of the reactor, which either contain microstructured channels or consist of metal foam. The steel microchannel units lead to a higher pressure drop compared to the metal foam. In the presence of a surfactant, the droplet size is reduced stepwise by the redispersion units. At a given flow rate, the steel insets deliver smaller mean diameter droplets compared to the foam insets. Drop coalescence comes into play in the absence of the surfactant. In this instance, the redispersion units recreate and maintain the interfacial area along the length of the reactor albeit with coalescence.
Weighting hyperspectral image data for improved multivariate curve resolution results
Authors: Jones Howland D. T. , Haaland David M. , Sinclair Michael B. , Melgaard David K. , Van Benthem Mark H. , Pedroso M. Cristina
Published: July 2008

The combination of hyperspectral confocal fluorescence microscopy and multivariate curve resolution (MCR) provides an ideal system for improved quantitative imaging when multiple fluorophores are present. However, the presence of multiple noise sources limits the ability of MCR to accurately extract pure‐component spectra when there is high spectral and/or spatial overlap between multiple fluorophores. Previously, MCR results were improved by weighting the spectral images for Poisson‐distributed noise, but additional noise sources are often present. We have identified and quantified all the major noise sources in hyperspectral fluorescence images. Two primary noise sources were found: Poisson‐distributed noise and detector‐read noise. We present methods to quantify detector‐read noise variance and to empirically determine the electron multiplying CCD (EMCCD) gain factor required to compute the Poisson noise variance. We have found that properly weighting spectral image data to account for both noise sources improved MCR accuracy. In this paper, we demonstrate three weighting schemes applied to a real hyperspectral corn leaf image and to simulated data based upon this same image. MCR applied to both real and simulated hyperspectral images weighted to compensate for the two major noise sources greatly improved the extracted pure emission spectra and their concentrations relative to MCR with either unweighted or Poisson‐only weighted data. Thus, properly identifying and accounting for the major noise sources in hyperspectral images can serve to improve the MCR results. These methods are very general and can be applied to the multivariate analysis of spectral images whenever CCD or EMCCD detectors are used. Copyright © 2008 John Wiley & Sons, Ltd.
Mechanische Flüssigkeitsabtrennung in der Lebensmittelverfahrenstechnik
Authors: Anlauf H. , Nirschl H.
Published: July 2008

In der Lebensmitteltechnologie findet sich eine Vielzahl sehr unterschiedlicher Aufgabenstellungen für die mechanische Flüssigkeitsabtrennung. Dies ist durch die stark differierenden Produkteigenschaften, die zulässigen Prozessbedingungen und die Forderungen an das Verfahrensergebnis begründet. Zur Lösung dieser Trennaufgaben kann im Prinzip auf die ganze Breite der mechanischen Trenntechnik zurückgegriffen werden, welche auch in anderen Branchen Anwendung findet. Die speziellen Eigenschaften der hier zu behandelnden Produkte und die Anforderungen zur Gewährleistung der geforderten Produktqualitäten machen meist eine entsprechende Anpassung der trenntechnischen Apparate an diese Erfordernisse notwendig. Dies betrifft insbesondere den hygienischen Umgang mit den zu trennenden Stoffen oder auch die Sensorik, welche durch den Verarbeitungsprozess nicht negativ beeinflusst werden darf. Insbesondere im Bereich der Abtrennung von Kolloiden und gelöst vorliegenden Makromolekülen erobern sich mechanische Membrantrennverfahren immer weitere Anwendungsfelder, welche traditionell thermischen Verfahren vorbehalten waren.
Einfluss des Membranwiderstands auf die Filtrationsleistung bei der Proteinfraktionierung entlang von Mikrofiltrationsmodulen
Authors: Kühnl W. , Piry A. , Kulozik U.
Published: July 2008

Adsorptionsprozesse und Deckschichtbildung limitieren Flux und Stoffpermeation bei der Proteinfraktionierung mittels Querstrommikrofiltration. Die abschnittsweise Erfassung des Stoffdurchgangs entlang einer Membran ermöglicht ein tiefer gehendes Verständnis der Stofftransportvorgänge und der Deckschichtbildung. Entscheidend ist, die anfängliche Schleppkraft zur Membran infolge des initialen Flux durch Optimierung des Membranwiderstands zu begrenzen.
Anreicherung von Minor‐Komponenten in Speiseölen mit überkritischem Kohlendioxid
Authors: Zacchi P. , Eggers R.
Published: July 2008

Die Entölung von konditionierter und unvorbehandelter Rapssaat wird mit Hilfe der überkritischen CO2‐Extraktion untersucht. Für die Vorbehandlung kommt ein Hochtemperatur‐Kurzzeit‐Verfahren mit Dampf zum Einsatz. Hiermit lässt sich ein erhöhter Polyphenolgehalt im Öl erreichen. Mit Hilfe einer zeitlichen Fraktionierung während der Extraktion können Öle mit erhöhten Gehalten an Tocopherolen, Polyphenolen und freien Sterolen erhalten werden. Veresterte Sterole sammeln sich verstärkt in der letzten Fraktion der Extraktion an. Der Einfluss der Prozessparameter auf die erzielbare Anreicherung der Minor‐Komponenten in den Einzelfraktionen wird vorgestellt, wobei Drücke und Temperaturen im Bereich von 20 MPa bis 50 MPa und von 40 °C bis zu 80 °C untersucht worden sind. Bessere Fraktionierergebnisse lassen sich bei erhöhten Temperaturen und niedrigeren Drücken erzielen. Zusätzlich wurden die Phasengleichgewichte des komplexen Systems aus freien und veresterten Sterolen in Rapsöl im Kontakt mit überkritischem CO2 ermittelt. Die freien Sterole zeigen in dem untersuchten Parameterbereich Verteilungskoeffizienten oberhalb von eins, wohingegen die veresterten Sterole ein umgekehrtes Verhalten aufweisen.
Innovative Verfahrensansätze in der Speiseölprozesstechnik
Authors: Eggers R.
Published: July 2008

In der Speiseölprozesstechnik ist die Einführung innovativer Verfahren ausgerichtet auf die Steigerung der Ölqualitäten und der Ölausbeuten. Dabei sollen sekundäre Begleitstoffe im Öl verbleiben und angereichert werden sowie lösungsmittelfreie Entölungsverfahren zum Zuge kommen. In diesem Übersichtsbeitrag werden zwei innovative Verfahren beschrieben, die in jüngster Zeit in der Speiseölprozesstechnik grundlegend untersucht wurden: Erstens ein thermisches Konditionierverfahren, das nur kurzzeitig die Ölsaat mit hohen Temperaturen beaufschlagt und so ohne Schädigung der Öle zu einem Anstieg antioxidativ wirkender Polyphenole im Öl führt. Der zweite Verfahrensansatz nutzt die hohe Einlösekapazität von überkritischem Kohlendioxid in vegetabiles Öl während der Abpressung von Ölsaaten, womit durch Viskositätsabsenkung und Verdrängungseffekte höhere Ölausbeuten möglich werden, die zudem lösungsmittelfrei gewonnen werden.
Ultrahochdrucktechnik für innovative Behandlungsverfahren von Lebensmitteln
Authors: Knorr D. , Mathys A.
Published: July 2008

Isostatischer Hochdruck bietet eine produktschonende Alternative zum konventionellen Konservieren bzw. Modifizieren von Lebensmitteln. Durch die Inaktivierung verschiedener Mikroorganismen und der druckbedingten Modifikation von Proteinen, Enzymen und Stärke werden zahlreiche potenzielle Prozessanwendungen eröffnet. Prozesstechnisch wird zwischen externen und internen Druckübersetzern unterschieden. Es existieren derzeit das Hochdruck‐Kurzzeit‐Verfahren (HP‐ST), das Hochdruck‐Hochtemperatur‐Kurzeit‐Verfahren (HP/T‐ST) sowie das Hochdruck‐Phasenwechsel‐Verfahren (HP‐PS). Bisherige Untersuchungen zeigten keine mikrobiellen, toxikologischen oder allergenen Risiken als Folge einer Hochdruckbehandlung, wodurch ein stetiger Anstieg der industriellen Anwendungen zu verzeichnen ist. Dieser Überblick diskutiert die grundlegenden Zusammenhänge und Mechanismen einer Hochdruckbehandlung von Lebensmitteln, zeigt Anregungen für potenzielle Produktvarianten sowie Forschungsbedarf für die Zukunft.
Energiesparende Homogenisierung von Milch mit etablierten sowie neuartigen Verfahren
Authors: Köhler K. , Kulozik U. , Schuchmann H. P. , Karasch S.
Published: July 2008

In der Milchindustrie werden heute in Deutschland jährlich ca. 12 Mio. t Milch und Milchprodukte hochdruckhomogenisiert. Konventionell werden hierzu zweistufig betriebene Flachdüsen eingesetzt. Parallel zur Vollstromhomogenisierung hat sich die Teilstromhomogenisierung etabliert. Diese ermöglicht deutliche Energieersparnisse, ist aber auf maximal 17 Vol.‐% Fettgehalt limitiert. Neue Forschungsergebnisse zeigen, dass eine auf die Milch angepasste Blenden‐ sowie die SHM‐Technologie (Simultanes Homogenisieren und Mischen) Vorteile beim Homogenisieren von Rahm mit höheren Fettanteilen in Bezug auf Energieersparnis bzw. Produktqualität bringen.
Lebensmittelextrusion bei extrem hohen Drehzahlen: Charakterisierung des Prozessverhaltens und Einfluss der Prozessparameter auf die Eigenschaften von extrudiertem Maisgrieß
Authors: Leeb C. V. , Schuchmann H. P.
Published: July 2008

Hochgeschwindigkeitsextruder sollen durch extrem hohe Drehzahlen (bis 1800 min–1) und spezifische Drehmomente eine Durchsatzerhöhung und Produktivitätssteigerung bei gleicher Produktcharakteristik ermöglichen. Für Lebensmittel werden diese Extruder bislang nicht eingesetzt. Gezeigt werden erste Untersuchungen zum Einfluss der Prozessparameter auf relevante Produkteigenschaften von extrudiertem Maisgrieß.
Bestimmung der Verweilzeitverteilung bei der Kochextrusion von Maisgrieß in einem Hochgeschwindigkeitsextruder
Authors: Leeb C. V. , Maiser B. , Schuchmann H. P.
Published: July 2008

Für die Qualität extrudierter Lebensmittel spielt die Verweilzeitverteilung im Prozessraum eine bedeutende Rolle. Gezeigt wurde, dass sowohl Salz als auch Farbpartikel geeignete inerte Tracer‐Partikel für die Messung darstellen, wobei die kolorimetrische Methode eine höhere Empfindlichkeit aufwies. Messungen an einem Hochgeschwindigkeitsextruder zeigten, dass bei hohen Drehzahlen sehr kurze Verweilzeiten mit enger Verteilung realisiert werden können. Mit abnehmendem Wassergehalt wurden die Verweilzeitspektren breiter.