Scalable Green Synthesis and Full‐Scale Test of the Metal–Organic Framework CAU‐10‐H for Use in Adsorption‐Driven Chillers

The demand for cooling devices has increased during the last years and this trend will continue. Adsorption‐driven chillers (ADCs) using water as the working fluid and low temperature waste energy for regeneration are an environmentally friendly alternative to currently employed cooling devices and can concurrently help to dramatically decrease energy consumption. Due to the ideal water sorption behavior and proven lifetime stability of [Al(OH)(m‐BDC)] ? x H₂O (m‐BDC^2? = 1,3‐benzenedicarboxylate), also denoted CAU‐10‐H, a green very robust synthesis process under reflux, with high yields up to 95% is developed and scaled up to kg‐scale. Shaping of the adsorbent is demonstrated, which is important for an application. Thus monoliths and coatings of CAU‐10‐H are produced using a water‐based binder. The composites are thoroughly characterized toward their mechanical stability and water sorption behavior. Finally a full‐scale heat exchanger is coated and tested under ADC working conditions. Fast adsorption dynamic leads to a high power output and a good power density. A low regeneration temperature of only 70 °C is demonstrated, allowing the use of low temperature sources like waste heat and solar thermal collectors.     

Poly(amidoamine)-alginate hydrogels: directing the behavior of mesenchymal stem cells with charged hydrogel surfaces

The surface charge of a biomaterial represents a promising tool to direct cellular behavior, which is crucial for therapeutic approaches in regenerative medicine. To expand the understanding of how the material surface charge affects protein adsorption and mesenchymal stem cell behavior, differently charged surfaces with zeta potentials spanning from ?25?mV to +15?mV were fabricated by the conjugation of poly(amidoamine) to alginate-based hydrogels. We showed that the increase of the biomaterials surface charge resulted in enhanced quantities of biologically available, surface-attached proteins. Since different surface charges were equalized after protein adsorption, mesenchymal stem cells interacted rather with diverse protein compositions instead of different surface features. Besides an enhanced cell attachment to increasingly positively charged surfaces, the cell spreading area and the expression of adhesion-related genes integrin α5 and tensin 1 were found to be increased after adhesion. Moreover, first results indicate a potential impact of the surface charge on mesenchymal stem cell differentiation towards bone and fat cells. The improved understanding of surface charge-related cell behavior has significant impact on the design of biomedical devices and artificial organs.

Open image in new window

     

Treatment of pediatric spinal deformity with use of recombinant human bone morphogenetic protein-2

In pediatric spine surgery nonunion is a challenging issue. Instability may cause neurological impairment and lead to numerous surgeries in order to achieve fusion. The use of rhBMP-2 for pediatric spinal fusion has not been widely reported. In this study, a series of 13 children (14 procedures) that underwent spinal rhBMP-2 application were analyzed in order to measure clinical and radiographic outcome. Therefore, patient data, diagnosis, construct of instrumentation, type of bone graft, quantity of BMP used, and fusion outcome were reviewed. The study cohort included four female and nine male patients with a mean age of 11.2 years (range 2.6–19.2?years) at the time of rhBMP-2 application. Rh-BMP-2 was used in both primary (n?=?6) and revision surgery (n?=?8) in patients with a high risk for the development of nonunion. The mean follow-up was 51 months (range 12–108 months). Fusion occurred in 11 patients. Complications that may be due to application of rhBMP-2 were seen after four operations. Three patients had an increased body temperature and in one case prolonged wound secretion was evident, treated by local wound care or observation. In one of these patients an extensive postoperative hematoma occurred, necessitating surgical treatment. In conclusion, we could detect high fusion rates following the use of rhBMP-2 in pediatric spine surgery without an increased complication rate attributable to its application. Therefore we consider recombinant human BMP-2 to be an option in selected pediatric spinal procedures, especially in cases with compromised bone healing due to congenital, systemic, or local conditions.

Open image in new window

     

The fen-phen finale: a study of weight loss and valvular heart disease

Exercise tolerance may be reduced in patients with cystic fibrosis, but it is not always possible to predict this from standard lung function measurements. Formal exercise testing may, therefore, be necessary, and the test should be simple and readily available. We have developed a "3-minute step test" and compared it with the standard 6-minute walking test. Subjects stepped up and down a 15-cm-high single step at a rate of 30 steps per minute for 3 minutes. The effect of the step test on spirometry was tested first in 31 children with CF (mean age, 12.0 years), who had a mean (range) baseline forced expired volume in 1 second (FEV1) of 64% (18-94%) of predicted values. The step test was then compared with the standard 6-minute walk in a further 54 patients with cystic fibrosis (mean age, 12.5 years), with mean (range) baseline FEV1 of 61% (14-103%) of predicted values. Outcome measures were minimum arterial oxygen saturation (SaO2), maximum pulse rate, and the modified Borg dyspnea score. Post-step test spirometry showed mean (95% CI) changes of -1.1% (-6.0 + 3.9%) for forced vital capacity, of -1.6% (-4.2 + 1.1%) for FEV1, and +0.25% (-2.8 + 3.3%) for peak expiratory flow, although 5/31 children showed >15% drop in one or more parameters. The step and walk tests both produced significant changes (P < 0.0001) in all outcomes, with a mean (range) minimum SaO2 of 92% (75-98%) versus 92% (75-97%), a maximum pulse rate of 145 b.p.m. (116-189) versus 132 (100-161), and a Borg score of 2.5 (0-9) versus 1.0 (0-5), respectively. Comparison of the two tests showed that the step test increased breathlessness (mean change Borg score, 2.3 vs. 0.8; P < 0.0001) and pulse rate (mean change, 38% vs. 24%, P < 0.0001) significantly more than the walk, whereas the decrease in SaO2 was similar (mean change, -2.9% vs. -2.6%; P = 0.12). Some patients with a significant drop in SaO2 (>4%) would not have the decrease predicted from their baseline lung function. Reproducibility for the two tests was similar. The step test is quick, simple and portable, and is not dependent on patient motivation. Although the step test is more tiring, its effect on SaO2 is similar to the 6-minute walking test. It is a safe test that may prove to be a valuable measure of exercise tolerance in children with pulmonary disease, although longitudinal studies are now needed.     

On Restricted-Focus-of-Attention Learnability of Boolean Functions

In the k-Restricted-Focus-of-Attention (k-RFA) model, only k of the n attributes of each example are revealed to the learner, although the set of visible attributes in each example is determined by the learner. While thek -RFA model is a natural extension of the PAC model, there are also significant differences. For example, it was previously known that learnability in this model is not characterized by the VC-dimension and that many PAC learning algorithms are not applicable in the k-RFA setting.In this paper we further explore the relationship between the PAC and k -RFA models, with several interesting results. First, we develop an information-theoretic characterization of k-RFA learnability upon which we build a general tool for proving hardness results. We then apply this and other new techniques for studying RFA learning to two particularly expressive function classes,k -decision-lists (k-DL) and k-TOP, the class of thresholds of parity functions in which each parity function takes at most k inputs. Among other results, we prove a hardness result for k-RFA learnability of k-DL,k n-2 . In sharp contrast, an (n-1)-RFA algorithm for learning (n-1)-DL is presented. Similarly, we prove that 1-DL is learnable if and only if at least half of the inputs are visible in each instance. In addition, we show that there is a uniform-distribution k-RFA learning algorithm for the class of k -DL. For k-TOP we show weak learnability by ak -RFA algorithm (with efficient time and sample complexity for constant k) and strong uniform-distribution k-RFA learnability of k-TOP with efficient sample complexity for constant k. Finally, by combining some of our k-DL and k-TOP results, we show that, unlike the PAC model, weak learning does not imply strong learning in the k -RFA model.     

Separation of nonionic surfactants by capillary electrophoresis and high-performance liquid chromatography

Fatty alcohol ethoxylates (FAEs) are applied in commercial formulations (laundry detergents) as complex mixtures of alkyl and ethoxylate homologues. Therefore, efficient analytical methods are required for product control. Capillary electrophoresis, a modern analytical separation technique, was used to separate FAEs in technical products and household formulations after derivatization with phthalic anhydride. The well-established high-performance liquid chromatography was used as reference and supplementary method. UV detection after derivatization with phenyl isocyanate or light scattering detection has been carried out. Sample components have been identified by standard addition or by comparison to known products. The peak pattern can be considered as a "fingerprint" of the product and is characteristic for a defined composition.     

Use of growth factors in therapy of chronic wounds. Experimental, clinical and financial aspects

Clinical trials on exogenous application of polypeptide growth factors in chronic wounds have not fulfilled the high expectations derived from results of experimental studies. There is no convincing evidence that growth factors may substitute for good wound care and efficient surgical approaches to wound closure. The ultimate goal of treatment of chronic ulcerations remains reconstitution of a durable skin envelope without unstable scarring. Therefore, optimization of current methods of wound therapy, including reconstructive vascular and plastic surgery and adequate metabolic and wound control, should be employed before any adjuvant growth factor therapy is attempted. As long as efficient and inexpensive therapy of chronic wounds by growth factors has not been demonstrated, empincal growth factor treatment should be rejected on scientific and economic grounds. Current use appears to be reasonable only under a regime of controlled clinical studies comparing growth factor treatment with conventional wound therapy and operative measures according to the rules of "good clinical practice".     

Faster discovery of faster system configurations with spectral learning

Despite the huge spread and economical importance of configurable software systems, there is unsatisfactory support in utilizing the full potential of these systems with respect to finding performance-optimal configurations. Prior work on predicting the performance of software configurations suffered from either (a) requiring far too many sample configurations or (b) large variances in their predictions. Both these problems can be avoided using the WHAT spectral learner. WHAT’s innovation is the use of the spectrum (eigenvalues) of the distance matrix between the configurations of a configurable software system, to perform dimensionality reduction. Within that reduced configuration space, many closely associated configurations can be studied by executing only a few sample configurations. For the subject systems studied here, a few dozen samples yield accurate and stable predictors—less than 10% prediction error, with a standard deviation of less than 2%. When compared to the state of the art, WHAT (a) requires 2–10 times fewer samples to achieve similar prediction accuracies, and (b) its predictions are more stable (i.e., have lower standard deviation). Furthermore, we demonstrate that predictive models generated by WHAT can be used by optimizers to discover system configurations that closely approach the optimal performance.     

Progression of mental models throughout the phases of a computer-based instructional simulation: Supportive information,practice, and performance

Students of chemical engineering (n = 26) participated in an experiment using a computer-based simulation of a chemical plant. The progression of participants’ mental models was examined throughout a computer-based instructional experience as they acquired the complex cognitive skills of troubleshooting. Participants’ mental models of the complex learning task were matched against an expert mental model at five observation points through the instruction. Progressions of learners’ mental models were examined before and after three phases of the instructional process: supportive information presentation, problem solving practice, and performance test. The results indicated a significant change in participants’ mental models after receiving the supportive information and little change after practice or performance. This paper presents the results of this investigation and discusses the findings and their implications for computer-based instruction and training.