Microbial Production of Short Chain Fatty Acids from Lignocellulosic Biomass:Current Processes and Market

Biological production of organic acids from conversion of biomass derivatives has received increased attention among scientists and engineers and in business because of the attractive properties such as renewability, sustainability, degradability, and versatility. The aim of the present review is to summarize recent research and development of short chain fatty acids production by anaerobic fermentation of nonfood biomass and to evaluate the status and outlook for a sustainable industrial production of such biochemicals. Volatile fatty acids (VFAs) such as acetic acid, propionic acid, and butyric acid have many industrial applications and are currently of global economic interest. The focus is mainly on the utilization of pretreated lignocellulosic plant biomass as substrate (the carbohydrate route) and development of the bacteria and processes that lead to a high and economically feasible production of VFA. The current and developing market for VFA is analyzed focusing on production, prices, and forecasts along with a presentation of the biotechnology companies operating in the market for sustainable biochemicals. Finally, perspectives on taking sustainable product of biochemicals from promise to market introduction are reviewed

Exploration of the scalability of SIMD processing for software defined radio

The idea of software defined radio (SDR) describes a signal processing system for wireless communications that allows performing major parts of the physical layer processing in software. SDR systems are more flexible and have lower development costs than traditional systems based on application-specific integrated circuits (ASICs). Yet, SDR requires programmable processor architectures that can meet the throughput and energy efficiency requirements of current third generation (3G) and future fourth generation (4G) wireless standards for mobile devices. Single instruction, multiple data (SIMD) processors operate on long data vectors in parallel data lanes and can achieve a good ratio of computing power to energy consumption. Hence, SIMD processors could be the basis of future SDR systems. Yet, SIMD processors only achieve a high efficiency if all parallel data lanes can be utilized. This thesis investigates the scalability of SIMD processing for algorithms required in 4G wireless systems; i. e. the scaling of performance and energy consumption with increasing SIMD vector lengths is explored. The basis of the exploration is a scalable SIMD processor architecture, which also supports long instruction word (LIW) execution and can be configured with four different permutation networks for vector element permutations. Radix-2 and mixed-radix fast Fourier transform (FFT) algorithms, sphere decoding for multiple input, multiple output (MIMO) systems, and the decoding of quasi-cyclic lowdensity parity check (LDPC) codes have been examined, as these are key algorithms for 4G wireless systems. The results show that the performance of all algorithms scales with the SIMD vector length, yet there are different constraints on the ratios between algorithm and architecture parameters. The radix-2 FFT algorithm allows close to linear speedups if the FFT size is at least twice the SIMD vector length, the mixed-radix FFT algorithm requires the FFT size to be a multiple of the squared SIMD width. The performance of the implemented sphere decoding algorithm scales linearly with the SIMD vector length. The scalability of LDPC decoding is determined by the expansion factor of the quasicyclic code. Wider SIMD processors offer better performance and also require less energy than processors with a shorter vector length for all considered algorithms. The results for different permutations networks show that a simple permutation network is sufficient for most applications

3D ultrastructural organization of whole Chlamydomonas reinhardtii cells studied by nanoscale soft x-ray tomography

The complex architecture of their structural elements and compartments is a hallmark of eukaryotic cells. The creation of high resolution models of whole cells has been limited by the relatively low resolution of conventional light microscopes and the requirement for ultrathin sections in transmission electron microscopy. We used soft x-ray tomography to study the 3D ultrastructural organization of whole cells of the unicellular green alga Chlamydomonas reinhardtii at unprecedented spatial resolution. Intact frozen hydrated cells were imaged using the natural x-ray absorption contrast of the sample without any staining. We applied different fiducial-based and fiducial-less alignment procedures for the 3D reconstructions. The reconstructed 3D volumes of the cells show features down to 30 nm in size. The whole cell tomograms reveal ultrastructural details such as nuclear envelope membranes, thylakoids, basal apparatus, and flagellar microtubule doublets. In addition, the x-ray tomograms provide quantitative data from the cell architecture. Therefore, nanoscale soft x-ray tomography is a new valuable tool for numerous qualitative and quantitative applications in plant cell biology

La epiqueya de Aristóteles en tiempos de crisis económica

Documento: La epiqueya de Aristóteles en tiempos de crisis económic

Zwei Beiträge zur Interpretation von statistischen Tests: Replik auf den Artikel "Von der Wahrscheinlichkeit des Irrtums" von W. Weihe

In seinem Heft 13/2004 vom 26.3.2004 veröffentlichte das Deutsche Ärzteblatt einen Artikel mit dem Titel "Von der Wahrscheinlichkeit des Irrtums", in dem der Autor Wolfgang Weihe eine seiner Meinung nach sowohl neue als auch ungewöhnliche Position bezüglich der Interpretation von statistischen Tests im Zusammenhang mit klinischen Studien zur Erprobung neuer Behandlungsmethoden einnimmt. Er nimmt dabei eine strenge Trennung zwischen den Begriffen Signifikanz und Irrtumswahrscheinlichkeit vor und legt dar, dass das Signifikanzniveau nichts darüber aussagt, wie hoch die tatsächliche Irrtumswahrscheinlichkeit ist. "Neu" im Sinne von höchst ungewöhnlich ist vor allem die These, dass zwei weitere Aspekte in die Interpretation mit aufgenommen werden müssen: 1. Gibt es weitere Studien bezüglich der Behandlungsmethode und wenn ja, zu welchen Ergebnissen sind die gekommen? 2. Wie ist die "Qualität" des Forschers (gemessen an seinem "Riecher" bezüglich der Wirksamkeit einer neuen Behandlungsform)? Der Artikel hat eine ganze Reihe von Reaktionen in Form von Leserbriefen hervorgerufen, die zum Teil auch im Deutschen Ärzteblatt abgedruckt wurden. Die Leserbriefe sind zum Teil zustimmend, zum Teil üben sie aber auch Kritik, gehen aber auf einen entscheidenden Makel in den Überlegungen Weihes nicht ein, nämlich dass diese überwiegend schlicht falsch sind. Die Autoren des vorliegenden Diskussionspapiers haben sich daher zum Ziel gesetzt aufzuzeigen, wo die Schwächen und Fehler bei Weihe liegen und wieso man seinen Schlussfolgerungen aus Sicht der klassischen Statistik nicht folgen kann. --

Continuous Fermentation of Wheat Straw Hydrolysate by Clostridium tyrobutyricum with In-Situ Acids Removal

The present study focused on fermentative butyric acid production by Clostridium tyrobutyricum from pre-treated and hydrolysed wheat straw (PHWS) based on continuous operation mode and in situ acids extraction by reverse electro enhanced dialysis (REED). Different dilutions of PHWS in a synthetic medium (60–100 % v/v) were tested. It was found that continuous fermentation of PHWS greatly enhanced the sugar consumption rates and butyric acid productivity compared to batch tests, while application of REED enhanced them even further. Specifically, applying combined continuous operation mode and REED system for the fermentation of 70 % PHWS resulted in 19- and 53-fold higher glucose (1.37 g L(−1) h(−1)) and xylose (0.80 g L(−1) h(−1)) consumption rates, respectively, compared to those obtained by batch processing. Fermentation of 100 % PHWS continued unhindered with just urea and K(2)HPO(4) added with butyric acid production rate, yield and selectivity being 1.30 g L(−1) h(−1), 0.45 g g(−1) sugars and 0.88 g g(−1) acids, respectively. These results were also confirmed in a 20 L pilot plant bioreactor system