Laser patterning of thin-film solar cells is essential to perform external serial and integrated monolithic interconnections for module application and has recently received increasing attention. Current investigations show, however, that the efficiency of thin-film Cu(In,Ga)Se2 (CIGS) modules is reduced due to laser scribing also with ultrashort laser pulses. Hence, to investigate the reasons of the laser-induced material modifications, thin-film CIGS solar cells were laser-scribed with femto- and picosecond laser pulses using different scribing procedures and laser processing parameters. Besides standard electrical current voltage (I–V) measurements, additional electrical and optical analysis were performed such as laser beam-induced current (LBIC), dark lock-in thermography (DLIT), and electroluminescence (EL) measurements to characterize and localize electrical losses due to material removal/modifications at the scribes that effecting the electrical solar cell properties. Both localized as well as distributed shunts were found at laser scribe edges whereas the laser spot intensity distribution affecting the shunt formation. Already laser irradiation below the ablation threshold of the TCO film causes material modification inside the thin film solar cell stack resulting in shunt formation as a result of materials melting near the TCO/CIGS interface that probably induces the damage of the pn-junction.

Page 1. PROGRAMS AS FIRST-CLASS CITIZENS IN A BIOLOGY-MOTIVATED MODEL OF COMPUTATION Lars Hartmann Neil D. Jones Jakob Grue Simonsen + Visualization by Søren Bjerregaard Vrist (All now or recently at the University of Copenhagen) Christopher Strachey lecture, Oxford (May 1, 2012) Sources: ▶ Conference CS2BIO Computer Science to Biology (ENTCS proceedings June 2010) ▶ Journal Scientific Annals of Computer Science (2011, Vol. XXI) ▶ Festschrift for Carolyn Talcott (November 2011, Springer Festschrift Series, LNCS vol. 7000) ▶ Article accepted to appear in Philosophical Transactions A of the Royal Society —0— Page 2. MY EARLY INSPIRATIONS ▶ Turing machines, studied since 1962 ▶ A compiler for algol 60, written in 1962-65 There were many unclear semantic points! But what was a semantics??? ▶ The IFIP Working Conference on Formal Language Descrip …

Computation via biological devices has been the subject of close scrutiny since von Neumann's early work some 60 years ago. In spite of the many relevant works in this field, the notion of programming biological devices seems to be, at best, ill-defined. While many devices are claimed or proved to be computationally universal in some sense, the full step to a bona fide programming language is rarely taken, and one question is noticeable by its absence: If the device is universal, where are the programs? We begin with an extensive review of the literature on programming-related biocomputing; and briefly identify some strengths and shortcomings from a programming perspective. To show concretely what one could see as programming in biocomputing, we outline (from recent work) a computation model and a small programming language that are biologically more plausible than existing silicon-inspired models. Whether or not the model is biologically plausible in an absolute sense, we believe it sets a standard for a biological device that can be both universal and programmable.

Our goal is to provide a top-down approach to biomolecular computation. In spite of widespread discussion about connections between biology and computation, one question seems notable by its absence: Where are the programs? We identify a number of common features in programming that seem conspicuously absent from the literature on biomolecular computing; to partially redress this absence, we introduce a model of computation that is evidently programmable, by programs reminiscent of low-level computer machine code; and at the same time biologically plausible: its functioning is defined by a single and relatively small set of chemical-like reaction rules. Further properties: the model is stored-program: programs are the same as data, so programs are not only executable, but are also compliable and interpretable. It is universal: all computable functions can be computed (in natural ways and without arcane encodings of data and algorithm); it is also uniform: new "hardware" is not needed to solve new problems; and (last but not least) it is Turing complete in a strong sense: a universal algorithm exists, that is able to execute any program, and is not asymptotically inefficient.

Our goal is to provide a top-down approach to biomolecular computation. In spite of widespread discussion about connections between biology and computation, one question seems notable by its absence: Where are the programs? We introduce a model of computation that is evidently programmable, by programs reminiscent of low-level computer machine code; and at the same time biologically plausible: its functioning is defined by a single and relatively small set of chemical-like reaction rules. Further properties: the model is stored-program: programs are the same as data, so programs are not only executable, but are also compilable and interpretable. It is universal: all computable functions can be computed (in natural ways and without arcane encodings of data and algorithm); it is also uniform: new ''hardware'' is not needed to solve new problems; and (last but not least) it is Turing complete in a strong sense: a universal algorithm exists, that is able to execute any program, and is not asymptotically inefficient. A prototype model has been implemented (for now in silico on a conventional computer). This work opens new perspectives on just how computation may be specified at the biological level.

The human (h) P2X(3) receptor and its mutants deficient in one out of four N-glycosylation sites were expressed in HEK293 cells. Concentration-response curves were generated by whole-cell recordings of alpha,beta-methylene ATP (alpha,beta- meATP)induced currents. A gradual change of external pH from the alkaline 8.0 to the acidic 5.0 successively decreased the maximum current amplitude (E-max) without affecting the EC50 value. The replacement of Asn-139 and -170 by Asp (N139D, N170D) abolished the pH sensitivity of the wild-type (WT) hP2X(3) receptor. In the case of N194D, the E-max was again the highest at the alkaline pH value with no change from 7.4 to 6.5, whereas in the case of N290D, there was an inverse pH sensitivity, with an increase of E-max in the acidic range. However, this effect appeared to be due to enhanced protonation by the insertion of Asp into the receptor, because replacement of Asn by the neutral Thr resulted in a comparable potency of alpha,beta- meATP at any of the pH values investigated. In accordance with the reported finding that His-206 is involved in the modulation of WT P2X(3) receptors by protons, we showed that the normal change of E-max by an acidic, but not alkaline pH was abolished after substitution of this His by Ala. However, the double mutant H206A + N290D did not react to acidification or alkalinization with any change in Emax. In conclusion, only fully N-glycosylated P2X3 receptors recognize external pH with a modified sensitivity towards alpha,beta-meATP.

Zn90Mn7.5Cu2.5O100 films have been prepared on a-plane sapphire substrates by pulsed laser deposition. Paramagnetism mainly caused by Mn2+ ions was observed in the films from room temperature down to 2 K. Magnetotransport properties (magnetoresistance (MR) and Hall effect) were studied from 5 K to 290 K up to a field of 6 T. Negative MR was observed at temperature above 100 K. Low field positive MR and high field, negative MR was observed at 5 K. Clear anomalous Hall effect with a kink at low field was observed below 20 K, indicating that there exist two different scattering mechanisms for the Mn2+ and Cu2+ ions. (c) 2007 Elsevier B.V. All rights reserved.

We report the clearly observed tunneling magnetoresistance at 5 K in magnetic tunnel junctions with Co-doped ZnO as a bottom ferromagnetic electrode and Co as a top ferromagnetic electrode prepared by pulsed laser deposition. Spin-polarized electrons were injected from Co-doped ZnO to the crystallized Al2O3 and tunnelled through the amorphous Al2O3 barrier. Our studies demonstrate the spin polarization in Co-doped ZnO and its possible application in future ZnO-based spintronics devices.

Mn-doped ZnO films with preferred c-axis growth orientation were prepared by pulsed laser deposition under N-2 atmosphere on a-plane sapphire substrates. Large positive magnetoresistance amounting to 60% was observed at 5 K. Clear anomalous Hall effect was observed at 20 K. Ferromagnetism with Curie temperature higher than 290 K has been observed, and a deep acceptor trap due to Zn vacancies with a thermal activation energy amounting to 0.815 eV has been detected by deep-level transient spectroscopy. For comparison, only paramagnetism was observed in Mn-doped ZnO films with donor traps prepared under O-2 atmosphere. Their results clearly demonstrate that the ferromagnetism in Mn-doped ZnO originates from the parallel alignment of magnetic moments mediated by acceptor defects.

The Co valence state and the location of Co dopant atoms in ZnO:Co thin films revealing anomalous Hall effect below 50K have been determined by electron energy-loss spectroscopy (EELS) measurements and atom location by channeling enhanced microanalysis (ALCHEMI), respectively. The method of ALCHEMI-EELS to investigate the dopant in materials was brought. It was used to determine that the intrinsic ferromagnetism in ZnO:Co thin films derives from the +2 Co which substitute for Zn atoms at Zn sites in the ZnO matrix. The divalent Co state in ZnO:Co has been unambiguously proven by modeling the corresponding EELS data.

The magnetoresistance (MR) effect in Co-doped ZnO films prepared by pulsed laser deposition on a-plane sapphire substrates with electron concentration at 5 K ranging from 8.3x10(17) cm(-3) to 9.9x10(19) cm(-3) has been studied experimentally and theoretically. A large positive MR of 124% has been observed in the film with the lowest electron concentration of 8.3x10(17) cm(-3), while only a negative MR of -1.9% was observed in the film with an electron concentration of 9.9x10(19) cm(-3) at 5 K. The positive MR is attributed to the quantum correction on the conductivity due to the s-d exchange interaction induced spin splitting of the conduction band. The negative MR is attributed to the magnetic field suppressed weak localization. The presented modeling of superimposed positive and negative MR well agrees with the experimentally observed MR and hints at the physical origin of MR in Co-doped ZnO.

Co-doped ZnO films with Co content above 7% have been grown by pulsed laser deposition on a-sapphire substrates. Temperature and magnetic field dependent magneto transport measurements have been performed on samples with electron concentration n around the critical electron concentration n(c)approximate to 4.9x10(19) cm(-3), where the metal-insulator transition (MIT) occurs. At 5 K we observed positive magnetoresistance (MR) in the insulating range (n < n(c)) and negative MR in die metallic range (n > n(c)). The MIT was determined from the NM and Hall effect at 5 K to occur at the electron concentration n(c)approximate to 4x10(19) cm(-3). In the vicinity of the MIT (n similar to n(c)) we observed negative MR at low field and positive MR at high field. Only for n < n(c) we observed clear anomalous Hall effect in the Co-doped ZnO films being of relevance for use in future spintronic devices.

Magnetotransport measurements were performed on n-type conducting Co-doped ZnO and Mn-doped ZnO films prepared by pulsed laser deposition on a-plane sapphire substrates, and positive magnetoresistance (MR) was observed at low temperature. The positive MR decreases drastically with the free electron concentration n exceeding 1019cm−3 and reveals almost the same dependency on n for Co-doped ZnO and Mn-doped ZnO. This hints towards a similar s-d exchange constant in both types of magnetic ZnO films. For Co-doped ZnO, the saturated anomalous Hall resistivity increases with decreasing electron concentration. No anomalous Hall effect was observed in Mn-doped ZnO. Within a free electron approximation the positive MR may be related with the spin polarization of conducting electrons due to s-d exchange interactions. The modeled spin splitting of the conduction band is smaller than 10meV.

Zn 0.90 Co 0.10 O films of different thicknesses (689, 408, 355nm) doped with 0.5 at. % Al were prepared by pulsed laser deposition on a-plane sapphire substrates. At 290K the resistivity increases drastically with decreasing film thickness, while the electron concentration and mobility decrease. Magnetoresistance (MR) effects were measured in the temperature range of 5–290K. At low temperature, the positive MR increases with decreasing film thickness. Positive MR decreases rapidly with increasing temperature. With increasing temperature, the MR of the thicker film changes to negative, while positive MR was still observed for the 355nm thick film at 290K. Anomalous Hall effect was observed in the 355nm thick film at 20K, indicating the possible ferromagnetism in Zn0.90Co0.10O.

ZnCoO : Al, ZnCoO : (Al, Cu), and reference samples without Co have been grown by pulsed laser deposition to investigate the influence of Co-dopants and Cu-codopants on the magneto transport properties of ZnO. Positive magnetoresistance and anomalous Hall effect have been observed for ZnCoO : (Al, Cu). Versatile theoretical approaches for modelling positive magnetoresistance in ZnO-based diluted magnetic semiconductors are still to be developed. Negative magnetoresistance due to the scattering of spin-polarized charge carriers at isolated magnetic impurities has been observed in ZnO : (Al, Cu) without Co-dopants and successfully modelled. Cu-codopants enhance the positive and negative magnetoresistance in ZnCoO : Al and ZnO : Al, respectively, by one order of magnitude.