■ Abstract Apoptosis is a genetically programmed, morphologically distinct form of cell death that can be triggered by a variety of physiological and pathological stimuli. Studies performed over the past 10 years have demonstrated that proteases play critical roles in initiation and execution of this process. The caspases, a family of cysteine-dependent aspartate-directed proteases, are prominent among the death proteases. Caspases are synthesized as relatively inactive zymogens that become activated by scaffold-mediated transactivation or by cleavage via upstream proteases in an intracellular cascade. Regulation of caspase activation and activity occurs at several different levels: ( a) Zymogen gene transcription is regulated; ( b) antiapoptotic members of the Bcl-2 family and other cellular polypeptides block proximity-induced activation of certain procaspases; and ( c) certain cellular inhibitor of apoptosis proteins (cIAPs) can bind to and inhibit active caspases. Once activated, caspases cleave a variety of intracellular polypeptides, including major structural elements of the cytoplasm and nucleus, components of the DNA repair machinery, and a number of protein kinases. Collectively, these scissions disrupt survival pathways and disassemble important architectural components of the cell, contributing to the stereotypic morphological and biochemical changes that characterize apoptotic cell death.

Mammalian caspases: structure ,a ctivation ,s ubstrates, and functions during apoptosis

The rise time of intense radiation determines the maximum field strength atoms can be exposed to before their polarizability dramatically drops due to the detachment of an outer electron. Recent progress in ultrafast optics has allowed the generation of ultraintense light pulses comprising merely a few field oscillation cycles. The arising intensity gradient allows electrons to survive in their bound atomic state up to external field strengths many times higher than the binding Coulomb field and gives rise to ionization rates comparable to the light frequency, resulting in a significant extension of the frontiers of nonlinear optics and (nonrelativistic) high-field physics. Implications include the generation of coherent harmonic radiation up to kiloelectronvolt photon energies and control of the atomic dipole moment on a subfemtosecond $(1{\mathrm{f}\mathrm{s}=10}^{\mathrm{\ensuremath{-}}15}\mathrm{}\mathrm{s})$ time scale. This review presents the landmarks of the 30-odd-year evolution of ultrashort-pulse laser physics and technology culminating in the generation of intense few-cycle light pulses and discusses the impact of these pulses on high-field physics. Particular emphasis is placed on high-order harmonic emission and single subfemtosecond extreme ultraviolet/x-ray pulse generation. These as well as other strong-field processes are governed directly by the electric-field evolution, and hence their full control requires access to the (absolute) phase of the light carrier. We shall discuss routes to its determination and control, which will, for the first time, allow access to the electromagnetic fields in light waves and control of high-field interactions with never-before-achieved precision.

Intense few-cycle laser fields: Frontiers of nonlinear optics

Bones of recent mammals in the Amboseli Basin, southern Kenya, exhibit distinctive weathering characteristics that can be related to the time since death and to the local conditions of temperature, humidity and soil chemistry. A categorization of weathering characteristics into six stages, recognizable on descriptive criteria, provides a basis for investigation of weathering rates and processes. The time necessary to achieve each successive weathering stage has been calibrated using known-age carcasses. Most bones decompose beyond recognition in 10 to 15 yr. Bones of animals under 100 kg and juveniles appear to weather more rapidly than bones of large animals or adults. Small-scale rather than widespread environmental factors seem to have greatest influence on weathering characteristics and rates. Bone weathering is potentially valuable as evidence for the period of time represented in recent or fossil bone assemblages, in- cluding those on archeological sites, and may also be an important tool in censusing populations of animals in modern ecosystems.

Taphonomic and Ecologic Information Form Bone Weathering

Summary form only given. Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated by the motion of electrons inside or between atoms. Electronic dynamics on atomic length scales tends to unfold within tens to thousands of attoseconds (1 attosecond [as] = 10-18 s). Recent breakthroughs in laser science are now opening the door to watching and controlling these hitherto inaccessible microscopic dynamics. The key to accessing the attosecond time domain is the control of the electric field of (visible) light, which varies its strength and direction within less than a femtosecond (1 femtosecond = 1000 attoseconds). Atoms exposed to a few oscillations cycles of intense laser light are able to emit a single extreme ultraviolet (XUV) burst lasting less than one femtosecond. Full control of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles have recently allowed the reproducible generation and measurement of isolated sub-femtosecond XUV pulses, demonstrating the control of microscopic processes (electron motion and photon emission) on an attosecond time scale. These tools have enabled us to visualize the oscillating electric field of visible light with an attosecond "oscilloscope", to control single-electron and probe multi-electron dynamics in atoms, molecules and solids. Recent experiments hold promise for the development of an attosecond X-ray source, which may pave the way towards 4D electron imaging with sub-atomic resolution in space and time.

Attosecond Physics

Researchers report sub-angstrom fundamental-wavelength lasing at the SPring-8 Angstrom Compact Free-Electron Laser in Japan. The output has a maximum power of more than 10 GW, a pulse duration of 10−14 s and a lasing wavelength of 0.634 A.

A compact X-ray free-electron laser emitting in the sub-ångström region

Figure 8 summarizes the results obtained with a plot of the measured R s values versus the junction depth (5×1018 cm−3, from SIMS) for the investigated annealing processes. It is evident that the RTP process was able to provide the lowest values of R s but this comes with a deep x j . On the other hand, SPER, being a no-diffusion annealing process, produced a very low junction depth but the electrical activation of the dopant did not allow to keep a low level of resistance. LA was better in terms of x j (actually the SPER implants were deeper, 3 keV against 2 keV) but with a similar low R s for the higher implanted doses, indicating a much higher dopant activation as confirmed by Hall effect measurements. Those findings are confirmed by the information about the atomic order around As atoms as probed by EXAFS: there is a clear correlation between the good ordered structures around As atoms and its electrical activation, not only qualitatively but also quantitatively when a fit of the FT of EXAFS functions is carried out assuming atomic structures as determined by DFT calculation [5]. In particular, when the 1×1015 cm−2,2 keV implant is laser annealed at 1300 °C, nearly one third of the dopant is in substitutional position and one third is the fraction electrically active. The increase of the implanted dose to 3×1015 cm−2 does not particularly improve the R s and the active fraction iss only 3%. EXAFS confirmed an expectedly low (5%) fraction of As atoms within the lattice sites, whereas the inactive dopant is mainly found in As 3 V and As 4 V clusters plus a relevant fraction in SiAs monoclinic precipitates. The high concentration of As in this sample and thus the easier formation of inactive clusters is the reason why the active fraction drops to extremely low values. Therefore, a good tuning of the ion implantation specifications joined with a msec annealing such as LA looks promising in terms of x j and R s . However,m further investigations are needed to understand and possibly limit the deactivation effect often observed for high metastable activated junctions in the 500–700°C range.

Characterization of junction activation and deactivation using non-equilibrium annealing: Solid phase epitaxy, spike annealing, laser annealing instructions for

A commercial Empyrean X-ray diffractometer was adapted for combined grazing incidence X-ray fluorescence analysis (GIXRF) measurements with X-ray reflectivity (XRR) measurements. An energy-dispersive silicon drift detector was mounted and integrated in the angle-dependent data acquisition of the Empyrean. Different monochromator/X-ray optics units have been compared with the values obtained by the Atominstitut GIXRF + XRR spectrometer. Data evaluation was performed by JGIXA, a special software for combined GIXRF + XRR data fitting, developed at Atominstitut. A sample consisting of a ~50 nm nickel layer on a silicon substrate was used to compare the performance criteria (i.e. divergence and intensity) of the incident beam optics. An Empyrean X-ray diffractometer was successfully refitted to measure both GIXRF and XRR data.

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Refitting an X-ray diffraction system for combined GIXRF and XRR measurements

When a firearm is fired, gunshot residues (GSRs) are dispersed in the area around the shooter. It is very important for a police investigation at a crime scene to gain as much information from such residues as possible. Due to the minute amounts of residue available, total reflection x-ray fluorescence analysis (TXRF) seems well suited for GSR analysis. For this research, three shooting experiments were conducted. For each shot, sample carriers were distributed in the area in front of the shooter and were analyzed afterwards using TXRF. Due to the heterogeneity of the GSRs no reproducible results could be obtained. The elemental composition of the gunshot residue particles as well as the total amount being deposited showed high variation, even when the shot and the position were the same. Because of this variability, these results must be classified as statistically not very reliable. Results found with TXRF in the used configuration can neither be used neither to determine weapon or cartridge specific elemental profiles nor to estimate the shooting distance. Nevertheless Pb from the GSRs could be detected at a distance of up to 8 m from the muzzle.

Christina Streli

Papers

Characterization of junction activation and deactivation using non-equilibrium annealing: Solid phase epitaxy, spike annealing, laser annealing instructions for

Refitting an X-ray diffraction system for combined GIXRF and XRR measurements

Gunshot residue investigations using txrf