Far infrared sub-nanosecond pulse generation in GaP with a time-synchronized mode-locked double-frequency Nd: Glass laser system

Light pulses of 149 m wavelength and 700 ps duration are generated by non-collinear phase-matched difference frequency mixing of laser pulses at 1053.5 and 1061 nm in a (110) cut GaP crystal. The pump laser pulses are generated in a time-synchronized mode-locked double-frequency Nd:glass laser system consisting of a silicate glass branch and a phosphate glass branch. A photon conversion efficiency of 4 × 10^–6 is achieved. The non-linear susceptibility constant of GaP is determined to be d ₁₄ = (10 ± 1) pm V^–1.     

Identification of a core-periphery structure among participants of a business climate survey

Processes of social opinion formation might be dominated by a set of closely connected agents who constitute the cohesive ‘core’ of a network and have a higher influence on the overall outcome of the process than those agents in the more sparsely connected ‘periphery’. Here we explore whether such a perspective could shed light on the dynamics of a well known economic sentiment index. To this end, we hypothesize that the respondents of the survey under investigation form a core-periphery network, and we identify those agents that define the core (in a discrete setting) or the proximity of each agent to the core (in a continuous setting). As it turns out, there is significant correlation between the so identified cores of different survey questions. Both the discrete and the continuous cores allow an almost perfect replication of the original series with a reduced data set of core members or weighted entries according to core proximity. Using a monthly time series on industrial production in Germany, we also compared experts’ predictions with the real economic development. The core members identified in the discrete setting showed significantly better prediction capabilities than those agents assigned to the periphery of the network.     

Operation of a Raman laser in bulk silicon

A Raman laser based on a bulk silicon single crystal with 1.127 μm emission wavelength is demonstrated. The Si crystal with 30 mm length was placed into an external cavity and pumped by a Q-switched Nd:YAG master oscillator power amplifier system. Strong defocusing of the pump and Raman laser beam by free carriers was compensated by an intracavity lens. Raman laser operation with a pulse duration of 2.5 ns was identified by a Raman laser threshold significantly lower than the single-pass stimulated Raman-scattering threshold. Linear absorption losses of the 1.06415 μm pump radiation are strongly reduced by cooling the Si crystal to a temperature of 10 K.     

Stimulated Raman scattering in natural crystals of fluorapatite,Ca5(PO4)3F

Hexagonal Ca₅(PO₄)₃F, known as natural crystal fluorapatite and oldest host‐crystal for Ln³⁺‐lasant ions, is presented as a Raman‐active material. High‐order Raman‐induced χ⁽³⁾‐nonlinear processes are discovered in natural crystals of fluorapatite under picosecond pumping at 1.064 μm and 0.532 μm wavelength. A multitude of Stokes and anti‐Stokes components is generated in the ultraviolet, visible and near‐infrared spectral region by stimulated Raman scattering (SRS) and Raman four‐wave mixing (FWHM), resulting in a frequency comb with a width of 520 THz. The spectral lines are identified and attributed to the ν₁(A_g) vibration mode of the tetrahedral [PO₄] units which is related to a Raman shift of ω_SRS ≈ 965 cm⁻¹. The first Stokes steady‐state Raman gain coefficient in the near‐infrared spectral range is estimated to be >0.38 cm·GW⁻¹. Finally, a short review of SRS‐promoting vibration modes and observed χ⁽³⁾‐ nonlinear interactions in all known SRS‐active natural crystals (minerals) is given.

     

2‐Sulfoethylammonium hexafluoridoantimonate

The title salt, (C₂H₈NO₃S)[SbF₆], which contains the protonated form of taurine (2‐aminoethanesulfonic acid), was synthesized in anhydrous hydrofluoric acid and recrystallized as colourless block‐shaped crystals from liquid SO₂. In the solid state, a three‐dimensional network is observed. This is formed by intra‐ and intermolecular N—H...O, N—H...F and O—H...F hydrogen bonds.     

AFM investigation of silicon substrates for chemical vapour deposition of diamond films

AFM has been used to study surface modifications on silicon (100) substrates for CVD diamond deposition during bias pretreatment in a hot-filament reactor under various conditions. Both topographical images, force-distance measurements and chemical etching with HF have been implemented to obtain information on the processes involved. The results show, that the observed roughening, which strongly depends on the gas phase composition, is caused by chemical etching of the surface dominated by removal of elemental silicon via formation of silicon hydride.     

The decomposition numbers of the hecke algebra of typeF 4

LetW be the finite Coxeter group of typeF ₄, andH _r (q) be the associated Hecke algebra, with parameter a prime powerq, defined over a valuation ringR in a large enough extension field ofQ, with residue class field of characteristicr. In this paper, ther-modular decomposition numbers ofH _R (q) are determined for allq andr such thatr does not divideq. The methods of the proofs involve the study of the generic Hecke algebra of typeF ₄ over the ringA = ℤ[u ^1/2,u ^-1/2] of Laurent polynomials in an indeterminateu ^1/2 and its specializations onto the ring of integers in various cyclotomic number fields. Substancial use of computers and computer program systems (GAP, MAPLE, Meat-Axe) has been made.     

Activation-analysis investigation of the behaviour of biological trace elements during wound healing: The roles of calcium and iron

Summary Instrumental neutron-activation analysis was used for the determination of Ca, Cr, Fe, Co, Ni, Zn, Mo, Ag, Sb, and Hg. Blood and tissue samples of 70 mg each were analysed and, from these, changes in the concentrations of calcium, iron, and zinc in affected tissue were established. In this article the results of the behaviour of calcium and iron are reported. The calcium concentration of the fracture haematoma blood (FHB) is about 20 times higher than that of arterial or venous blood (rabbits). The level and the change with time of the calcium concentration in FHB-deposits (rabbits) can be explained by the participation of calcium in the haemolysis of the erythrocytes of the FHB which has been injected for the formation of the deposits. The behaviour of the iron in the FHB-deposits is in agreement with this explanation. The change in calcium concentration in the crust of punch-hole wounds in the skin (rats) can be attributed to the mobilization of calcium for fibrin formation. As a reason for the level and the change with time of the iron concentration in the tissue in the area of fascia and muscle incision wounds (rabbits) the participation of iron in the formation of collagen is discussed. From comparison of the behavoiur of the iron in the FHB-deposits with that in the area of incision wounds it follows that iron enrichments in the area of a complication-free wound are not predominantly caused by a wound haematoma.

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Zusammenfassung Die Untersuchungen erfolgten mit Hilfe der instrumentellen Neutronenaktivierungsanalyse. Das Verfahren war für die Erfassung der Gehalte an Ca, Cr, Fe, Co, Ni, Zn, Mo, Ag, Sb und Hg ausgelegt. Es wurden Blut bzw. Gewebeproben von jeweils etwa 70 mg analysiert und dabei Änderungen der Calcium-, Eisen- und Zinkgehalte des betroffenen Gewebes festgestellt. In diesem Artikel wird über das Verhalten des Calciums und Eisens berichtet. Der Calciumgehalt des Frakturhämatombluts (FHB) ist etwa 20mal höher als der von arteriellem oder venösem Blut (Kaninchen). Höhe und zeitlicher Verlauf der Calciumgehalte von FHB-Depots (Kaninchen) lassen sich mit der Beteiligung des Calciums an der Hämolyse der Erythrozyten des FHB erklären, das zur Bildung der Depots injiziert wurde. Das Verhalten des Eisens in den FHB-Depots stimmt mit dieser Erklärung überein. Der Verlauf der Calciumgehalte des Schorfes von Hautstanzwunden (Ratten) kann auf die Mobilisierung von Calcium für die Fibrinbildung zurückgeführt werden. Als Ursache für Höhe und zeitlichen Verlauf der Eisengehalte des Gewebes im Bereich von Faszie- und Muskelschnittwunden (Kaninchen) wird die Beteiligung des Eisens an der Kollagenbildung diskutiert. Aus dem Vergleich des Verhaltens des Eisens in FHB-Depots und im Bereich von Schnittwunden folgt, daß die Eisenanreicherungen im Bereich einer komplikationslosen Schnittwunde nicht vorwiegend durch ein Wundhämatom bedingt sind.

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Auszug aus der Dissertation des Herrn Danilo Boani, Technische Universität München. This work was supported by the Bundesministerium für Forschung und Technologie and the Fonds der Chemischen Industrie, and the paper was presented at the International Symposium on Microchemical Techniques, Davos, May 1977.