Compact magnetospectrometer for pulsed magnets based on infrared quantum cascade lasers

In this paper we present a portable quantum cascade laser (QCL) based infrared magnetospectrometer covering the spectral range from 5 to 120 μm. The variation of the excitation wavelength is enabled by an easy change of the QCL plug-in modules, while the use of any other external source is also possible. The performance of the setup is illustrated via cyclotron-resonance studies under pulsed magnetic fields up to 60 T.

[Modified two-rescuer resuscitation algorithm. Alternative for international missions of the German Armed Forces!]

BACKGROUND

The aim of this study was to examine whether it is possible to perform resuscitation according to the present European Resuscitation Council (ERC) guidelines with a modified algorithm in the case of special, e.g. military, circumstances. On international missions of the German Armed Forces a rescue team only consists of an emergency physician and a paramedic. As the German Armed Forces require the same means of medical aid for all soldiers on every type of mission worldwide the algorithm must meet the ERC requirements.

MATERIAL AND METHODS

In the study 20 medical teams specialized in resuscitation were examined. Of these teams 10 were from the German Armed Forces (the physician is a certified emergency physician) and 10 were civilian (the emergency physicians had up to 28 years experience). Each team was monitored as they performed resuscitation on a simulator for a period of 10 min. The patient's airway was secured by a laryngeal tube (LT) and over-the-head chest compressions were performed by the emergency physician. During resuscitation both team members held their position. In addition to comparing all results to the ERC guidelines both groups were analyzed separately and compared to each other.

RESULTS

The median time needed for securing the airway was 17 s without any differences between the 2 groups. In 75% of the cases the time needed for successfully securing the airway on the first attempt was less than the allowed 30 s. In 5 cases (25%) the teams did not manage to successfully install the LT during the first attempt (4 failed attempts were performed by civilian teams and 1 by the military emergency teams); however, all 5 teams were successful at the second attempt. In the cases where the placement of the LT was not successful at the first attempt the time required for the final and successful placement was nevertheless less than 40 s. During the 10 min resuscitation procedure the hands-off fraction was on average 22.4%. No differences between the two groups were noted concerning the hands-off time (133.5 s for the civilian teams and 134.5 s for the teams of the German Armed Forces). The frequency of chest compressions was above the required 100/min (for the civilian teams 110/min and for the teams of the German Armed Forces 116.5/min).

CONCLUSION

During military missions of the German Armed Forces there are no other options to perform resuscitation than by performing this procedure with only two rescuers. Using the algorithm in a modified way securing of the airway with an LT, the performance of over-the-head chest compressions and an effective resuscitation with advanced cardiac life support according to the ERC guidelines of 2005 are feasible even with 2 rescuers. Using the LT instead of endotracheal intubation to secure the airway particularly contributed to shortening the hands-off time.

Excitation wavelength dependence of phase matched terahertz emission from a GaAs slab

We report on phase matched THz emission from GaAs using the anomalous dispersion introduced by optical phonon absorption at the reststrahlenband in GaAs. For this system tunability of the emitted THz frequencies by changing the near infrared excitation wavelength is predicted. We investigate this phenomenon for an oversized double metallized GaAs waveguide. A shift in the THz spectra is observed when the near-infrared wavelength is varied. Enhanced emission is found when phase matching is achieved at 1.4 µm.

Impulsive terahertz radiation with high electric fields from an amplifier-driven large-area photoconductive antenna

We report on the generation of impulsive terahertz (THz) radiation with 36 kV/cm vacuum electric field (1.5 mW average thermal power) at 250 kHz repetition rate and a high NIR-to-THz conversion efficiency of 2 x 10(-3). This is achieved by photoexciting biased large-area photoconductive emitter with NIR fs pulses of microJ pulse energy. We demonstrate focussing of the THz beam by tailoring the pulse front of the exciting laser beam without any focussing element for the THz beam. A high dynamic range of 10(4) signal-to-noise is obtained with an amplifier based system.

Long lifetimes of quantum-dot intersublevel transitions in the terahertz range

Carrier relaxation is a key issue in determining the efficiency of semiconductor optoelectronic device operation. Devices incorporating semiconductor quantum dots have the potential to overcome many of the limitations of quantum-well-based devices because of the predicted long quantum-dot excited-state lifetimes. For example, the population inversion required for terahertz laser operation in quantum-well-based devices (quantum-cascade lasers) is fundamentally limited by efficient scattering between the laser levels, which form a continuum in the plane of the quantum well. In this context, semiconductor quantum dots are a highly attractive alternative for terahertz devices, because of their intrinsic discrete energy levels. Here, we present the first measurements, and theoretical description, of the intersublevel carrier relaxation in quantum dots for transition energies in the few terahertz range. Long intradot relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to approximately 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. Our studies pave the way for quantum-dot terahertz device development, providing the fundamental knowledge of carrier relaxation times required for optimum device design.

Terahertz two-photon quantum well infrared photodetector

A two-photon detector based on intersubband transitions in GaAs/AlGaAs quantum wells operating in the Terahertz regime below the Reststrahlenband is reported. Resonantly enhanced optical nonlinearities enables sensitive quadratic detection at pJ pulse energies. We demonstrate its use in a quadratic autocorrelator for far-infrared picosecond pulses at around 7 THz.

Superconducting state in a gallium-doped germanium layer at low temperatures

We demonstrate that the third elemental group-IV semiconductor, germanium, exhibits superconductivity at ambient pressure. Using advanced doping and annealing techniques of state-of-the-art semiconductor processing, we have fabricated a highly Ga-doped Ge (GeratioGa) layer in near-intrinsic Ge. Depending on the detailed annealing conditions, we demonstrate that superconductivity can be generated and tailored in the doped semiconducting Ge host at temperatures as high as 0.5 K. Critical-field measurements reveal the quasi-two-dimensional character of superconductivity in the approximately 60 nm thick GeratioGa layer. The Cooper-pair density in GeratioGa appears to be exceptionally low.

Fano signatures in the intersubband terahertz response of optically excited semiconductor quantum wells

Absorption and transmission spectra of broadband terahertz pulses are measured to probe the intersubband response of an optically excited quantum-well heterostructure. While the terahertz absorption shows the single peak of the resonant intersubband transition, the transmission spectra display strong Fano signatures due to the phase sensitive superposition of ponderomotive and terahertz currents as predicted by our microscopic theory.

Terahertz Bessel-Gauss beams of radial and azimuthal polarization from microstructured photoconductive antennas

We report on emission and detection of pulsed terahertz radiation of radial and azimuthal polarization by microstructured photoconductive antennas. To this end the electrode geometry of the emitter is inverse to the desired THz field pattern and a second periodic structure prevents destructive interference effects. Beam profiles of freely propagating THz waves are studied for divergent and refocused beams. They can be well described as the lowest order Bessel-Gauss modes with a divergence comparable to linearly polarized Gaussian beams. Additionally, mode sensitive detection is demonstrated for radially polarized radiation.

KDEL-tailed cysteine endopeptidases involved in programmed cell death, intercalation of new cells, and dismantling of extensin scaffolds

KDEL-tailed cysteine endopeptidases are a group of papain-type peptidases found in senescing tissue undergoing programmed cell death (PCD). Their genes have so far been cloned and analyzed in 12 angiosperms. They are synthesized as proenzymes with a C-terminal KDEL endoplasmatic reticulum retention signal, which is removed with the prosequence to activate enzyme activity. We previously identified three genes for KDEL-tailed cysteine endopeptidases (AtCEP1, AtCEP2, AtCEP3) in Arabidopsis thaliana. Transgenic plants of A. thaliana expressing β-glucuronidase (GUS) under the control of the promoters for the three genes were produced and analyzed histochemically. GUS activity was promoter- and tissue-specific GUS activity during seedling, flower, and root development, especially in tissues that collapse during final stages of PCD, and in the course of lateral root formation. KDEL-tailed cysteine endopeptidases are unique in being able to digest the extensins that form the basic scaffold for cell wall formation. The broad substrate specificity is due to the structure of the active site cleft of the KDEL-tailed cysteine endopeptidase that accepts a wide variety of amino acids, including proline and glycosylated hydroxyproline of the hydroxyproline rich glycoproteins of the cell wall.

Anisotropy contrast in phonon-enhanced apertureless near-field microscopy using a free-electron laser

We demonstrate the imaging of ferroelectric domains in BaTiO3, using an infrared-emitting free-electron laser as a tunable optical source for scattering scanning near-field optical microscopy and spectroscopy. When the laser is tuned into the spectral vicinity of a phonon resonance, ferroelectric domains can be resolved due to the anisotropy of the dielectric properties of the material. Slight detuning of the wavelength gives rise to a contrast reversal clearly evidencing the resonant character of the excitation. The near-field domain contrast shows that the orientation of the dielectric tensor with respect to the sample surface has a clear influence on the near-field signal.

[Trauma management under military conditions. A German field hospital in Afghanistan in comparison with the National Trauma Registry]

BACKGROUND

The German armed forces run a role-III field hospital in Kabul, Afghanistan. Emergency room (ER) management is of utmost importance as a link between pre- and in-hospital treatment.

PATIENTS AND METHODS

Prospective data were acquired of all patients admitted to the ER over a 3-month period. The quality of ER management was tested using established audit filters and comparing the results with those of the National Trauma Registry.

RESULTS

A total of 353 patients were admitted to the ER (48.4% trauma cases). Fifty-nine patients were major trauma cases, and the proportion of combat-related injury was 33.2%. In comparison to the National Trauma Registry, significant differences were observed regarding age (25.2 vs 41.7 years, P<0.0001) and injury severity (NISS 18.8 vs 28.8, P<0.0001). The demands on the quality of ER management have increased. Using the audit filters of the National Trauma Registry, significant differences were observed regarding ER management.

CONCLUSION

In a military setting, medical treatment of major trauma victims is influenced by multiple adverse factors significantly affecting the quality of trauma management.

[Advanced Trauma Life Support. A training concept also for Europe]

Advanced Trauma Life Support (ATLS) is a concept for rapid initial assessment and primary management of an injured patient, starting at the time of injury and continuing through initial assessment, lifesaving interventions, re-evaluation, stabilization and, when needed, transfer to a trauma centre. Despite some shortcomings, it is the only standardized concept for emergency room management, which is internationally accepted. Because of its simple and clear structure, it is flexible and can be universally integrated into existing emergency room algorithms under consideration of local, regional as well as national and international peculiarities in the sense of a "common language of trauma". Under these aspects ATLS also seems to be a valid concept for Europe.

Spectroscopic THz near-field microscope

We demonstrate a scattering-type scanning near-field optical microscope (s-SNOM) with broadband THz illumination. A cantilevered W tip is used in tapping AFM mode. The direct scattering spectrum is obtained and optimized by asynchronous optical sampling (ASOPS), while near-field scattering is observed by using a space-domain delay stage and harmonic demodulation of the detector signal. True near-field interaction is determined from the approach behavior of the tip to Au samples. Scattering spectra of differently doped Si are presented.