Nonlinear Terahertz Polarizability of Electrons Solvated in a Polar Liquid.

The nonlinear polaronic response of electrons solvated in liquid 2-propanol is studied by two-dimensional terahertz spectroscopy. Solvated electrons with a concentration of c_{e}≈800  μM are generated by femtosecond photoionization of alcohol molecules. Electron relaxation to a localized ground state impulsively excites coherent polaron oscillations with a frequency of 3.

Comparison of two joint-preserving treatments for osteonecrosis of the femoral head: core decompression and core decompression with additional cancellous bone grafting.

Objective: Femoral head necrosis (FHN) affects mostly young and active people. The most common operative therapy is core decompression (CD) with optional cancellous bone grafting (CBG). Because little information is available on the long-term results of these procedures, we investigated the effectiveness of CD and CD + CBG in patients with ARCO stage II FHN in terms of postoperative pain, range of motion, patient-reported outcome measures (Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, EuroQol 5D, and Short Form 36 Questionnaire), and disease progression.

Influence of avascular necrosis of the femoral head on hip prosthesis integration: a radiological analysis.

Background: Avascular osteonecrosis of the femoral head (AVN) often results in total hip arthroplasty (THA). The cause for increased THA revision rates among patients with AVN is not yet fully understood.

Purpose: To perform a comparative radiological analysis of implant integration between patients with AVN and osteoarthritis (OA).

Intraoperative control by Schanz-screws is inaccurate to achieve the exact amount of correction in de-rotational osteotomies.

Purpose: The accuracy of intraoperative control of correction commonly is achieved by K-wires or Schanz-screws in combination with goniometer in de-rotational osteotomies. The purpose of this study is to investigate the accuracy of intraoperative torsional control in de-rotational femoral and tibial osteotomies. It is hypothesized, that intraoperative control by Schanz-screws and goniometer in de-rotational osteotomies around the knee is a safe and well predictable method to control the surgical torsional correction intraoperatively.

Coherent polaron dynamics of electrons solvated in polar liquids.

An electron solvated in a polar liquid is an elementary quantum system with properties governed by electric interactions with a fluctuating molecular environment. In the prevailing single particle picture, the quantum ground and excited states are determined by a self-consistent potential, as defined by the particular local configuration of the solvation shell. This description neglects collective many-body excitations, which arise from the coupling of electronic degrees of freedom and nuclear motions of the environment.

Avascular necrosis of the femoral head: three-dimensional measurement of drilling precision reveals high accuracy and no difference between fluoroscopically controlled core decompression and cancellous bone grafting.

Introduction: Avascular osteonecrosis of the femoral head (AVN) is a widespread disease affecting mostly young and active people, often exacerbating in progressive stages, ending in joint replacement. The most common joint preserving operative therapy for early stages is core decompression (CD), optional with cancellous bone grafting (CBG). For success it is vital that the necrotic area is hit and the sclerotic rim is broken by drilling into the defect zone to relieve intraosseous pressure.

Phonon-Induced Relocation of Valence Charge in Boron Nitride Observed by Ultrafast X-Ray Diffraction.

The impact of coherent phonon excitations on the valence charge distribution in cubic boron nitride is mapped by femtosecond x-ray powder diffraction. Zone-edge transverse acoustic (TA) two-phonon excitations generated by an impulsive Raman process induce a steplike increase of diffracted x-ray intensity. Charge density maps derived from transient diffraction patterns reveal a spatial transfer of valence charge from the interstitial region onto boron and nitrogen atoms.

Field-Induced Electron Generation in Water: Solvation Dynamics and Many-Body Interactions.

The solvated electron represents an elementary quantum system in a liquid environment. Electrons solvated in water have raised strong interest because of their prototypical properties, their role in radiation chemistry, and their relevance for charge separation and transport. Nonequilibrium dynamics of photogenerated electrons in water occur on ultrafast time scales and include charge transfer, localization, and energy dissipation processes.

Underdamped longitudinal soft modes in ionic crystallites-lattice and charge motions observed by ultrafast x-ray diffraction.

Soft modes in crystals are lattice vibrations with frequencies that decrease and eventually vanish as the temperature approaches a critical point, e.g., a structural change due to a phase transition.

Two-color two-dimensional terahertz spectroscopy: A new approach for exploring even-order nonlinearities in the nonperturbative regime.

Nonlinear two-dimensional terahertz (2D-THz) spectroscopy at frequencies of the emitted THz signal different from the driving frequencies allows for exploring the regime of (off-)resonant even-order nonlinearities in condensed matter. To demonstrate the potential of this method, we study two phenomena in the nonlinear THz response of bulk GaAs: (i) The nonlinear THz response to a pair of femtosecond near-infrared pulses unravels novel fourth- and sixth-order contributions involving interband shift currents, Raman-like excitations of transverse-optical phonon and intervalence-band coherences. (ii) Transient interband tunneling of electrons driven by ultrashort mid-infrared pulses can be effectively controlled by a low-frequency THz field with amplitudes below 50 kV/cm.

Two-dimensional terahertz spectroscopy of condensed-phase molecular systems.

Nonlinear terahertz (THz) spectroscopy relies on the interaction of matter with few-cycle THz pulses of electric field amplitudes up to megavolts/centimeter (MV/cm). In condensed-phase molecular systems, both resonant interactions with elementary excitations at low frequencies such as intra- and intermolecular vibrations and nonresonant field-driven processes are relevant. Two-dimensional THz (2D-THz) spectroscopy is a key method for following nonequilibrium processes and dynamics of excitations to decipher the underlying interactions and molecular couplings.

Terahertz Polaron Oscillations of Electrons Solvated in Liquid Water.

The terahertz (THz) response of solvated electrons in liquid water is studied in nonlinear ultrafast pump-probe experiments. Free electrons with concentrations from c_{e}=4 to 140×10^{-6} moles/liter are generated by high-field THz or near-infrared multiphoton excitation. The time-resolved change of the dielectric function as mapped by broadband THz pulses exhibits pronounced oscillations persisting up to 30 ps.

Compact high-flux hard X-ray source driven by femtosecond mid-infrared pulses at a 1 kHz repetition rate.

A novel, to the best of our knowledge, table-top hard X-ray source driven by femtosecond mid-infrared pulses provides 8 keV pulses at a 1 kHz repetition rate with an unprecedented flux of up to 1.5×10 X-ray photons/s. Sub-100 fs pulses at a center wavelength of 5 µm and multi-millijoule energy are generated in a four-stage optical parametric chirped-pulse amplifier and focused onto a thin Cu tape target.

Spatial distribution of electric-field enhancement across the gap of terahertz bow-tie antennas.

The electric-field enhancement in terahertz (THz) antennas designed for nonlinear THz spectroscopy of soft matter is characterized by spatially resolved electrooptic sampling. To mimic the relevant interaction geometry, metallic, resonant bow-tie antennas are deposited on a thin zinc telluride crystal of 10 µm thickness. The THz electric field transmitted through the antenna gap is recorded by electrooptic sampling.

Field-Induced Tunneling Ionization and Terahertz-Driven Electron Dynamics in Liquid Water.

Liquid water at ambient temperature displays ultrafast molecular motions and concomitant fluctuations of very strong electric fields originating from the dipolar HO molecules. We show that such random intermolecular fields induce the tunnel ionization of water molecules, which becomes irreversible if an external terahertz (THz) pulse imposes an additional directed electric field on the liquid. Time-resolved nonlinear THz spectroscopy maps charge separation, transport, and localization of the released electrons on a few-picosecond time scale.

Frequency Upshift of the Transverse Optical Phonon Resonance in GaAs by Femtosecond Electron-Hole Excitation.

The impact of transient electric currents on the transverse optical (TO) phonon resonance is studied after excitation by two femtosecond near-infrared pulses via the fourth-order nonlinear terahertz emission. Nonlinear signals due to interband shift currents and heavy-hole-light-hole polarizations are separated from Raman-induced TO phonon coherences. The latter display a frequency upshift by some 100 GHz upon interband excitation of an electron-hole plasma.

Terahertz Driven Amplification of Coherent Optical Phonons in GaAs Coupled to a Metasurface.

We demonstrate amplification of longitudinal optical (LO) phonons by polar-optical interaction with an electron plasma in a GaAs structure coupled to a metallic metasurface using two-color two-dimensional spectroscopy. In a novel scheme, the metamaterial resonator enhances broadband terahertz fields, which generate coherent LO phonons and drive free electrons in the conduction band of GaAs. The time evolution of the LO phonon amplitude is monitored with midinfrared pulses via the LO-phonon-induced Kerr nonlinearity of the sample, showing an amplification of the LO phonon amplitude by up to a factor of 10, in agreement with a theoretical estimate.

Recent advances in ultrafast X-ray sources.

Over more than a century, X-rays have transformed our understanding of the fundamental structure of matter and have been an indispensable tool for chemistry, physics, biology, materials science and related fields. Recent advances in ultrafast X-ray sources operating in the femtosecond to attosecond regimes have opened an important new frontier in X-ray science. These advances now enable: (i) sensitive probing of structural dynamics in matter on the fundamental timescales of atomic motion, (ii) element-specific probing of electronic structure and charge dynamics on fundamental timescales of electronic motion, and (iii) powerful new approaches for unravelling the coupling between electronic and atomic structural dynamics that underpin the properties and function of matter.

Phonon driven charge dynamics in polycrystalline acetylsalicylic acid mapped by ultrafast x-ray diffraction.

The coupled lattice and charge dynamics induced by phonon excitation in polycrystalline acetylsalicylic acid (aspirin) are mapped by femtosecond x-ray powder diffraction. The hybrid-mode character of the 0.9 ± 0.

Predicting Outcome after Total Hip Arthroplasty: The Role of Preoperative Patient-Reported Measures.

Choosing the appropriate patient for surgery is crucial for good outcome in total hip arthroplasty (THA). Therefore, parameters predicting outcome preoperatively are of major interest. In the current study, we compared the predictive power of different presurgical measures in minimally invasive THA.

Resonant Second-Order Nonlinear Terahertz Response of Gallium Arsenide.

The second-order nonlinear response of bulk GaAs in the terahertz (THz) range is mapped via the THz field emitted after near-infrared interband excitation. Phase-resolved THz detection reveals three nonlinear processes occurring in parallel, the Raman excitation of transverse optical phonons, the creation of coherent polarizations on heavy-hole-light-hole transitions, and the generation of displacive shift currents with a THz spectrum controlled by the near-infrared optical phase. Theoretical calculations reproduce the data and demonstrate the interband character of shift currents.

Surgical training does not affect operative time and outcome in total knee arthroplasty.

Training the next generation of orthopaedic surgeons in total knee arthroplasty (TKA) is crucial, but might affect operative time and outcome. We hypothesized that the learning curve of residents in TKA has an impact on (1) operative time, (2) complication rates and (3) early postoperative outcome. In a retrospective analysis of 738 primary TKAs from our institutional joint registry, operative time, complication rates, patient-reported outcome measures (EQ-5D, WOMAC) within the first year and responder rates for positive outcome as defined by the OMERACT-OARSI criteria were compared between trainee and senior surgeons differentiating between conventional and navigated TKA.

Soft-mode driven polarity reversal in ferroelectrics mapped by ultrafast x-ray diffraction.

Quantum theory has linked microscopic currents and macroscopic polarizations of ferroelectrics, but the interplay of lattice excitations and charge dynamics on atomic length and time scales is an open problem. Upon phonon excitation in the prototypical ferroelectric ammonium sulfate [(NH)SO], we determine transient charge density maps by femtosecond x-ray diffraction. A newly discovered low frequency-mode with a 3 ps period and sub-picometer amplitudes induces periodic charge relocations over some 100 pm, a hallmark of soft-mode behavior.

Predictors of Outcome After Primary Total Joint Replacement.

Background: Total hip and knee replacements are frequently performed curative treatment options in end-stage arthritis. In this study, we analyzed clinical outcome, complications, and predictors of outcome in modern joint replacement.

Methods: In a retrospective analysis of over 2000 primary total hip and knee replacements from our institutional joint registry, responder rates for positive outcome as defined by the OMERACT-OARSI criteria, postoperative complication rates, and patient-reported outcome measures (EQ-5D, WOMAC) within the first year were compared between hip and knee replacements.

Mid-infrared beam splitter for ultrashort pulses.

A design is presented for a beam splitter suitable for ultrashort pulses in the mid-infrared and terahertz spectral range consisting of a structured metal layer on a diamond substrate. Both the theory and experiment show that this beam splitter does not distort the temporal pulse shape.