Structural insight into the cooperativity of spin crossover compounds.

Spin-crossover (SCO) compounds are promising materials for a wide variety of industrial applications. However, the fundamental understanding of their nature of transition and its effect on the physical properties are still being fervently explored; the microscopic knowledge of their transition is essential for tailoring their properties. Here an attempt is made to correlate the changes in macroscopic physical properties with microscopic structural changes in the orthorhombic and monoclinic polymorphs of the SCO compound Fe(PM-Bia)2(NCS)2 (PM = N-2'-pyridylmethylene and Bia = 4-aminobiphenyl) by employing single-crystal X-ray diffraction, magnetization and DSC measurements. The dependence of macroscopic properties on cooperativity, highlighting the role of hydrogen bonding, π-π and van der Waals interactions is discussed. Values of entropy, enthalpy and cooperativity are calculated numerically based on the Slichter-Drickamer model. The particle size dependence of the magnetic properties is probed along with the thermal exchange and the kinetic behavior of the two polymorphs based on the dependence of magnetization on temperature scan rate and a theoretical model is proposed for the calculation of the non-equilibrium spin-phase fraction. Also a scan-rate-dependent two-step behavior observed for the orthorhombic polymorph, which is absent for the monoclinic polymorph, is reported. Moreover, it is found that the radiation dose from synchrotron radiation affects the spin-crossover process and shifts the transition region to lower temperatures, implying that the spin crossover can be tuned with radiation damage.

Dynamics in the Plastic Crystalline Phases of Cyclohexanol and Cyclooctanol Studied by Quasielastic Neutron Scattering.

Plastic crystals are a promising candidate for solid state ionic conductors. In this work, quasielastic neutron scattering is employed to investigate the center of mass diffusive motions in two types of plastic crystalline cyclic alcohols: cyclohexanol and cyclooctanol. Two separate motions are observed which are attributed to long-range translational diffusion (α-process) and cage rattling (fast ß-process). Residence times and diffusion coefficients are calculated for both processes, along with the confinement distances for the cage rattling. In addition, a binary mixture of these two materials is measured to understand how the dynamics change when a second type of molecule is added to the matrix. It is observed that, upon the addition of the larger cyclooctanol molecules into the cyclohexanol solution, the cage size decreases, which causes a decrease in the observed diffusion rates for both the α- and fast ß-processes.

Glycerol Hydrogen-Bonding Network Dominates Structure and Collective Dynamics in a Deep Eutectic Solvent.

The deep eutectic solvent glyceline formed by choline chloride and glycerol in 1:2 molar ratio is much less viscous compared to glycerol, which facilitates its use in many applications where high viscosity is undesirable. Despite the large difference in viscosity, we have found that the structural network of glyceline is completely defined by its glycerol constituent, which exhibits complex microscopic dynamic behavior, as expected from a highly correlated hydrogen-bonding network. Choline ions occupy interstitial voids in the glycerol network and show little structural or dynamic correlations with glycerol molecules. Despite the known higher long-range diffusivity of the smaller glycerol species in glyceline, in applications where localized dynamics is essential (e.g., in microporous media), the local transport and dynamic properties must be dominated by the relatively loosely bound choline ions.

Assessing psychological and supportive care needs in glioma patients - feasibility study on the use of the Supportive Care Needs Survey Short Form (SCNS-SF34-G) and the Supportive Care Needs Survey Screening Tool (SCNS-ST9) in clinical practice.

Neuro-oncological patients experience high symptom and psychosocial burden. The aim was to test feasibility and practicability of the Supportive Care Needs Survey Short Form (SCNS-SF34-G) and the SCNS-Screening Tool (SCNS-ST9) to assess supportive care needs of neuro-oncological patients in clinical routine. A total of 173 patients, most with a primary diagnosis of high-grade glioma (81%), were assessed first using SCNS-SF34-G in comparison to two well-established patient-reported outcome measures, the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQC30 + QLQ-BN20) and Distress Thermometer (DT). In a follow-up assessment, SCNS-ST9 was used in a subgroup (n = 90). Questionnaires were completed either with personal guidance offered (group A) or by patients alone (group B). Feasibility was compared between instruments and groups for possible associations with patient and treatment-related factors. Missing values occurred in similar frequencies in all instruments. Errors in completion occurred in SCNS-SF34-G in 20% and in SCNS-ST9 in 16%; difficulties in completion were observed more often in SCNS-SF34-G and SCNS-ST9 (39%) compared to DT and EORTC (13%, p < .001). Distress was found to be associated with difficulties in completion of SCNS (OR 1.4, [95% CI 1.1-1.9], p = .013). SCNS-SF34 and SCNS-ST9 are suitable tools for glioma patients as long as personal guidance is offered.

Polymer dynamics under cylindrical confinement featuring a locally repulsive surface: A quasielastic neutron scattering study.

We investigated the effect of intermediate cylindrical confinement with locally repulsive walls on the segmental and entanglement dynamics of a polymer melt by quasielastic neutron scattering. As a reference, the corresponding polymer melt was measured under identical conditions. The locally repulsive confinement was realized by hydrophilic anodic alumina nanopores with a diameter of 20 nm. The end-to-end distance of the hydrophobic infiltrated polyethylene-alt-propylene was close to this diameter. In the case of hard wall repulsion with negligible local attraction, several simulations predicted an acceleration of segmental dynamics close to the wall. Other than in attractive or neutral systems, where the segmental dynamics is slowed down, we found that the segmental dynamics in the nanopores is identical to the local mobility in the bulk. Even under very careful scrutiny, we could not find any acceleration of the surface-near segmental motion. On the larger time scale, the neutron spin-echo experiment showed that the Rouse relaxation was not altered by confinement effects. Also the entanglement dynamics was not affected. Thus at moderate confinement conditions, facilitated by locally repulsive walls, the dynamics remains as in the bulk melt, a result that is not so clear from simulations.

Incorporation of aspirin modulates the dynamical and phase behavior of the phospholipid membrane.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most widely used medications in the world for their analgesic, antipyretic, and anti-inflammatory actions, despite a well-known incidence of a wide spectrum of their adverse effects. To a great extent, beneficial action and side effects of NSAIDs are associated with the interaction of these drugs at the cell membrane level. Here, we use neutron scattering to combine elastic intensity scans, quasielastic and neutron spin echo (NSE) measurements to understand the effect of aspirin, a commonly used NSAID, on the dynamical and phase behavior of the membrane of dimyristoylphosphatidylcholine (DMPC), a prominent representative of phospholipids residing in the outer leaflet of the human erythrocyte membrane. Elastic intensity scans reveal that addition of aspirin not only eliminates the pre-transition (solid gel to ripple phase), but also broadens the main phase transition (ripple to fluid phase) in the membrane. Moreover, the main phase transition becomes shifted toward a lower temperature. These results are found to be consistent with our differential scanning calorimetry measurements. Elastic intensity scans further suggest that aspirin inhibits the membrane from going into the ordered phase and overall induces disorder in the membrane, thus indicating enhancement in the fluidity of the membrane. Quasielastic neutron scattering (QENS) data show that aspirin affects both lateral lipid motion within the leaflet and the localized internal motion of the lipid. Aspirin accelerates both lateral and internal motions, with the more pronounced effect observed for the ordered phase of the neat membrane. Intermediate scattering function as observed by NSE has been analyzed using the Zilman Granek model, which indicates that addition of aspirin alters the bending modulus of the membrane to make the membrane softer. Our study provides a quantitative description of the effect of an archetypal NSAID, aspirin, on the various physical properties of the model biological membrane, which is essential for understanding the complex drug-membrane interaction.

Effect of adding nanometre-sized heterogeneities on the structural dynamics and the excess wing of a molecular glass former.

We present the relaxation dynamics of glass-forming glycerol mixed with 1.1 nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric spectroscopy (DS) and two different neutron scattering (NS) techniques. Both, the reorientational dynamics as measured by DS and the density fluctuations detected by NS reveal a broadening of the α relaxation when POSS molecules are added. Moreover, we find a significant slowing down of the α-relaxation time. These effects are in accord with the heterogeneity scenario considered for the dynamics of glasses and supercooled liquids. The addition of POSS also affects the excess wing in glycerol arising from a secondary relaxation process, which seems to exhibit a dramatic increase in relative strength compared to the α relaxation.

Nanoscale Motion of Soft Nanoparticles in Unentangled and Entangled Polymer Matrices.

We have studied the motion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles modified with poly(ethylene glycol) (PEG) arms immersed in PEG matrices of different molecular weight. Employing neutron spin echo spectroscopy in combination with pulsed field gradient (PFG) NMR we found the following. (i) For entangled matrices the center of mass mean square displacement (MSD) of the PEG-POSS particles is subdiffusive following a t^{0.56} power law. (ii) The diffusion coefficient as well as the crossover to Fickian diffusion is independent of the matrix molecular weight and takes place as soon as the center of mass has moved a distance corresponding to the particle radius-this holds also for unentangled hosts. (iii) For the entangled matrices Rubinstein's scaling theory is validated; however, the numbers indicate that beyond Rouse friction the entanglement constraints appear to strongly increase the effective friction even on the nanoparticle length scale imposing a caveat on the interpretation of microrheological experiments. (iv) The oligomer decorated PEG-POSS particles exhibit the dynamics of a Gaussian star with an internal viscosity that rises with an increase of the host molecular weight.

Characteristic length scales of the secondary relaxations in glass-forming glycerol.

We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends on the time scale of the relaxation of interest. We use neutron backscattering to identify the characteristic length scale of 0.7 Å for the faster secondary relaxation described in the framework of the mode-coupling theory (MCT). Neutron spin-echo is employed to probe the slower secondary relaxation of the excess wing type at a low temperature ( ∼ 1.13T g . The characteristic length scale for this excess wing dynamics is approximately 4.7 Å. Besides the Q -dependence, the direct coupling of neutron scattering signal to density fluctuation makes this technique indispensable for measuring the length scale of the microscopic relaxation dynamics.

Nanometer-sized dynamic entities in an aqueous system.

Using neutron spin-echo and backscattering spectroscopy, we have found that at low temperatures water molecules in an aqueous solution engage in center-of-mass dynamics that are different from both the main structural relaxations and the well-known localized motions in the transient cages of the nearest neighbor molecules. While the latter localized motions are known to take place on the picosecond time scale and Angstrom length scale, the slower motions that we have observed are found on the nanosecond time scale and nanometer length scale. They are associated with the slow secondary relaxations, or excess wing dynamics, in glass-forming liquids. Our approach, therefore, can be applied to probe the characteristic length scale of the dynamic entities associated with slow dynamics in glass-forming liquids, which presently cannot be studied by other experimental techniques.

Excess wing in glass-forming glycerol and LiCl-glycerol mixtures detected by neutron scattering.

The relaxational dynamics in glass-forming glycerol and glycerol mixed with LiCl is investigated using different neutron scattering techniques. The performed neutron spin echo experiments, which extend up to relatively long relaxation time scales of the order of 10 ns, should allow for the detection of contributions from the so-called excess wing. This phenomenon, whose microscopic origin is controversially discussed, arises in a variety of glass formers and, until now, was almost exclusively investigated by dielectric spectroscopy and light scattering. Here we show that the relaxational process causing the excess wing can also be detected by neutron scattering, which directly couples to density fluctuations.

Postsurgical screening for psychosocial disorders in neurooncological patients.

BACKGROUND: The diagnosis of a brain tumor can cause severe psychosocial distress, which can have a variety of negative consequences on patients' physical and mental well-being. The detection of psychosocial distress in daily clinical routine is difficult and subsequent referral to mental health professionals is rare. The aim of this study was to determine the incidence of psychological disorders of patients early postoperatively and to investigate both the Hornheide Screening Instrument (HSI) and Distress Thermometer (DT) as screening tools in neurooncological practice. METHODS: One hundred and thirty-four patients with brain tumors of different histology were postoperatively evaluated by the Distress Thermometer and Hornheide Screening Instrument. Additionally, correlation to gender, age, localization of the tumor, Karnofsky performance score and tumor entity were analyzed. RESULTS: After initial surgery 36 patients (26.9 %) showed pathologic results in the HSI and 50 patients (36.7 %) were severely distressed (DT Score≥6). Women had the highest rate of psychological disorders, followed by patients suffering from gliomas and meningiomas. Further highlighting the results of both tests, over 80 % of those patients who scored pathologically in both tests were in need of professional psychiatric help due to depression. CONCLUSION: Both the DT and HSI are suitable instruments for identifying patients in psychological distress after brain tumor surgery in neurooncological routine. Our results confirm that nearly one third of patients are unable to overcome the difficulties facing the diagnosis of a brain tumor in this early situation and should be supported by mental health professionals.

Slow dynamics of water molecules in an aqueous solution of lithium chloride probed by neutron spin-echo.

Aqueous solutions of lithium chloride are uniquely similar to pure water in the parameters such as glass transition temperature, Tg, yet they could be supercooled without freezing down to below 200 K even in the bulk state. This provides advantageous opportunity to study low-temperature dynamics of water molecules in water-like environment in the bulk rather than nano-confined state. Using high-resolution neutron spin-echo data, we argue that the critical temperature, Tc, which is also common between lithium chloride aqueous solutions and pure water, is associated with the split of a secondary relaxation from the main structural relaxation on cooling down. Our results do not allow distinguishing between a well-defined separate secondary relaxation process and the "excess wing" scenario, in which the temperature dependence of the secondary relaxation follows the main relaxation. Importantly, however, in either of these scenarios the secondary relaxation is associated with density-density fluctuations, measurable in a neutron scattering experiment. Neutron scattering could be the only experimental technique with the capability of providing information on the spatial characteristics of the secondary relaxation through the dependence of the signal on the scattering momentum transfer. We propose a simple method for such analysis.

Effect of nanoconfinement on polymer dynamics: surface layers and interphases.

We present neutron spin echo experiments that address the much debated topic of dynamic phenomena in polymer melts that are induced by interacting with a confining surface. We find an anchored surface layer that internally is highly mobile and not glassy as heavily promoted in the literature. The polymer dynamics in confinement is, rather, determined by two phases, one fully equal to the bulk polymer and another that is partly anchored at the surface. By strong topological interaction, this phase confines further chains with no direct contact to the surface. These form the often invoked interphase, where the full chain relaxation is impeded through the interaction with the anchored chains.

A new interpretation of dielectric data in molecular glass formers.

Literature dielectric data of glycerol, propylene carbonate, and ortho-terphenyl show that the measured dielectric relaxation is a decade faster than the Debye expectation but still a decade slower than the breakdown of the shear modulus. From a comparison of time scales, the dielectric relaxation seems to be due to a process which relaxes not only the molecular orientation but also the entropy, the short range order, and the density. On the basis of this finding, we propose an alternative to the Gemant-DiMarzio-Bishop extension of the Debye picture.

Magnetic neutron scattering study of YVO3: evidence for an orbital Peierls state.

Neutron spectroscopy has revealed a highly unusual magnetic structure and dynamics in YVO3, an insulating pseudocubic perovskite that undergoes a series of temperature-induced phase transitions between states with different spin and orbital ordering patterns. A good description of the neutron data is obtained by a theoretical analysis of the spin and orbital correlations of a quasi-one-dimensional model. This leads to the tentative identification of one of the phases of YVO3 with the "orbital Peierls state," a theoretically proposed many-body state comprised of orbital singlet bonds.

Salmonella: a model for bacterial pathogenesis.

Salmonellae are gram-negative bacteria that cause gastroenteritis and enteric fever. Salmonella virulence requires the coordinated expression of complex arrays of virulence factors that allow the bacterium to evade the host's immune system. All Salmonella serotypes share the ability to invade the host by inducing their own uptake into cells of the intestinal epithelium. In addition, Salmonella serotypes associated with gastroenteritis orchestrate an intestinal inflammatory and secretory response, whereas serotypes that cause enteric fever establish systemic infection through their ability to survive and replicate in mononuclear phagocytes. This review explores the molecular basis of selected Salmonella virulence strategies, with an emphasis on general themes of bacterial pathogenesis as exemplified by Salmonella.

Bartonella quintana and urban trench fever.

Contemporary Bartonella quintana infections have emerged in diverse regions of the world, predominantly involving socially disadvantaged persons. Available data suggest that the human body louse Pediculus humanus is the vector for transmission of B. quintana. Descriptions of the clinical manifestations associated with contemporary B. quintana infections have varied considerably and include asymptomatic infection, a relapsing febrile illness, headache, leg pain, "culture-negative" endocarditis, and, in human immunodeficiency virus-infected persons, bacillary angiomatosis. Laboratory diagnosis is most convincing when B. quintana is isolated in blood culture, but growth often takes 20-40 days; problems exist with both sensitivity and specificity of serological assays. On the basis of available information, use of doxycycline, erythromycin, or azithromycin to treat B. quintana infections is recommended. Treatment of uncomplicated B. quintana bacteremia for 4-6 weeks and treatment of B. quintana endocarditis (in a person who does not undergo valve surgery) for 4-6 months are recommended, with the addition of a bactericidal agent (such as a third-generation cephalosporin or an aminoglycoside) during the initial 2-3 weeks of therapy for endocarditis.