Upward Arrow Research Articles

Context-dependent semantic priming in number naming.

Previous research has shown that time to name single-digit Arabic numbers is about 15 ms slower when naming trials are interleaved with simple multiplication (e.g., state product of 2 x 3) than when naming digits is interleaved with magnitude comparison (e.g., state larger; 2 upward arrow 3). To explain this phenomenon, J. I. D. Campbell and A. W. S. Metcalfe (2008) proposed that the comparison context enables both semantic and asemantic pathways for digit naming but that number-fact retrieval inhibits the semantic route and slows digit naming relative to the comparison context. To test this hypothesis, the authors modified the naming context paradigm by introducing a semantic priming manipulation. They replicated the digit-naming response time advantage for comparison relative to the multiplication context and observed semantic priming only in the comparison context. In comparison blocks, digit naming was 8 ms faster immediately after naming near digit primes (+/-1) compared to far primes (>or=3), but in multiplication blocks there was no priming. The results reinforce the theory that number-fact retrieval can inhibit the semantic route for digit naming (L. Cohen & S. Dehaene, 1995) and thereby reconfigure the cognitive architecture for naming digits.

Logarithmic current fluctuations in nonequilibrium quantum spin chains

We study zero-temperature quantum spin chains, which are characterized by a nonvanishing current. For the XX model starting from the initial state mid R:cdots, three dots, centered upward arrow upward arrow upward arrow downward arrow downward arrow downward arrowcdots, three dots, centered we derive an exact expression for the variance of the total spin current. We show that asymptotically the variance exhibits an anomalously slow logarithmic growth; we also extract the subleading constant term. We then argue that the logarithmic growth remains valid for the XXZ model in the critical region.

Semifluxon Molecule under Control

Josephson junctions with a phase drop of pi in the ground state allow us to create vortices of supercurrent carrying only half of the magnetic flux quantum Phi0 approximately 2.07 x 10(-15) Wb. Such semifluxons have twofold degenerate ground states denoted upward arrow (with flux +Phi0/2 and supercurrent circulating clockwise) and downward arrow (with flux -Phi0/2 and supercurrent circulating counterclockwise). We investigate a molecule consisting of two coupled semifluxons in a 0-pi-0 long Josephson junction. The fluxes (polarities) of semifluxons are measured by two on-chip SQUIDs. By varying the dc bias current applied to the 0-pi-0 junction, we demonstrate controllable manipulation and switching between two states, upward arrow downward arrow and downward arrow upward arrow, of a semifluxon molecule. These results provide a major step towards employing semifluxons as bits or qubits for classical and quantum digital electronics.

A Randomized Controlled Trial of the Effects of a Combination of Static and Dynamic Magnetic Fields on Carpal Tunnel Syndrome

To determine if a physics-based combination of simultaneous static and time-varying dynamic magnetic field stimulation to the wrist 4 hours/day for 2 months can reduce subjective neuropathic pain and influence objective electrophysiologic parameters of patients with carpal tunnel syndrome (CTS). Randomized, double-blinded, placebo-controlled trial of 36 symptomatic hands. Primary endpoints were visual analog scale (VAS) and neuropathic pain scale (NPS) scores at baseline and 2 months and a Patient's Global Impression of Change (PGIC) questionnaire at the end of 2 months. Secondary endpoints were neurologic examination, median nerve distal latencies (compound muscle action potential [CMAP]/sensory nerve action potential [SNAP]), dynamometry, pinch gauge readings, and current perception threshold (CPT) scores. An "active" device was provided gratis at the end of the study, with 15 subjects voluntarily remaining within the open protocol an additional 2-10 months and using the preselected primary and secondary parameters. (two months). Of the 31 hands, 25 (13 magnet, 12 sham) had moderate to severe pain (VAS > 4). The VAS and PGIC revealed a nonsignificant pain reduction. NPS analyses (anova) demonstrated a statistically significant reduction of "deep" pain (35% downward arrow vs 12% upward arrow, P = 0.018), NPS Total Composite (decreases of 42% vs 24%, P = 0.042), NPS Total Descriptor Score (NPS 8; 43% vs 24%), and NPS 4 (42% vs 11%). Motor strength, CMAP/SNAP, and CPT scores were not significantly changed. Of the 15 hands with up to 10 months of active PEMF (pulsed electromagnetic fields) exposure, there was objective improvement in nerve conduction (CMAP = 53%, SNAP = 40%, >1 SD), and subjective improvement on examination (40%), pain scores (50%), and PGIC (70%). No detectable changes in motor strength and CPT. PEMF exposure in refractory CTS provides statistically significant short- and longterm pain reduction and mild improvement in objective neuronal functions. Neuromodulation appears to influence nociceptive-C and large A-fiber functions, probably through ion/ligand binding.

Genetic Susceptibility Sets for Alzheimer's Disease Identified from Diverse Candidate Loci

Alzheimer's disease (AD) has been demonstrated to be associated with gene variants of APOE, but numerous additional candidate loci exist with varying levels of statistical support. We defined susceptibility sets for AD based on information on 18 genetic loci on chromosome 10q (32 loci) and elsewhere (34 loci) and quantitative traits, including CSF tau and Abeta(42) levels. The 938 AD patients and 397 control subjects were enrolled in Scotland and Sweden. A fuzzy latent classification approach -- grade-of-membership analysis (GoM) -- was taken to identify risk sets. Individuals were automatically related to each set via GoM scores. Set I: unaffected + (downward arrow) CSF tau + (upward arrow) CSF Abeta(42) + multiple protective alleles. High intrinsic risk sets II-VI differed in onset age and relevant alleles: close resemblance (i.e., >75% aggregate membership) multiplied risk of AD >100-fold at ages 65 to 84. It is likely that AD has multiple determinants, including APOE polymorphism and gene variants located on chromosome 10q and elsewhere.

Cardiorenal Interactions: Insights From the ESCAPE Trial

We examined the ESCAPE (Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness) database to understand the impact and pathophysiology of renal dysfunction in patients hospitalized with advanced decompensated heart failure (HF). Baseline renal insufficiency (RI) (estimated glomerular filtration rate [eGFR] <60 ml/min) and worsening renal function (WRF) (upward arrow serum creatinine [SCr] >or=0.3 mg/dl) during treatment of decompensated HF are associated with adverse outcomes. We used a Cox proportional hazards model to evaluate the impact of renal function on 6-month outcomes. Renal parameters were correlated with hemodynamic measurements. The impact of a strategy using pulmonary artery catheter (PAC) guidance on WRF and outcomes in patients with baseline RI was compared with treatment based on clinical assessment alone. Baseline and discharge RI, but not WRF, were associated with an increased risk of death and death or rehospitalization. Among the hemodynamic parameters measured in patients randomized to the PAC arm (n = 194), only right atrial pressure correlated weakly with baseline SCr (r = 0.165, p = 0.03). There was no correlation between baseline hemodynamics or change in hemodynamics and WRF. A PAC-guided strategy was associated with less average increase in creatinine but did not decrease the incidence of defined WRF during hospitalization or affect renal function after discharge relative to clinical assessment alone. Among patients with advanced decompensated HF, baseline RI impacts outcomes more than WRF. Poor forward flow alone does not appear to account for the development of RI or WRF in these patients. The addition of hemodynamic monitoring to clinical assessment does not prevent WRF or improve renal function after discharge.

White matter microstructural abnormalities in children with spina bifida myelomeningocele and hydrocephalus: A diffusion tensor tractography study of the association pathways

To quantify microstructural abnormalities in the major association pathways of children affected by spina bifida myelomeningocele (SBM) and shunted hydrocephalus using whole-brain diffusion tensor imaging (DTI). The institutional review board approved this Health Insurance Portability and Accountability Act (HIPAA)-compliant study and written informed consent/assent were obtained prior to the study. The 69 participants included 38 children with SBM and shunted hydrocephalus (age mean +/- SD = 12.30 +/- 2.10 years; 22 boys; 10 left-handed) and 31 age- and sex-matched normally-developing children (11.56 +/- 2.72 years; 15 boys, four left-handed). Diffusion tensor tractography (DTT) was performed to delineate and quantify bilaterally four major association pathways (arcuate, inferior longitudinal, inferior fronto-occipital, and uncinate fasciculi). The group with SBM did not exhibit the pattern of age-related decreases in the diffusivities observed in the controls. The transverse and axial diffusivities were significantly elevated in most of the white matter pathways of the participants with SBM. The fractional anisotropy (FA) was significantly lower in most of the association pathways. Many of the association pathways were not traceable in some participants with SBM compared to the controls at the selected FA thresholds. DTT revealed diffusion tensor characteristics of abnormal development (nonvisualization/poor visualization of tracts, downward arrow FA, upward arrow diffusivities), impairment in myelination (upward arrow transverse diffusivity) as well as abnormalities in intrinsic axonal characteristics and extraaxonal/extracellular space (upward arrow axial diffusivity) in the association pathways of the SBM children. The differences in the diffusion metrics observed in the children with SBM are suggestive of abnormal white matter development and persistent degeneration with increased age.

Spin-Crossover Behavior in Cyanide-bridged Iron(II)−Gold(I) Bimetallic 2D Hofmann-like Metal−Organic Frameworks

The synthesis and characterization of new two-dimensional (2D) cyanide-bridged iron(II)-gold(I) bimetallic coordination polymers formulated, {Fe(3-Xpy)2[Au(CN)2]2} (py = pyridine; X = F (1), Cl (2), Br (3), and I (4)) and the clathrate derivative {Fe(3-Ipy)2[Au(CN)2]2}.1/2(3-Ipy) (5), are reported. The iron(II) ion lies in pseudoctahedral [FeN6] sites defined by four [Au(CN)2](-) bridging ligands and two 3-Xpy ligands occupying the equatorial and axial positions, respectively. Although only compounds 2 and 4 can be considered strictly isostructurals, all of the components of this family are made up of parallel stacks of corrugated {Fe[Au(CN)2]2}n grids. The grids are formed by edge sharing of {Fe4[Au(CN)2]4} pseudosquare moieties. The stacks are constituted of double layers sustained by short aurophilic contacts ranging from 3.016(2) to 3.1580(8) A. The Au...Au distances between consecutive double layers are in the range of 5.9562(9)-8.790(2) A. Compound 5, considered a clathrate derivative of 4, includes one-half of a 3-Ipy molecule per iron(II) atom between the double layers. Compound 1 undergoes a half-spin transition with critical temperatures Tc downward arrow = 140 K and Tc upward arrow = 145 K. The corresponding thermodynamic parameters derived from differential scanning calorimetry (DSC) are Delta H = 9.8 +/- 0.4 kJ mol(-1) and Delta S = 68.2 +/- 3 J K mol(-1). This spin transition is accompanied by a crystallographic phase transition from the monoclinic P2(1)/c space group to the triclinic P1 space group. At high temperatures, where 1 is 100% high-spin, there is only one crystallographically independent iron(II) site. In contrast, the low temperature structural analysis shows the occurrence of two crystallographically independent iron(II) sites with equal population, one high-spin and the other low-spin. Furthermore, 1 undergoes a complete two-step spin transition at pressures as high as 0.26 GPa. Compounds 2- 4 are high-spin iron(II) complexes according to their magnetic and [FeN6] structural characteristics. Compound 5, characterized for having two different iron(II) sites, displays a two-step spin transition with critical temperatures of Tc(1) = 155 K, Tc(2) downward arrow = 97 K, and Tc(2) upward arrow = 110 K. This change of spin state takes place in both sites simultaneously. All of these results are compared and discussed in the context of other {Fe(L) x [M(I)(CN)2]} coordination polymers, particularly those belonging to the homologous compounds {Fe(3-Xpy)2[Ag(CN)2]2} and their corresponding clathrate derivatives.

Ferroelectricity in an Ising Chain Magnet

We report discovery of collinear-magnetism-driven ferroelectricity in the Ising chain magnet Ca3Co2-xMn(x)O6 (x approximately 0.96). Neutron diffraction shows that Co2+ and Mn4+ ions alternating along the chains exhibit an up-up-down-down ( upward arrow upward arrow downward arrow downward arrow) magnetic order. The ferroelectricity results from the inversion symmetry breaking in the upward arrow upward arrow downward arrow downward arrow spin chain with an alternating charge order. Unlike in spiral magnetoelectrics where antisymmetric exchange coupling is active, the symmetry breaking in Ca3(Co,Mn)2O6 occurs through exchange striction associated with symmetric superexchange.

Dynamic structural conversion in a spin-crossover cobalt(ii) compound with long alkyl chains

A cobalt(ii) compound [Co(C14-terpy)(2)](BF(4))(2).MeOH (1) with long alkyl chains was prepared, and exhibited unique SCO at T(1) = 50 K and spin transition at T(2) upward arrow = 206 K and T(2) downward arrow = 184 K with hysteresis (DeltaT = 22 K) accompanying the motion of the long alkyl chains.

Cooperative Iron(II) Spin Crossover Complexes with N4O2Coordination Sphere

Two new spin crossover complexes [FeL(py)(2)] (1) and [FeL(DMAP)(2)] (2) with L being a tetradentate N(2)O(2)(2-) coordinating Schiff-base-like ligand [([3,3']-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentanedionato)(2-)-N,N',O(2),O(2)'], py = pyridine and DMAP = p-dimethylaminopyridine have been investigated using temperature-dependent susceptibility and thermogravimetric and photomagnetic measurements as well as Mössbauer spectroscopy and X-ray structure analysis. Both complexes show a cooperative spin transition with an approximately 9 K wide thermal hysteresis loop in the case of 2 (T(1/2) upward arrow = 183 K and T(1/2) downward arrow = 174 K) and an approximately 2 K wide thermal hysteresis loop in the case of the pyridine diadduct 1 (T(1/2) upward arrow = 191 K and T(1/2) downward arrow = 189 K). The spin transition was additionally followed by different temperature-scanning calorimetry and Mössbauer spectroscopy for 2, and a good agreement for the transition temperatures obtained with the different methods was found. Results from X-ray structure analysis indicate that the cooperative interactions are due to elastic interactions in both compounds. They are more pronounced in the case of 2 with very short intermolecular iron-iron distances of 7.2 A and several intense C-C contacts. The change of the spin state at the iron center is accompanied by a change of the O-Fe-O angle, the so-called bit of the equatorial ligand, from 108 degrees in the high-spin state to 90 degrees in the low-spin state. The reflectivity measurements of both compounds give at low temperature indication that at the sample surface the light-induced excited spin state trapping (LIESST) effect occurs. In bulk condition using a SQUID magnetometer the complex 2 displays some photomagnetic properties with an photoexcitation level of 60% and a T(LIESST) value of 53 K.

Incidence of Responses at the Lower Audiometric Limits

To put forward a symbol extension, consisting of an upward arrow added to current symbols, to denote that a patient continued to respond at the audiometric limit (i.e., -10 dB HL). Also, to present survey data to characterize the incidence of these responses. A retrospective survey of 2,821 sequential audiometric evaluations was performed. Responses at the audiometric limits were counted, along with the stimulus conditions (i.e., transducer, frequency, and masking) and the age of the patient. A total of 307 instances of responses at the lower audiometric limits were seen in 173 of these cases (6.13%), with the majority by bone conduction. The overall rate of responses at the audiometric limits was low, as expected. However, these responses were primarily seen in the age group from 4 to 15 years, and at least one such response occurred in 26% of cases in that age range.

Structural, Thermal, and Magnetic Study of Solvation Processes in Spin-Crossover [Fe(bpp)2][Cr(L)(ox)2]2·nH2O Complexes

The influence of lattice water in the magnetic properties of spin-crossover [Fe(bpp)2]X2.nH2O salts [bpp = 2,6-bis(pyrazol-3-yl)pyridine] is well-documented. In most cases, it stabilizes the low-spin state compared to the anhydrous compound. In other cases, it is rather the contrary. Unraveling this mystery implies the study of the microscopic changes that accompany the loss of water. This might be difficult from an experimental point of view. Our strategy is to focus on some salts that undergo a nonreversible dehydration-hydration process without loss of crystallinity. By comparison of the structural and magnetic properties of original and rehydrated samples, several rules concerning the role of water at the microscopic level can be deduced. This paper reports on the crystal structure, thermal studies, and magnetic properties of [Fe(bpp)2][Cr(bpy)(ox)2]2.2H2O (1), [Fe(bpp)2][Cr(phen)(ox)2]2.0.5H2O.0.5MeOH (2), and [Fe(bpp)2][Cr(phen)(ox)2]2.5.5H2O.2.5MeOH (3). Salt 1 contains both high-spin (HS) and low-spin (LS) Fe2+ cations in a 1:1 ratio. Dehydration yields the anhydrous spin-crossover compound with T1/2 downward arrow = 353 K and T1/2 upward arrow = 369 K. Rehydration affords the dihydrate [Fe(bpp)2][Cr(bpy)(ox)2]2.2H2O (1r) with 100% HS Fe2+ sites. Salt 2 also contains both HS and LS Fe2+ cations in a 1:1 ratio. Dehydration yields the anhydrous spin-crossover compound with T1/2 downward arrow = 343 K and T1/2 upward arrow = 348 K. Rehydration affords [Fe(bpp)2][Cr(phen)(ox)2]2.0.5H2O (2r) with 72% Fe2+ sites in the LS configuration. The structural, magnetic, and thermal properties of these rehydrated compounds 1r and 2r are also discussed. Finally, 1 has been dehydrated and resolvated with MeOH to give [Fe(bpp)2][Cr(bpy)(ox)2]2.MeOH (1s) with 33% HS Fe2+ sites. The influence of the guest solvent in the Fe2+ spin state can anticipate the future applications of these compounds in solvent sensing.

Testing if the Interstitial Atom,X, of the Nitrogenase Molybdenum−Iron Cofactor Is N or C: ENDOR, ESEEM, and DFT Studies of theS=3/2Resting State in Multiple Environments

A high-resolution (1.16 A) X-ray structure of the nitrogenase molybdenum-iron (MoFe) protein revealed electron density from a single N, O, or C atom (denoted X) inside the central iron prismane ([6Fe]) of the [MoFe7S9:homocitrate] FeMo-cofactor (FeMo-co). We here extend earlier efforts to determine the identity of X through detailed tests of whether X = N or C by interlocking and mutually supportive 9 GHz electron spin echo envelope modulation (ESEEM) and 35 GHz electron-nuclear double resonance (ENDOR) measurements on 14/15N and 12/13C isotopomers of FeMo-co in three environments: (i) incorporated into the native MoFe protein environment; (ii) extracted into N-methyl formamide solution; and (iii) incorporated into the NifX protein, which acts as a chaperone during FeMo-co biosynthesis. These measurements provide powerful evidence that X not equal N/C, unless X in effect is magnetically decoupled from the S = 3/2 electron spin system of resting FeMo-co. They reveal no signals from FeMo-co in any of the three environments that can be assigned to X from either 14/15N or 13C: If X were either element, its maximum observed hyperfine coupling at all fields of measurement is estimated to be A(14/15NX) < 0.07/0.1 MHz, A(13CX) < 0.1 MHz, corresponding to intrinsic couplings of about half these values. In parallel, we have explicitly calculated the hyperfine tensors for X = 14/15N/13C/17O, nuclear quadrupole coupling constant e2qQ for X = 14N, and hyperfine constants for the Fe sites of S = 3/2 FeMo-co using density functional theory (DFT) in conjunction with the broken-symmetry (BS) approach for spin coupling. If X = C/N, then the decoupling required by experiment strongly supports the "BS7" spin coupling of the FeMo-co iron sites, in which a small X hyperfine coupling is the result of a precise balance of spin density contributions from three spin-up and three spin-down (3 upward arrow:3 downward arrow) iron atoms of the [6Fe] prismane "waist" of FeMo-co; this would rule out the "BS6" assignment (4 upward arrow:2 downward arrow for [6Fe]) suggested in earlier calculations. However, even with the BS7 scheme, the hyperfine couplings that would be observed for X near g2 are sufficiently large that they should have been detected: we suggest that the experimental results are compatible with X = N only if aiso(14/15NX) < 0.03-0.07/0.05-0.1 MHz and aiso(13CX) < 0.05-0.1 MHz, compared with calculated values of aiso(14/15NX) = 0.3/0.4 MHz and aiso(13CX) = 1 MHz. However, the DFT uncertainties are large enough that the very small hyperfine couplings required by experiment do not necessarily rule out X = N/C.

Magnetic Excitations in an Itinerant Ferromagnet near Quantum Criticality

We determine the initial temperature dependence of the exchange splitting Delta(T) in the weak itinerant ferromagnet ZrZn2 (T{C}=28 K) using the de Haas-van Alphen effect. There is a large decrease in Delta with temperature in the range 0.5< or =T< or =4 K. A comparison of Delta(T) with the magnetization M(T) shows that the dominant process responsible for the reduction of M is not the thermal excitation of spin waves, but a repopulation of the spin- upward arrow and spin- downward arrow Fermi surfaces. This contrasts with the behavior in Fe where there is no observable change in Delta and the thermal excitation of spin waves is the only observable spin-flipping process at low temperatures.

Molecular insight into mechanism of antimicrobial action of the β‐hairpin peptide arenicin: Specific oligomerization in detergent micelles

Arenicins are 21-residue cationic antimicrobial peptides isolated from marine polychaeta Arenicola marina. The peptides exhibit potent broad-spectrum antimicrobial activity. In water solution arenicin-2 adopts a beta-hairpin conformation, stabilized by one disulfide and nine hydrogen bonds. To determine the propensity for the peptide oligomerization in membrane mimetic systems, the recombinant arenicin-2 was overexpressed as a fused form in Escherichia coli. The arenicin-2 oligomerization and intermolecular packing in membrane mimicking environment were investigated using high-resolution NMR spectroscopy. The present studies show that arenicin-2 preserves a beta-hairpin structure and forms asymmetric dimers upon incorporation into the dodecylphosphocholine micelle. Two monomers of arenicin-2 are aligned parallel to each other by the N-terminal strands of the beta-hairpin (CN upward arrow upward arrowNC type of association). Polyacrylamide gel electrophoresis analysis indicated that in environment of anionic SDS micelles the arenicin-2 might undergo further oligomerization and form tetramers. Our results afford further molecular insight into possible mechanism of antimicrobial action of arenicins.

Thermal- and Pressure-Induced Cooperative Spin Transition in the 2D and 3D Coordination Polymers {Fe(5-Br-pmd)z[M(CN)x]y} (M = AgI, AuI, NiII, PdII, PtII)

A new family of cyanide-based spin-crossover polymers with the general formula {Fe(5-Br-pmd)z[M(CN)x]y} [M=AgI (1), AuI (2), NiII (3), PdII (4), PtII (5); 5-Br-pmd=5-bromopyrimidine; z=1 or 2, x=2 or 4, and y=2 or 1] have been synthesized and characterized using single-crystal X-ray diffraction (XRD), X-ray powder diffraction (XRPD), magnetic susceptibility measurements, and differential scanning calorimetry (DSC). At 293 K, compound 1 presents the monoclinic space group C2/c, whereas at 120 K, it changes to the monoclinic space group P21/c. At 293 K, the crystal structure of 1 displays an uninodal three-dimensional network whose nodes, constituted of FeII, lie at the inversion center of an elongated octahedron. The equatorial bond lengths are defined by the N atoms of four [AgI(CN)2]- groups belonging to two crystallographically nonequivalent AgI atoms, Ag(1) and Ag(2). They are shorter than those of the axial positions occupied by the N atoms of the 5-Br-pmd ligands. The Fe-N average bond length of 2.1657(7) A is consistent with a high-spin (HS) state for the FeII ions. At 120 K, the crystal structure changes refer mainly to the FeII environment. There are two crystallographically independent FeII ions at this temperature, Fe(1) and Fe(2), which adopt the HS and low-spin (LS) states, respectively. The average Fe-N bond length for Fe(1) [2.174(5) A] and Fe(2) [1.955(5) A] agrees well with the reported magnetic data at this temperature. The spin transition of the FeII ions labeled as Fe(1) is found to be centered at Tc downward arrow=149 K and Tc upward arrow=167 K and accompanied by a drastic change of color from orange (HS) to red (LS). Magnetic susceptibility measurements under applied hydrostatic pressure performed on 1 have shown a linear displacement of the transition to higher temperatures while the hysteresis width remains unaltered in the interval of pressures of 105 Pa to 0.34 GPa. A further increase of the pressure induces the spin transition in the Fe(2) ions, which is completely accomplished at 1.12 GPa (T1/2=162 K). Compounds 1 and 2 are isostructural, but 2 does not exhibit spin-transition properties; the FeII centers remain in the HS state in the temperature range investigated, 5-300 K. Compounds 3-5 are not similar or isostructural with 1. A two-dimensional structure for 3-5 has been proposed on the basis of analytical data and the XRPD patterns. Compounds 3-5 undergo first-order spin transition where the critical temperatures for the cooling (Tc downward arrow) and warming (Tc upward arrow) modes are 170 and 180 K (3), 204 and 214 K (4), and 197 and 223 K (5), respectively. It is worth mentioning the color change from yellow to orange observed in 3-5 upon spin transition. The thermodynamic parameters associated with the spin transition estimated from DSC measurements are DeltaH=6 kJ mol(-1) (1), 11 kJ mol(-1) (3), 16 kJ mol(-1) (4), and 16 kJ mol(-1) (5) and DeltaS=38 J K(-1) mol(-1) (1), 62 J K(-1) mol(-1) (3), 76 J K-1 mol(-1) (4), and 81 J K(-1) mol(-1) (5).

Physiological and transcriptional characterization ofSaccharomyces cerevisiaestrains with modified expression of catabolic regulators

A comparative physiological and transcriptional study is presented on wild-type Saccharomyces cerevisiae and mutants with altered levels of catabolic regulators: hxk2Delta lacking hexokinase2, HAP4 / overproducing hap4p and hxk2 Delta HAP4 upward arrow. Relative to the wild-type, HAP4 / showed the same growth rate with some increased yield on glucose, and hxk2Delta grew 28% slower but with a dramatically improved yield. Hxk2 Delta HAP4 / grew 14% slower but showed fully oxidative growth. A higher yield correlated with increased respiration. For both hxk2 Delta strains, glucose repression was suppressed (upregulation of high-affinity sugar transporters, invertase and oxidative phosphorylation). T-profiler analysis showed that genes under control of the hap2/3/4/5-binding motif were significantly altered in expression in all strains. HAP4 overexpression, directly or in hxk2 knockouts, led to repression of the genes containing the Zap1p motif including ZAP1 itself, indicating altered zinc metabolism. Whereas HAP4 overexpression resulted in a shift towards oxidative metabolism only, deletion of HXK2 resulted in a strain that, in addition to being oxidative, almost completely lacked the ability to sense glucose. As the double mutant had an energy efficiency close to the maximum even with excess glucose and was derepressed to a larger extent and over a broader range, the functioning of the two regulators is in general considered to be additive.

Biologic Effects of 3 Tesla (T) MR Imaging Comparing Traditional 1.5 T and 0.6 T in 1023 Consecutive Outpatients

The recent use of high and ultra-high magnetic field (MF) systems (3.0 T and above) have raised concerns about biologic effects and safety. Sensory symptoms (magnetophosphenes, dizziness/vertigo, headaches, metallic taste, pain changes, and cognitive effects) have been reported. We monitored 1023 consecutive outpatients undergoing MRI after recent introduction of a 3 T MR unit in our community. Observational study utilizing a pretest and posttest symptom rating scale (0-10) questionnaire presented to subjects undergoing MRI at three different facilities with five MRI machines, specifically a 3 T (Philips), three units with 1.5 T (GE, GE, Philips), and one 0.6 T (Fonar) unit to record symptoms before and after study. 147 subjects (14%) experienced either new (N= 69; 6.7%) or changes (N= 78; 8%) in symptoms. New onset symptoms occurred predominantly with 3 T and female preponderance (75%) [P= .002]. Vertigo/dizziness (N= 28, 5.6%) [P= .001], headache (N= 8), spine pain (N= 11) occurred more frequently on 3 T, whereas magnetophosphenes (N= 8) and metallic mouth symptoms (N= 4) occurred principally in 1.5 T. Seventy-eight subjects (8%) experienced pain symptoms upward arrow downward arrow with 75% occurring with 1.5 T. Females were 60%. Forty-three percent of individuals had brain MRIs. Symptoms of vertigo/dizziness, headaches, and magnetophosphenes were more commonly seen in individuals undergoing brain MRIs but other body sites were also represented. Although no harmful effects were reported in 1023 cases, an unexpected high rate of 14% of individuals experienced sensory stimulation in both 3 T and 1.5 T units. Females appear to be more magnetically sensitive.

Measurements and Quasi-Quantum Modeling of the Steric Asymmetry and Parity Propensities in State-to-State Rotationally Inelastic Scattering of NO (2Π1/2) with D2

Relative integrated cross sections are measured for spin-orbit-conserving, rotationally inelastic scattering of NO (2Pi1/2), hexapole-selected in the upper Lambda-doublet level of the ground rotational state (j = 0.5), in collisions with D2 at a nominal energy of 551 cm-1. The final state of the NO molecule is detected by laser-induced fluorescence (LIF). The state-selected NO molecule is oriented with either the N end or the O end toward the incoming D2 molecule by application of a static electric field E in the scattering region. This field is directed parallel or antiparallel to the relative velocity vector v. Comparison of signals taken for the different applied field directions gives the experimental steric asymmetry SA, defined by SA = (sigma v upward arrow downward arrow E - sigma v upward arrow upward arrow E)/(sigma v upward arrow downward arrow E + sigma v upward arrow upward arrow E), which is equal to within a factor of -1 to the molecular steric effect, Si-->f identical with (sigmaD2-->NO - sigmaD2-->ON)/(sigmaD2-->NO + sigmaD2-->ON). The dependence of the integral inelastic cross section on the incoming Lambda-doublet component is also measured as a function of the final rotational (jfinal) and Lambda-doublet (epsilonfinal) state. The measured steric asymmetries are similar to those previously observed for NO-He scattering. Spin-orbit manifold-conserving collisions exhibit a larger propensity for parity conservation than their NO-He counterparts. The results are interpreted in the context of the recently developed quasi-quantum treatment (QQT) of rotationally inelastic scattering [Gijsbertsen, A.; Linnartz, H.; Taatjes, C. A.; Stolte, S. J. Am. Chem. Soc. 2006, 128, 8777]. The QQT predictions can be inverted to obtain a fitted hard-shell potential that reproduces the experimental steric asymmetry; this fitted potential gives an empirical estimate of the anisotropy of the repulsive interaction between NO and D2. QQT computation of the differential cross section using this simple model potential shows reasonable agreement with the measured differential cross sections.