Infrared Nanoimaging of Hydrogenated Perovskite Nickelate Memristive Devices

Solid-state devices made from correlated oxides, such as perovskite nickelates, are promising for neuromorphic computing by mimicking biological synaptic function. However, comprehending dopant action at the nanoscale poses a formidable challenge to understanding the elementary mechanisms involved. Here, we perform operando infrared nanoimaging of hydrogen-doped correlated perovskite, neodymium nickel oxide (H-NdNiO3, H-NNO), devices and reveal how an applied field perturbs dopant distribution at the nanoscale. This perturbation leads to stripe phases of varying conductivity perpendicular to the applied field, which define the macroscale electrical characteristics of the devices. Hyperspectral nano-FTIR imaging in conjunction with density functional theory calculations unveils a real-space map of multiple vibrational states of H-NNO associated with OH stretching modes and their dependence on the dopant concentration. Moreover, the localization of excess charges induces an out-of-plane lattice expansion in NNO which was confirmed by in situ X-ray diffraction and creates a strain that acts as a barrier against further diffusion. Our results and the techniques presented here hold great potential for the rapidly growing field of memristors and neuromorphic devices wherein nanoscale ion motion is fundamentally responsible for function.

Ultrafast Nanoimaging of Spin-Mediated Shear Waves in an Acoustic Cavity

Strong spin-lattice coupling in van der Waals (vdW) magnets shows potential for innovative magneto-mechanical applications. Here, nanoscale and picosecond imaging by ultrafast electron microscopy reveal heterogeneous spin-mediated coherent acoustic phonon dynamics in a thin-film cavity of the vdW antiferromagnet FePS3. The harmonics of the interlayer shear acoustic modes are observed, in which the even and odd harmonics exhibit distinct nanoscopic dynamics. Corroborated by acoustic wave simulation, the role of defects in forming even harmonics is elucidated. Above the Néel temperature (TN), the interlayer shear acoustic harmonics are suppressed, while the in-plane traveling wave is predominantly excited. The dominant acoustic dynamics shifts from the out-of-plane shear to the in-plane traveling wave across TN, demonstrating that magnetic properties can influence phonon scattering pathways. The spatiotemporally resolved structural characterization provides valuable nanoscopic insights for interlayer-shear-mode-based acoustic cavities, opening up possibilities for magneto-mechanical applications of vdW magnets.

Coupling to octahedral tilts in halide perovskite nanocrystals induces phonon-mediated attractive interactions between excitons

Understanding the origin of electron-phonon coupling in lead halide perovskites is key to interpreting and leveraging their optical and electronic properties. Here we show that photoexcitation drives a reduction of the lead-halide-lead bond angles, a result of deformation potential coupling to low-energy optical phonons. We accomplish this by performing femtosecond-resolved, optical-pump-electron-diffraction-probe measurements to quantify the lattice reorganization occurring as a result of photoexcitation in nanocrystals of FAPbBr3. Our results indicate a stronger coupling in FAPbBr3 than CsPbBr3. We attribute the enhanced coupling in FAPbBr3 to its disordered crystal structure, which persists down to cryogenic temperatures. We find the reorganizations induced by each exciton in a multi-excitonic state constructively interfere, giving rise to a coupling strength that scales quadratically with the exciton number. This superlinear scaling induces phonon-mediated attractive interactions between excitations in lead halide perovskites.

Characteristics of the ID-NOW™ test for the rapid detection of SARS-CoV-2

OBJECTIVE

To determine the sensitivity and specificity of the Abbott ID-NOW™ test in the diagnosis of COVID-19. The test is based on the detection of the SARS-CoV-2 gene by isothermal amplification technology.

METHODS

From 303 individuals, two nasopharyngeal swabs and one oropharyngeal swab were collected to be tested in parallel by the ID-NOW™ test and PCR test (Allplex™ SARS-CoV-2 Assay). A subgroup of 107 individuals presented to the public collection point for covid-19 at the Motol University Hospital during the dominance of the Delta variant, and the others were tested via the Adult Emergency Admission Department during the dominance of the Omicron variant.

RESULTS

Of 297 valid samples, 43 were positive by the PCR assay and 33 were positive by the ID-NOW™ test (sensitivity 76.74%; 95% CI 61.37 to 88.24%). ID-NOW™ detected three samples as positive, but the positivity was not confirmed by PCR (specificity 98.82%; 95% CI 96.59 to 99.76%). A significant increase in sensitivity up to 100% is observed for samples with a higher viral load (with a PCR threshold cycle value below 30 or from patients with symptoms of COVID-19). The Delta or Omicron variant has no significant effect on the sensitivity of the test.

CONCLUSION

Due to its ease of use and speed of result, ID-NOW™ is a suitable diagnostic tool for prompt assessment of a patient's infectivity. If, despite the negative ID-NOW™ result, the patient has symptoms of COVID-19, it is advised to perform a classic PCR test for SARS-CoV-2.

Light-Driven Ultrafast Polarization Manipulation in a Relaxor Ferroelectric

Relaxor ferroelectrics have been intensely studied for decades based on their unique electromechanical responses which arise from local structural heterogeneity involving polar nanoregions or domains. Here, we report first studies of the ultrafast dynamics and reconfigurability of the polarization in freestanding films of the prototypical relaxor 0.68PbMg_1/3Nb_2/3O₃-0.32PbTiO₃ (PMN-0.32PT) by probing its atomic-scale response via femtosecond-resolution, electron-scattering approaches. By combining these structural measurements with dynamic phase-field simulations, we show that femtosecond light pulses drive a change in both the magnitude and direction of the polarization vector within polar nanodomains on few-picosecond time scales. This study defines new opportunities for dynamic reconfigurable control of the polarization in nanoscale relaxor ferroelectrics.

Dynamical criticality of spin-shear coupling in van der Waals antiferromagnets

The interplay between a multitude of electronic, spin, and lattice degrees of freedom underlies the complex phase diagrams of quantum materials. Layer stacking in van der Waals (vdW) heterostructures is responsible for exotic electronic and magnetic properties, which inspires stacking control of two-dimensional magnetism. Beyond the interplay between stacking order and interlayer magnetism, we discover a spin-shear coupling mechanism in which a subtle shear of the atomic layers can have a profound effect on the intralayer magnetic order in a family of vdW antiferromagnets. Using time-resolved X-ray diffraction and optical linear dichroism measurements, interlayer shear is identified as the primary structural degree of freedom that couples with magnetic order. The recovery times of both shear and magnetic order upon optical excitation diverge at the magnetic ordering temperature with the same critical exponent. The time-dependent Ginzburg-Landau theory shows that this concurrent critical slowing down arises from a linear coupling of the interlayer shear to the magnetic order, which is dictated by the broken mirror symmetry intrinsic to the monoclinic stacking. Our results highlight the importance of interlayer shear in ultrafast control of magnetic order via spin-mechanical coupling.

Van der Waals materials are characterized by two dimensional layers weakly held together by interlayer van der Waals forces. Here, the authors study how shear motions between these layers influence the magnetic properties of the van der Waals antiferromagnets FePS3, MnPS3, and NiPS3. ‘

Neohygrocybe pseudoingrata, a new grassland species from Slovakia and the Czech Republic

Neohygrocybe pseudoingrata, a new waxcap species known from Slovakia and the Czech Republic, is characterised by its pale greyish coloured and often robust basidiomata (or sporocarps), nitrous smell, context without colour changes, hollow, contorted and compressed stipe and smooth or slightly fibrillose pileus surface. Based on morphology and DNA analysis of ITS and LSU sequences of the collected specimens, N. pseudoingrata belongs to Neohygrocybe sect. Neohygrocybe together with N. ovina, N. nitrata and N. ingrata. Collections of N. pseudoingrata form a well-supported clade in phylogenetic trees.

Citation: Fuljer F, Zajac M, Boertmann D, Szabóová D, Kautmanová I (2022). Neohygrocybe pseudoingrata, a new grassland species from Slovakia and the Czech Republic. Fungal Systematics and Evolution9: 11–17. doi: 10.3114/fuse.2022.09.02

Highly Efficient Uniaxial In-Plane Stretching of a 2D Material via Ion Insertion

On-chip dynamic strain engineering requires efficient micro-actuators that can generate large in-plane strains. Inorganic electrochemical actuators are unique in that they are driven by low voltages (≈1 V) and produce considerable strains (≈1%). However, actuation speed and efficiency are limited by mass transport of ions. Minimizing the number of ions required to actuate is thus key to enabling useful "straintronic" devices. Here, it is shown that the electrochemical intercalation of exceptionally few lithium ions into WTe₂ causes large anisotropic in-plane strain: 5% in one in-plane direction and 0.1% in the other. This efficient stretching of the 2D WTe₂ layers contrasts to intercalation-induced strains in related materials which are predominantly in the out-of-plane direction. The unusual actuation of Li_x WTe₂ is linked to the formation of a newly discovered crystallographic phase, referred to as Td', with an exotic atomic arrangement. On-chip low-voltage (<0.2 V) control is demonstrated over the transition to the novel phase and its composition. Within the Td'-Li_{0.5- δ} WTe₂ phase, a uniaxial in-plane strain of 1.4% is achieved with a change of δ of only 0.075. This makes the in-plane chemical expansion coefficient of Td'-Li_0.5-δ WTe₂ far greater than of any other single-phase material, enabling fast and efficient planar electrochemical actuation.

Universal phase dynamics in VO2 switches revealed by ultrafast operando diffraction

Understanding the pathways and time scales underlying electrically driven insulator-metal transitions is crucial for uncovering the fundamental limits of device operation. Using stroboscopic electron diffraction, we perform synchronized time-resolved measurements of atomic motions and electronic transport in operating vanadium dioxide (VO₂) switches. We discover an electrically triggered, isostructural state that forms transiently on microsecond time scales, which is shown by phase-field simulations to be stabilized by local heterogeneities and interfacial interactions between the equilibrium phases. This metastable phase is similar to that formed under photoexcitation within picoseconds, suggesting a universal transformation pathway. Our results establish electrical excitation as a route for uncovering nonequilibrium and metastable phases in correlated materials, opening avenues for engineering dynamical behavior in nanoelectronics.

The sensitivity of SARS-CoV-2 antigen tests in the view of large-scale testing

OBJECTIVES

Antigen tests have emerged as an alternative to SARS-CoV-2 diagnostic PCR, thought to be valuable especially for the screening of bigger communities. To check appropriateness of the antigen based testing, we determined sensitivity of two point-of-care antigen tests when applied to a cohort of COVID-19 symptomatic, COVID-19 asymptomatic and healthy persons.

METHODS

We examined nasopharyngeal swabs with antigen test 1 (Panbio Covid-19 Ag Rapid Test, Abbott) and antigen test 2 (Standard F Covid-19 Ag FIA, SD Biosensor). An additional nasopharyngeal and oropharyngeal swab of the same individual was checked with PCR (Allplex SARS-nCoV-2, Seegene). Within a 4-day period in October 2020, we collected specimens from 591 subjects. Of them, 290 had COVID-19 associated symptoms.

RESULTS

While PCR positivity was detected in 223 cases, antigen test 1 and antigen test 2 were found positive in 148 (sensitivity 0.664, 95%CI 0.599, 0.722) and 141 (sensitivity 0.623, 95%CI 0.558, 0.684) patients, respectively. When only symptomatic patients were analysed, sensitivity increased to 0.738 (95%CI 0.667, 0.799) for the antigen test 1 and to 0.685 (95%CI 0.611, 0.750) for the antigen test 2. The substantial drop in sensitivity to 12.9% (95%CI 0.067, 0.234) was observed for samples with the PCR threshold cycle above &gt; 30.

CONCLUSIONS

Low sensitivity of antigen tests leads to the considerable risk of false negativity. It is advisable to implement repeated testing with high enough frequency if the antigen test is used as a frontline screening tool, and to follow with PCR if it is applied to vulnerable populations.

Nonequilibrium Thermodynamics of Colloidal Gold Nanocrystals Monitored by Ultrafast Electron Diffraction and Optical Scattering Microscopy

Metal nanocrystals exhibit important optoelectronic and photocatalytic functionalities in response to light. These dynamic energy conversion processes have been commonly studied by transient optical probes to date, but an understanding of the atomistic response following photoexcitation has remained elusive. Here, we use femtosecond resolution electron diffraction to investigate transient lattice responses in optically excited colloidal gold nanocrystals, revealing the effects of nanocrystal size and surface ligands on the electron-phonon coupling and thermal relaxation dynamics. First, we uncover a strong size effect on the electron-phonon coupling, which arises from reduced dielectric screening at the nanocrystal surfaces and prevails independent of the optical excitation mechanism (i.e., inter- and intraband). Second, we find that surface ligands act as a tuning parameter for hot carrier cooling. Particularly, gold nanocrystals with thiol-based ligands show significantly slower carrier cooling as compared to amine-based ligands under intraband optical excitation due to electronic coupling at the nanocrystal/ligand interfaces. Finally, we spatiotemporally resolve thermal transport and heat dissipation in photoexcited nanocrystal films by combining electron diffraction with stroboscopic elastic scattering microscopy. Taken together, we resolve the distinct thermal relaxation time scales ranging from 1 ps to 100 ns associated with the multiple interfaces through which heat flows at the nanoscale. Our findings provide insights into optimization of gold nanocrystals and their thin films for photocatalysis and thermoelectric applications.

Pulsed photo-ionization spectroscopy of traps in as-grown and neutron irradiated ammonothermally synthesized GaN

GaN-based structures are promising for production of radiation detectors and high-voltage high-frequency devices. Particle detectors made of GaN are beneficial as devices simultaneously generating of the optical and electrical signals. Photon-electron coupling cross-section is a parameter which relates radiation absorption and emission characteristics. On the other hand, photon-electron coupling cross-section together with photo-ionization energy are fingerprints of deep centres in material. In this work, the wafer fragments of the GaN grown by ammonothermal (AT) technology are studied to reveal the dominant defects introduced by growth procedures and reactor neutron irradiations in a wide range, 10¹²-10¹⁶ cm^-2, of fluences. Several defects in the as-grown and irradiated material have been revealed by using the pulsed photo-ionization spectroscopy (PPIS) technique. The PPIS measurements were performed by combining femtosecond (40 fs) and nanosecond (4 ns) laser pulses emitted by optical parametric oscillators (OPO) to clarify the role of electron-phonon coupling. Variations of the operational characteristics of the tentative sensors, made of the AT GaN doped with Mg and Mn, under radiation damage by reactor neutrons have been considered.

Abstract 664: Analytical validation and clinical utility of an immunohistochemical PD-L1 diagnostic assay for treatment with durvalumab in urothelial carcinoma patients

Background: A high quality programmed cell death ligand-1 (PD-L1) diagnostic may help to identify patients (pts) most likely to respond to anti-PD-L1/programmed cell death-1 (PD-1) therapy. Here we describe a PD-L1 immunohistochemical (IHC) diagnostic test developed for urothelial carcinoma (UC) pts treated with durvalumab.

Methods: The IHC assay uses an anti-human PD-L1 rabbit mAb optimized for detection of both tumor cell (TC) and tumor-associated immune cell (IC) PD-L1 expression with the OptiView DAB IHC Detection Kit on the automated VENTANA BenchMark ULTRA platform. The assay was validated for intended use in UC formalin-fixed, paraffin-embedded samples in a series of studies that addressed sensitivity, specificity, robustness and precision and implemented in Study CD-ON-MEDI4736-1108 (NCT01693562). Pts were evaluated using the VENTANA PD-L1 (SP263) Assay at a prespecified PD-L1 expression cut-off. Efficacy was analyzed in pts with PD-L1 low/negative (defined as TC &lt;25% and IC &lt;25%) UC and in pts with PD-L1 high (defined as TC ≥25% or IC ≥25%) UC.

Results: The VENTANA PD-L1 (SP263) Assay met all the predefined acceptance criteria (average positive agreement and average negative agreement &gt;85%), showing analytical specificity, sensitivity and precision. It demonstrated ≥97% and ≥85% inter-reader precision agreement for TC and IC respectively. For intra-reader precision, it demonstrated &gt;96% and &gt;87% agreement for TC and IC respectively. For intra-day performance, the assay demonstrated ≥96% agreement for TC and IC and for inter-day performance, it demonstrated ≥98% and 100% agreement for TC and IC respectively. Precision studies for inter-antibody lot, inter-detection kit lot and intra-platform demonstrated &gt;97% agreement for both TC and IC. Inter-laboratory testing was performed at 3 external laboratories and demonstrated an overall agreement rate of 92.3%. The VENTANA PD-L1 (SP263) Assay was implemented in Study CD-ON-MEDI4736-1108 and durvalumab demonstrated clinical activity and durability of response in both PD-L1 high and PD-L1 low/negative subgroups, yet with different response rates. In addition, given the high negative predictive value of the assay, it is especially helpful in evaluating the likelihood of response to durvalumab; pts who were classified as PD-L1 high with the VENTANA PD-L1 (SP263) Assay tended to have a higher objective response rate per RECIST v1.1 than pts who were PD-L1 low/negative.

Conclusions: These data show that determination of PD-L1 expression in TC and IC in UC pts using the VENTANA PD-L1 (SP263) Assay is precise and highly reproducible and highlight the utility of the assay in a clinical setting. The VENTANA SP263 Assay is especially helpful in informing pts and physicians on the likelihood of response to durvalumab, but not for the purpose of restricting treatment to only PD-L1 high pts.

Citation Format: M Zajac, A M. Boothman, Y Ben, A Gupta, J Antal, X Jin, A Nielsen, G Manriquez, C Barker, P Wang, P Patil, N Schechter, M Rebelatto, J Walker. Analytical validation and clinical utility of an immunohistochemical PD-L1 diagnostic assay for treatment with durvalumab in urothelial carcinoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 664. doi:10.1158/1538-7445.AM2017-664

Abstract 656: PD-L1 expression in primary lesions vs metastatic sites and by demographics in advanced urothelial carcinoma samples

Background: Determination of programmed cell death ligand-1 (PD-L1) expression levels in tumors may help physicians understand which patients (pts) are most likely to respond to anti-PD-1/PD-L1 therapies in urothelial carcinoma (UC). Understanding the impact of different sample types and demographics on PD-L1 expression is important to determine suitability of tumor biopsies for testing.

Methods: As of July 24, 2016, 363 pts screened in the UC cohort of Study CD-ON-MEDI4736-1108 (NCT01693562) had tissue available for analysis and 47 pts had provided paired primary and metastatic samples. FFPE samples were tested in a central laboratory with the VENTANA PD-L1 (SP263) Assay using a BenchMark ULTRA instrument. Pts were classified as having either PD-L1 high (PD-L1 expression ≥25% either on tumour cells [TC] or immune cells [IC]) or PD-L1 low/negative (&lt;25% on TC and IC) tumors. PD-L1 high prevalence was reported in primary vs metastatic sites, and by age, sex and race.

Results: PD-L1 status was evaluable for 332/363 (91.5%) pts (175/332 [52.7%] PD-L1 high and 157/332 [47.3%] PD-L1 low/negative) whose UC specimens were tested (intent to diagnose [ITD] population). Overall percentage agreement between paired primary and metastatic samples, based on combined TC/IC scoring ≥25%, was 74.5% (95% CI 59.7 - 86.1%). In the ITD population, using only the samples from which patient PD-L1 expression status was determined, PD-L1 high prevalence in primary and metastatic samples was 57.1% and 50.9% respectively (p=0.343, not significant). The proportion of pts with PD-L1 high status was not enriched in any demographic group (Table).

Conclusions: Initial data from UC pts in Study 1108 showed similar PD-L1 high prevalence in primary and metastatic lesions and good concordance between paired primary and metastatic samples. These results build optimism that samples obtained from either location could be used to determine PD-L1 status. Further data are needed to confirm these findings.

Patients screened for UC cohort with evaluable PD-L1 result - ITD population (n = 332)ParameterPD-L1 high, n (%)P valueAge, years&lt;65 (n=131)73 (55.7%)0.438≥65 (n=201)102 (50.8%)SexMale (n=236)127 (53.8%)0.610Female (n=96)48 (50.0%)RaceAsian (n=52)23 (44.2%)Asian vs White: 0.406Black or African American (n=10)6 (60.0%)White (n=218)113 (51.8%)Other (n=9)4 (44.4%)

Citation Format: M Zajac, A M. Boothman, Y Ben, A Gupta, X Jin, J Antal, A Sharpe, M Scott, M Rebelatto, J Walker. PD-L1 expression in primary lesions vs metastatic sites and by demographics in advanced urothelial carcinoma samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 656. doi:10.1158/1538-7445.AM2017-656

Popular species of edible mushrooms as a good source of zinc to be released to artificial digestive juices

Because fruiting bodies of edible mushrooms accumulate elements very effectively, in this study for the first time we aimed at determining the degree of the release of zinc(II) ions to artificial digestive juices imitating the human gastrointestinal tract from freeze-dried popular edible mushroom fruiting bodies, such as Agaricus bisporus, Boletus badius and Cantharellus cibarius. For the analysis, anodic stripping voltammetry method was used. The amount of zinc released to artificial saliva within 1 minute ranged from 0.03 to 1.14 mg/100 g d.w. In gastric juice, the amounts were higher and ranged from 0.75 to 2.07 mg/100 g d.w. depending on the incubation time. After incubation of the freeze-dried edible mushroom fruiting bodies for 1 minute in artificial saliva, 15 in artificial gastric juice and then 150 minutes in artificial intestinal juice, it was found that the concentration of the released zinc in artificial intestinal juice was the highest and amounted to 6.44 mg/100 g d.w. The total average amount of zinc released from Boletus badius was the highest and this was estimated at 4.13 mg/100 g d.w. For the remaining two investigated species of A. bisporus and C. cibarius, the total amounts of zinc released into artificial digestive juices were only slightly lower and were estimated at 2.23 and 3.29 mg/100 g d.w. on average, respectively. It was demonstrated for the first time that mushrooms release zinc to artificial digestive juices imitating conditions in the human digestive tract and are a good source of this element.

[Diagnosis of Clostridium difficile infections: comparative study of two immuno enzyme assays with confirmation by PCR and culture followed by PCR ribotyping]

STUDY OBJECTIVE

Comparison of two commercially avail-able tests for the detection of Clostridium difficile Glutamate Dehydrogenase (GDH) and toxins A and B for their sensitivity and specificity.

MATERIAL AND METHODS

Eighty-six stool samples from patients hospitalised in the Motol University Hospital were analysed. GDH and toxins A and B were assayed in parallel by two tests: C. difficile Quik Chek Complete® (Techlab, USA) and Liaison® C. difficile GDH and Toxins AαB (DiaSorin, USA). From the stool samples, nucleic acids were also isolated using the UltraClean® Fecal DNA kit (MoBio Laboratories, USA). The commercially available C. difficile Elite MGB® kit (Nanogen, Italy) was used for the polymerase chain reaction (PCR). Anaerobic culture on C. difficile selective medium (Oxoid) was performed for all positive samples at least in one test. Pure isolates were characterized by PCR ribotyping.

RESULTS

Thirty-six (42%) samples were GDH negative and toxin A/B negative by both tests. Twenty (23%) samples were GDH positive and toxin A/B positive by both tests. Nine (10%) samples were GDH positive and toxin negative by both tests, but were positive by PCR. Eleven (13%) samples that were GDH positive and toxin negative by both tests remained negative by PCR. Six (7%) samples only were GDH positive and toxin positive by the Liaison® test alone. Four (5%) samples were GDH-positive by theLiaison® test alone. Culture failure was observed in 11 (13%) samples, of which seven were positive by PCR. PCR was inhibited in five (6%) samples. The following toxigenic ribotypes: AI-3, 001, 002, 012,014, 017, 020, 049, 054, 078, 176, 203, and 413 and non-toxigenic ribotypes: AI-34, AI-61, 010, 485, 495, and 596 were identified.

CONCLUSION

The Liaison® test had seven percent higher sensitivity for the detection of toxins A/B. The two-step protocol of the tests is also cost-saving. The savings can be used e.g. for incorporating the PCR techniques into the diagnostic algorithm of the laboratory.

Noncollinear magnetization structure at the thickness-driven spin-reorientation transition in epitaxial Fe films on W(110)

An in-plane spin-reorientation transition occurring during the growth of epitaxial Fe films on W(110) was studied in situ by using the nuclear resonant scattering of synchrotron radiation. The spin-reorientation transition originates at the Fe/W(110) interface and proceeds via a noncollinear spin structure resembling a planar domain wall that propagates towards the surface with increasing film thickness.

Tailoring of the perpendicular magnetization component in ferromagnetic films on a vicinal substrate

We have engineered the magnetic properties of 1-8 nm Co films epitaxially grown on an Au-buffered bifacial W(110)/W(540) single crystal. The surface of Au/W(110) was atomically flat, whereas the Au/W(540) followed the morphology of the vicinal W surface, showing a regular array of monoatomic steps. For Co grown on Au/W(540), the existence of the out-of-plane magnetization component extended strongly to a thickness d of about 8 nm, which was accompanied by an anomalous increase of the out-of-plane switching field with increasing d. In addition, the process of up-down magnetization switching could be realized with both a perpendicular and in-plane external magnetic field.

Phonons at the Fe(110) surface

The in-plane density of phonon states of clean Fe(110) surface was measured separately for the first, second, and further atomic monolayers using nuclear inelastic scattering of synchrotron radiation. The results show that atoms of the first layer vibrate with frequencies significantly lower and amplitudes much larger than those in the bulk, and that vibrational spectra along two perpendicular in-surface directions are different. The vibrations of the second layer are already very close to those of the bulk. The good agreement of the experimental results and the first-principles calculations allows for detailed understanding of the observed phenomena.

[EBV quantification in children after allogeneic hematopoietic stem cell transplantation]

BACKGROUND

Patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT) are endangered by developing Epstein-Barr virus-related post-transplant lymfoprolipherative disease (EBV-LPD). The aims of the study were to retrospectively characterise the viral loads in four patients who died of this complication, and to test possible risk factors for EBV reactivation in a prospectively observed cohort of children after AHSCT.

METHODS AND RESULTS

Serial DNA samples extracted from whole blood from four patients who died of post-transplant EBV-LPD in year 2000 were retrospectively analysed for EBV load using quantitative real-time PCR. First detection of EBV activation preceded death by 24-91 days. All four patients exceeded a viral load of one million EBV copies per 100,000 human genome equivalents. A cohort of 72 children undergoing AHSCT between 2001-2004 was prospectively followed-on using the same quantification method from regularly obtained samples of whole blood, and clinical and laboratory data were recorded on a weekly basis, totalling at 3,896 person-weeks of observation. Approximately one half of the cohort experienced at least one episode of EBV reactivation during the first 100 days after AHSCT, four of the episodes being accompanied with viral loads higher than our provisional threshold of 10,000 copies per 100,000 human genome equivalents. Three of the four patients developed EBV-LPD and were successfully treated by intravenous administration of anti-CD20 antibody. Testing of possible clinical and laboratory predictors of EBV reactivation did not reveal any clinically useful association.

CONCLUSIONS

The cornerstone of predicting EBV-LPD in AHSCT is a regular monitoring of EBV viral load using quantitative methods. Using this strategy with a threshold of 10,000 EBV copies per 100,000 human genome equivalents was proved to be effective, as shown by no death of EBV for the study period, compared to four cases in the year before the quantitative monitoring.

Prediction of vernalisation in three Australian Vrn responsive wheats

This study sought to better estimate vernalisation in winter wheats, so that their early development and time of anthesis can be better predicted. For this, an accurate relationship between temperature and the effectiveness of vernalisation is required. Using previously published data, our study found that the relationship between temperature and effectiveness of vernalisation can be suitably described by a quadratic function. In contrast, most previous studies used linear interpolation functions to describe vernalising effectiveness. These consist of a series of linear functions of temperature over adjoining temperature ranges. An advantage of quadratic functions is that they allow effectiveness of vernalisation to be described in terms of underlying physiological processes, and require the estimation of fewer parameters to predict wheat development. Our study found the cardinal temperatures for vernalisation to be –3�C, 6.5�C, and 15.9�C, that is for the lower, optimum, and maximum temperatures respectively. To allow for different upper temperature limits for vernalisation, 2 quadratic temperature-vernalising effectiveness functions were used to predict accumulated daily vernalisation at 3 field sites. These predictions of daily vernalisation were compared with corresponding estimates produced with 3 previously proposed linear interpolation functions. Varying degrees of agreement were found between estimates produced by the 2 types of vernalising effectiveness functions. Equations that have been developed to predict floral initiation in winter wheats have not been previously evaluated in Australian field environments. These equations utilise the same underlying relationship between accumulated daily vernalisation and a measure of floral initiation, often the appearance of double ridges. Two of these equations were used to predict the appearance of double ridges for a field-grown Australian winter wheat, JF87%014. Neither equation could satisfactorily predict the timing of the double ridge development stage for this wheat, whatever vernalising effectiveness function was used to predict vernalisation in the field. Both equations had greatest difficulty in predicting the double ridge stage, in environments where vernalisation most delayed development. This finding suggests that equations currently predicting floral initiation in winter wheats do not utilise an accurate relationship between accumulated vernalisation and floral initiation. An alternative method of predicting anthesis in winter wheats is to predict final leaf number, but this approach has not been reliably applied in environments where vernalising temperatures vary.

Stability of cefodizime disodium in solid state

The stability of the lyophilized substance of cefodizime disodium was investigated. The test for the stability in solid state with and without presence of humidity was arried out by the HPLC method. Kinetic and thermodynamic parameters of the decomposition reaction were calculated.

Stability of cetirizine dihydrochloride in solid state

Influence of temperature and relative humidity on stability of cetirizine dihydrochloride in solid state was followed by HPLC method in this study.

Stability of cefotaxime sodium in solid state

The influence of temperature and relative humidity on the stability of cefotaxime sodium in the solid state was investigated. Changes in the concentration of cefotaxime sodium were followed by a HPLC method with UV detection. The kinetic and thermodynamic parameters of the decomposition reaction were calculated.

Model of convergent extension in animal morphogenesis

We argue that energy minimization can explain the pattern of cell movements in the morphogenetic process known as convergent extension provided that the cell-cell adhesive energy has a certain type of anisotropy, which we describe. This single simple property suffices to cause the cell elongation, cell alignment, and lengthening of a cellular array that characterize convergent extension. We show that the final aspect ratio of the array of cells depends on the anisotropy and is independent of the initial configuration and of the degree of cell elongation.

UV/VIS spectrophotometric methods for determination of caffeine and phenylephrine hydrochloride in complex pharmaceutical preparations. Validation of the methods

The contents of active substances were determined in a preparation TP-4 (tablets) containing paracetamol, ascorbic acid, caffeine and phenylephrine hydrochloride. For determination of caffeine and phenylephrine hydrochloride, UV/VIS spectrophotometric method was used. The VIS spectrophotometric method based on the reaction of phenylephrine with ninhydrine in sulphuric acid (1.127 kg/l). Validation of methods performed for model mixtures proved those methods were accurate, precise, repeatable and linear in the range from 50% to 150% of the amount declared in the preparation. The content of caffeine and phenylephrine hydrochloride in TP-4, Thompyrin, Panadol Extra, Ring N satisfies the FP V demands.

Determination of cetirizine dichloride in tablets by HPLC method

A HPLC method for the determination of the cetirizine dichloride in tablets was developed and validated. The determination was performed with a LiChrosorb RP-18 column, mobile phase of KH2PO4 (0.01 mol/l)--acetonitrile 65:35 (v/v), flow rate: 2 ml.min-1, UV detection at 230 nm and methyl paraben as an internal standard.

Redox methods validation of paracetamol and ascorbic acid in pharmaceutical preparations

The contents of active substances were determined in a preparation TP-4 (tablets) containing paracetamol, ascorbic acid, caffeine and phenylephrine hydrochloride. For the determination of paracetamol and ascorbic acid a non-specific (cerometric and titration of 2,6-dichloroindophenol) method based on a redox reaction was used. Validation of the methods, performed on model mixtures, proved those methods to be accurate, precise, reproducible and linear within the range from 50% to 150% of the amount declared in the preparation. The content of paracetamol and ascorbic acid in TP-4, Thompayrin, Panadol Extra, Ring N, Polopiryna C, Efferalgan Vitamin C and Vitaminum C 0.2 satisfies the FP V demands (+/- 10% of the declared amount).

The mechanism of ceftazidime degradation in aqueous solutions

Degradation of ceftazidime in aqueous solutions was studied at 298 K in acidic, basic and neutral conditions. The subsequent stage of hydrolysis involved the hydrolysis of the group at C-3, opening of the beta-lactam ring, and epimerization at C-6 or C-7. The decomposition of ceftazidime and the formation and identification of product C (pyridine) was followed by HPLC.