Cooling rate dependence of the antiferromagnetic domain structure of a single crystalline charge ordered manganite

The low temperature phase of single crystals of Nd$_{0.5}$Ca$_{0.5}$MnO$_3$ and Gd$_{0.5}$Ca$_{0.5}$MnO$_3$ manganites is investigated by squid magnetometry. Nd$_{0.5}$Ca$_{0.5}$MnO$_3$ undergoes a charge-ordering transition at $T_{CO}$=245K, and a long range CE-type antiferromagnetic state is established at $T_N$=145K. The dc-magnetization shows a cooling rate dependence below $T_N$, associated with a weak spontaneous moment. The associated excess magnetization is related to uncompensated spins in the CE-type antiferromagnetic structure, and to the presence in this state of fully orbital ordered regions separated by orbital domain walls. The observed cooling rate dependence is interpreted to be a consequence of the rearrangement of the orbital domain state induced by the large structural changes occurring upon cooling.Comment: REVTeX4; 7 pages, 4 figures. Revised 2001/12/0

Neurological Dysfunction in Coeliac Disease and Non-Coeliac Gluten Sensitivity

OBJECTIVES: Non-coeliac gluten sensitivity (NCGS) refers to patients with primarily gastrointestinal symptoms without enteropathy that symptomatically benefi t from gluten-free diet (GFD). Little is known about its pathophysiology, propensity to neurological manifestations, and if these differ from patients with coeliac disease (CD). We investigated the clinical and immunological characteristics of patients presenting with neurological manifestations with CD and those with NCGS. METHODS: We compared clinical, neurophysiological, and imaging data of patients with CD and NCGS presenting with neurological dysfunction assessed and followed up regularly over a period of 20 years. RESULTS: Out of 700 patients, 562 were included. Exclusion criteria included no bowel biopsy to confi rm CD, no HLA type available, and failure to adhere to GFD. All patients presented with neurological dysfunction and had circulating anti-gliadin antibodies. Out of 562 patients, 228 (41%) had evidence of enteropathy (Group 1, CD) and 334 (59%) did not (Group 2, NCGS). The most common neurological manifestations were cerebellar ataxia, peripheral neuropathy, and encephalopathy. There was a greater proportion of patients with encephalopathy in Group 1 and with a greater proportion of neuropathy in Group 2. The severity of ataxia did not differ between the two groups. Patients in Group 1 had more severe neuropathy. All patients from both groups responded to gluten-free diet. Anti-tissue transglutaminase (TG2) antibodies were found in 91% of patients in Group 1 and in 29% of patients in Group 2. Comparison between those patients in Group 2 with HLA-DQ2/DQ8 and those without as well as those with positive TG2 compared with those with negative TG2 antibodies identifi ed no differences within these subgroups. Serological positivity for TG6 antibodies was similar in the two groups (67 and 60%). CONCLUSIONS: The neurological manifestations of CD and NCGS are similar and equally responsive to a GFD suggestive of common pathophysiological mechanisms

Vaccination pattern affects immunological response

The response of the immune system to different vaccination patterns is studied with a simple model. It is argued that the history and characteristics of the pattern defines very different secondary immune responses in the case of infection. The memory function of the immune response can be set to work in very different modes depending on the pattern followed during immunizations. It is argued that the history and pattern of immunizations can be a decisive (and experimentally accessible) factor to tailor the effectiveness of a specific vaccine.Comment: 4 pages, five figure

Chronic idiopathic axonal polyneuropathy: Prevalence of pain and impact on quality of life

BACKGROUND AND AIM: Chronic idiopathic axonal polyneuropathy (CIAP) is a term describing axonal neuropathies of insidious onset, with slow or no progression of the disease over at least 6 months and with no etiology being identified despite appropriate investigations. We aimed to establish the prevalence of pain in patients with CIAP and investigate the impact of pain on quality of life (QoL). METHODS: All consecutive patients with CIAP attending a specialist neuropathy clinic were invited to participate. Pain was assessed via the DN4 questionnaire and the visual analogue scale (VAS). Overall Neuropathy Limitations Scale (ONLS) was used to assess the severity of neuropathy. The SF-36 questionnaire was used to measure participants' quality of life. RESULTS: Fifty-five patients with CIAP were recruited (63.6% male, mean age 73.4 ± 8.7 years). Based on the DN4 questionnaire, peripheral neuropathic pain was present in 33 patients (60.0%). After having adjusted for age, gender and disease severity pain showed significant negative correlations with the energy/fatigue domain of QoL (β = -0.259, p = 0.049), with the emotional well-being domain (β = -0.368, p = 0.007) and the general health perception domain (β = -0.356, p = 0.007). CONCLUSION: Pain is very prevalent in CIAP and is associated with poorer emotional well-being, worse general health perception, and increased fatigue

S. N, PD Shenoy, KR Venugopal, and LM Patnaik. Moving vehicle identification using background registration technique for traffic surveillance

Real-time segmentation of moving regions in image sequences is a fundamental step in many vision systems including automated visual surveillance and human-machine interface. In this paper we present a framework for detecting some important but unknown knowledge like vehicle identification and traffic flow count. The objective is to monitor activities at traffic intersections for detecting congestions, and then predict the traffic flow which assists in regulating traffic. The present algorithm for vision-based detection and counting of vehicles in monocular image sequences for traffic scenes are recorded by a stationary camera. The method is based on the establishment of correspondences between regions and vehicles, as the vehicles move through the image sequence. Background subtraction is used which improves the adaptive background mixture model and makes the system learn faster and more accurately, as well as adapt effectively to changing environments. The resulting system robustly identifies vehicles at intersection, rejecting background and tracks vehicles over a specific period of time. Real-life traffic video sequences are used to illustrate the effectiveness of the proposed algorithm

Phase diagram of the La1−x_{1-x}Cax_{x}MnO3_{3} compound for 0.5≤x≤0.90.5\leq x\leq 0.9

We have studied the phase diagram of La$_{1-x}$Ca$_{x}$MnO$_{3}$ for $0.5\leq x\leq 0.9$ using neutron powder diffraction and magnetization measurements. At 300 K all samples are paramagnetic and single phase with crystallographic symmetry $Pnma$. As the temperature is reduced a structural transition is observed which is to a charge-ordered state only for certain x. On further cooling the material passes to an antiferromagnetic ground state with Neel temperature $T_N$ that depends on x. For $0.8\leq x\leq 0.9$ the structural transformation occurs at the same temperature as the magnetic transition. Overall, the neutron diffraction patterns were explained by considering four phase boundaries for which La$_{1-x}$Ca$_x$MnO$_3$ forms a distinct phase: the CE phase at $x=0.5-0.55$, the charge-ordered phase at x=2/3, the monoclinic and C-type magnetic structure at $x=0.80-0.85$ and the G-type magnetic structure at x=1. Between these phase boundaries the magnetic reflections suggest the existence of mixed compounds containing both phases of the adjacent phase boundaries in a ratio determined by the lever rule

Modelling of strain effects in manganite films

Thickness dependence and strain effects in films of $La_{1-x}A_xMnO_3$ perovskites are analyzed in the colossal magnetoresistance regime. The calculations are based on a generalization of a variational approach previously proposed for the study of manganite bulk. It is found that a reduction in the thickness of the film causes a decrease of critical temperature and magnetization, and an increase of resistivity at low temperatures. The strain is introduced through the modifications of in-plane and out-of-plane electron hopping amplitudes due to substrate-induced distortions of the film unit cell. The strain effects on the transition temperature and transport properties are in good agreement with experimental data only if the dependence of the hopping matrix elements on the $Mn-O-Mn$ bond angle is properly taken into account. Finally variations of the electron-phonon coupling linked to the presence of strain turn out important in influencing the balance of coexisting phases in the filmComment: 7 figures. To be published on Physical Review

Collecting the data but missing the point: Validity of hand hygiene audit data

Background: Monitoring of hand hygiene compliance (HHC) by observation has been used in healthcare for more than a decade to provide assurance of infection control practice. The validity of this information is rarely tested. Aim: To examine the process and validity of collecting and reporting HHC data based on direct observation of compliance. Methods: Five years of HHC data routinely collected in one large National Health Service hospital trust were examined. The data collection process was reviewed by survey and interview of the auditors. HHC data collected for other research purposes undertaken during this period were compared with the organizational data set. Findings: After an initial increase, the reported HHC remained unchanged close to its intended target throughout this period. Examination of the data collection process revealed changes, including local interpretations of the data collection system, which invalidated the results. A minority of auditors had received formal training in observation and feedback of results. Conclusion: Whereas observation of HHC is the current gold standard, unless data collection definitions and methods are unambiguous, published, carefully supervised, and regularly monitored, variations may occur which affect the validity of the data. If the purpose of HHC monitoring is to improve practice and minimize transmission of infection, then a focus on progressively improving performance rather than on achieving a target may offer greater opportunities to achieve this

Interatomic potentials for atomistic simulations of the Ti-Al system

Semi-empirical interatomic potentials have been developed for Al, alpha-Ti, and gamma-TiAl within the embedded atomic method (EAM) by fitting to a large database of experimental as well as ab-initio data. The ab-initio calculations were performed by the linear augmented plane wave (LAPW) method within the density functional theory to obtain the equations of state for a number of crystal structures of the Ti-Al system. Some of the calculated LAPW energies were used for fitting the potentials while others for examining their quality. The potentials correctly predict the equilibrium crystal structures of the phases and accurately reproduce their basic lattice properties. The potentials are applied to calculate the energies of point defects, surfaces, planar faults in the equilibrium structures. Unlike earlier EAM potentials for the Ti-Al system, the proposed potentials provide reasonable description of the lattice thermal expansion, demonstrating their usefulness in the molecular dynamics or Monte Carlo studies at high temperatures. The energy along the tetragonal deformation path (Bain transformation) in gamma-TiAl calculated with the EAM potential is in a fairly good agreement with LAPW calculations. Equilibrium point defect concentrations in gamma-TiAl are studied using the EAM potential. It is found that antisite defects strongly dominate over vacancies at all compositions around stoichiometry, indicating that gamm-TiAl is an antisite disorder compound in agreement with experimental data.Comment: 46 pages, 6 figures (Physical Review B, in press