Quantum Phase Transition from a Spin-liquid State to a Spin-glass State in the Quasi-1D Spin-1 System Sr1-xCaxNi2V2O8

We report a quantum phase transition from a spin-liquid state to a spin-glass state in the quasi-one dimensional (1D) spin-1 system Sr1-xCaxNi2V2O8, induced by a small amount of Ca-substitution at Sr site. The ground state of the parent compound (x = 0) is found to be a spin-liquid type with a finite energy gap of 26.6 K between singlet ground state and triplet excited state. Both dc-magnetization and ac-susceptibility studies on the highest Ca-substituted compound (x = 0.05) indicate a spin-glass type magnetic ground state. With increasing Ca-concentration, the spin-glass ordering temperature increases from 4.5 K (for the x = 0.015 compound) to 6.25 K (for the x = 0.05 compound). The observed results are discussed in the light of the earlier experimental reports and the theoretical predictions for a quasi-1D spin-1 system.Comment: 26 pages, 8 figures, 3 table

A secure data outsourcing scheme based on Asmuth – Bloom secret sharing

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Data outsourcing is an emerging paradigm for data management in which a database is provided as a service by third-party service providers. One of the major benefits of offering database as a service is to provide organisations, which are unable to purchase expensive hardware and software to host their databases, with efficient data storage accessible online at a cheap rate. Despite that, several issues of data confidentiality, integrity, availability and efficient indexing of users’ queries at the server side have to be addressed in the data outsourcing paradigm. Service providers have to guarantee that their clients’ data are secured against internal (insider) and external attacks. This paper briefly analyses the existing indexing schemes in data outsourcing and highlights their advantages and disadvantages. Then, this paper proposes a secure data outsourcing scheme based on Asmuth–Bloom secret sharing which tries to address the issues in data outsourcing such as data confidentiality, availability and order preservation for efficient indexing

Enhanced grain surface effect on magnetic properties of nanometric La0.7Ca0.3MnO3 manganite : Evidence of surface spin freezing of manganite nanoparticles

We have investigated the effect of nanometric grain size on magnetic properties of single phase, nanocrystalline, granular La0.7Ca0.3MnO3 (LCMO) sample. We have considered core-shell structure of our LCMO nanoparticles, which can explain its magnetic properties. From the temperature dependence of field cooled (FC) and zero-field cooled (ZFC) dc magnetization (DCM), the magnetic properties could be distinguished into two regimes: a relatively high temperature regime T > 40 K where the broad maximum of ZFC curve (at T = Tmax) is associated with the blocking of core particle moments, whereas the sharp maximum (at T = TS) is related to the freezing of surface (shell) spins. The unusual shape of M (H) loop at T = 1.5 K, temperature dependent feature of coercive field and remanent magnetization give a strong support of surface spin freezing that are occurring at lower temperature regime (T < 40 K) in this LCMO nanoparticles. Additionally, waiting time (tw) dependence of ZFC relaxation measurements at T = 50 K show weak dependence of relaxation rate [S(t)] on tw and dM/dln(t) following a logarithmic variation on time. Both of these features strongly support the high temperature regime to be associated with the blocking of core moments. At T = 20 K, ZFC relaxation measurements indicates the existence of two different types of relaxation processes in the sample with S(t) attaining a maximum at the elapsed time very close to the wait time tw = 1000 sec, which is an unequivocal sign of glassy behavior. This age-dependent effect convincingly establish the surface spin freezing of our LCMO nanoparticles associated with a background of superparamagnetic (SPM) phase of core moments.Comment: 41 pages, 10 figure

Long-range and short-range magnetic correlations, and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14

Spin-spin correlations and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14 have been investigated by powder neutron diffraction. The present study reveals a 3D long-range magnetic ordering below 16 K where the magnetic structure consists of ferromagnetic trimers that are coupled ferromagnetically along the spin-chain. The moment components along the a and c axes arrange antiferromagnetically. Our study establishes that the uncompensated moment components along the b axis result in a net magnetization per unit cell. The magnetic structure, determined in the present study, is in agreement with the results of recent first principles calculation; however, it is in contrast to a fascinating experimental prediction of ferrimagnetic ordering based on the periodicity of the exchange interactions in CaNi3P4O14. Our study also confirms the presence of broad diffuse magnetic scattering, due to 1D short-range spin-spin correlations, over a wide temperature range below ~50 K down to a temperature well below the Tc. Total neutron scattering analysis by the RMC method reveals that the dominating spin-spin correlation above Tc is ferromagnetic and along the b axis. The nearest neighbour spin-spin correlations along the a and c axes are found to be weakly antiferromagnetic. The nature of the trimer spin structure of the short-range state is similar to that of the 3D long-range ordered state. The present investigation of microscopic nature of the magnetic ground state also explains the condition required for the 1/3 magnetization plateau to be observed in the trimer spin-chains. In spite of the S=1 trimer chain system, the present compound CaNi3P4O14 is found to be a good realization of 3D magnet below the Tc=16 K with full ordered moment values of ~2 mu_B/Ni2+ (1.98 and 1.96 mu_B/Ni2+ for two Ni sites, respectively) at 1.5 K.Comment: 10 pages, 8 figure

Synthesis of Magnetic Nanocomposite with Natural Base Material for Thorium Adsorbent

Synthesis of magnetic nanocomposite adsorbent from iron oxide with montmorillonite and bentonite minerals has been done. The aim of this research is to improve quality of adsorbent. The composite have been made by mixing Fe3+/Fe2+ salt solution within clay suspension. Iron cations will transform to iron oxides within composite after precipitation and heating process. The result of x-ray diffraction of composite showed that the iron oxide is of Fe3O4/γ-Fe2O3 phase. The magnetic properties measured with Vibrating Sample Magnetometer (VSM) showed that the composite have superparamagnetic properties. The composite is attracted to permanent magnetic field, after adsorbing a contaminant in water. Adsorbtion efficiency of these magnetic nanocomposite adsorbent is 80%-84% for thorium

Bleeding after dental extractions in patients taking warfarin.

ObjectiveTo assess the incidence of bleeding after dental extractions in subjects taking warfarin continuously before and after extractions whose International Normalised Ratio (INR) was below 4.0 at the time of extraction.MethodsThis was a case series study of 150 patients without controls who required extraction of at least one tooth under local anaesthetic. All sockets were subsequently packed with absorbable oxycellulose and sutured.ResultsA total of 58 women and 92 men were included (mean age 66 years); their ages were similar. The mean INR (S.D.) was 2.5 (0.56), although most patients had an INR less than 2.5 (n=101). Ten patients (7%) bled after extraction, enough to require a return to hospital. Five patients of 101 with an INR2.5 out of 49 bled after extraction (p=0.29). Bleeding after extraction was not associated with operative antibiotics. All patients who bled were managed conservatively and none was admitted to hospital.ConclusionPatients taking warfarin whose INR is up to 4.0 and who have dental extractions in hospital do not have clinically significant bleeds post-operatively

Comparative Assessment of the Environmental Dynamics of Dissolved Organic Nitrogen (DON) and Dissolved Organic Phosphorus (DOP) from Three Wetlands in Northern Nigeria

This study assessed comparatively the environmental dynamics of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in water samples obtained from three locations (Lokoja, Jebba and Hadejia-Nguru) with five sampling sites in Northern Nigeria. These sites include Jebba, Matara-Uku, Lokoja, Baturiya and Nguru. Samples were collected during the dry and wet seasons of the year 2015 and levels of nitrogen and phosphorus determined using the persulphate wet-oxidation method. The average values for DON and DOP obtained ranged from 9.49±1.83 mg/l to 21.8±14.7 mg/l and 1.65±0.38 mg/l to 6.11±0.58 mg/l respectively. The values obtained for DON during the dry and wet seasons were Jebba (14.1±3.92), Matara-Uku (13.7±3.43), Lokoja (21.0±5.04), Baturiya (21.8±14.7), Nguru (7.14±2.40) and Jebba (13.9±1.97), Matara-Uku (11.3±2.62), Lokoja (9.59±1.46), Baturiya (9.49±1.83), Nguru (11.1±1.78) mg/l respectively. The mean values for DOP were Jebba (1.85±0.07), Matara-Uku (2.60±0.55), Lokoja (2.65±0.31), Baturiya (2.52±0.46), Nguru (1.65±0.38) and Jebba (3.70±0.16), Matara-Uku (5.55±0.24), Lokoja (6.11±0.58), Baturiya (4.93±0.90), Nguru (3.65±0.37) mg/l in the dry and wet seasons respectively. The DON concentrations were significantly higher (p&lt;0.05) in the dry season when compared with the wet season while the DOP concentrations were significantly higher (p&lt;0.05) in the wet season when compared with the dry season. This dynamics was attributed to run off from agricultural farm lands, hydrology and the rate of utilization of these nutrients by water plants. High concentrations of DOP and DON supportgood yield of agricultural produce of the farmlands around the wetlands.Keywords: Dissolved organic nitrogen, dissolved organic phosphorus, dissolved organic matter, wetland

Occurrence of Klebsiella Species in Cultured African Catfish in Oyo State, South-West Nigeria

Over the years, the increase in population, incomes, and demograph has lead to the increase in the consumption of fish as a result of its nutritional values. Clarias gariepinus is the most cultured fish species in Nigeria and attracts significant economic value making it a species of interest. Fish is capable of habouring diseases and therefore, must be safe and free of infectious pathogens if aquaculture should fulfill its potential. Infectious disease has being one of the major causes of death worldwide in recent times. Klebsiella species in the family of enterobacteriacea causes urinary tract infections, pneumonia, septicemias and soft tissue infections in human. They are opportunistic pathogens found the gastrointestinal tract of the host and spread rapidly thereby capable of causing nosocomial outbreaks. The study examined the prevalence of Klebisiella species in fish tissues in Oyo State, Nigeria. A total of seven hundred and fifty-six (756) fish organs from one hundred and eight (108) fish were examined for Klebsiella investigation. Fish of body weight ranges between 300g to 1300g were used for this study using stratified methods. The samples were examined using standard methods, biochemical characterization methods were employed in this study and data obtained were analysed using descriptive statistics. The results show that all the 66 isolates were gram-negative, did not haemolysis sheep blood, catalase positive, oxidase negative, non-motile, and ferment lactose, sucrose and mannitol sugars. Percentages of klebsiella species occurrence were 22.22% in forest zone and 40.72% in savannah zone. Fish with total length 51-60cm had highest incidence (52.17%), and body weight of 601-900g had highest incidence (57.14%). Generally, skin, gill, liver and muscle were the major location of Klebsiella species occurrence ranges from 11% to 14.81%. Therefore occurrence of Klebsiella species in higher in savannah zone than forest zone. The distribution of the klebsiella in fish in Oyo State shows that it is a problem present in fish tissues.Key words: Klebsiella, Occurrence, Diseases, infection

COVID-19 Vaccination Prioritization Based on Cardiovascular Risk Factors and Number-Needed-to-Vaccinate to Prevent Death

The supply limitations of COVID-19 vaccines have led to the need to prioritize vaccine distribution. Obesity, diabetes and hypertension have been associated with an increased risk of severe COVID-19 infection. Approximately half as many individuals with a cardiovascular risk factor need to be vaccinated against COVID-19 to prevent related death as compared with individuals without a risk factor. Adults with body-mass index ≥30kg/m2, diabetes or hypertension should be of a similar priority for COVID-19 vaccination to adults 10 years older with a body-mass index 20 to <30kg/m2, no diabetes and no hypertension