Bandgap engineering through nanocrystalline magnetic alloy grafting on reduced graphene oxide

Grafting of nanocrystalline Co₈₀Ni₂₀on reduced graphene oxide causes a significantly large moment (1.2μ_B), ∼10 times localization of conductivity and significant magnetoconductance of hybrid-materials, which is promising toward spintronic applications.

Citric acid modifies surface properties of commercial CeO2 nanoparticles reducing their toxicity and cerium uptake in radish (Raphanus sativus) seedlings

Little is known about the mobility, reactivity, and toxicity to plants of coated engineered nanoparticles (ENPs). Surface modification may change the interaction of ENPs with living organisms. This report describes surface changes in commercial CeO2 NPs coated with citric acid (CA) at molar ratios of 1:2, 1:3, 1:7, and 1:10 CeO2:CA, and their effects on radish (Raphanus sativus) seed germination, cerium and nutrients uptake. All CeO2 NPs and their absorption by radish plants were characterized by TEM, DLS, and ICP-OES. Radish seeds were germinated in pristine and CA coated CeO2 NPs suspensions at 50mg/L, 100mg/L, and 200mg/L. Deionized water and CA at 100mg/L were used as controls. Results showed ζ potential values of 21.6 mV and -56 mV for the pristine and CA coated CeO2 NPs, respectively. TEM images showed denser layers surrounding the CeO2 NPs at higher CA concentrations, as well as better distribution and smaller particle sizes. None of the treatments affected seed germination. However, at 200mg/L the CA coated NPs at 1:7 ratio produced significantly (p ≤ 0.05) more root biomass, increased water content and reduced by 94% the Ce uptake, compared to bare NPs. This suggests that CA coating decrease CeO2 NPs toxicity to plants.

Differences between X-ray and MRI-determined knee cartilage thickness in weight-bearing and non-weight-bearing conditions

OBJECTIVE

Determine the effect of loading upon MRI-based mean medial femorotibial cartilage thickness (mMFT_th) and radiograph-based minimum joint space width (mJSW), and determine loading's effect on the relationship between these measures.

METHODS

MRI and radiographs were analyzed of 25 knees in weight-bearing and non-weight-bearing conditions. Eight subjects had a Kellgren-Lawrence (KL) grade of 0, indicating no evidence of radiographic OA. The rest were KL = 2 or KL = 3, indicating mild to moderate OA. The change from unloaded to loaded conditions was calculated.

RESULTS

Joint space measures decreased from unloaded to loaded conditions for both radiographs (mJSW = 3.29 mm unloaded to 3.16 mm loaded, P < 0.05) and MRI (mMFT_th = 2.70 mm unloaded to 2.55 mm loaded P < 0.001). The mean absolute difference measured from radiographs was larger for the OA group than the control group, at -0.20 mm for OA vs +0.01 mm for control. Loaded X-ray and loaded MRI joint space values from our study were no better correlated to one another than loaded X-ray and unloaded MRI.

CONCLUSION

Knee loading does not add a very significant value to the study of joint space on healthy knees, but loading may play a role in the study of OA knees. Unloaded MRI assessments of cartilage thickness are as correlated to loaded JSW as to loaded MRI measurements. More study is necessary to determine whether loaded MRI adds significant value to the study of OA progression.

Postmenopausal women treated with combination parathyroid hormone (1-84) and ibandronate demonstrate different microstructural changes at the radius vs. tibia: the PTH and Ibandronate Combination Study (PICS)

SUMMARY

In postmenopausal women receiving combination parathyroid hormone (PTH) (1-84) therapy and ibandronate, we evaluated bone microarchitecture and biomechanics using high-resolution peripheral quantitative computed tomography (HR-pQCT). Cortical and trabecular changes were different at the nonweight-bearing radius vs. the weight-bearing tibia, with more favorable overall changes at the tibia.

INTRODUCTION

PTH therapy and bisphosphonates decrease fracture risk in postmenopausal osteoporosis, but their effects on bone microstructure and strength have not been fully characterized, particularly during combination therapy. PTH increases trabecular bone mineral density (BMD) substantially but may decrease cortical BMD, possibly by stimulating intracortical remodeling. We evaluated bone microarchitecture and biomechanics with HR-pQCT at the radius (a nonweight-bearing site) and tibia (weight bearing) in women receiving combination PTH(1-84) and ibandronate.

METHODS

Postmenopausal women with low bone mass (n = 43) were treated with 6 months of PTH(1-84) (100 μg/day), either as one 6- or two 3-month courses, in combination with ibandronate (150 mg/month) over 2 years. HR-pQCT was performed before and after therapy.

RESULTS

Because changes in HR-pQCT parameters did not differ between treatment arms, groups were pooled into one cohort for analysis. Trabecular BMD increased at both radius and tibia (p < 0.01 for each). Cortical thickness and BMD decreased at the radius (p < 0.01), consistent with changes in dual-energy X-ray absorptiometry, while these parameters did not change at the tibia (p ≤ 0.02 for difference between radius and tibia). In contrast, cortical porosity increased at the tibia (p < 0.01) but not radius. Stiffness and failure load decreased at the radius (p < 0.0001) but did not change at the tibia.

CONCLUSIONS

Cortical and trabecular changes in response to the PTH/ibandronate treatment combinations utilized in this study were different at the nonweight-bearing radius vs. the weight-bearing tibia, with more favorable overall changes at the tibia. Our findings support the possibility that weight bearing may optimize the effects of osteoporosis therapy.

Analysis of electronic structure and its effect on magnetic properties in (001) and (110) oriented La0.7Sr0.3MnO3 thin films

Epitaxial thin films of half-metallic oxide La0.7Sr0.3MnO3 (LSMO) have been grown in two crystalline orientations, one with the c-axis out-of-plane, the (001) orientation, and one with the c-axis in-plane, the (110) orientation. For the (110) oriented growth, there is no polar discontinuity at the substrate-film interface and hence no dead layer formation, which improves ferromagnetic interaction in the LSMO, making it highly attractive for spintronic applications. In our experiments, with x-ray diffraction, x-ray photoelectron spectroscopy and magnetic measurements, we have demonstrated that in the (110) oriented LSMO the lattice is more relaxed, leading to less deformation of electronic density around the La atom or in the MnO6 octahedra. This improved crystal and electronic structure improves the ferromagnetic properties of the films, making the Curie temperature higher by almost 15 K, which is of potential interest for spintronics. However, substrate strain induced magnetic anisotropy causes domain formation with out-of-plane components in these films, which poses some concern for practical spintronic devices.

Magnetic and electric properties of CaMn7O12 based multiferroic compounds: effect of electron doping

The mixed valent multiferroic compound CaMn7O12 is studied for its magnetic and electric properties. The compound undergoes magnetic ordering below 90 K with a helimagnetic structure followed by a low temperature magnetic anomaly observed around 43 K. This study shows that the magnetic anomaly at 43 K is associated with thermal hysteresis indicating the first order nature of the transition. The compound also shows field-cooled magnetic memory and relaxation below 43 K, although no zero-field-cooled memory is present. A clear magnetic hysteresis loop is present in the magnetization versus field measurements, signifying the presence of some ferromagnetic clusters in the system. We doped trivalent La at the site of divalent Ca expecting to enhance the fraction of Mn(3+) ions. The La doped samples show reduced magnetization, although the temperatures associated with the magnetic anomalies remain almost unaltered. Interestingly, the spontaneous electrical polarization below 90 K increases drastically on La substitution. We propose that the ground states of the pure as well as the La doped compositions contain isolated superparamagnetic like clusters, which can give rise to metastability in the form of field-cooled memory and relaxation. The ground state is certainly not spin glass type, as is evident from the absence of zero-field-cooled memory and frequency shift in the ac susceptibility measurements.

Instrumentation of broadband frequency domain thermoreflectance for measuring thermal conductivity accumulation functions

This paper describes the instrumentation for broadband frequency domain thermoreflectance (BB-FDTR), a novel, continuous wave laser technique for measuring the thermal conductivity accumulation function. The thermal conductivity accumulation function describes cumulative contributions to the bulk thermal conductivity of a material from energy carriers with different mean free paths. It can be used to map reductions in thermal conductivity in nano-devices, which arise when the dimensions of the device are commensurate to the mean free path of energy carriers. BB-FDTR uses high frequency surface temperature modulation to generate non-diffusive phonon transport realized through a reduction in the perceived thermal conductivity. By controlling the modulation frequency it is possible to reconstruct the thermal conductivity accumulation function. A unique heterodyning technique is used to down-convert the signal, therein improving our signal to noise ratio and enabling results over a broader range of modulation frequencies (200 kHz-200 MHz) and hence mean free paths.

A Griffiths-like phase in antiferromagnetic R0.5Eu0.5MnO3 (R = Pr, Nd, Sm)

We report a Griffiths-like phase in isovalent doped rare-earth manganites R(0.5)Eu(0.5)MnO(3) (R = Pr, Nd, Sm). Rietveld refinement of the structural data reveals strong orthorhombic and Jahn-Teller distortions. The dc and ac magnetic studies nicely demonstrate aspects of Griffiths phase-like behaviour. The presence of short range ferromagnetically correlated spin clusters is observed above the antiferromagnetic transition temperature. A disorder driven phase inhomogeneity arising from strong structural distortion is the possible origin of this behaviour.

The effect of oxygen on the Jahn-Teller distortion and magnetization dynamics of Pr0.9Ca0.1MnO3 thin films

We report on the effect of oxygen on the Jahn-Teller distortion and dynamic magnetic properties of low hole-doped Pr(0.9)Ca(0.1)MnO(3) thin films, using micro-Raman spectroscopy and the temperature dependent ac susceptibility, as a function of the frequency, dc field bias, and thermal cycles. The as-grown and vacuum annealed thin films show a high amount of magnetic frustration and inferior ferromagnetic ordering compared with the oxygen annealed thin films. It has been found that the amount of magnetic frustration in the film is interlinked with the Jahn-Teller distortion and domain wall dynamics. An attempt has been made to understand the origin and nature of the magnetic frustration.

Bone and cartilage demonstrate changes localized to bone marrow edema-like lesions within osteoarthritic knees

OBJECTIVE

Our objective is to understand the biological and mechanical pathways linking cartilage, bone, and marrow changes in the progression of osteoarthritis (OA). The aim of the present study was to evaluate bone structure and composition within bone marrow edema-like lesion (BMEL) regions associated with knee OA.

METHODS

Tibial plateau specimens (n = 18) were collected from 10 subjects with knee OA during total knee arthroplasty (TKA). Magnetic resonance (MR) imaging was used to identify BMEL and quantify metrics of cartilage composition. Micro-computed tomography (μCT) and high-resolution peripheral quantitative computed tomography (HR-pQCT) were used to quantify density and microstructure of the subchondral trabecular bone. Fourier transform infrared (FTIR) spectroscopy was used to quantify tissue composition.

RESULTS

Trabecular bone within BMEL was higher in volume fraction, with more and thicker trabeculae that were more plate-like in structure compared to unaffected regions. BMEL trabecular tissue composition had decreased phosphate and carbonate content. Marrow infiltration by a fibrous collagen network and evidence of increased bone remodeling were present. Structural and compositional changes were specifically localized to regions underlying cartilage degradation.

CONCLUSION

These results support the paradigm of focal interactions among bone, marrow, and cartilage in the progression of knee OA. Quantitative evaluation of tissue changes and interactions may aid in the understanding of disease pathophysiology and provide imaging markers for disease progression.

Disaster management in flash floods in leh (ladakh): a case study

Background:

On August 6, 2010, in the dark of the midnight, there were flash floods due to cloud burst in Leh in Ladakh region of North India. It rained 14 inches in 2 hours, causing loss of human life and destruction. The civil hospital of Leh was badly damaged and rendered dysfunctional. Search and rescue operations were launched by the Indian Army immediately after the disaster. The injured and the dead were shifted to Army Hospital, Leh, and mass casualty management was started by the army doctors while relief work was mounted by the army and civil administration.

Objective:

The present study was done to document disaster management strategies and approaches and to assesses the impact of flash floods on human lives, health hazards, and future implications of a natural disaster.

Materials and Methods:

The approach used was both quantitative as well as qualitative. It included data collection from the primary sources of the district collectorate, interviews with the district civil administration, health officials, and army officials who organized rescue operations, restoration of communication and transport, mass casualty management, and informal discussions with local residents.

Results:

234 persons died and over 800 were reported missing. Almost half of the people who died were local residents (49.6%) and foreigners (10.2%). Age-wise analysis of the deaths shows that the majority of deaths were reported in the age group of 25–50 years, accounting for 44.4% of deaths, followed by the 11–25-year age group with 22.2% deaths. The gender analysis showed that 61.5% were males and 38.5% were females. A further analysis showed that more females died in the age groups <10 years and ≥50 years.

Conclusions:

Disaster preparedness is critical, particularly in natural disasters. The Army's immediate search, rescue, and relief operations and mass casualty management effectively and efficiently mitigated the impact of flash floods, and restored normal life.

An agglomeration induced glassy magnetic state in a carbon nanotube/NiO nanocomposite system

A series of nanocomposite materials were synthesized using multi-walled carbon nanotubes (MWCNTs) and NiO nanoparticles by varying the concentration of NiO in the MWCNT host matrix. Such an increment in the NiO particle density actually tunes the degree of isolation among the magnetic nanoparticles. Careful investigation by transmission electron microscopy shows that particle agglomeration increases substantially with NiO particle density. Field dependence of magnetization measurements depict a gradual enhancement of coercivity with increasing NiO concentration, signifying the enhancement of magnetic anisotropy in this nanocomposite system. Furthermore, field cooled and zero field cooled memory effect as well as magnetization relaxation measurements show that a glassy magnetic state gradually develops when the concentration increases. Analysis based on the result of high resolution transmission electron microscopy along with the magnetization data reveals that interparticle magnetic exchange interaction in the presence of interfacial disorders plays the major role in the emergence of the glassy magnetic state in this nanocomposite system.

Metastability and inverse magnetocaloric effect in doped manganite (Nd(0.25)Sm(0.25)Sr(0.5)MnO3) and ferromagnetic shape memory alloy (Ni2Mn(1.36)Sn(0.64)): a comparison

The manganite Nd(0.25)Sm(0.25)Sr(0.5)MnO(3) (NSSMO) shows a first-order metal to insulator transition on cooling, which is concomitant with a magnetic transition from the ferromagnetic to antiferromagnetic state. In some respect the sample shows a striking similarity with Ni-Mn-Sn based ferromagnetic shape memory alloys (FSMAs) undergoing a first-order magneto-structural transition, and efforts have been made to highlight the similarities and dissimilarities of the studied manganite with one such FSMA of composition Ni(2)Mn(1.36)Sn(0.64). From our transport and magnetic investigations, the region of transition in the NSSMO is found to be highly metastable, with a clear indication of a magnetically arrested state which persists even when the sample is cooled down to the lowest temperature of measurement. Interestingly, the studied manganite shows an inverse magnetocaloric effect similar to the FSMA. However, a striking difference between the two compositions is evident in the low-temperature magneto-transport behavior: while a clear signature of tunneling magnetoresistance is present in NSSMO due to the coexisting metallic and insulating clusters of nanometer dimension, the studied FSMA do not show such behavior due to the absence of any insulating phase in the intermetallic alloy.

Absence of traditional magnetoresistivity mechanisms in Sr2FeMoO6 thin films grown on SrTiO3, MgO and NdGaO3 substrates

Magnetoresistive double perovskite Sr(2)FeMoO(6) thin films were grown with two different deposition pressures on SrTiO(3), MgO and NdGaO(3) substrates by pulsed laser deposition and thorough structural, magnetic and magneto-transport characterization was made. According to x-ray diffraction, all the films were phase pure and fully textured. Indication of substrate dependent strain and low angle grain boundaries was found, especially in films on MgO. Both the deposition pressure and the choice of the substrate have a strong influence on the saturation magnetization, M(s), and Curie temperature, T(C). The structural and magnetic data indicate the presence of anti-site disorder (ASD) in the films. The temperature dependence of resistivity showed semiconductive behaviour at temperatures below 100 K and metallic behaviour at higher temperatures. The semiconductive behaviour was found to increase with increasing ASD. In good quality films, up to 12% negative magnetoresistance (MR) was observed and films grown on MgO and NGO substrates also showed low field MR. However, the most significant observation of this study was that the magnetoresistivity of these Sr(2)FeMoO(6) thin films could not be explained with any traditional MR mechanism, but carried the clear signature of superposition of different mechanisms, in particular low angle grain boundary tunnelling and suppression of antiferromagnetically ordered domains under a magnetic field.

Association of MR relaxation and cartilage deformation in knee osteoarthritis

We assessed the relationship between cartilage MR relaxation times and biomechanical response of tibiofemoral articular cartilage to physiological loading in healthy subjects and patients with osteoarthritis (OA). Female subjects above 40 years of age with (N(1)  = 20) and without (N(2)  = 10) OA were imaged on a 3T MR scanner using a custom made loading device. MR images were acquired with the knee flexed at 20° with and without a compressive load of 50% of the subject's bodyweight. The subjects were categorized based on the clinical MRI scoring of medial and lateral cartilage surfaces. Data were stratified twice into two equal groups (low and high) at the median value of T(1ρ) and T(2) relaxation time. The change in contact area and cartilage deformation was measured within these groups. Paired Student's t-test (α = 0.05) was used to analyze the effect of loading on contact area and deformation. The average area of the contact region in the medial compartment was significantly higher in OA subjects compared with normal subjects in both unloaded (314 ± 112 mm(2) vs. 227 ± 106 mm(2), p = 0.023) and loaded (425 ± 128 mm(2) vs. 316 ± 107 mm(2), p = 0.01) conditions. The overall relative change of cartilage thickness in the medial compartment was significantly higher than the lateral compartment (-5.3 ± 9.9% vs. -1.9 ± 9.2%, p = 0.042). When cartilage was divided into deep and superficial layers, superficial layers showed higher changes in relaxation time (T(1ρ) and T(2)) than the changes in relaxation time of whole cartilage (Normal: 12.5% vs. 6.9%; OA: 10.9% vs. 4.6%). The average T(1ρ) and T(2) times, change in area of contact region, and change in cartilage thickness in subjects with OA were higher when compared to normal subjects. This study provides support for a relationship between the mechanical response of cartilage to physiological loading (cartilage-on-cartilage contact area and cartilage deformation) and MR relaxation times (T(1ρ) and T(2)) in both OA patients and normal subjects.

Irreversible metamagnetic transition and magnetic memory in small-bandwidth manganite Pr(1-x)Ca(x)MnO3 (x = 0.0-0.5)

The present paper reports detailed structural and magnetic characterization of the low-bandwidth manganite Pr(1-x)Ca(x)MnO(3) (with x = 0.0-0.5) (PCMO) polycrystalline samples. With increasing Ca content, reduction of the unit cell volume and improvement in perovskite structure symmetry was observed at room temperature. Magnetic characterization shows the signature of coexisting AFM-FM ordering and spin-glass phase at the low doping range (x = 0.0-0.2) while increased hole doping (x = 0.3-0.5) leads to charge ordering, training effect and an irreversible metamagnetic phenomenon. The large irreversible metamagnetism in the CO phase of PCMO and the corresponding spin memory effect is a direct consequence of hysteretic first-order phase transition arising from the weakening of the CO state under the external magnetic field and trapping of the spins due to a strong pinning potential in the material.

Evolution of structural and magnetic properties with varying oxygen content in low-bandwidth manganite Pr0.9Ca0.1MnO3 thin films

The effects of ex situ vacuum and oxygen annealing treatments on thin films of the low-bandwidth compound Pr(1-x)Ca(x)MnO(3) (PCMO) are investigated. Structural and magnetic measurements reveal that increased ferromagnetism can be achieved by oxygen annealing treatment, which is linked to the increased Mn(4+) ion content, as observed from x-ray photoelectron spectroscopy (XPS) measurements, as well as relaxation of the substrate-induced tensile strain of the PCMO unit cell. The increased number of Mn(4+) ions and partial release of strain lead to stronger double-exchange interaction in the system. Vacuum annealing increases the ferromagnetic (FM) interaction as well; however, the increased FM ordering is not directly related to the improved double-exchange interaction, as XPS measurement reveals an indication of a slight increase in Mn(3+) ions in this case. Trapping of carriers in the oxygen vacancies and formation of magnetic polarons have been suggested as the causes of the increase in ferromagnetic ordering, and this is also supported by the large coercivity and longer spin memory in the vacuum annealed PCMO.