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The analogy between viral dynamics in humans and in computers is a detailed and useful one. At first glance, the extension to infectious disease epidemiology on human social networks and communication in wireless networks is also a compelling analogy. Mathematical epidemiology has a long history and seems to offer a biological inspiration for communication network design. In this paper, however, we argue that while epidemiology as a metaphor may hold insights into communication networks, the relationship is not concrete enough to permit us to adapt solutions from one domain to another. Our conclusion is that it is certain new mathematics and methodologies, rather than the results themselves, that are most likely to generalize well to communication systems.

To study the efficacy of low molecular weight heparin (LMWH) in the treatment of viper envenomation to combat the haematotoxicity and disseminated intravascular coagulation (DIC).Eighty patients with viper bite and incoagulable blood were randomized into two groups of 40 each. One group (Test group) received LMWH, in addition to the antisnake venom (ASV) and other routine measures received by the other group (Control group). Efficacy was assessed by monitoring the bleeding time (BT), whole blood clotting time (CT), prothrombin time (PT), platelet count, fibrinogen, blood urea (BU), serum creatinine, development of complications and overall outcome.LMWH group showed favourable outcome in all the parameters except in the incidence of renal failure which was reversible in the majority of the cases. However the differences between the two groups were statistically not significant.LMW heparin seems to have a beneficial role in the treatment of viper bites, but this needs to be confirmed by a larger trial using a higher dose of heparin.

Recently, there has been substantial interest in the design of cross-layer protocols for wireless networks. These protocols optimize certain performance metric(s) of interest (e.g. latency, energy, rate) by jointly optimizing the performance of multiple layers of the protocol stack. Algorithm designers often use geometric-graph-theoretic models for radio interference to design such cross-layer protocols. In this paper we study the problem of designing cross-layer protocols for multi-hop wireless networks using a more realistic Signal to Interference plus Noise Ratio (SINR) model for radio interference. The following cross-layer latency minimization problem is studied: Given a set V of transceivers, and a set of source-destination pairs, (i) choose power levels for all the transceivers, (ii) choose routes for all connections, and (iii) construct an end-to-end schedule such that the SINR constraints are satisfied at each time step so as to minimize the make-span of the schedule (the time by which all packets have reached their respective destinations). We present a polynomial-time algorithm with provable worst-case performance guarantee for this cross-layer latency minimization problem. As corollaries of the algorithmic technique we show that a number of variants of the cross-layer latency minimization problem can also be approximated efficiently in polynomial time. Our work extends the results of Kumar et al. (Proc. SODA, 2004) and Moscibroda et al. (Proc. MOBIHOC, 2006). Although our algorithm considers multiple layers of the protocol stack, it can naturally be viewed as compositions of tasks specific to each layer --- this allows us to improve the overall performance while preserving the modularity of the layered structure.

Hydrolytic kinetic resolution (HKR) developed by Jacobsen has emerged in recent times as a powerful tool to synthesize both terminal epoxides and their corresponding diols in highly enantiomerically pure form. In this review we have covered the application of HKR method for the first time in the synthesis of biologically active compounds. Figure options Download full-size image Download as PowerPoint slide

The present paper describes the analysis of ferry wake wash along a proposed route between San Francisco and a new ferry terminal at Hercules. The steady wave field generated by a candidate catamaran ferry was calculated for a range of vessel speeds and water depths, using established computational fluid dynamics (CFD) techniques. The matrix of cases analyzed span the range of vessel speeds (5 to 35 knots) and water depths (3 to 32 m) anticipated for ferry service along the proposed route. The free-wave spectra which fully characterize the ship-generated wave system in the far field are also calculated and presented, including for shallow-water cases. The calculated ferry wakes and the free-wave spectra enable the propagation and transformation of the wave system into the far field over varying bathymetry, so that the impact of ferry wakes on the shoreline may be studied. The analysis is part of a broader “shoreline and biological response” approach to wake wash impact analysis. The approach contains site-specific elements, but the process may also be applied to evaluate wake wash impact of specific, yet-to-be-built ferries on other future routes.

This chapter addresses the need of cryptographic algorithm to prepare unbreakable cipher. Though the performance of symmetric key algorithms is far better than asymmetric key algorithms, it still suffers with key distribution problems. It is highly evident that there is always a demand for an algorithm to transfer the secret key in a secure manner between the participants. This chapter argues that by providing the randomness to the secret key, it would be increasingly difficult to hack the secret key. This chapter proposes an algorithm effectively utilizes the random nature of stock prices inconjunction with plain text to generate random cipher. This algorithm can be used to exchange the secret key in a secure manner between the participants.

We observe exchange bias (EB) in a single magnetic film Fe3O4 at temperature T < 200 K. Irrespective of crystallographic orientations of grown Fe3O4; they exhibit similar nature of EB for (100) epitaxial, (111) oriented and polycrystalline Fe3O4 thin films. Growth induced defects such as anti-phase boundaries (APBs) in epitaxial Fe3O4 thin film is known to have an influence on the magnetic interaction. But, it is noticed that according to the common consensus of APBs alone cannot explain the origin of EB. If majority of APBs end up with mainly anti-ferromagnetic interactions across these boundaries together with the internal ordering modification in Fe3O4, then EB can emerge at low temperatures. Hence, we propose the idea of directional anti-ferromagnetic APB induced EB in Fe3O4 triggered by internal ordering for T

Nanocomposites of hard (SrFe12O19) and soft ferrite (CoFe2O4) are prepared by mixing individual ferrite components at appropriate weight ratio and subsequent heat treatment. The magnetization of the composites showed hysteresis loop that is characteristic of the exchange spring system. The variation of J(r)/J(r)(infinity) vs. J(d)/J(r)(infinity) for these nanocomposites are investigated to understand the presence of both the interacting field and the disorder in the system. This is further corroborated with the First Order Reversal Curve analysis (FORC) on the nanocomposites of 1:4 (Cobalt Ferrite: Strontium Ferrite) and 1:16 (Cobalt Ferrite: Strontium Ferrite). The FORC distribution reveals that the pinning mechanism is stronger in the nanocomposite of 1:4 compared to 1:16. However, the nanocomposite of 1:16 exhibit superior exchange coupling strength in contrast to 1:4. The asymmetric nature of the FORC distribution at H-c = 0 Oe for both the nanocomposites validates the intercoupling between the reversible and irreversible magnetization. (C) 2015 Author(s).

Active powders of Ni–Zn ferrite were synthesized by soft chemical approaches and were processed with varying concentrations of Bi2O3. The sintered products were characterized extensively using a vibrating sample magnetometer, scanning electron microscopy, and resistivity techniques. The loss factor and the permeability have been evaluated. At an optimum concentration of Bi2O3 doping the loss factor has been reduced by 20%. The rotational responses are found to be strongly dependent on particle size.

There has recently been renewed interest among various research communities in understanding the structure of social and infrastructure networks. Motivated by this line of research, we conduct an in-depth structural analysis of large ad hoc networks derived by placing nodes randomly as well as by placing them in realistic urban environments, a scenario that is rapidly gaining interest (K. Jain, et al, 2003). We use structural analysis in two illustrative settings. First, we use it to study the performance of network protocols. Our results indicate that structural analysis of interference graphs that model ad hoc networks can yield a good first order prediction of the overall protocol performance. Second, we study the robustness of a network to random node and edge failures. This study is important in the context of ad hoc networks wherein one expects nodes/edges to fail due various natural or system dependent reasons. The experimental results presented in this paper show the following: (i) structural properties of ad hoc networks depend crucially on the spatial distribution of the nodes. (ii) Structural properties of the network significantly affect the performance of protocols. (iii) Graph theoretic measures can provide good first order insights into the network protocol performance. (iv) The measures are also useful in characterizing the robustness of such networks.

Summary Addition of interleukin-2 receptor antagonist (IL-2RA) induction to calcineurin inhibitor (CNI)-based regimens reduces biopsy-proven acute rejection by 30–40%. IL-2RA induction facilitates early withdrawal of steroids, and supports the safe use of reduced-exposure CNI or delayed CNI introduction. IL-2RAs and rabbit antithymocyte globulin (Thymoglobulin®) show comparable efficacy in patients at standard or low immunologic risk, but the adverse event profiles of lymphocyte-depleting agents are less favorable. IL-2RAs, uniquely, provide effective immunosuppression with similar tolerability to placebo.

An efficient stereoselective total synthesis of (+)-boronolide from valeraldehyde is described. The key steps include a Sharpless asymmetric hydroxylation, a chelation-controlled vinyl Grignard reaction followed by a Sharpless asymmetric epoxidation, hydrolytic kinetic resolution, and a ring-closing metathesis.

Wireless technology is increasingly finding its way into industrial communication because of the tremendous advantages it is capable of offering. However, the high bit error rate characteristics of wireless channel due to conditions like attenuation, noise, channel fading and interference seriously impact the timeliness and guarantee that need to be provided for real-time traffic. Existing wired protocols including the popular PROFIBUS perform unfavorably when extended or adapted to the wireless context. Other wireless protocols proposed either do not adapt well to erroneous channel conditions or do not provide real-time guarantees. In this paper, we present a novel real-time MAC (Medium Access Control) protocol that is specifically tailored to the message characteristics and requirements of the industrial environments. The protocol exploits both the spatial and temporal diversity of the wireless channel to effectively schedule real-time messages in the presence of bursty channel error conditions. Simulation results show that the proposed protocol achieves much better loss rate compared to baseline protocols under bursty channel conditions.

Active powders of Ni–Zn ferrite were synthesized by soft chemical approaches and were extensively characterized using x-ray diffraction, scanning electron micrographs, vibrating sample magnetometer, resistivity, and permeability/loss factor techniques. The variation in the sintering conditions established a useful microstructure–magnetic permeability correlation.

Active powders of Ni–Zn ferrite were synthesized by soft chemical approaches and were processed with varying concentrations of Bi2O3. The sintered products were characterized extensively using a vibrating sample magnetometer, scanning electron microscopy, and resistivity techniques. The loss factor and the permeability have been evaluated. At an optimum concentration of Bi2O3 doping the loss factor has been reduced by 20%. The rotational responses are found to be strongly dependent on particle size.

An efficient enantio- and stereocontrolled total synthesis of (+)-boronolide from valeraldehyde is described. The key steps include a Sharpless asymmetric dihydroxylation, a chelation controlled Grignard reaction followed by Sharpless asymmetric epoxidation and a ring closing metathesis.

We present provably efficient parallel algorithms for sweep scheduling on unstructured meshes. Sweep scheduling is a commonly used technique in radiation transport problems, and involves inverting an operator by iteratively sweeping across a mesh. Each sweep involves solving the operator locally at each cell. However, each direction induces a partial order in which this computation can proceed. On a distributed computing system, the goal is to schedule the computation, so that the length of the schedule is minimized. Several heuristics have been proposed for this problem; but none of the heuristics have worst case performance guarantees. We present a simple, almost linear time randomized algorithm which (provably) gives a schedule of length at most O(log/sup 2/n) times the optimal schedule for instances with n cells, when the communication cost is not considered, and a slight variant, which coupled with a much more careful analysis, gives a schedule of (expected) length O(logmlogloglogm) times the optimal schedule for m processors. These are the first such provable guarantees for this problem. We also design a priority based list schedule using these ideas, with the same theoretical guarantee, but much better performance in practice. We complement our theoretical results with extensive empirical analysis. The results show that (i) our algorithm performs very well and has significantly better performance guarantee in practice and (ii) the algorithm compares favorably with other natural and efficient parallel algorithms proposed in the literature [S. Pautz, (2002), S. Plimpton et al., (2001)].

We present polylogarithmic approximations for the R|prec|Cmax and R|prec|∑jwjCj problems, when the precedence constraints are “treelike” – i.e., when the undirected graph underlying the precedences is a forest. We also obtain improved bounds for the weighted completion time and flow time for the case of chains with restricted assignment – this generalizes the job shop problem to these objective functions. We use the same lower bound of “congestion+dilation”, as in other job shop scheduling approaches. The first step in our algorithm for the R|prec|Cmax problem with treelike precedences involves using the algorithm of Lenstra, Shmoys and Tardos to obtain a processor assignment with the congestion + dilation value within a constant factor of the optimal. We then show how to generalize the random delays technique of Leighton, Maggs and Rao to the case of trees. For the weighted completion time, we show a certain type of reduction to the makespan problem, which dovetails well with the lower bound we employ for the makespan problem. For the special case of chains, we show a dependent rounding technique which leads to improved bounds on the weighted completion time and new bicriteria bounds for the flow time.

Both the enantiomers of trans-3-hydroxypipecolic acid have been synthesized employing the Sharpless asymmetric dihydroxylation and epoxidation as the key steps starting from a commercially available starting material 1,4-butanediol.

A variety of amines react with chloroformates in the presence of catalytic amount of yttria-zirconia based catalyst to afford the corresponding carbamates in excellent yields.

Carboxylic acids are regenerated from their corresponding allyl or cinnamyl esters by H-β zeolite under environmentally safe, heterogeneous reaction conditions in excellent yields.

We study topology control problems in ad hoc networks where network nodes get to choose their power levels in order to ensure desired connectivity properties. Unlike most other work on this topic, we assume that the network nodes are owned by different entities, whose only goal is to maximize their own utility that they get out of the network without considering the overall performance of the network. Game theory is the appropriate tool to study such selfish nodes: we define several topology control games in which the nodes need to choose power levels in order to connect to other nodes in the network to reach their communication partners while at the same time minimizing their costs. We study Nash equilibria and show that-among the games we define-these can only be guaranteed to exist if each network node is required to be connected to all other nodes (we call this the STRONG CONNECTIVITY GAME). For a variation called CONNECTIVITY GAME, where each node is only required to be connected (possibly via intermediate nodes) to a given set of nodes, we show that Nash equilibria do not necessarily exist. We further study how to find Nash equilibria with incentive-compatible algorithms and compare the cost of Nash equilibria to the cost of a social optimum, which is a radius assignment that minimizes the total cost in a network where nodes cooperate. We also study variations of the games; one where nodes not only have to be connected, but k-connected, and one that we call the REACHABILITY GAME, where nodes have to reach as many other nodes as possible, while keeping costs low. We extend our study of the STRONG CONNECTIVITY GAME and the CONNECTIVITY GAME to wireless networks with directional antennas and wireline networks, where nodes need to choose neighbors to which they will pay a link. Our work is a first step towards game-theoretic analyses of topology control in wireless and wireline networks.

A new PCC-mediated carboncarbon bond cleavage reaction during oxidation of homobenzylic alcohols leading to the formation of benzylic carbonyl compounds has been observed. Homobenzylic alcohols with no benzylic substitution (R 1 =H) gave benzylic aldehydes without further oxidation, while those with benzylic substitution (R 1 =Me, Et, Ar) gave benzylic ketones. In contrast, homoallylic alcohols gave products arising from double bond migration, cis - to trans -olefin isomerization and/or allylic oxidation.

We show that no Markovian coupling argument can prove rapid mixing of the Jerrum-Sinclair Markov chain for sampling almost uniformly from the set of perfect and near perfect matchings of a given graph. In particular, we show that there exists a bipartite graph G such that any Markovian coupling argument on the Jerrum-Sinclair Markov chain for G must necessarily take time exponential in the number of vertices in G. This holds even when the coupling argument is time-variant, i.e., the transition probabilities used by the coupling process depend upon the history of the process. In contrast, the above Markov chain on G has been shown to mix in polynomial time using conductance arguments.

By making use of advanced methods for the calculation of electron trajectories in the presence of space charge fields we have designed and built a novel electron energy-loss spectrometer for the purpose of measuring spin flip excitations at surfaces. The measurement of the spin asymmetry requires a deflection angle between the photocathode and the sample position which amounts to 90degrees in total. That deflection angle is not provided by standard electron deflectors, or by a combination of those. We show that a 90degrees deflection angle can be realized by a combination of two novel deflectors with 90degrees and 180degrees deflection angles each. The performance of the new spectrometer matches the performance of the best electron spectrometers developed for surface vibration spectroscopy. (C) 2003 American Institute of Physics.

The realm of high energy, large wave vector spin waves in ultrathin films and at surfaces is unexplored because a suitable method was not available up to now. We present experimental data for an 8 ML thick Co film deposited on Cu(001) which show that spin-polarized electron energy loss spectroscopy can be used to measure spin-wave dispersion curves of ultrathin ferromagnetic films up to the surface Brillouin zone boundary.

The calcineurin inhibitors, cyclosporine and tacrolimus, are the mainstay of current immunosuppressive regimens for the prevention of acute rejection in organ transplantation. The choice of the individual agent used often depends on the preference of the Transplant Center and patient type. Adverse effects associated with tacrolimus may impact its clinical utility in many patients. This study characterizes the clinical outcomes of transplant recipients who experienced adverse effects from tacrolimus and were converted to cyclosporine-microemulsion-based (Neoral([cyclosporine, USP] MODIFIED) therapy.Hepatic or renal allograft recipients unable to maintain adequate immunosuppression with a tacrolimus-based regimen for reasons of toxicity or efficacy were recruited for this study and converted to cyclosporine-microemulsion-based therapy. Data were collected on drug dosing, trough concentrations, and treatment duration, as well as detailed information on tacrolimus-associated toxicities that prompted rescue with cyclosporine-microemulsion. Furthermore, clinical and laboratory data related to the clinical course of the patients after conversion to cyclosporine-microemulsion were recorded for up to 1 yr following conversion.One hundred and fifty-seven transplant recipients were enrolled in this study. Predominant reasons for discontinuation of tacrolimus were neurotoxicity (55%), diabetes (24%), nephrotoxicity (15%), and gastrointestinal intolerance (24%). Patients frequently had multiple symptoms prompting rescue therapy with cyclosporine-microemulsion. Over 70% of subjects had improvement or resolution of their tacrolimus-associated adverse symptoms within 3 months post-conversion. Acute rejection episodes occurred in 27% of patients converted to cyclosporine-microemulsion.Cyclosporine-microemulsion rescue therapy in patients experiencing adverse clinical effects associated with tacrolimus is an effective treatment option which leads to resolution of these adverse effects in the majority of patients, and allows for satisfactory clinical outcomes.

We continue the study initiated in [13] on Stackelberg Scheduling Strategies. We are given a set of m independent parallel machines or equivalently a set of m parallel edges, each with a load dependent latency function. The setting is that of a non-cooperative game: players route their flow so as minimize their individual latencies. Additionally, there is a single player (the leader), who controls an a fraction of the total flow. The goal is to find a strategy for the leader (i.e. an assignment of flow to individual links) such that the selfish users react so as to minimize the total latency of the system. Building on the recent results in [13,14], we devise a fully polynomial approximate Stackelberg scheme that runs in time poly(m, 1/?) and results in an assignment whose cost is within a (1 + ?) factor of the optimum Stackelberg strategy. We also study the generalization to multiple rounds. It is easy to see that more than two rounds do not help. We show that the two round Stackelberg strategy (denoted 2SS) always dominates the one round scheme. We also consider extensions of the above results to special graphs, and special kind of latency functions.

We describe the factors that control the transfer ratio of the spin-valve transistor. An increase in transfer ratio is obtained by a systematic variation of the height of emitter and collector Schottky barrier, and of the nonmagnetic metals. Next, we found that in some cases, a thicker base leads to a higher transfer ratio. Finally, the thickness of the magnetic layers in the Ni 80 Fe 20 /Au/Co spin-valve base can be optimized for a maximum absolute change of collector current. An overall increase by a factor of 24 was achieved, without loss of the magnetocurrent.

The magneto-dielectric coupling in (l00) oriented LaMn0.5Co0.5O3 single crystals has been investigated using temperature, frequency, and magnetic field dependent dielectric response. Electronic transport data divulges that polaronic hopping arises due to Emin-Holstein adiabatic small polarons. Spin realignment through external magnetic field favors faster polaronic hopping by lowering activation energy for dielectric relaxation. Finally, positive magneto-dielectricity and magnetoloss under increasing magnetic field at high frequency of the exciting ac field confirms intrinsic magneto-dielectric effect in disordered ferromagnetic-insulator LaMn0.5Co0.5O3. This study also emphasizes the need to use single crystals as well as the frequencies higher than the corresponding inverse relaxation time. (C) 2014 AIP Publishing LLC.

The acylphosphoranes formed in a sequential manner from the reaction of the silyl ester of O-acyl(aroyl)salicylic acids and (trimethylsilyl)methylenetriphenylphosphorane undergo intramolecular Wittig cyclization on the ester carbonyl to afford the 4H-chromen-4-ones in good to excellent yields.

The temperature dependence of magneto current in the spin spin valve transistor system is theoretically explored based on phenomenological model. We find that the collector current strongly depends on the relative orientation of magnetic moment of ferromagnetic metals due to spin mixing effect. For example, the collector current is decreasing in the parallel case with increasing temperature, and it is increasing in anti-parallel configuration. We then obtain decreasing magneto current with increasing temperature. The result accords with the experimental data in qualitative manner. This phenomenological model calculations suggest that spin mixing effect may play an important role in the spin valve transistor system at finite temperature., Comment: 8 pages and 4 figures

Spin-dependent transport of hot electrons across a spin valve has been studied as function of temperature using a spin-valve transistor with a soft Ni80Fe20/Au/Co spin-valve base. Spin-dependent scattering makes the collector current highly sensitive to small magnetic fields that change the magnetic state of the base. The magnetocurrent approaches 400% at 100K but decays to about 240% at room temperature. The reduction is attributed to mixing of the two spin channels due to spin-flip scattering of hot electrons by thermal spin waves.

We study some versions of the problem of finding the minimum size 2-connected subgraph. This problem is NP-hard (even on cubic planar graphs) and MAX SNP-hard. We show that the minimum 2-edge connected subgraph problem can be approximated to within 4/3-Ɛ for general graphs, improving upon the recent result of Vempala and Vetta [14]. Better approximations are obtained for planar graphs and for cubic graphs.We also consider the generalization, where requirements of 1 or 2 edge or vertex disjoint paths are specified between every pair of vertices, and the aim is to find a minimum subgraph satisfying these requirements. We show that this problem can be approximated within 3/2, generalizing earlier results for 2-connectivity. We also analyze the classical local optimization heuristics. For cubic graphs, our results imply a new upper bound on the integrality gap of the linear programming formulation for the 2-edge connectivity problem.

In this paper we present a spin-valve transistor made with a silicon on insulator wafer as emitter and a double sided polished Si wafer as collector. Using vacuum metal bonding we obtain a three terminal device in which a spin-valve layer is sandwiched between two Si wafers. We measure a 217% change in the collector current with magnetic field using a spin valve that shows only 0.5% resistance change in a current in plane measurement.

A new fabrication technology that allows miniaturization of the spin-valve transistor is presented. The spin-valve transistor consists of a spin-valve base (Pt 2 nm/NiFe 3 nm/Au 3.5 nm/Co 3 nm/Au 4 nm) sandwiched between a Si emitter and collector. With the use of a silicon-on-insulator wafer and vacuum metal bonding, spin-valve transistors down to a few tens of micron size are realized through conventional photolithography and etching processes. These spin-valve transistors show 275% magnetocurrent at 87 K and 170% at room temperature in small magnetic fields.

An efficient synthesis of lactone moiety of compactin has been achieved. The stereogenic centers were generated by means of iterative proline-catalyzed sequential α-aminoxylation and Horner–Wadsworth–Emmons (HWE) olefination of aldehydes.

The acylphosphoranes formed in a sequential manner from the reaction of the silyl ester of O-acyl(aroyl)salicylic acids and (trimethylsilyl)methylenetriphenylphosphorane undergo intramolecular Wittig cyclization on the ester carbonyl to afford the 4H-chromen-4-ones in good to excellent yields.

The role of thermal scattering in spin-dependent transport of hot electrons at 0.9 eV is studied using a spin-valve transistor with a soft Ni(80)Fe(20)/Au/Co base. Spin-dependent scattering makes the collected electron current depend sensitively on the magnetic state of the base. The magnetocurrent reaches 560% at 100 K, decays with increasing temperature, and a huge effect of 350% still remains at room temperature. The results demonstrate that thermal spin waves produce quasielastic spin-flip scattering of hot electrons, resulting in mixing of the two spin channels.

We consider a restricted version of the general Set Covering problem in which each set in the given set system intersects with any other set in at most 1 element. We show that the Set Covering problem with intersection 1 cannot be approximated within a o(log n) factor in random polynomial time unless N P ⊆ ZTIME(nO(log log n)). We also observe that the main challenge in derandomizing this reduction lies in finding a hitting set for large volume combinatorial rectangles satisfying certain intersection properties. These properties are not satisfied by current methods of hitting set construction. An example of a Set Covering problem with the intersection 1 property is the problem of covering a given set of points in two or higher dimensions using straight lines; any two straight lines intersect in at most one point. The best approximation algorithm currently known for this problem has an approximation factor of θ(log n), and beating this bound seems hard. We observe that this problem is Max-SNP-Hard.

A spin-valve transistor (SVT) that employs hot electrons is shown to exhibit a huge magnetotransport effect at room temperature in small magnetic fields. The SVT is a ferromagnet-semiconductor hybrid structure in which hot electrons are injected into a NiFe/Au/Co spin valve, and collected on the other side with energy and momentum selection. This makes the collector current extremely sensitive to spin-dependent scattering. The hot-electron current output of the device changes by more than a factor of three in magnetic fields of only a few Oe, corresponding to a magnetocurrent above 200% at room temperature.

Temperature dependence of the electrical resistivity of La 1−x Ca x MnO 3 (x = 0.2, 0.3) samples sintered at two different temperatures are compared to understand the origin of the double-maxima-type resistivity curves of some doped perovskite manganates reported in the literature. It is shown that compositional inhomogeneity is responsible for the anomalous electrical properties of the substituted manganate samples processed at low temperatures.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem-cell disorder in which the affected cells are deficient in glycosylphosphatidylinositol (GPI)-anchored proteins. Paroxysmal nocturnal hemoglobinuria is frequently associated with aplastic anemia, although the basis of this relation is unknown.To assess the PNH status of patients with diverse marrow failure syndromes.Correlation of cytofluorometric data with clinical features.Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland.115 patients with aplastic anemia, 39 patients with myelodysplasia, 28 patients who had recently undergone bone marrow transplantation, 18 patients with cancer that was treated with chemotherapy, 13 patients with large granular lymphocytosis, 20 controls who had received renal allografts, and 21 healthy participants.Patients with aplastic anemia, myelodysplasia, or renal allografts received antithymocyte globulin.Flow cytometry was used to assess expression of GPI-anchored proteins on granulocytes.Evidence of PNH was found in 25 of 115 (22%) patients with aplastic anemia. No patient with normal GPI-anchored protein expression at presentation developed PNH after therapy (n = 16). Nine of 39 (23%) patients with myelodysplasia had GPI-anchored protein-deficient cells. Abnormal cells were not detected in patients with constitutional or other forms of bone marrow failure or in renal allograft recipients who had received antithymocyte globulin. Aplastic anemia is known to respond to immunosuppressive therapy; in myelodysplasia, the presence of a PNH population was strongly correlated with hematologic improvement after administration of antithymocyte globulin (P = 0.0015).Flow cytometric analysis is superior to the Ham test and permits concomitant diagnosis of PNH in about 20% of patients with myelodysplasia (a rate similar to that seen in patients with aplastic anemia). The presence of GPI-anchored protein-deficient cells in myelodysplasia predicts responsiveness to immunosuppressive therapy. Early emergence of GPI-anchored protein-deficient hematopoiesis in a patient with marrow failure may point to an underlying immune pathogenesis.