Mpemba effect in pure spin systems : A universal picture of the role of spatial correlations at initial states.

The quicker freezing of hotter water, than a colder sample, when quenched to a common lower temperature, is referred to as the Mpemba effect (ME). While this counter-intuitive fact remains a surprize since long, efforts have begun to identify similar effect in other systems. We investigate the ME in a rather general context concerning magnetic phase transitions. From Monte Carlo simulations of model systems, viz., the Ising model and the q-state Potts model, with varying range of interaction and space dimension, we assert that hotter paramagnets undergo ferromagnetic ordering faster than the colder ones. This conclusion we have arrived at following the analyses of the simulation results on decay of energy and growth in ordering following quenches from different starting temperatures, to fixed final temperatures below the Curie points. The general observation, in all the considered models, without any element of frustration, is a crucial and important fact of our study. Furthermore, we have obtained an important scaling picture, on the strength of the effect, with respect to the variation in spatial correlation in the initial states. This behavior appears true irrespective of the nature of order-parameter fluctuation and even order of transition. The observations are expected to be relevant to the understanding of ME in a rather general class of systems.

Pseudomagic Quantum States.

Notions of nonstabilizerness, or "magic," quantify how nonclassical quantum states are in a precise sense: states exhibiting low nonstabilizerness preclude quantum advantage. We introduce "pseudomagic" ensembles of quantum states that, despite low nonstabilizerness, are computationally indistinguishable from those with high nonstabilizerness. Previously, such computational indistinguishability has been studied with respect to entanglement, introducing the concept of pseudoentanglement. However, we demonstrate that pseudomagic neither follows from pseudoentanglement nor implies it. In terms of applications, the study of pseudomagic offers fresh insights into the theory of quantum scrambling: it uncovers states that, even though they originate from nonscrambling unitaries, remain indistinguishable from scrambled states to any physical observer. Additional applications include new lower bounds on state synthesis problems, property testing protocols, and implications for quantum cryptography. Our Letter is driven by the observation that only quantities measurable by a computationally bounded observer-intrinsically limited by finite-time computational constraints-hold physical significance. Ultimately, our findings suggest that nonstabilizerness is a "hide-able" characteristic of quantum states: some states are much more magical than is apparent to a computationally bounded observer.

Nonuniversal aging during phase separation with long-range interaction.

Issues concerning the kinetics of phase transitions are not well established for the cases where the order parameter remains conserved with time, particularly when the interatomic interactions are long-range in nature. Here we present results on structure, growth, and aging from Monte Carlo simulations of the two-dimensional long-range Ising model. In our computer simulations, random initial configurations, for 50:50 compositions of up and down spins, mimicking high-temperature equilibrium states, have been quenched to temperatures inside the coexistence curve. Our analyses of the simulation data, for such a protocol, show interesting dependence of the aging exponent, λ, on σ, the parameter, within the Hamiltonian, that controls the range of interaction. These nonuniversal values of λ are compared with a theoretical result for lower bounds. For this purpose, we extracted information on relevant aspects of structural properties during the evolution. To estimate λ, as is necessary, we also calculated the average domain size and analyzed its time dependence to obtain the growth exponent α which also is nonuniversal. The trends in the values of λ and α, as well as an anomaly in structure, suggest that a crossover from the long-range to the short-range variety occurs at σ≃1. The location of this boundary and the nonuniversality provide a picture that is surprisingly different from that of the corresponding static critical phenomena. Furthermore, our results suggest an important scaling law combining α and λ.

Complexity Phase Transitions Generated by Entanglement.

Entanglement is one of the physical properties of quantum systems responsible for the computational hardness of simulating quantum systems. But while the runtime of specific algorithms, notably tensor network algorithms, explicitly depends on the amount of entanglement in the system, it is unknown whether this connection runs deeper and entanglement can also cause inherent, algorithm-independent complexity. In this Letter, we quantitatively connect the entanglement present in certain quantum systems to the computational complexity of simulating those systems. Moreover, we completely characterize the entanglement and complexity as a function of a system parameter. Specifically, we consider the task of simulating single-qubit measurements of k-regular graph states on n qubits. We show that, as the regularity parameter is increased from 1 to n-1, there is a sharp transition from an easy regime with low entanglement to a hard regime with high entanglement at k=3, and a transition back to easy and low entanglement at k=n-3. As a key technical result, we prove a duality for the simulation complexity of regular graph states between low and high regularity.

Tailoring the Weight of Surface and Intralayer Edge States to Control LUMO Energies.

The energies of the frontier molecular orbitals determine the optoelectronic properties in organic films, which are crucial for their application, and strongly depend on the morphology and supramolecular structure. The impact of the latter two properties on the electronic energy levels relies primarily on nearest-neighbor interactions, which are difficult to study due to their nanoscale nature and heterogeneity. Here, an automated method is presented for fabricating thin films with a tailored ratio of surface to bulk sites and a controlled extension of domain edges, both of which are used to control nearest-neighbor interactions. This method uses a Langmuir-Schaefer-type rolling transfer of Langmuir layers (rtLL) to minimize flow during the deposition of rigid Langmuir layers composed of π-conjugated molecules. Using UV-vis absorption spectroscopy, atomic force microscopy, and transmission electron microscopy, it is shown that the rtLL method advances the deposition of multi-Langmuir layers and enables the production of films with defined morphology. The variation in nearest-neighbor interactions is thus achieved and the resulting systematically tuned lowest unoccupied molecular orbital (LUMO) energies (determined via square-wave voltammetry) enable the establishment of a model that functionally relates the LUMO energies to a morphological descriptor, allowing for the prediction of the range of accessible LUMO energies.

Bifacial Dye Membranes: Ultrathin and Free-Standing although not Being Covalently Bound.

Layers of aligned dyes are key to photo-driven charge separation in dye sensitized solar cells, but cannot be exploited as rectifying membranes in photocatalysis to separate half-cells because they are not sufficiently stable. While impressive work on the fabrication of stable noncovalent membranes has been recently demonstrated, these membranes are inherently suffering from non-uniform orientation of the constituting dyes. To stabilize layers made from uniformly assembled and aligned dyes, they can be covalently cross-linked via functional groups or via chromophores at the expense of their optical properties. Here stable membranes from established dyes are reported that do not need to be elaborately functionalized nor do their chromophores need to be destroyed. These membranes are free-standing, although being only non-covalently linked. To enable uniform dye-alignment, Langmuir layers made from linear, water-insoluble dyes are used. That water-soluble charge transfer dyes adsorb onto and intercalate into the Langmuir layer from the aqueous subphase, thus yielding free-standing, molecularly thin membranes are demonstrated. The developed bifacial layers consist almost entirely of π-conjugated units and thus can conduct charges and can be further engineered for optoelectronic and photocatalytic applications.

Best Fit DNA-Based Cryptographic Keys: The Genetic Algorithm Approach.

DNA (Deoxyribonucleic Acid) Cryptography has revolutionized information security by combining rigorous biological and mathematical concepts to encode original information in terms of a DNA sequence. Such schemes are crucially dependent on corresponding DNA-based cryptographic keys. However, owing to the redundancy or observable patterns, some of the keys are rendered weak as they are prone to intrusions. This paper proposes a Genetic Algorithm inspired method to strengthen weak keys obtained from Random DNA-based Key Generators instead of completely discarding them. Fitness functions and the application of genetic operators have been chosen and modified to suit DNA cryptography fundamentals in contrast to fitness functions for traditional cryptographic schemes. The crossover and mutation rates are reducing with each new population as more keys are passing fitness tests and need not be strengthened. Moreover, with the increasing size of the initial key population, the key space is getting highly exhaustive and less prone to Brute Force attacks. The paper demonstrates that out of an initial 25 × 25 population of DNA Keys, 14 keys are rendered weak. Complete results and calculations of how each weak key can be strengthened by generating 4 new populations are illustrated. The analysis of the proposed scheme for different initial populations shows that a maximum of 8 new populations has to be generated to strengthen all 500 weak keys of a 500 × 500 initial population.

Supramolecular Reorientation During Deposition Onto Metal Surfaces of Quasi-Two-Dimensional Langmuir Monolayers Composed of Bifunctional Amphiphilic, Twisted Perylenes.

Supramolecular dye structures, which are often ruled by π-π interactions between planar chromophores, crucially determine the optoelectronic properties of layers and interfaces. Here, we present the interfacial assembly of perylene monoanhydride and monoimide that do not feature a planar chromophore but contain chlorine substituents in the bay positions to yield twisted chromophores and hence modified π-stacking. The assembly of the twisted perylene monoanhydride and monoimide is driven by their amphiphilicity that ensures proper Langmuir layer formation. The shielding of the hydrophilic segment upon attaching an alkyl chain to the imide moiety yielded a more rigid Langmuir layer, even though the degrees of freedom were increased due to this modification. For the characterization of the Langmuir layer's supramolecular structure, the layers were deposited onto glass, silver, and gold substrates via Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques and were investigated with atomic force microscopy and surface-enhanced resonance Raman spectroscopy (SERRS). From the similarity between all SERR spectra of the LS and LB layers, we concluded that the perylenes have changed their orientation upon LB deposition to bind to the silver surface of the SERRS substrate via sulfur atoms. In the Langmuir layer, the perylenes, which are π-stacked with half of the twisted chromophores, must already be inclined and cannot achieve full parallel alignment because of the twisting-induced steric hindrance. However, upon rotation, the energetically most favorable antiparallel aligned structures can be formed and bind to the SERRS substrate. Thus, we present, to the best of our knowledge, the first fabrication of quasi-two-dimensional films from twisted amphiphilic perylene monoimides and their reassembly during LB deposition. The relation between the molecular structure, supramolecular interfacial assembly, and its adoption during adsorption revealed here is crucial for the fabrication of defined functionalizations of metal surfaces, which is key to the development of organic (opto)electronic devices.

Langmuir-Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity.

In this work, we present the formation of H- and J-aggregates of amphiphilic centrosymmetric diketopyrrolopyrroles containing aliphatic or aromatic amino groups. The inherent amphiphilicity of these dyes predestines their assembly at interfaces to form ordered supramolecular structures. In this work, we employed the Langmuir-Blodgett (LB) technique to generate, manipulate, and deposit such supramolecular structures. The aforementioned amines provide an additional means to control the formation of the supramolecular assemblies. In the resulting LB films, both H- and J-aggregates of the dyes can be realized, leading to very broad absorption spectra. In contrast to many reports on H- and J-aggregates, the interactions between the symmetric diketopyrrolopyrroles are controlled via interface assembly and π-stacking and not by dipolar interactions. We show that in the case of the aliphatic, but not for the aromatic amine functionalization, the usage of an acidic subphase enables the transition from H- to J-aggregate-dominated LB films via an increase in the surface pressure during deposition.

Clinical, laboratory, and management profile in patients of liver abscess from northern India.

Objective. To describe the clinical profile, microbiological aetiologies, and management outcomes in patients with liver abscess. Methods. A cross-sectional study was conducted from May, 2011, to April, 2013, on 200 consecutive liver abscess patients at PGIMER and Dr. RML Hospital, New Delhi. History, examination, and laboratory investigations were recorded. Ultrasound guided aspiration was done and samples were investigated. Chi-square test and multivariate regression analysis were performed to test association. Results. The mean age of patients was 41.13 years. Majority of them were from lower socioeconomic class (67.5%) and alcoholic (72%). The abscesses were predominantly in right lobe (71%) and solitary (65%). Etiology of abscess was 69% amoebic, 18% pyogenic, 7.5% tubercular, 4% mixed, and 1.5% fungal. Percutaneous needle aspiration was done in 79%, pigtail drainage in 17%, and surgical intervention for rupture in 4% patients. Mortality was 2.5%, all reported in surgical group. Solitary abscesses were amoebic and tubercular whereas multiple abscesses were pyogenic (P = 0.001). Right lobe was predominantly involved in amoebic and pyogenic abscesses while in tubercular abscesses left lobe involvement was predominant (P = 0.001). Conclusions. The commonest presentation was young male, alcoholic of low socioeconomic class having right lobe solitary amoebic liver abscess. Appropriate use of minimally invasive drainage techniques reduces mortality.

Acrocyanosis in a young adult: a rare presentation of extra-adrenal pheochromocytoma.

Extra-adrenal pheochromocytomas (EAPs) are rare catecholamine-secreting tumours. The patient commonly present with headache, palpitation, anxiety, diaphoresis, raised blood pressure and heart rate which can be sustained or episodic and less commonly Raynaud's phenomenon. We present a case of an adult woman who presented with unilateral upper limb acrocyanosis and hypertension which was secondary to EAP and resolved completely after surgical removal of the tumour.

Alport syndrome: a rare cause of uraemia.

Alport syndrome (AS) is a heterogeneous basement membrane disease characterised by haematuria with progressive hereditary nephritis, high-frequency sensorineural hearing loss (SNHL) and pathognomonic ocular lesions. It is one of the spectra of diseases representing hereditary nephritis, which inevitably leads to end-stage renal disease (ESRD). Microscopic or frank haematuria persistent from childhood constitutes the clinical clue for its early recognition. It occurs as a result of genetically inherited or de novo mutations in type IV collagen genes. The most common mode of inheritance is X-linked and men are more severely affected. We report a case of a young woman, in her fourth decade of life presenting with overt nephropathy, having persistent haematuria associated with SNHL and lenticonus with dot and fleck retinopathy on detailed clinical examination, diagnosed as a previously undetected case of Alport syndrome.

A Study of Clinical, Microbiological, and Echocardiographic Profile of Patients of Infective Endocarditis.

Infective endocarditis, a great masquerader, is a clinical entity which may present with a myriad of manifestations. Its changing epidemiological profile has been studied in the previous decades in both the developed and the developing nations. In this study, we strived to uphold the evolving clinical profile and its outcome from a government tertiary care hospital in Northern India. It was a descriptive, cross-sectional, observational study conducted over two years' period involving 44 patients diagnosed with definite infective endocarditis, according to modified Dukes' criteria. Demographic, clinical, microbiological, and echocardiographic data were analysed. Mean age of patients was 31 years. Rheumatic heart disease with regurgitant lesions was the commonest risk factor. Dyspnea and fever were the predominant symptom, and pallor and heart failure the commonest sign. Cultures were positive in 52% with Staphylococcus, the major isolate. Transesophageal echocardiography fared better than transthoracic one to define the vegetations. Mortality is reported in 4.5%. Prolonged duration of fever, pallor, hematuria, proteinuria, rheumatoid factor positivity, and large vegetations proved to be poor prognostic variables. Culture positive endocarditis, with persistent bacteremia, had higher incidence of acute renal failure. Right sided endocarditis was frequent in congenital lesions or IV drug user, whereas left sided endocarditis mostly presented with atrial fibrillation.

Acquired urethral meatal stenosis: a rare sequel of an aggressive form of Behçet's disease.

Behçet's disease (BD) is characterised by the triad of recurrent oral and genital aphthous ulceration, skin lesions and ocular inflammation. This disease frequently affects other systems including neurological, locomotor, cardiac or vascular systems. Recurrent oral and genital aphthous ulcerations are the hallmarks of BD. We hereby report a case of rapidly evolving and aggressive form of BD in a young man presenting with extensive ulcerative lesions in orogenital region leading to obstructive uropathy resulting in acquired urethral meatal stenosis due to inflammatory activity.

Multidrug resistant citrobacter: an unusual cause of liver abscess.

Liver abscesses are infectious, space occupying lesions in the liver, the two most common abscesses being pyogenic and amoebic. A pyogenic liver abscess (PLA) is a rare condition with a reported incidence of 20 per 100 000 hospital admissions in the western population. The right lobe of the liver is the most common site in both types of liver abscess. Clinical presentation is elusive with complaints of fever, right upper quadrant pain in the abdomen and hepatomegaly with or without jaundice. The aetiology of PLA has changed in the past few decades and may be of biliary, portal, arterial or traumatic origin, but many cases are still cryptogenic. The most common organisms causing PLA are Gram-negative aerobes, especially Escherichia coli and Klebsiella pneumoniae. Studies have shown a high degree of antimicrobial susceptibility of isolated organism resulting in an overall lower mortality in PLA. Here, we present a case of PLA caused by multidrug-resistant Citrobacter freundii, which is an unusual organism to be isolated.

A rare case of dengue encephalitis.

Dengue fever has a variable clinical spectrum ranging from asymptomatic infection to life-threatening dengue haemorrhagic fever and dengue shock syndrome. However, neurological complications, in general, are unusual. Dengue encephalopathy is not an unknown entity; however, dengue encephalitis, a direct neuronal infiltration by the dengue virus, is an extremely rare disease. Although dengue is classically considered a non-neurotropic virus, there is increasing evidence for dengue viral neurotropism, suggesting that, in a proportion of cases, there may be an element of direct viral encephalitis. An MRI brain rarely shows focal abnormalities in dengue encephalitis. We report an interesting case of dengue encephalitis during an outbreak in Delhi, India. The diagnosis was confirmed by blood and cerebrospinal fluid dengue serology and (NS1) antigen assay. The case showed extensive lesions involving the midbrain, cerebellum, thalamus and medial temporal region on both sides of the MRI brain, which is an uncommon manifestation of dengue fever.

Pituitary macroadenoma: a rare cause of thyrotoxic hypokalaemic periodic paralysis.

Thyrotoxic hypokalaemic periodic palsy (THPP) is a well-recognised but under-diagnosed complication of hyperthyroidism and is commonly seen in Asian males. Patients usually present fully conscious with acute onset of severe motor weakness. Baseline investigation reveals severe hypokalaemia due to Na(+)/K(+) ATPase overactivity causing a massive influx of intracellular potassium ions. The most common cause of THPP identified in the medical literature is Graves' disease. We report an interesting and unusual case of THPP due to previously undiagnosed hyperthyroidism secondary to a pituitary macroadenoma. The patient was consequently found to have a tumour secreting gonadotropin and thyrotropin.