The Quantum Refrigerator: The quest for absolute zero

The scaling of the optimal cooling power of a reciprocating quantum refrigerator is sought as a function of the cold bath temperature as $T_c \to 0$. The working medium consists of noninteracting particles in a harmonic potential. Two closed-form solutions of the refrigeration cycle are analyzed, and compared to a numerical optimization scheme, focusing on cooling toward zero temperature. The optimal cycle is characterized by linear relations between the heat extracted from the cold bath, the energy level spacing of the working medium and the temperature. The scaling of the optimal cooling rate is found to be proportional to $T_c^{3/2}$ giving a dynamical interpretation to the third law of thermodynamics

Guided assembly of nanoparticles on electrostatically charged nanocrystalline diamond thin films

We apply atomic force microscope for local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films deposited on silicon, to induce electrostatically driven self-assembly of colloidal alumina nanoparticles into micro-patterns. Considering possible capacitive, sp2 phase and spatial uniformity factors to charging, we employ films with sub-100 nm thickness and about 60% relative sp2 phase content, probe the spatial material uniformity by Raman and electron microscopy, and repeat experiments at various positions. We demonstrate that electrostatic potential contrast on the NCD films varies between 0.1 and 1.2 V and that the contrast of more than ±1 V (as detected by Kelvin force microscopy) is able to induce self-assembly of the nanoparticles via coulombic and polarization forces. This opens prospects for applications of diamond and its unique set of properties in self-assembly of nano-devices and nano-systems

Transitionless quantum drivings for the harmonic oscillator

Two methods to change a quantum harmonic oscillator frequency without transitions in a finite time are described and compared. The first method, a transitionless-tracking algorithm, makes use of a generalized harmonic oscillator and a non-local potential. The second method, based on engineering an invariant of motion, only modifies the harmonic frequency in time, keeping the potential local at all times.Comment: 11 pages, 1 figure. Submitted for publicatio

Prognosis in patients with myocardial infarction with ST-elevation depending on the timing of interventional revascularization

Проверена е прогнозата (болничния и следболничния леталитет до края на 6-ия месец) при 300 болни (212 мъже и 88 жени) с първи миокарден инфаркт със ST- елевация (STEMI) на средна възраст 62.9 год. в зависимост от срока на извършената първична коронарна интервенция (PCI) след началото на симптомите. В зависимост от срока на извършената РСІ болните са разделени на 4 групи: до 3-ия, до 6-ия, до 12-ия и до 24-ия час след началото на инфаркта. Болничният леталитет за всички болни е 6.3%, a до края на 6-ия месец - 13.3%, еднакъв при І-ва и ІІ-ра група и достоверно по-малък, отколкото при ІІІ-та и ІV-та група, по-голям при жените, при болните над 65 г., с ФИ <35.0% и с тромботична оклузия на LM и LAD.The prognosis (in-hospital and post-hospitalization lethality by the end of the 6th moth) of 300 patients (212 men and 88 women) with a first myocardial infarction with ST-elevation (STEMI) at an average age of 62.9 years was studied depending on the timing of the conducted primary coronary intervention (PCI) after the onset of symptoms. Depending on the timing of the conducted PCI, the patients were divided into 4 groups: by the 3rd, 6th, 12th, and 24th hour after the onset of the infarction. The patients` in-hospital lethality was 6.3%, and that by the end of the 6th month - 13.3%. It was the same for groups I and II and significantly lower than in groups III and IV; higher in women, in patients over 65 years of age, with ejection fraction (EF) <35.0% and with thrombotic occlusion of LM and LAD

Synthesis, structure, and opto-electronic properties of organic-based nanoscale heterojunctions

Enormous research effort has been put into optimizing organic-based opto-electronic systems for efficient generation of free charge carriers. This optimization is mainly due to typically high dissociation energy (0.1-1 eV) and short diffusion length (10 nm) of excitons in organic materials. Inherently, interplay of microscopic structural, chemical, and opto-electronic properties plays crucial role. We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties. By adjusting parameters of contact- and tapping-mode atomic force microscopy (AFM), we perform morphologic and mechanical characterizations (nanoshaving) of organic layers, measure their electrical conductivity by current-sensing AFM, and deduce work functions and surface photovoltage (SPV) effects by Kelvin force microscopy using high spatial resolution. These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data. We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond

The smallest refrigerators can reach maximal efficiency

We investigate whether size imposes a fundamental constraint on the efficiency of small thermal machines. We analyse in detail a model of a small self-contained refrigerator consisting of three qubits. We show analytically that this system can reach the Carnot efficiency, thus demonstrating that there exists no complementarity between size and efficiency.Comment: 9 pages, 1 figure. v2: published versio

The quantum refrigerator: The quest for absolute zero

Abstract -The emergence of the laws of thermodynamics from the laws of quantum mechanics is an unresolved issue. The generation of the third law of thermodynamics from quantum dynamics is analysed. The scaling of the optimal cooling power of a reciprocating quantum refrigerator is sought as a function of the cold bath temperature as Tc → 0. The working medium consists of noninteracting particles in a harmonic potential. Two closed-form solutions of the refrigeration cycle are analyzed, and compared to a numerical optimization scheme, focusing on cooling toward zero temperature. The optimal cycle is characterized by linear relations between the heat extracted from the cold bath, the energy level spacing of the working medium and the temperature. The scaling of the optimal cooling rate is found to be proportional to T 3/2 c giving a dynamical interpretation to the third law of thermodynamics. Copyright c EPLA, 2009 Walter Nernst stated the third law of thermodynamics as follows: &quot;it is impossible by any procedure, no matter how idealized, to reduce any system to the absolute zero of temperature in a finite number of operations&quot; The second law of thermodynamics already imposes a restriction on δ T c &gt;Q c . This forcesQ c → 0asT c → 0 and, expanding Q c as a series near T c = 0, the dominant power δ inQ c ∝ T δ must satisfy δ 1 .S u c ha ne x p o n e n t has been realized in refrigerator models (a) E-mail: [email protected] Our goal in the present study is to set more stringent limits on the exponent δ for a reciprocating four stroke cooling cycle. The cooling rate is replaced by the average refrigeration power R c = Q c /τ where τ is the cycle period. The quantum Otto heat pump. -We consider a refrigerator using a controllable quantum medium as its working fluid. Our objective is to optimize the cooling rate in the limit when the temperature T c of the cold bath approaches absolute zero. A necessary condition for operation is that upon contact with the cold bath the temperature of the working medium be lower than the bath temperature T int T c The cooling cycle consists of two heat exchange branches alternating with two adiabatic branches (se

In Vivo Biotransformation of 3,3′,4,4′-Tetrachlorobiphenyl by Whole Plants−Poplars and Switchgrass

Polychlorinated biphenyls (PCBs) are widely distributed persistent organic pollutants. In vitro research has shown that plant cell cultures might transform lower chlorinated congeners to hydroxylated PCBs, but there are few studies on in vivo metabolism of PCBs by intact whole plants. In this research, poplar plants (Populus deltoides × nigra, DN34) and switchgrass (Panicum vigratum, Alamo) were hydroponically exposed to 3,3′,4,4′-tetrachlorobiphenyl (CB77). Metabolism in plants occurred rapidly, and metabolites were detected after only a 24 h exposure. Rearrangement of chlorine atoms and dechlorination of CB77 by plants was unexpectedly observed. In addition, poplars were able to hydroxylate CB77 and the metabolite 6-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (6-OH-CB77) was identified and quantified. Hybrid poplar was able to hydroxylate CB77, but switchgrass was not, suggesting that enzymatic transformations are plant specific. Sulfur-containing metabolites (from the action of sulfotransferases) were investigated in this study, but they were not detected in either poplar or switchgrass

Construct validity of the post-COVID-19 functional status scale in adult subjects with COVID-19

Background An increasing number of subjects are recovering from COVID-19, raising the need for tools to adequately assess the course of the disease and its impact on functional status. We aimed to assess the construct validity of the Post-COVID-19 Functional Status (PCFS) Scale among adult subjects with confirmed and presumed COVID-19. Methods Adult subjects with confirmed and presumed COVID-19, who were members of an online panel and two Facebook groups for subjects with COVID-19 with persistent symptoms, completed an online survey after the onset of infection-related symptoms. The number and intensity of symptoms were evaluated with the Utrecht Symptom Diary, health-related quality of life (HrQoL) with the 5-level EQ-5D questionnaire, impairment in work and activities with the Work Productivity and Activity Impairment questionnaire and functional status with the PCFS Scale. Results 1939 subjects were included in the analyses (85% women, 95% non-hospitalized during infection) about 3 months after the onset of infection-related symptoms. Subjects classified as experiencing 'slight', 'moderate' and 'severe' functional limitations presented a gradual increase in the number/intensity of symptoms, reduction of HrQoL and impairment in work and usual activities. No differences were found regarding the number and intensity of symptoms, HrQoL and impairment in work and usual activities between subjects classified as experiencing 'negligible' and 'no' functional limitations. We found weak-to-strong statistical associations between functional status and all domains of HrQoL (r: 0.233-0.661). Notably, the strongest association found was with the 'usual activities' domain of the 5-level EQ-5D questionnaire. Conclusion We demonstrated the construct validity of the PCFS Scale in highly-symptomatic adult subjects with confirmed and presumed COVID-19, 3 months after the onset of symptoms.Clinical epidemiolog