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1.
J Infect Public Health ; 16(1): 104-106, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36521328

RESUMO

After more than two years from the first COVID-19 detected case in Brescia, Northern Italy, monoclonal antibodies and antiviral therapy aimed at early treatment of mild COVID-19 in patients at risk of progression and of hospitalization has been approved in Italy. Here we report the characteristics of the population eligible for the COVID-19 early treatments at our COVID-19 Early Therapy Unit of the Infectious Diseases Department of the ASST Spedali Civili of Brescia, with the aim to evaluate the characteristics of the foreign and native groups. Up to March the 31st, 2022, a total of 559 patients were referred to our Unit for COVID-19 early treatment, where 7.6% were foreigners, a group significantly younger than natives (p < 0.05). Particular differences are noticed between the native and the foreign population, where people aged > 65 years old were significantly more frequent among italians (39.7% vs 16.3%, p < 0.01), while primary or acquired immunodeficiencies were more frequent in foreigners (55.8% vs 38.9%, p = 0.03). Substantial differences are noted between native and foreign populations, where 14% and 26% (p < 0.05) respectively have never been vaccinated for COVID-19. Overall, 71% of the referred patients received an early treatment for mild COVID-19, with no differences between the two groups. Overall, on day 28 after treatment, 23 (4%) patients had been hospitalized due to COVID-19 related complications and four died (0,7%), no one was foreigner. In conclusion, while the treatment offered for mild COVID-19 appears to be rather uniform between the native and the foreign populations, some differences, especially in preventive vaccination COVID-19, must be taken into account.


Assuntos
COVID-19 , Emigrantes e Imigrantes , Humanos , Idoso , COVID-19/epidemiologia , COVID-19/terapia , Itália/epidemiologia , Hospitalização
2.
Biosensors (Basel) ; 12(9)2022 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-36140055

RESUMO

In the present work, highly multiplexed diagnostic KITs based on an Interferometric Optical Detection Method (IODM) were developed to evaluate six Coronavirus Disease 2019 (COVID-19)-related biomarkers. These biomarkers of COVID-19 were evaluated in 74 serum samples from severe, moderate, and mild patients with positive polymerase chain reaction (PCR), collected at the end of March 2020 in the Hospital Clínico San Carlos, in Madrid (Spain). The developed multiplexed diagnostic KITs were biofunctionalized to simultaneously measure different types of specific biomarkers involved in COVID-19. Thus, the serum samples were investigated by measuring the total specific Immunoglobulins (sIgT), specific Immunoglobulins G (sIgG), specific Immunoglobulins M (sIgM), specific Immunoglobulins A (sIgA), all of them against SARS-CoV-2, together with two biomarkers involved in inflammatory disorders, Ferritin (FER) and C Reactive Protein (CRP). To assess the results, a Multiple Linear Regression Model (MLRM) was carried out to study the influence of IgGs, IgMs, IgAs, FER, and CRP against the total sIgTs in these serum samples with a goodness of fit of 73.01% (Adjusted R-Squared).


Assuntos
Teste para COVID-19 , COVID-19 , Biomarcadores , Proteína C-Reativa , COVID-19/diagnóstico , Teste para COVID-19/instrumentação , Ferritinas , Humanos , Imunoglobulina A Secretora , Kit de Reagentes para Diagnóstico , SARS-CoV-2
3.
Phys Rev Lett ; 129(3): 030603, 2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35905355

RESUMO

Modeling noisy oscillations of active systems is one of the current challenges in physics and biology. Because the physical mechanisms of such processes are often difficult to identify, we propose a linear stochastic model driven by a non-Markovian bistable noise that is capable of generating self-sustained periodic oscillation. We derive analytical predictions for most relevant dynamical and thermodynamic properties of the model. This minimal model turns out to describe accurately bistablelike oscillatory motion of hair bundles in bullfrog sacculus, extracted from experimental data. Based on and in agreement with these data, we estimate the power required to sustain such active oscillations to be of the order of 100 k_{B}T per oscillation cycle.


Assuntos
Células Ciliadas Auditivas , Física , Animais , Modelos Lineares , Rana catesbeiana
4.
Dialect Anthropol ; 46(2): 163-182, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35729915

RESUMO

This article addresses the Seasonal Agricultural Worker Program (SAWP) between Mexico and Canada by examining the forms of disposability and job insecurity of Mexicans employed in Canadian agribusiness. We argue that the Seasonal Agricultural Worker Program has exacerbated the precarity and disposability of Mexican workers by restructuring family dynamics and care chains. This article represents a critique of the SAWP as a model of regulated labor migration, serving as a basis for analyzing the consequences of the proletarianization of the Mexican peasantry and its use as disposable labor for export.

7.
J Endocrinol Invest ; 44(9): 1971-1979, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33515211

RESUMO

PURPOSE: Hypogonadism is frequent in HIV-infected men and might impact on metabolic and sexual health. Low testosterone results from either primary testicular damage, secondary hypothalamic-pituitary dysfunction, or from liver-derived sex-hormone-binding-globulin (SHBG) elevation, with consequent reduction of free testosterone. The relationship between liver fibrosis and hypogonadism in HIV-infected men is unknown. Aim of our study was to determine the prevalence and type of hypogonadism in a cohort of HIV-infected men and its relationship with liver fibrosis. METHODS: We performed a cross-sectional retrospective study including 107 HIV-infected men (median age 54 years) with hypogonadal symptoms. Based on total testosterone (TT), calculated free testosterone, and luteinizing hormone, five categories were identified: eugonadism, primary, secondary, normogonadotropic and compensated hypogonadism. Estimates of liver fibrosis were performed by aspartate aminotransferase (AST)-to-platelet ratio index (APRI) and Fibrosis-4 (FIB-4) scores. RESULTS: Hypogonadism was found in 32/107 patients (30.8%), with normogonadotropic (10/107, 9.3%) and compensated (17/107, 15.8%) being the most frequent forms. Patients with secondary/normogonadotropic hypogonadism had higher body mass index (BMI) (p < 0001). Patients with compensated hypogonadism had longer HIV infection duration (p = 0.031), higher APRI (p = 0.035) and FIB-4 scores (p = 0.008), and higher HCV co-infection. Univariate analysis showed a direct significant correlation between APRI and TT (p = 0.006) and SHBG (p = 0.002), and between FIB-4 and SHBG (p = 0.045). Multivariate analysis showed that SHBG was independently associated with both liver fibrosis scores. CONCLUSION: Overt and compensated hypogonadism are frequently observed among HIV-infected men. Whereas obesity is related to secondary hypogonadism, high SHBG levels, related to liver fibrosis degree and HCV co-infection, are responsible for compensated forms.


Assuntos
Infecções por HIV/complicações , Hipogonadismo/etiologia , Cirrose Hepática/etiologia , Aspartato Aminotransferases/sangue , Estudos de Coortes , Estudos Transversais , Infecções por HIV/epidemiologia , Humanos , Hipogonadismo/epidemiologia , Cirrose Hepática/epidemiologia , Hormônio Luteinizante/sangue , Masculino , Pessoa de Meia-Idade , Prevalência , Estudos Retrospectivos , Globulina de Ligação a Hormônio Sexual/análise , Testosterona/sangue
8.
HIV Med ; 21(8): 523-535, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32578947

RESUMO

OBJECTIVES: The aim of this study was to evaluate the factors that can influence an incomplete viral response (IVR) after acute and early HIV infection (AEHI). METHODS: This was a retrospective, observational study including patients with AEHI (Fiebig stages I-V) diagnosed between January 2008 and December 2014 at 20 Italian centres. IVR was defined by: (1) viral blip (51-1000 HIV-1 RNA copies/mL after achievement of < 50 HIV-1 RNA copies/mL); (2) virologic failure [> 1000 copies/mL after achievement of < 200 copies/mL, or ≥ 200 copies/mL after 24 weeks on an antiretroviral therapy (ART)]; (3) suboptimal viral response (> 50 copies/mL after 48 weeks on ART or two consecutive HIV-1 RNA levels with ascending trend during ART). Cox regression analysis was used to calculate the hazard ratios (HRs) and 95% confidence intervals (95% CIs) for IVR. RESULTS: In all, 263 patients were studied, 227 (86%) males, with a median [interquartile range (IQR)] age of 38 (30-46) years. During a median follow-up of 13.0 (5.7-31.1) months, 38 (14.4%) had IVR. The presence of central nervous system (CNS) symptoms was linked to a higher risk of IVR (HR = 4.70, 95% CI: 1.56-14.17), while a higher CD4/CD8 cell count ratio (HR = 0.13, 95% CI: 0.03-0.51 for each point increase) and first-line ART with three-drug regimens recommended by current guidelines (HR = 0.40, 95% CI: 0.18-0.91 compared with other regimens including four or five drugs, older drugs or non-standard backbones) were protective against IVR. CONCLUSIONS: Patients with lower CD4/CD8 ratio and CNS symptoms could be at a higher risk of IVR after AEHI. The use of recommended ART may be relevant for improving short-term viral efficacy in this group of patients.


Assuntos
Fármacos Anti-HIV/uso terapêutico , Doenças do Sistema Nervoso Central/etiologia , Infecções por HIV/tratamento farmacológico , HIV-1/genética , Doença Aguda , Adulto , Fármacos Anti-HIV/farmacologia , Contagem de Linfócito CD4 , Feminino , Infecções por HIV/sangue , Infecções por HIV/virologia , HIV-1/efeitos dos fármacos , Humanos , Itália , Masculino , Pessoa de Meia-Idade , RNA Viral/genética , Análise de Regressão , Estudos Retrospectivos , Fatores de Risco , Falha de Tratamento , Carga Viral/efeitos dos fármacos
9.
Ann Hematol ; 99(8): 1741-1747, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32399706

RESUMO

To describe and compare the characteristics of necrotizing fasciitis (NF) in patients with and without haematological malignancy. All adult patients diagnosed with NF and treated at our hospital were included (January 2010-March 2019). Diagnosis was based on intraoperative findings or consistent clinical/radiological characteristics, and patients were classified as group A (with haematological malignancy) or group B (without haematological malignancy). Student's t (quantitative), Fisher's exact (qualitative), and Kaplan-Meyer tests were used for the statistical analysis. The study included 29 patients: 8 in group A and 21 in group B. All haematological patients had severe neutropenia (0.2 [0.02-0.5] ×109 cells/L; p < 0.001) and positive blood cultures (100% vs. 61.9%; p = 0.04) at diagnosis. Gram-negative bacilli NF was more common in group A (87.5% vs. 9.5%; p = 0.001), predominantly due to Escherichia coli (50% vs. 9.5%; p = 0.056). Surgical treatment was less common in haematological patients (5 [62.5%] vs. 21 [100%]; p = 0.015). Overall, 9 (31%) patients died: 4 (50%) in group A and 5 (23.8%) in group B (p = 0.17). The univariate analysis showed that mortality tended to be higher (OR 3.2; 95%CI 0.57-17.7; p = 0.17) and to occur earlier (2.2 ± 2.6 vs. 14.2 ± 19.9 days; p = 0.13) in haematological patients. The LRINEC index > 6 did not predict mortality in either group. In our study, NF in patients with haematological malignancies was mainly due to Gram-negative bacilli, associated to high and early mortality rates. In our experience, the LRINEC scale was not useful for predicting mortality.


Assuntos
Infecções por Escherichia coli/mortalidade , Escherichia coli , Fasciite Necrosante/mortalidade , Neoplasias Hematológicas/mortalidade , Neutropenia , Adulto , Idoso , Intervalo Livre de Doença , Infecções por Escherichia coli/terapia , Fasciite Necrosante/microbiologia , Fasciite Necrosante/terapia , Feminino , Neoplasias Hematológicas/microbiologia , Neoplasias Hematológicas/terapia , Humanos , Masculino , Pessoa de Meia-Idade , Neutropenia/microbiologia , Neutropenia/terapia , Estudos Retrospectivos , Espanha/epidemiologia , Taxa de Sobrevida
10.
Environ Manage ; 64(6): 783-793, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31732774

RESUMO

Environmental Management Systems (EMS) based on international standard ISO 14001 are recognized as a tool to improve the environment and the sustainability of organizations. Green Chemistry (GC) seeks to reduce the use and generation of hazardous substances in chemical processes. This paper studies the relationship between EMS based on ISO 14001 and GC. We have analysed their similarities, difficulties, advantages, and synergies that can be developed with a joint implementation in general and in particular on university campuses. The results show that both disciplines have in common the philosophy of Continuous Improvement in the Processes (CIP) and that their joint application is possible, since each principle of GC are related to, at least, one clause of ISO 14001. It is shown that this joint application to different university areas can generate benefits, such as the reduction of hazardous waste and the promotion of green purchases, which favour the environmental improvement of universities. However, there are problems in their joint application related to the lack of specific knowledge and the difficulty of identifying products manufactured following the criteria of GC. Furthermore, a case study in the San Jorge University showing that both disciplines can be treated together is shown. Results were the following: seven GC initiatives (proposed by a small group of GC students) were submitted to the EMS office; only one was considered nonviable and two were implemented, achieving two main goals: Reduction of the environmental impact of laboratories and promotion of green purchasing in the laboratories of San Jorge University.


Assuntos
Resíduos Perigosos , Universidades , Comércio , Conservação dos Recursos Naturais , Humanos
11.
Immun Ageing ; 16: 26, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31636688

RESUMO

BACKGROUND: While immunosenescence, defined as reduced production of new lymphocytes, restriction of T-cell receptor repertoire and telomeres shortening, has been extensively evaluated in HIV-infected children and adults, no data about these parameters are available in perinatally-infected patients with very long-lasting HIV infection. METHODS: We compared thymic and bone marrow output, telomere length (measured by Real-Time PCR) and T-cell receptor repertoire (determined by spectratyping) of 21 perinatally HIV-infected subjects (with a median of 27 years of infection) with those of 19 age-matched non-perinatally HIV-infected patients and 40 healthy controls. All patients received a combined antiretroviral therapy. RESULTS: While thymic and bone marrow output were not different among the analyzed groups, telomere length in peripheral blood cells and T-cell receptor diversity were significantly lower in HIV-perinatally and non-perinatally infected individuals compared to healthy controls. CONCLUSIONS: In HIV-infected subjects, a normal thymic output together with a reduced telomere length and a restricted T-cell receptor repertoire could be explained by the shift of newly produced cells into memory subsets. This phenomenon may allow to control viral infection and maintain peripheral homeostasis.

12.
Int J STD AIDS ; 29(13): 1345-1347, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30049261

RESUMO

We report a case of a human immunodeficiency virus (HIV)/hepatitis C virus-co-infected patient with an optimal virological status but with a poor CD4+ cell profile, followed up in the University Department of Infectious and Tropical Diseases of Brescia, Italy. He presented several autoimmune diseases (ADs) over the years concomitant with CD4+ cell increase episodes following severe immune depression of unknown cause. We studied T- and B-cell subsets and found low levels of K-deleting Recombination Excision Circles, T-cell Receptor Excision Circles and B and T memory subpopulations, which indicated that the bone marrow and thymic outputs were lower than in healthy controls. The most relevant phenotypic alteration was in the regulatory T-cell (Treg) population, because total Tregs as well as naïve, central memory and effector memory cells were detected at very low levels. This was the first case of polyautoimmunity defined as the presence of more than one AD in the same individual, occurring in an HIV patient. Several factors may be implicated, including genetic susceptibility, environmental factors, concomitant therapies and dysregulation of immune system cells. The extremely low number of Tregs found in our patient may play a major role in the regulation of the immune response and the development of all ADs.


Assuntos
Coinfecção , Infecções por HIV/imunologia , Hepatite C Crônica/imunologia , Linfócitos T Reguladores/imunologia , Terapia Antirretroviral de Alta Atividade , Contagem de Linfócito CD4 , Infecções por HIV/tratamento farmacológico , Infecções por HIV/genética , Hepatite C Crônica/tratamento farmacológico , Hepatite C Crônica/genética , Humanos , Masculino , Pessoa de Meia-Idade
13.
SEMERGEN, Soc. Esp. Med. Rural Gen. (Ed. Impr.) ; 44(3): 168-173, abr. 2018. tab
Artigo em Espanhol | IBECS | ID: ibc-173468

RESUMO

Introducción. La disfagia orofaríngea es uno de los síndromes geriátricos menos conocidos, a pesar de su enorme impacto sobre la capacidad funcional, la calidad de vida y la salud de los individuos afectados. Material y método. Estudio descriptivo y prospectivo, por parte del Servicio de Geriatría del hospital de Barbastro (Huesca), desde marzo del 2012 hasta octubre del 2014, con fin de revisiones semestrales y anuales en octubre del 2015. Incluidos todos los paciente a los que se realizó método de exploración clínica de volumen-viscosidad (test MECV-V) por sospecha de disfagia. Resultados. El estudio incluyó a 266 pacientes, con una edad media de 82,35+/-12,3 años, con una puntuación media en el índice de Barthel de 20,5±25,4 y en el índice de Charlson de 1,77±1,6. El motivo de realización del test fue en 105 casos accidente cerebrovascular (40%), en 53 demencia (20%), en 24 parkinsonismos (9%) y por otros motivos diferentes en 80 (31%). Fueron diagnosticados de disfagia 228 casos (86%). Se instauró nutrición enteral en 25 casos (10,9%). Se reflejaron los resultados del test en el informe de alta en el 45% de los mismos con resultado positivo. La supervivencia media obtenida en los pacientes fallecidos desde la realización de test fue de 230,8±256,5 días. Encontramos diferencias en la supervivencia a los 12 meses en pacientes con test positivo, sin una clara relación con la situación funcional ni con la comorbilidad. Conclusiones. La disfagia conlleva una importante mortalidad, debiendo reflejarse adecuadamente el uso de espesantes tras su detección


Introduction. Oropharyngeal dysphagia is one of the lesser known geriatric syndromes, despite its enormous impact on functional capacity, quality of life, and health of those affected. Material and methods. A descriptive and prospective study was conducted by the Geriatric Department of Barbastro Hospital (Huesca), from March 2012 to October 2014, as biannual and annual reviews in October 2015. This study included all patients on whom a volume-viscosity clinical examination (MECV-V test) was performed to suspecting dysphagia. Results. The study included 266 patients with a mean age of 82.35±12.3 years, and with a mean Barthel index score of 20.5±25.4, and mean Charlson index of 1.77±1.6. The test was performed in 105 cases after stroke (40%), 53 in dementia (20%), 24 in Parkinsonism (9%), and for other different reasons in 80 (31%). Dysphagia was diagnosed in 228 (86%) cases. Enteral nutrition was given in 25 (10.9%) cases. The test results were shown in the discharge report in 45% of the tests with positive result. The mean survival obtained after test in the patients who died was 230.8±256.5 days. Differences in survival at 12 months were found in patients with positive test, without finding a clear relationship with functional status and comorbidity. Conclusions. Dysphagia has a significant mortality, and the use of thickeners after its detection should be properly reported


Assuntos
Humanos , Masculino , Feminino , Idoso , Idoso de 80 Anos ou mais , Transtornos de Deglutição/prevenção & controle , Transtornos de Deglutição/diagnóstico , Avaliação Geriátrica/métodos , Demência/complicações , Demência/epidemiologia , Nutrição Enteral/métodos , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/epidemiologia , Transtornos de Deglutição/dietoterapia , Gastrostomia/métodos , Estudos Prospectivos , Espessantes , Fatores de Risco , Espanha , Taxa de Sobrevida , Transtornos de Deglutição , Geriatria , Mortalidade
14.
Semergen ; 44(3): 168-173, 2018 Apr.
Artigo em Espanhol | MEDLINE | ID: mdl-28457769

RESUMO

INTRODUCTION: Oropharyngeal dysphagia is one of the lesser known geriatric syndromes, despite its enormous impact on functional capacity, quality of life, and health of those affected. MATERIAL AND METHODS: A descriptive and prospective study was conducted by the Geriatric Department of Barbastro Hospital (Huesca), from March 2012 to October 2014, as biannual and annual reviews in October 2015. This study included all patients on whom a volume-viscosity clinical examination (MECV-V test) was performed to suspecting dysphagia. RESULTS: The study included 266 patients with a mean age of 82.35±12.3 years, and with a mean Barthel index score of 20.5±25.4, and mean Charlson index of 1.77±1.6. The test was performed in 105 cases after stroke (40%), 53 in dementia (20%), 24 in Parkinsonism (9%), and for other different reasons in 80 (31%). Dysphagia was diagnosed in 228 (86%) cases. Enteral nutrition was given in 25 (10.9%) cases. The test results were shown in the discharge report in 45% of the tests with positive result. The mean survival obtained after test in the patients who died was 230.8±256.5 days. Differences in survival at 12 months were found in patients with positive test, without finding a clear relationship with functional status and comorbidity. CONCLUSIONS: Dysphagia has a significant mortality, and the use of thickeners after its detection should be properly reported.


Assuntos
Transtornos de Deglutição/diagnóstico , Nutrição Enteral/métodos , Avaliação Geriátrica/métodos , Qualidade de Vida , Idoso , Idoso de 80 Anos ou mais , Transtornos de Deglutição/epidemiologia , Transtornos de Deglutição/mortalidade , Demência/complicações , Demência/epidemiologia , Feminino , Humanos , Masculino , Doença de Parkinson/complicações , Doença de Parkinson/epidemiologia , Estudos Prospectivos , Fatores de Risco , Espanha , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/epidemiologia , Taxa de Sobrevida
15.
Zoonoses Public Health ; 64(4): 272-280, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-27762078

RESUMO

The aim of this research was to study the phenotypic resistances to disinfectants and antibiotics in strains of methicillin-resistant Staphylococcus aureus (MRSA) obtained from Canary black pigs. Analyses were performed on 54 strains of MRSA, isolated in Canary black pigs from the province of Tenerife (Spain); all of them carried the mecA gene. The strains were isolated by means of nasal swab samples of healthy pigs, collected under veterinarian supervision. Bactericidal activity of antiseptics and disinfectants was tested by means of the dilution-neutralization method. Susceptibility to the disinfectants glutaraldehyde, peracetic acid and silver nitrate was assessed, as well as to the antiseptics chlorhexidine, benzalkonium chloride and povidone iodine. Susceptibility to a wide array of antibiotics representing the main groups was determined by means of the disc diffusion method. All the strains demonstrated susceptibility to the disinfectants tested at the recommended concentration, and even to dilutions equal to or lesser than 1/16. The most effective antiseptic and disinfectant were, respectively, chlorhexidine and silver nitrate. With regard to the antibiotics, the strains proved to be multiresistant. All presented phenotypic resistance to the ß-lactam antibiotics ampicillin, penicillin and cefoxitin, as well as to numerous aminoglycosides, tetracycline and trimethoprim-sulfamethoxazole. It was also observed that 61.1% of the strains were carriers of plasmids. Our results underline that in the strains such as MRSA, which show multiple resistances to antibiotics, the antiseptics and disinfectants show great efficacy. Moreover, as other authors also suggest, for the treatment and prevention of infections caused by MRSA, the use of ß-lactam and aminoglycoside antibiotics may be less effective.


Assuntos
Antibacterianos/farmacologia , Desinfetantes/farmacologia , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Infecções Estafilocócicas/veterinária , Doenças dos Suínos/microbiologia , Animais , Staphylococcus aureus Resistente à Meticilina/classificação , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Fenótipo , Espanha/epidemiologia , Infecções Estafilocócicas/epidemiologia , Infecções Estafilocócicas/microbiologia , Suínos , Doenças dos Suínos/epidemiologia
17.
Nat Phys ; 12(1): 67-70, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27330541

RESUMO

The Carnot cycle imposes a fundamental upper limit to the efficiency of a macroscopic motor operating between two thermal baths1. However, this bound needs to be reinterpreted at microscopic scales, where molecular bio-motors2 and some artificial micro-engines3-5 operate. As described by stochastic thermodynamics6,7, energy transfers in microscopic systems are random and thermal fluctuations induce transient decreases of entropy, allowing for possible violations of the Carnot limit8. Here we report an experimental realization of a Carnot engine with a single optically trapped Brownian particle as the working substance. We present an exhaustive study of the energetics of the engine and analyse the fluctuations of the finite-time efficiency, showing that the Carnot bound can be surpassed for a small number of non-equilibrium cycles. As its macroscopic counterpart, the energetics of our Carnot device exhibits basic properties that one would expect to observe in any microscopic energy transducer operating with baths at different temperatures9-11. Our results characterize the sources of irreversibility in the engine and the statistical properties of the efficiency-an insight that could inspire new strategies in the design of efficient nano-motors.

18.
J Evol Biol ; 29(6): 1168-77, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-26969911

RESUMO

Competition between spermatozoa of rival males to gain fertilizations has led to a wide array of modifications in sperm structure and function. Sperm cells of most muroid rodents have hook-shaped extensions in the apical-ventral tip of the head, but the function of this structure is largely unknown. These 'hooks' may facilitate aggregation of spermatozoa in so-called 'trains', as an adaptation to sperm competition, because sperm in trains may swim faster than free-swimming cells. However, there is controversy regarding the role of the hook in train formation, and in relation to whether it is selected by sperm competition. We examined spermatozoa from muroid rodents with varying levels of sperm competition to assess whether (i) sperm aggregates are common in these taxa, (ii) presence of a hook relates to the formation of sperm aggregations, and (iii) formation of sperm aggregations is explained by sperm competition. Our analyses in 25 muroid species revealed that > 92% of spermatozoa swim individually in all species, with the exception of the wood mouse, Apodemus sylvaticus, which has ~50% spermatozoa swimming freely. Species with hooked spermatozoa had higher sperm competition levels and longer sperm than species whose sperm lack a hook. Neither the presence of hook nor sperm competition levels were related to the percentage of sperm in aggregations. Thus, (i) sperm aggregates in muroid rodents are an exceptional trait found only in a few species, (ii) evolution of the sperm hook is associated to sperm competition levels, but (iii) the hook is unlikely to be related to the formation of sperm aggregates. The evolutionary significance of the sperm head hook thus remains elusive, and future studies should examine potential roles of this pervasive structure in sperm's hydrodynamic efficiency and sperm-female tract interactions.


Assuntos
Evolução Biológica , Espermatozoides , Animais , Movimento Celular , Feminino , Masculino , Camundongos , Murinae , Cabeça do Espermatozoide
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