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1.
Proc Natl Acad Sci U S A ; 121(8): e2313610121, 2024 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-38359292

RESUMEN

During the COVID-19 pandemic, some US states mandated vaccination for certain citizens. We used state-level data from the CDC to test whether vaccine mandates predicted changes in COVID-19 vaccine uptake, as well as related voluntary behaviors involving COVID-19 boosters and seasonal influenza vaccines. Results showed that COVID-19 vaccine adoption did not significantly change in the weeks before and after states implemented vaccine mandates, suggesting that mandates did not directly impact COVID-19 vaccination. Compared to states that banned vaccine restrictions, however, states with mandates had lower levels of COVID-19 booster adoption as well as adult and child flu vaccination, especially when residents initially were less likely to vaccinate for COVID-19. This research supports the notion that governmental restrictions in the form of vaccination mandates can have unintended negative consequences, not necessarily by reducing uptake of the mandated vaccine, but by reducing adoption of other voluntary vaccines.


Asunto(s)
COVID-19 , Vacunas contra la Influenza , Adulto , Niño , Humanos , Vacunas contra la COVID-19 , Vacunación Obligatoria , Pandemias/prevención & control , COVID-19/epidemiología , COVID-19/prevención & control , Vacunación
2.
Proc Natl Acad Sci U S A ; 120(27): e2216248120, 2023 Jul 04.
Artículo en Inglés | MEDLINE | ID: mdl-37368928

RESUMEN

The US global leadership in science and technology has greatly benefitted from immigrants from other countries, most notably from China in the recent decades. However, feeling the pressure of potential federal investigations since the 2018 launch of the China Initiative, scientists of Chinese descent in the United States now face higher incentives to leave the United States and lower incentives to apply for federal grants. Analyzing data pertaining to institutional affiliations of more than 200 million scientific papers, we find a steady increase in the return migration of scientists of Chinese descent from the United States to China. We also conducted a survey of scientists of Chinese descent employed by US universities in tenured or tenure-track positions (n = 1,304), with results revealing general feelings of fear and anxiety that lead them to consider leaving the United States and/or stop applying for federal grants. If the situation is not corrected, American science will likely suffer the loss of scientific talent to China and other countries.

3.
Proc Natl Acad Sci U S A ; 120(48): e2301642120, 2023 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-37983511

RESUMEN

Science is among humanity's greatest achievements, yet scientific censorship is rarely studied empirically. We explore the social, psychological, and institutional causes and consequences of scientific censorship (defined as actions aimed at obstructing particular scientific ideas from reaching an audience for reasons other than low scientific quality). Popular narratives suggest that scientific censorship is driven by authoritarian officials with dark motives, such as dogmatism and intolerance. Our analysis suggests that scientific censorship is often driven by scientists, who are primarily motivated by self-protection, benevolence toward peer scholars, and prosocial concerns for the well-being of human social groups. This perspective helps explain both recent findings on scientific censorship and recent changes to scientific institutions, such as the use of harm-based criteria to evaluate research. We discuss unknowns surrounding the consequences of censorship and provide recommendations for improving transparency and accountability in scientific decision-making to enable the exploration of these unknowns. The benefits of censorship may sometimes outweigh costs. However, until costs and benefits are examined empirically, scholars on opposing sides of ongoing debates are left to quarrel based on competing values, assumptions, and intuitions.


Asunto(s)
Censura de la Investigación , Ciencia , Responsabilidad Social , Costos y Análisis de Costo
4.
Proc Natl Acad Sci U S A ; 120(30): e2300903120, 2023 Jul 25.
Artículo en Inglés | MEDLINE | ID: mdl-37459538

RESUMEN

Strange metals appear in a wide range of correlated materials. Electronic localization-delocalization and the expected loss of quasiparticles characterize beyond-Landau metallic quantum critical points and the associated strange metals. Typical settings involve local spins. Systems that contain entwined degrees of freedom offer new platforms to realize unusual forms of quantum criticality. Here, we study the fate of an SU(4) spin-orbital Kondo state in a multipolar Bose-Fermi Kondo model, which provides an effective description of a multipolar Kondo lattice, using a renormalization-group method. We show that at zero temperature, a generic trajectory in the model's parameter space contains two quantum critical points, which are associated with the destruction of Kondo entanglement in the orbital and spin channels, respectively. Our asymptotically exact results reveal an overall phase diagram, provide the theoretical basis to understand puzzling recent experiments of a multipolar heavy fermion metal, and point to a means of designing different forms of quantum criticality and strange metallicity in a variety of strongly correlated systems.

5.
Proc Natl Acad Sci U S A ; 119(19): e2117622119, 2022 05 10.
Artículo en Inglés | MEDLINE | ID: mdl-35512090

RESUMEN

SignificanceMany protocols used in material design and training have a common theme: they introduce new degrees of freedom, often by relaxing away existing constraints, and then evolve these degrees of freedom based on a rule that leads the material to a desired state at which point these new degrees of freedom are frozen out. By creating a unifying framework for these protocols, we can now understand that some protocols work better than others because the choice of new degrees of freedom matters. For instance, introducing particle sizes as degrees of freedom to the minimization of a jammed particle packing can lead to a highly stable state, whereas particle stiffnesses do not have nearly the same impact.

6.
Proc Natl Acad Sci U S A ; 119(44): e2203150119, 2022 11.
Artículo en Inglés | MEDLINE | ID: mdl-36306328

RESUMEN

This study explores how researchers' analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers' expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each team's workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers' results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.


Asunto(s)
Análisis de Datos , Investigadores , Humanos , Incertidumbre , Reproducibilidad de los Resultados
7.
Am J Physiol Heart Circ Physiol ; 326(1): H25-H31, 2024 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-37889255

RESUMEN

Since 2010, the number of life science doctoral graduates opting into academic postdoctoral employment has steadily declined. In recent years, this decline has made routine headlines in academic news cycles, and faculty members, universities, and funding bodies alike have begun to take notice. In November 2022, the National Institutes of Health (NIH) convened a special interest group to address the problems in postdoctoral recruitment and retention. In response, the American Physiological Society Science Policy Committee highlighted several key issues in postdoctoral training and working conditions and offered the NIH solutions to consider. There are known issues that affect postdoctoral recruitment and retention efforts: low wages relative to other employment sectors, a heavy workload, and poor job prospects to name a few. Unfortunately, these concerns are frequently dismissed as "the price of doing business in academia," and postdoctoral scholars are promised that if they overcome the trials and tribulations of this training period, the reward at the end, a career with academic freedom to pursue your own interests, justifies the means. However, academic freedom cannot and should not be used as the band-aid in a system where most of us will never actually experience academic freedom. Instead, we should systematically embrace solutions that improve the personal and professional health of early career researchers in all levels of training and independence if the goal is to truly shore up the academic workforce.


Asunto(s)
Investigadores , Condiciones de Trabajo , Humanos , Estados Unidos , Recursos Humanos , Investigadores/educación
8.
J Comput Chem ; 2024 Jun 29.
Artículo en Inglés | MEDLINE | ID: mdl-38944673

RESUMEN

Conformational ensemble generation and the search for the global minimum conformation are important problems in computational chemistry. In this work, a variant on the conformer-rotamer ensemble sampling tool (CREST) iterative metadynamics (iMTD) algorithm designed for determining structural ensembles and energetics of noncovalent clusters of flexible molecules is presented. We term this new algorithm a low-energy diversity-enhanced variant on CREST, or LEDE-CREST. As with CREST, the energies are evaluated using the semiempirical GFN2-xTB extended tight binding approach. The utility of the algorithm is highlighted by generating ensembles for a variety of noncovalent clusters of flexible or rigid monomers using both CREST and LEDE-CREST.

9.
Cytotherapy ; 26(4): 404-409, 2024 04.
Artículo en Inglés | MEDLINE | ID: mdl-38310500

RESUMEN

The premature marketing of investigational stem cell interventions (SCIs) is a growing market in the US. Several US states have passed legislation to permit and promote unproven and experimental SCIs for individuals with terminal or chronic diseases. These SCI medical freedom laws, which are largely based on right-to-try legislation, increase access to experimental SCIs with little to no oversight. They undermine federal regulatory authority and can compromise patient safety and informed decision-making. SCI medical freedom laws have gone largely unnoticed by scientific societies interested in the responsible translation of stem cell medicine. In this article, we analyze state SCI medical freedom laws and describe their detrimental impact on patients and society. We contend that scientific and medical societies are uniquely poised to advocate against state-based policy promoting unproven SCIs but recognize resource and other constraints to advocate for or against legislation in 50 states. We recommend societies establish coalitions and share resources to address state-based SCI medical freedom laws and other legislation surrounding unproven SCIs.


Asunto(s)
Seguridad del Paciente , Células Madre , Humanos , Estados Unidos , Libertad
10.
Epilepsia ; 2024 Jul 11.
Artículo en Inglés | MEDLINE | ID: mdl-38990082

RESUMEN

Delineation of seizure onset regions using intracranial electroencephalography (icEEG) is vital in the surgical workup of drug-resistant epilepsy cases. However, it is unknown whether the complete resection of these regions is necessary for seizure freedom, or whether postsurgical seizure recurrence can be attributed to the incomplete removal of seizure onset regions. To address this gap, we retrospectively analyzed icEEG recordings from 63 subjects, identifying seizure onset regions visually and algorithmically. We assessed onset region resection and correlated this with postsurgical seizure control. The majority of subjects had more than half of their onset regions resected (82.46% and 80.65% of subjects using visual and algorithmic methods, respectively). There was no association between the proportion of the seizure onset zone (SOZ) that was subsequently resected and better surgical outcomes (area under the receiver operating characteristic curve [AUC] < .7). Investigating the spatial extent of onset regions, we found no substantial evidence of an association with postsurgical seizure control (all AUC < .7). Although seizure onset regions are typically resected completely or in large part, incomplete resection is not associated with worse postsurgical outcomes. We conclude that postsurgical seizure recurrence cannot be attributed to an incomplete resection of the icEEG SOZ alone. Other network mechanisms beyond icEEG seizure onset likely contribute.

11.
BMC Med Res Methodol ; 24(1): 152, 2024 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-39020325

RESUMEN

When different researchers study the same research question using the same dataset they may obtain different and potentially even conflicting results. This is because there is often substantial flexibility in researchers' analytical choices, an issue also referred to as "researcher degrees of freedom". Combined with selective reporting of the smallest p-value or largest effect, researcher degrees of freedom may lead to an increased rate of false positive and overoptimistic results. In this paper, we address this issue by formalizing the multiplicity of analysis strategies as a multiple testing problem. As the test statistics of different analysis strategies are usually highly dependent, a naive approach such as the Bonferroni correction is inappropriate because it leads to an unacceptable loss of power. Instead, we propose using the "minP" adjustment method, which takes potential test dependencies into account and approximates the underlying null distribution of the minimal p-value through a permutation-based procedure. This procedure is known to achieve more power than simpler approaches while ensuring a weak control of the family-wise error rate. We illustrate our approach for addressing researcher degrees of freedom by applying it to a study on the impact of perioperative p a O 2 on post-operative complications after neurosurgery. A total of 48 analysis strategies are considered and adjusted using the minP procedure. This approach allows to selectively report the result of the analysis strategy yielding the most convincing evidence, while controlling the type 1 error-and thus the risk of publishing false positive results that may not be replicable.


Asunto(s)
Investigadores , Humanos , Investigadores/estadística & datos numéricos , Proyectos de Investigación , Interpretación Estadística de Datos , Investigación Biomédica/métodos , Modelos Estadísticos , Complicaciones Posoperatorias/prevención & control
12.
BMC Vet Res ; 20(1): 72, 2024 Feb 24.
Artículo en Inglés | MEDLINE | ID: mdl-38402170

RESUMEN

BACKGROUND: Cranial closing wedge osteotomy (CCWO) is a functional stabilisation technique for cranial cruciate ligament (CrCL) ruptures. This biomechanical study aimed to evaluate the influence of CCWO on the stability of the stifle joint. Eighteen Beagle stifle joints were divided into two groups: control and CCWO. The stifle joints were analyzed using a six-degree-of-freedom robotic joint biomechanical testing system. The joints were subjected to 30 N in the craniocaudal (CrCd) drawer and proximal compression tests and 1 Nm in the internal-external (IE) rotation test. Each test was performed with an extension position, 135°, and 120° of joint angle. RESULTS: The stifle joints were tested while the CrCLs were intact and then transected. In the drawer test, the CCWO procedure, CrCL transection, and stifle joint flexion increased CrCd displacement. The CCWO procedure and CrCL transection showed an interaction effect. In the compression test, the CCWO procedure decreased and CrCL transection and stifle joint flexion increased displacement. In the IE rotation test, CCWO, CrCL transection, and stifle joint flexion increased the range of motion. CONCLUSIONS: CCWO was expected to provide stability against compressive force but does not contribute to stability in the drawer or rotational tests. In the CCWO-treated stifle joint, instability during the drawer test worsened with CrCL transection. In other words, performing the CCWO procedure when the CrCL function is present is desirable for stabilizing the stifle joint.


Asunto(s)
Lesiones del Ligamento Cruzado Anterior , Enfermedades de los Perros , Perros , Animales , Rodilla de Cuadrúpedos/cirugía , Tibia/cirugía , Fenómenos Biomecánicos , Ligamento Cruzado Anterior/cirugía , Lesiones del Ligamento Cruzado Anterior/cirugía , Lesiones del Ligamento Cruzado Anterior/veterinaria , Osteotomía/veterinaria , Osteotomía/métodos
13.
BMC Geriatr ; 24(1): 192, 2024 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-38408921

RESUMEN

BACKGROUND: Locked doors remain a common feature of dementia units in nursing homes (NHs) worldwide, despite the growing body of knowledge on the negative effects of restricted freedom on residents. To date, no previous studies have explored the health effects of opening locked NH units, which would allow residents to move freely within the building and enclosed garden. This study examines the association between increased freedom of movement and the health of NH residents with dementia. METHODS: This longitudinal, pre-post study involved a natural experiment in which NH residents with dementia (N = 46) moved from a closed to a semi-open location. Data on dimensions of positive health were collected at baseline (T0; one month before the relocation), at one (T1), four (T2) and nine (T3) months after the relocation. Linear mixed models were used to examine changes in positive health over time. RESULTS: Cognition, quality of life and agitation scores improved significantly at T1 and T2 compared to the baseline, while mobility scores decreased. At T3, improvements in agitation and quality of life remained significant compared to the baseline. Activities of daily living (ADL) and depression scores were stable over time. CONCLUSIONS: Increasing freedom of movement for NH residents with dementia is associated with improved health outcomes, both immediately and over time. These findings add to the growing evidence supporting the benefits of freedom of movement for the overall health of NH residents with dementia.


Asunto(s)
Demencia , Calidad de Vida , Humanos , Estudios Longitudinales , Demencia/diagnóstico , Demencia/terapia , Actividades Cotidianas , Libertad de Circulación , Casas de Salud
14.
Childs Nerv Syst ; 40(6): 1799-1806, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38489033

RESUMEN

PURPOSE: Rasmussen encephalitis (RE) is a very rare chronic neurological disorder of unilateral inflammation of the cerebral cortex. Hemispherotomy provides the best chance at achieving seizure freedom in RE patients, but with significant risks and variable long-term outcomes. The goal of this study is to utilize our multicenter pediatric cohort to characterize if differences in pathology and/or imaging characterization of RE may provide a window into post-operative seizure outcomes, which in turn could guide decision-making for parents and healthcare providers. METHODS: This multi-institutional retrospective review of medical record, imaging, and pathology samples was approved by each individual institution's review board. Data was collected from all known pediatric cases of peri-insular functional hemispherotomy from the earliest available electronic medical records. Mean follow-up time was 4.9 years. Clinical outcomes were measured by last follow-up visit using both Engel and ILAE scoring systems. Relationships between categorical and continuous variables were analyzed with Pearson correlation values. RESULTS: Twenty-seven patients met study criteria. No statistically significant correlations existed between patient imaging and pathology data. Pathology stage, MRI brain imaging stages, and a combined assessment of pathology and imaging stages showed no statistically significant correlation to post-operative seizure freedom rates. Hemispherectomy Outcome Prediction Scale scoring demonstrated seizure freedom in only 71% of patients receiving a score of 1 and 36% of patients receiving a score of 2 which were substantially lower than predicted. CONCLUSIONS: Our analysis did not find evidence for either independent or combined analysis of imaging and pathology staging being predictive for post peri-insular hemispherotomy seizure outcomes, prompting the need for other biomarkers to be explored. Our data stands in contrast to the recently proposed Hemispherectomy Outcome Prediction Scale and does not externally validate this metric for an RE cohort.


Asunto(s)
Encefalitis , Hemisferectomía , Imagen por Resonancia Magnética , Humanos , Hemisferectomía/métodos , Femenino , Masculino , Imagen por Resonancia Magnética/métodos , Encefalitis/cirugía , Encefalitis/diagnóstico por imagen , Encefalitis/patología , Preescolar , Niño , Estudios Retrospectivos , Lactante , Resultado del Tratamiento , Adolescente
15.
Childs Nerv Syst ; 40(2): 503-509, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-37698648

RESUMEN

INTRODUCTION: Present study attempted to analyze seizure freedom and detailed functional outcomes after functional hemispherotomy and utility of hemispherotomy outcome prediction scale (HOPS) scores in predicting outcomes. METHODS: Patients who underwent functional hemispherotomy were analyzed for clinical presentation, neuroimaging, seizure outcomes, and functional outcomes. RESULTS: A total of 76 procedures were performed on 69 patients. Mean age at the surgery was 8 ± 6.1 years. Fourteen patients were < 2 years. Age of onset epilepsy of the cohort was 2.0 ± 3.3 years. All had severe catastrophic epilepsy with multiple daily seizures. All patients had motor deficits with 36 (52%) patients had contralateral dysfunctional hand. Perinatal stroke (49%) was most common substrate followed by cortical malformations (21.7%). Eight patients had contralateral imaging abnormalities. Fifty-nine (86.76%) patients remained seizure free (Engle 1a) at 41 + -20.9 months. HOPS scores were available for 53 patients and lowest seizure outcome was 71% for HOPS score of 4. Lower HOPS scores predicted better seizure outcomes. Cortical malformations operated earlier than 2 years predicted poor seizure outcomes (66.6%). Positive functional outcomes are recorded in 80% of patients with 78% reporting improvement from the pre-surgical level. Five (7.2%) patients underwent shunt surgery. One mortality recorded. CONCLUSIONS: Hemispherotomy has excellent seizure outcomes. Early surgery in cortical malformations appears to be predictor of poorer seizure outcomes. HOPS score is a good tool to predict the seizure outcomes. Hemispherotomy is perceived to improve the Cognitive and functional performance.


Asunto(s)
Epilepsia , Hemisferectomía , Humanos , Lactante , Preescolar , Niño , Adolescente , Resultado del Tratamiento , Hemisferectomía/métodos , Estudios Retrospectivos , Convulsiones/cirugía , Epilepsia/cirugía
16.
Bioethics ; 38(4): 326-334, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38363981

RESUMEN

Divergences and controversies are inevitable in the discussion of freedoms and rights, especially in the matter of reproduction. The Chinese first social egg freezing lawsuit raises the question: is the freedom to freeze eggs for social reasons justified because it is an instance of reproductive rights? This paper accepts social egg freezing as desirable reproductive freedom, but following Harel's approach and considering two theories of rights, the choice and interest theories of rights, we argue that social egg freezing is not a reproductive right because one cannot justify a right or an instance of rights via merely describing the function of those instances that have been justified as right, that is, the choice theory lacks justifying normativity. Since reserving fertility and a suspension from reproduction do not serve reproductive ends per se, the sufficient reason for demanding social egg freezing as a right should be found in other ends rather than in right-to-reproduce, that is, the interest theory denies the demand as a right-to-reproduce. Permitting it on any grounds without guaranteeing adequate and accessible resources, especially in light of cross-border reproductive care, raises serious questions about reproductive equality and violates the idea of reproductive rights. Therefore, any ground for social egg freezing should be weighed against whether more pressing reproductive needs, specifically those that are justified as rights, have been met. It would be social progress to shoulder these burdens for the vulnerable and then allow social egg freezing-if right-to-reproduce were not the only privilege of the few.


Asunto(s)
Preservación de la Fertilidad , Turismo Médico , Humanos , Criopreservación , Derechos Sexuales y Reproductivos , Reproducción
17.
Aging Ment Health ; : 1-9, 2024 Jul 11.
Artículo en Inglés | MEDLINE | ID: mdl-38990123

RESUMEN

OBJECTIVES: To examine in-depth experiences of loneliness and freedom after late-life divorce from an intergenerational familial/dyadic perspective in a family-oriented society that also values self-determination. Considering the expansion of late-life divorce, it is important to understand its consequences for the family wellbeing. METHOD: According to phenomenology tradition, data was collected through 51 semi-structured qualitative interviews, comprised from 7 family units (n = 33) including all/most family members and 9 parent-child dyads (n = 18), using thematic-analysis and dyadic interview-analysis principles. Analyzing family units enables a more complex examination of the phenomena, providing a holistic view of family life. RESULTS: Loneliness and freedom experienced simultaneously was the most common. A gap was identified between generations regarding benefits and costs of late-life divorce. Whereas most divorcees emphasized the benefits of freedom, most of their adult-children mainly described the disadvantages of loneliness, perceiving both loneliness and freedom as negative. CONCLUSION: Late-life divorce is a complex experience comprised of both loneliness and freedom. Each generation experiences the benefits and costs of late-life divorce differently. Unique aspects of freedom and loneliness at old age in a socio-cultural context located between self-determination and family-oriented are discussed, including strategies of coping with loneliness. Implications for families and professionals are presented.

18.
Sensors (Basel) ; 24(5)2024 Feb 24.
Artículo en Inglés | MEDLINE | ID: mdl-38475007

RESUMEN

Multi-degree-of-freedom piezoelectric motors have the advantages of high torque and resolution, simple structure, and direct drive, which are widely used in robot wrist joints, deep-sea mechanisms, medical equipment, and space mechanisms. To solve the problems of high force/torque coupling degree and ball low stator and rotor bonding strength of the traditional traveling wave type three-degree-of-freedom piezoelectric spherical motor, a new structure of ball-hinged piezoelectric spherical motor is proposed. Through coordinate transformation and force analysis, the driven mathematical model of the spherical motor is given. The model shows that the three degrees of freedom of the motor are coupled with each other. According to the mathematical model of the spherical motor, the mechanical properties of the motor are analyzed by the computer simulation. The results show that the stalling torque coefficient kt has a linear relationship with the friction coefficient ε and the stator preload Fc, has a nonlinear relationship with the stator radius R and the rotor radius r, and increases with the increase of R and decreases with the increase of r. The no-load speed of motor ωn is not related to the friction coefficient ε and the stator preload Fc, and increases with the increase of R and decreases with the increase of r. The anisotropic characteristics of torque and speed of a spherical motor are further analyzed, which lays a theoretical foundation for the drive control of a spherical motor.

19.
Sensors (Basel) ; 24(3)2024 Jan 26.
Artículo en Inglés | MEDLINE | ID: mdl-38339525

RESUMEN

Sparse arrays are widely employed in array signal processing due to their obvious advantages in array element distribution and uniform degrees of freedom (uDOFs). In this paper, a generalized augmented multi-subarray nested array (GAMSNA-I) and its variant, GAMSNA-II are proposed, with the objective of increasing uDOFs and reducing mutual coupling. Based on two subarrays of the prototype nested array (NA), GAMSNA-I is constructed by reconfiguring the dense uniform linear array (ULA) and forward-shifting the sparse ULA. GAMSNA-II is obtained by sparsifying the dense part of GAMSNA-I, ensuring constant uDOFs while further reducing mutual coupling. Subsequently, the closed-form expression for the uDOFs of GAMSNA-I with an arbitrary number of sensors is derived, and the proof is provided that the uDOFs of GAMSNA-II remain unchanged relative to that of GAMSNA-I. Compared to some existing array configurations, both GAMSNA-I and GAMSNA-II exhibit improved uDOFs, with GAMSNA-II achieving lower mutual coupling. Simulation results show the superior performance of the proposed GAMSNA-I and GAMSNA-II.

20.
Sensors (Basel) ; 24(3)2024 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-38339623

RESUMEN

In this paper, an ultracompact combined sensor for displacement and angle-synchronous measurement is proposed based on the self-imaging effect of optical microgratings. Using a two-grating structure, linear and angular displacement can be measured by detecting the change of phase and amplitude of the optical transmission, respectively, within one single structure in the meantime. The optically transmitted properties of the two-grating structure are investigated in both theory and simulation. Simulated results indicate that optical transmission changes in a sinusoidal relationship to the input linear displacement. Meanwhile, the amplitude of the curve decreases with an input pitch angle, indicating the ability for synchronous measurement within one single compact structure. The synchronous measurement of the linear displacement and the angle is also demonstrated experimentally. The results show a resolution down to 4 nm for linear displacement measurement and a maximum sensitivity of 0.26 mV/arcsec within a range of ±1° for angle measurement. Benefiting from a simple common-path structure without using optical components, including reflectors and polarizers, the sensor shows ultra-high compactness for multiple-degrees-of-freedom measuring, indicating the great potential for this sensor in fields such as integrated mechanical positioning and semiconductor fabrication.

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