Optical dopamine monitoring with dLight1 reveals mesolimbic phenotypes in a mouse model of neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder whose neurodevelopmental symptoms include impaired executive function, attention, and spatial learning that could be due to perturbed mesolimbic dopaminergic circuitry. However, these circuits have never been directly assayed in vivo. We employed the genetically encoded optical dopamine sensor dLight1 to monitor dopaminergic neurotransmission in the ventral striatum of NF1 mice during motivated behavior. Additionally, we developed novel systemic AAV vectors to facilitate morphological reconstruction of dopaminergic populations in cleared tissue. We found that NF1 mice exhibit reduced spontaneous dopaminergic neurotransmission that was associated with excitation/inhibition imbalance in the ventral tegmental area and abnormal neuronal morphology. NF1 mice also had more robust dopaminergic and behavioral responses to salient visual stimuli, which were stimulus-dependent, independent of learning, and rescued by optogenetic inhibition of non-dopaminergic neurons in the VTA. Overall, these studies provide a first in vivo characterization of dopaminergic circuit function in the context of NF1 and reveal novel pathophysiological mechanisms

Optical dopamine monitoring with dLight1 reveals mesolimbic phenotypes in a mouse model of neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder whose neurodevelopmental symptoms include impaired executive function, attention, and spatial learning that could be due to perturbed mesolimbic dopaminergic circuitry. However, these circuits have never been directly assayed in vivo. We employed the genetically encoded optical dopamine sensor dLight1 to monitor dopaminergic neurotransmission in the ventral striatum of NF1 mice during motivated behavior. Additionally, we developed novel systemic AAV vectors to facilitate morphological reconstruction of dopaminergic populations in cleared tissue. We found that NF1 mice exhibit reduced spontaneous dopaminergic neurotransmission that was associated with excitation/inhibition imbalance in the ventral tegmental area and abnormal neuronal morphology. NF1 mice also had more robust dopaminergic and behavioral responses to salient visual stimuli, which were stimulus-dependent, independent of learning, and rescued by optogenetic inhibition of non-dopaminergic neurons in the VTA. Overall, these studies provide a first in vivo characterization of dopaminergic circuit function in the context of NF1 and reveal novel pathophysiological mechanisms

Spectrum and energy efficient digital modulation techniques for practical visible light communication systems

The growth in mobile data traffic is rapidly increasing in an unsustainable direction given the radio frequency (RF) spectrum limits. Visible light communication (VLC) offers a lucrative solution based on an alternative license-free frequency band that is safe to use and inexpensive to utilize. Improving the spectral and energy efficiency of intensity modulation and direct detection (IM/DD) systems is still an on-going challenge in VLC. The energy efficiency of inherently unipolar modulation techniques such as pulse-amplitude modulation discrete multitone modulation (PAM-DMT) and asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) degrades at high spectral efficiency. Two novel superposition modulation techniques are proposed in this thesis based on PAM-DMT and ACO-OFDM. In addition, a practical solution based on the computationally efficient augmented spectral efficiency discrete multi-tone (ASE-DMT) is proposed. The system performance of the proposed superposition modulation techniques offers significant electrical and optical power savings with up to 8 dB in the electrical signal-to-noise ratio (SNR) when compared with DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM). The theoretical bit error ratio (BER) performance bounds for all of the proposed modulation techniques are in agreement with the Monte-Carlo simulation results. The proposed superposition modulation techniques are promising candidates for spectrum and energy efficient IM/DD systems. Two experimental studies are presented for a VLC system based on DCO-OFDM with adaptive bit and energy loading. Micrometer-sized Gallium Nitride light emitting diode (m-LED) and light amplification by stimulated emission of radiation diode (LD) are used in these studies due to their high modulation bandwidth. Record data rates are achieved with a BER below the forward error correction (FEC) threshold at 7.91 Gb/s using the violet m-LED and at 15 Gb/s using the blue LD. These results highlight the potential of VLC systems in practical high speed communication solutions. An additional experimental study is demonstrated for the proposed superposition modulation techniques based on ASE-DMT. The experimentally achieved results confirm the theoretical and simulation based performance predictions of ASE-DMT. A significant gain of up to 17.33 dB in SNR is demonstrated at a low direct current (DC) bias. Finally, the perception that VLC systems cannot work under the presence of sunlight is addressed in this thesis. A complete framework is presented to evaluate the performance of VLC systems in the presence of solar irradiance at any given location and time. The effect of sunlight is investigated in terms of the degradations in SNR, data rate and BER. A reliable high speed communication system is achieved under the sunlight effect. An optical bandpass blue filter is shown to compensate for half of the reduced data rate in the presence of sunlight. This thesis demonstrates data rates above 1 Gb/s for a practical VLC link under strong solar illuminance measured at 50350 lux in clear weather conditions

Inter-layer adhesion in material extrusion 3D printing: effect of processing and molecular variables

There has been extensive research in the field of material-extrusion (Mat-Ex) 3D printing to improve the inter-layer bonding process. Much research focusses on how various printing conditions may be detrimental to weld strength; many different feedstocks have been investigated along with various additives to improve strength. Surprisingly, there has been little attention on how fundamental molecular properties of the feedstock, in particular the average molar mass of the polymer, may contribute to microstructure of the weld. Here we show that weld strength increases with decreasing average molar mass, contrary to common observations in specimens processed in more traditional ways, e.g., by compression molding. Using a combination of synchrotron infra-red polarization modulation microspectroscopy measurements and continuum modelling, we demonstrate how residual molecular anisotropy in the weld region leads to poor strength and how it can be eradicated by decreasing the relaxation time of the polymer. This is achieved more effectively by reducing the molar mass than by the usual approach of attempting to govern the temperature in this hard to control non-isothermal process. Thus, we propose that molar mass of the polymer feedstock should be considered as a key control parameter for achieving high weld strength in Mat-Ex

행동적 항상성 조절의 신경회로: 섭식 행동과 체온조절 행동 중심으로

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 협동과정 뇌과학전공, 2022. 8. 김성연.Maintaining physiological conditions (e.g., nutrients, water, and body temperature) within a narrow range is a distinct quality of living organisms. Among them, animals utilize diverse behaviors to suffice materials in need to maintain internal stability, called homeostasis. As such, understanding the neural mechanisms for behavioral regulations of homeostatic conditions has been a key interest in neurobiology and physiology. However, despite the importance of this question, neural processes underlying some of the fundamental behaviors for maintaining organismal homeostasis are still elusive. In this dissertation, I describe the data revealing neural circuit mechanisms underlying two basic behaviors for regulating homeostasis: ingestive and thermoregulatory behaviors. Chapter one of this dissertation briefly overviews the origin of the homeostasis concept and provides a short historical perspective on studying neural processes for behavioral regulation of homeostasis. Chapter two describes a molecularly defined neural population in a hindbrain area called the parabrachial nucleus for monitoring and suppressing ingestion and demonstrates a gut-to-brain neural circuit spanning from the peripheral sensory ganglia to the hypothalamus for mechanosensory feedback control of ingestion. Chapter three describes a parabrachial-to-hypothalamic neural circuit for thermoregulatory behaviors and the neural coding of motivational aspects of thermal stimuli by a subpopulation of hypothalamic neurons. Chapter four describes a summary of the data presented in this dissertation and provides directions for further investigations. Together, this dissertation presents studies on understanding neural circuit mechanisms underlying fundamental behaviors for regulating crucial homeostatic conditions, including energy, fluid, and body temperature.영양분과 체온 등 체내 환경을 일정 수준으로 유지하는 성질인 항상성은 생명체의 중요한 특징이다. 여러 생물 종 중에서 특별히 동물들은 행동을 통해 자신의 필요를 채워 체내 항상성을 유지하는데, 따라서 항상성을 유지하기 위한 동물 행동을 매개하는 신경 기작을 이해하는 것은 신경생물학 및 생리학의 오랜 과제였다. 수십 년에 걸친 연구들로 많은 부분이 밝혀졌으나, 몇몇 근본적인 항상성 유지 행동을 매개하는 신경회로 기작은 여전히 알려지지 않고 있었다. 본 연구는 섭식 행동과 체온 유지 행동을 조절하는 데 관여하는 새로운 신경회로 기작을 밝힘으로써, 항상성 유지의 신경학적 원리에 대한 이해를 넓히는 것을 목표로 한다. 1장에서는 항상성 개념의 형성과 그 이후 이어진 항상성 조절 신경 기작에 관한 연구의 역사를 간략히 살펴보고자 한다. 2장에서는 소화관의 물리적 감각 신호를 이용하여 섭식을 모니터링하고 이에 따라 음식물의 섭취를 조절하는 후뇌부 신경세포 집단과, 그 집단을 중심으로 말초 신경절에서 시상하부까지 이어지는 장-뇌 신경회로에 관한 연구를 기술한다. 3장에서는 다양한 체온조절 행동에 필수적인 시상하부 신경 집단과 이를 중심으로 체온 조절 행동을 매개하는 신경회로 기작에 관한 연구를 기술한다. 4장에서는 본 논문에 기술된 연구 결과를 간략히 정리하고 그 의의에 관해 살펴본다. 본 연구들은 섭식 행동과 체온 조절 행동을 매개하는 신경회로 기작에 관한 새로운 이해를 더함으로써, 생명 유지에 필수적인 항상성 조절 행동의 신경학적 기반을 완전히 밝히는 데 기여할 것으로 기대한다.Chapter 1. Introduction 1 Chapter 2. A neural circuit mechanism for mechanosensory feedback control of ingestion 6 Chapter 3. A forebrain neural substrate for behavioral thermoregulation 80 Chapter 4. Conclusion 167 Bibliography 173 Abstract in Korean 186박

Photonic Technology for Precision Metrology

Photonics has had a decisive influence on recent scientific and technological achievements. It includes aspects of photon generation and photon–matter interaction. Although it finds many applications in the whole optical range of the wavelengths, most solutions operate in the visible and infrared range. Since the invention of the laser, a source of highly coherent optical radiation, optical measurements have become the perfect tool for highly precise and accurate measurements. Such measurements have the additional advantages of requiring no contact and a fast rate suitable for in-process metrology. However, their extreme precision is ultimately limited by, e.g., the noise of both lasers and photodetectors. The Special Issue of the Applied Science is devoted to the cutting-edge uses of optical sources, detectors, and optoelectronics systems in numerous fields of science and technology (e.g., industry, environment, healthcare, telecommunication, security, and space). The aim is to provide detail on state-of-the-art photonic technology for precision metrology and identify future developmental directions. This issue focuses on metrology principles and measurement instrumentation in optical technology to solve challenging engineering problems

Optical investigations of nanostructured oxides and semiconductors

This work is motivated by the prospect of building a quantum computer: a device that would allow physicists to explore quantum mechanics more deeply, and allow everyone else to keep their credit card numbers safe on the internet. In this thesis we explore materials that are relevant to a proposed quantum computer architecture.Systems with a ferroelectric to paraelectric transition in the vicinity of room temperature areuseful for devices. Adjusting the ferroelectric transition temperature is traditionally accomplished by chemical substitution, as in barium strontium titanate. We investigate strained-strontium titanate, which is ferroelectric at room-temperature, and a composite material of barium strontium titanate and magnesium oxide.We present optical techniques to measure electron spin dynamics with GHz dynamical bandwidth,transform-limited spectral selectivity, and phase-sensitive detection. We demonstrate the technique with a measurement of GHz-spin precession in n-GaAs. We also describe our efforts to measure single quantum dots optically.Nanoscale devices with photonic properties have been the subject of intense research over the past decade. Potential nanophotonic applications include communications, polarization-sensitive detectors, and solar power generation. Here we show photosensitivity of a nanoscale detectorwritten at the interface between two oxides

Doctor of Philosophy

dissertationThe forefront of current nanoscience initiatives includes the investigation and development of semiconducting colloidal nanocrystals for optoelectronic device concepts. Being highly facile in their synthesis, a wide range of sizes, morphologies, materials, interactions, and effects can easily be engineered by current synthetic chemists. Their solution-processability also makes available the use of long established industrial fabrication techniques such as reel-to-reel processing or even simple inkjet printing, offering the prospect of extremely cheap device manufacturing. Aside from anticipated technologies, this material class also makes available a type of "playground" for generating and observing novel quantum effects within reduced dimensions. Since the surface-to-volume ratio is very large in these systems, unsatisfied surface states are able to dominate the energetics of these particles. Although simple methods for satisfying such states are usually employed, they have proven to be only semieffective, often due to a significant change in surface stoichiometry caused by complex atomic reorganization. Serving as charge "trap" states, their effect on observables is readily seen, for instance, in single particle photoluminescence (PL) blinking. Unfortunately, most methods used to observe their influence are inherently blind to the chemical identity of these sites. In absence of such structural information, systematically engineering a robust passivation system becomes problematic. The development of pulsed optically detected magnetic resonance (pODMR) as a method for directly addressing the chemical nature of optically active charges while under trapping conditions is the primary tenet of this thesis. By taking advantage of this technique, a great wealth of knowledge becomes immediately accessible to the researcher. The first chapter of this work imparts the relevant background needed to pursue spin resonance studies in colloidal nanocrystals; the second chapter addresses technical aspects of these studies. In Chapter 3, pODMR is used to explore shallow trap states that dominate the charge transfer process in CdSe/CdS heterostructure nanocrystals. Several trapping channels are observed, while two in particular are correlated, demonstrating for the first time that both electrons and holes are able to be trapped within the same nanoparticle at the same time. The intrinsically long spin coherence lifetime for these states allows for the spin multiplicity and degree of isolation to be explored. Demonstration of novel effects is also performed, such as coherent control of the light-harvesting process and remote readout of spin information. The study presented in Chapter 4 focuses on the spin-dependencies observed in the historically ill-described emissive CdS defect. By monitoring deep-level emission from nanorods of this material, it is shown that the cluster defect can ultimately be fed by the same shallow trap states explored in Chapter 3. The degree of interaction between trap states and the cluster defect is probed. Also, a surprisingly long spin coherence lifetime (T2 « 1.6 /is) for the defect itself is observed, which opens the possibility of highly precise chemical fingerprinting through electron spin echo envelop modulation (ESEEM). This dissertation lays the groundwork for further use of these, and more powerful magnetic resonance probes of the states that fundamentally limit the practical utility of colloidal nanocrystal optoelectronics devices. Furthermore, by gaining access to these optically active electronic states, novel methods of coherent quantum control may be exerted on the energetics of this material system

Contrast agents for cardiovascular optical imaging at molecular levelm

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 17-07-201

Integrated butt-coupled membrane laser for Indium Phosphide on Silicon platform

In this work we present the design and technology development for an integrated butt-coupled membrane laser in the IMOS (Indium Phosphide Membrane On Silicon) platform . Laser is expected to have a small footprint (less than 50 µm 2 ), 1 mA threshold current and a direct modulation frequency of 10 GHz