Dissemination of UTC(NIST) over 20 km of commercial optical fiber with active phase stabilization.

We demonstrate the transfer of a cesium frequency standard steered to UTC(NIST) over 20 km of dark telecom optical fiber. Our dissemination scheme uses an active stabilization technique with a phase-locked voltage-controlled oscillator. Out-of-loop characterization of the optical fiber link performance is done with dual-fiber and single-fiber transfer schemes. We observe a fractional frequency instability of 1.5 × 10-12 and 2 × 10-15 at averaging intervals of 1 s and 105 s, respectively, for the link. Both schemes are sufficient to transfer the cesium clock reference without degrading the signal, with nearly an order of magnitude lower fractional frequency instability than the cesium clocks over all time scales. The simplicity of the two-fiber technique may be useful in future long-distance applications where higher stability requirements are not paramount, as it avoids technical complications involved with the single-fiber scheme.

Statistics for quantifying aging in time transfer system delays.

Residual time delays in time transfer systems such as two-way satellite time and frequency transfer (TWSTFT), or GPS carrier phase (GPSCP) change over time. A double difference such as TWSTFT-GPSCP provides information on the changes in the relative time delays of the two systems. These changes are referred to as aging or time dispersion. A first difference statistic, RMS time interval error, TIERMS, provides the RMS time dispersion. The time deviation statistic (TDEV) or a variation on the Allan deviation (ADEV), referred to here as ADEVS, provide information on the nature of the random fluctuations in aging. This paper describes analytical and Monte Carlo techniques used to estimate the aging (time dispersion) from TDEV or ADEVS statistics, and finds that the aging can be more than a factor of four larger than TDEV or ADEVS. The use of ADEVS is recommended over TDEV since it is sensitive to time drift.

In-vitro maturation and transplantation of cryopreserved ovary tissue: understanding ovarian longevity.

RESEARCH QUESTION: Is it possible to use experience gained from 24 years of frozen ovarian transplantation, and from recent experience with in-vitro gametogenesis to accomplish simple and robust in-vitro maturation (IVM) of oocytes from human ovarian tissue? DESIGN: A total of 119 female patients between age 2 and 35 years old underwent ovary cryopreservation (as well as in-vitro maturation of oocytes and IVM in the last 13 individuals) over a 24-year period. Up to 22 years later, 17 returned to have their ovary tissue thawed and transplanted back. RESULTS: Every woman had a return of ovarian function 5 months after transplant, similar to previous observations. As observed before, anti-Müllerian hormone (AMH) concentration rose as FSH fell 4 months later. The grafts continued to work up to 8 years. Of the 17, 13 (76%) became pregnant with intercourse at least once, resulting in 19 healthy live births, including six live births from three women who had had leukaemia. Of the harvested germinal vesicle oocytes, 35% developed with simple culture media into mature metaphase II oocytes. CONCLUSIONS: The authors concluded the following. First, ovary tissue cryopreservation is a robust method for preserving fertility even for women with leukaemia, without a need to delay cancer treatment. Second, many mature oocytes can often be obtained from ovary tissue with simple media and no need for ovarian stimulation. Third, ovarian stimulation only be necessary for removing the oocyte from the ovary, which can also be accomplished by simple dissection at the time of ovary freezing. Finally, pressure and just eight 'core genes' control primordial follicle recruitment and development.

Red meat consumption, incident CVD and the influence of dietary quality in the Jackson Heart Study.

OBJECTIVES: We investigated the prospective associations between meat consumption and CVD and whether these relationships differ by dietary quality among African American (AA) adults. DESIGN: Baseline diet was assessed with a regionally specific FFQ. Unprocessed red meat included beef and pork (120 g/serving); processed meat included sausage, luncheon meats and cured meat products (50 g/serving). Incident total CVD, CHD, stroke and heart failure were assessed annually over 9·8 years of follow-up. We characterised dietary quality using a modified Healthy Eating Index-2010 score (m-HEI), excluding meat contributions. SETTING: Jackson, MS, USA. PARTICIPANTS: AA adults (n 3242, aged 55 y, 66 % female). RESULTS: Mean total, unprocessed red and processed meat intakes were 5·7 ± 3·5, 2·3 ± 1·8 and 3·3 ± 2·7 servings/week, respectively. Mostly, null associations were observed between meat categories and CVD or subtypes. However, greater intake of unprocessed red meat (three servings/week) was associated with significantly elevated risk of stroke (hazard ratio = 1·43 (CI: 1·07,1·90)). With the exception of a more positive association between unprocessed meat consumption and stroke among individuals in m-HEI Tertile 2, the strength of associations between meat consumption categories and CVD outcomes did not differ by m-HEI tertile. In formal tests, m-HEI did not significantly modify meat-CVD associations. CONCLUSIONS: In this cohort of AA adults, total and processed meat were not associated with CVD outcomes, with the exception that unprocessed red meat was related to greater stroke risk. Dietary quality did not modfiy these associations. Research is needed in similar cohorts with longer follow-up and greater meat consumption to replicate these findings.

Action guidance for addressing pollution from inhalational anaesthetics.

Climate change is a real and accelerating existential danger. Urgent action is required to halt its progression, and everyone can contribute. Pollution mitigation represents an important opportunity for much needed leadership from the health community, addressing a threat that will directly and seriously impact the health and well-being of current and future generations. Inhalational anaesthetics are a significant contributor to healthcare-related greenhouse gas emissions and minimising their climate impact represents a meaningful and achievable intervention. A challenge exists in translating well-established knowledge about inhalational anaesthetic pollution into practical action. CODA is a medical education and health promotion charity that aims to deliver climate action-oriented recommendations, supported by useful resources and success stories. The CODA-hosted platform is designed to maximise engagement of the global healthcare community and draws upon diverse experiences to develop global solutions and accelerate action. The action guidance for addressing pollution from inhalational anaesthetics is the subject of this article. These are practical, evidence-based actions that can be undertaken to reduce the impact of pollution from inhalational anaesthetics, without compromising patient care and include: removal of desflurane from drug formularies; decommissioning central nitrous oxide piping; avoidance of nitrous oxide use; minimising fresh gas flows during anaesthesia; and prioritising total intravenous anaesthesia and regional anaesthesia when clinically safe to do so. Guidance on how to educate, implement, measure and review progress on these mitigation actions is provided, along with means to share successes and contribute to the essential, global transition towards environmentally sustainable anaesthesia.

Principles of environmentally-sustainable anaesthesia: a global consensus statement from the World Federation of Societies of Anaesthesiologists.

The Earth's mean surface temperature is already approximately 1.1°C higher than pre-industrial levels. Exceeding a mean 1.5°C rise by 2050 will make global adaptation to the consequences of climate change less possible. To protect public health, anaesthesia providers need to reduce the contribution their practice makes to global warming. We convened a Working Group of 45 anaesthesia providers with a recognised interest in sustainability, and used a three-stage modified Delphi consensus process to agree on principles of environmentally sustainable anaesthesia that are achievable worldwide. The Working Group agreed on the following three important underlying statements: patient safety should not be compromised by sustainable anaesthetic practices; high-, middle- and low-income countries should support each other appropriately in delivering sustainable healthcare (including anaesthesia); and healthcare systems should be mandated to reduce their contribution to global warming. We set out seven fundamental principles to guide anaesthesia providers in the move to environmentally sustainable practice, including: choice of medications and equipment; minimising waste and overuse of resources; and addressing environmental sustainability in anaesthetists' education, research, quality improvement and local healthcare leadership activities. These changes are achievable with minimal material resource and financial investment, and should undergo re-evaluation and updates as better evidence is published. This paper discusses each principle individually, and directs readers towards further important references.

Intrapersonal, interpersonal and environmental correlates of moderate to vigorous physical activity and sedentary time in adolescents with intellectual and developmental disabilities.

BACKGROUND: Although correlates of physical activity (PA) have been extensively examined in both children and adolescents who are typically developing, little is known about correlates of moderate to vigorous physical activity (MVPA) and sedentary time in adolescents with intellectual and developmental disabilities (IDD). Therefore, we examined intrapersonal, interpersonal and environmental factors and their association with device-based MVPA and sedentary time in adolescents with IDD. METHODS: MVPA and sedentary time was assessed using a hip-worn ActiGraph model wGT3x-BT tri-axial accelerometer across a 7-day period in adolescents with IDD and one of their parents. Pearson and point-biserial correlations were calculated to inspect the associations of PA (MVPA, sedentary time) with intrapersonal factors (demographic characteristic, BMI, waist circumference, motor ability, muscle strength, grip strength, cardiovascular fitness and self-efficacy for PA), interpersonal factors (parent demographics, parent BMI, parent MVPA and sedentary time, family social support for PA, parent barriers and support for PA, parent's beliefs/attitudes towards PA and number of siblings), and environmental factors (meteorologic season and COVID-19). Ordinary least squares regression was used to estimate the unique contributions of key factors to PA after controlling for participants' age, sex, race, waist circumference and total wear time. RESULTS: Ninety-two adolescents (15.5 ± 3.0 years old, 21.7% non-White, 6.5% Hispanic, 56.5% female) provided valid accelerometer data. Average sedentary time was 494.6 ± 136.4 min/day and average MVPA was 19.8 ± 24.2 min/day. Age (r = 0.27, P = 0.01), diagnosis of congenital heart disease (r = -0.26, P = 0.01) and parent sedentary time (r = 0.30, P = 0.01) were correlated with sedentary time. BMI (r = -0.24, P = 0.03), waist circumference (r = -0.28, P = 0.01), identifying as White (r = -0.23, P = 0.03) and parent MVPA (r = 0.56, P < 0.001) were correlated with MVPA. After adjusting for the adolescent's age, sex, race, waist circumference, and total wear time, the association between parent and adolescent MVPA remained significant (b = 0.55, P < 0.01, partial η2  = 0.11). CONCLUSION: The results of this study provide evidence that race, waist circumference and parental MVPA may influence the amount of MVPA in adolescents with IDD. The limited available information and the potential health benefits of increased MVPA highlight the need to evaluate the effectiveness of multi-component interventions targeting both intrapersonal and interpersonal levels to promote increased PA in adolescents with IDD.

Associations between dietary fatty acid patterns and cognitive function in the Hispanic Community Health Study/Study of Latinos.

Our objective was to quantify the cross-sectional associations between dietary fatty acid (DFA) patterns and cognitive function among Hispanic/Latino adults. This study included data from 8,942 participants of the Hispanic Community Health Study/Study of Latinos, a population-based cohort study (weighted age 56.2 y and proportion female 55.2%). The NCI (National Cancer Institute) method was used to estimate dietary intake from two 24-hr recalls. We derived DFA patterns using principal components analysis with 26 fatty acid and total plant and animal monounsaturated fatty acid (MUFA) input variables. Global cognitive function was calculated as the average z-score of 4 neurocognitive tests. Survey linear regression models included multiple potential confounders such as age, sex, education, depressive symptoms, physical activity, energy intake, and cardiovascular disease. DFA patterns were characterized by consumption of long-chain saturated fatty acids (SFA), animal-based MUFA, and trans fatty acids (Factor 1); short to medium-chain SFA (Factor 2); very-long-chain omega-3 polyunsaturated fatty acids (PUFA) (Factor 3); very-long-chain SFA and plant-based MUFA and PUFA (Factor 4). Factor 2 was associated with greater scores for global cognitive function (ß=0.037 ± 0.012) and the Digit Symbol Substitution (DSS) (ß=0.56±0.17), Brief Spanish English Verbal Learning-Sum (B-SEVLT) (ß=0.23 ± 0.11), and B-SEVLT-Recall (ß=0.11 ± 0.05) tests (P<0.05 for all). Factors 1 (ß=0.04 ± 0.01) and 4 (ß=0.70 ± 0.18) were associated with the DSS test (P<0.05 for all). Consumption of short to medium-chain SFA may be associated with higher cognitive function among U.S.-residing Hispanic/Latino adults. Prospective studies are necessary to confirm these findings.

Comparison of energy intake assessed by image-assisted food records to doubly labelled water in adolescents with intellectual and developmental disabilities: a feasibility study.

BACKGROUND: There are currently no validated methods for energy intake assessment in adolescents with intellectual and developmental disabilities (IDD). The purpose of this study was to determine the feasibility of collecting 3-day image-assisted food records (IARs) and doubly labelled water (TDEEDLW ) data in adolescents with IDD and to obtain preliminary estimates of validity and reliability for energy intake estimated by IAR. METHODS: Adolescents with IDD completed a 14-day assessment of mean daily energy expenditure using doubly labelled water. Participants were asked to complete 3-day IARs twice during the 14-day period. To complete the IAR, participants were asked to fill out a hard copy food record over three consecutive days (two weekdays/one weekend day) and to take before and after digital images of all foods and beverages consumed using an iPad tablet provided by the study. Energy intake from the IAR was calculated using Nutrition Data System for Research. Mean differences, intraclass correlations and Bland-Altman limits of agreement were performed. RESULTS: Nineteen adolescents with IDD, mean age 15.1 years, n = 6 (31.6%) female and n = 6 (31.6%) ethnic/racial minorities, enrolled in the trial. Participants successfully completed their 3-day food records and self-collected doubly labelled water urine samples for 100% of required days. Images were captured for 67.4 ± 30.1% of all meals recorded at assessment 1 and 72.3 ± 29.5% at assessment 2. The energy intake measured by IAR demonstrated acceptable test-retest reliability (intraclass correlation = 0.70). On average, IAR underestimated total energy intake by -299 ± 633 kcal/day (mean per cent error = -9.6 ± 22.2%); however, there was a large amount of individual variability in differences between the IAR and TDEEDLW (range = -1703 to 430). CONCLUSIONS: The collection of IAR and TDEEDLW is feasible in adolescents with IDD. While future validation studies are needed, the preliminary estimates obtained by this study suggest that in adolescents with IDD, the IAR method has acceptable reliability and may underestimate energy intake by ~9%.

Unraveling transcriptome dynamics in human spermatogenesis.

Spermatogenesis is a dynamic developmental process that includes stem cell proliferation and differentiation, meiotic cell divisions and extreme chromatin condensation. Although studied in mice, the molecular control of human spermatogenesis is largely unknown. Here, we developed a protocol that enables next-generation sequencing of RNA obtained from pools of 500 individually laser-capture microdissected cells of specific germ cell subtypes from fixed human testis samples. Transcriptomic analyses of these successive germ cell subtypes reveals dynamic transcription of over 4000 genes during human spermatogenesis. At the same time, many of the genes encoding for well-established meiotic and post-meiotic proteins are already present in the pre-meiotic phase. Furthermore, we found significant cell type-specific expression of post-transcriptional regulators, including expression of 110 RNA-binding proteins and 137 long non-coding RNAs, most of them previously not linked to spermatogenesis. Together, these data suggest that the transcriptome of precursor cells already contains the genes necessary for cellular differentiation and that timely translation controlled by post-transcriptional regulators is crucial for normal development. These established transcriptomes provide a reference catalog for further detailed studies on human spermatogenesis and spermatogenic failure.

Exploring the effectiveness of an 18-month weight management intervention in adults with Down syndrome using propensity score matching.

BACKGROUND: Down syndrome (DS) is one of the most common birth defects in the USA associated with high levels of overweight and obesity. Unique characteristics of adults with DS that may contribute to the high levels of obesity are high rates of hypothyroidism, poor muscle tone, altered gait and lower resting metabolic rate. Due to these factors, it is unknown if the same weight management interventions that are effective in adults with intellectual or developmental disability (IDD) without DS are as effective in those with DS. Therefore, the purpose of this secondary analysis was to compare changes in weight, diet and physical activity between participants with DS-related and non-DS-related IDD participating in an 18-month weight management trial. METHODS: We used propensity score methods to adjust baseline variables of overweight/obese adults with and without DS participating in an 18-month effectiveness trial with 6 months weight loss and 12 months weight maintenance. Participants followed one of two reduced calorie diet plans, obtained 150 min of moderate-vigorous intensity physical activity (MVPA) per week, and logged dietary intake daily. A health educator held monthly at-home visits with participants and a caregiver to give feedback on intervention compliance. RESULTS: Out of the 124 participants that met the criteria for inclusion, 21 were diagnosed with DS and 103 with non-DS-related IDD. Twenty out of 21 participants with DS were successfully matched. Clinically significant weight loss was seen at 18 months in participants with DS (-5.2%) and non-DS-related IDD (-6.8%), with no difference between groups (P = 0.53). Significant reductions in energy intake were seen across the 18-month intervention in both DS and non-DS-related IDD groups with between-group differences at 12 months only (1119 vs. 1492 kcal/day, respectively; P = 0.003). Although MVPA did not increase in either group across the intervention, those with non-DS-related IDD had higher levels of MVPA compared with those with DS across 18 months. CONCLUSION: Participants with DS lost a clinically significant amount of weight across the 18-month intervention. Compared with those with non-DS-related IDD, those with DS lost similar amounts of weight, had similar decreases in energy intake and participated in less MVPA across the 18-month intervention. Although individuals with DS have physiological factors that may contribute to obesity, weight management interventions designed for individuals with IDD may be equally effective in this population.

When "facts" are not facts: what does p value really mean, and how does it deceive us?

The recent paper in JAMA alleging that frozen embryo transfer causes twice the risk of childhood cancer in the offspring is an excellent example of the erroneous use of statistical tests (and the misinterpretation of p value) that is common in much of the medical literature, even in very high impact journals. These myths backed by misleading statements of "statistical significance" can cause far-reaching harm to patients and doctors who might not understand the pitfalls of specious statistical testing.

Observation of Gap Opening in 1T' Phase MoS2 Nanocrystals.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) manifest in various polymorphs, which deliver different electronic properties; the most prominent among them include the semiconducting 2H phase and metallic 1T (or distorted 1T' phase) phase. Alkali metal intercalation or interface strain has been used to induce semiconductor-to-metal transition in a monolayer MoS2 sheet, leading to exotic quantum states or improved performance in catalysis. However, the direct growth of 1T or 1T' phase MoS2 is challenging due to its metastability. Here, we report MBE growth of isolated 1T' and 2H MoS2 nanocrystals on a Au substrate; these nanocrystals can be differentiated unambiguously by their electronic states using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). By studying the initial stages of nucleation during molecular beam epitaxy (MBE) of MoS2, we could identify atomic clusters (30-50 atoms) with intralayer stacking corresponding to 1T' and 2H separately, which suggests a deterministic growth mechanism from initial nuclei. Furthermore, a topological insulator type behavior was observed for the 1T' MoS2 crystals, where an energy gap opening of 80 meV was measured by STS in the basal plane at 5 K, with the edge of the nanocrystals remaining metallic.

Mo-Terminated Edge Reconstructions in Nanoporous Molybdenum Disulfide Film.

The catalytic and magnetic properties of molybdenum disulfide (MoS2) are significantly enhanced by the presence of edge sites. One way to obtain a high density of edge sites in a two-dimensional (2D) film is by introducing porosity. However, the large-scale bottom-up synthesis of a porous 2D MoS2 film remains challenging and the correlation of growth conditions to the atomic structures of the edges is not well understood. Here, using molecular beam epitaxy, we prepare wafer-scale nanoporous MoS2 films under conditions of high Mo flux and study their catalytic and magnetic properties. Atomic-resolution electron microscopy imaging of the pores reveals two new types of reconstructed Mo-terminated edges, namely, a distorted 1T (DT) edge and the Mo-Klein edge. Nanoporous MoS2 films are magnetic up to 400 K, which is attributed to the presence of Mo-terminated edges with unpaired electrons, as confirmed by density functional theory calculation. The small hydrogen adsorption free energy at these Mo-terminated edges leads to excellent activity for the hydrogen evolution reaction.

Cryopreservation and transplantation of ovarian tissue: results from one center in the USA.

PURPOSE: To report the results of cryopreserved ovary tissue transplantation for leukemia and other cancers, in a single US center. METHODS: One hundred eight females between age 6 and (median age 24) 35 were referred for possible ovary tissue cryopreservation over a 20-year period, with either slow freeze or vitrification. Thus far 13 patients returned up to 18 years later to have their tissue transplanted back. RESULTS: All 13 patients had return of ovarian function 5 months post transplant with regular menstrual cycling. AMH rose to very high levels as the FSH declined to normal. Four months later, the AMH again declined to very low levels. Nonetheless, the grafts remained functional for up to 5 years or longer. Ten of the 13 (77%) became spontaneously pregnant at least once, resulting in 13 healthy babies. A total of 24 healthy babies have been born 11 from fresh transplanted ovarian tissue and 13 from cryopreserved transplanted ovarian tissue. CONCLUSIONS: (1) Ovary tissue cryopreservation is a robust method for preserving a woman's fertility. (2) Cortical tissue pressure may be a key regulator of primordial follicle arrest, recruitment, and ovarian longevity. (3) This is the only such series yet reported in the USA.

Resolving the Spatial Structures of Bound Hole States in Black Phosphorus.

Understanding the local electronic properties of individual defects and dopants in black phosphorus (BP) is of great importance for both fundamental research and technological applications. Here, we employ low-temperature scanning tunnelling microscope (LT-STM) to probe the local electronic structures of single acceptors in BP. We demonstrate that the charge state of individual acceptors can be reversibly switched by controlling the tip-induced band bending. In addition, acceptor-related resonance features in the tunnelling spectra can be attributed to the formation of Rydberg-like bound hole states. The spatial mapping of the quantum bound states shows two distinct shapes evolving from an extended ellipse shape for the 1s ground state to a dumbbell shape for the 2px excited state. The wave functions of bound hole states can be well-described using the hydrogen-like model with anisotropic effective mass, corroborated by our theoretical calculations. Our findings not only provide new insight into the many-body interactions around single dopants in this anisotropic two-dimensional material but also pave the way to the design of novel quantum devices.

Gate-Tunable Giant Stark Effect in Few-Layer Black Phosphorus.

Two-dimensional black phosphorus (BP) has sparked enormous research interest due to its high carrier mobility, layer-dependent direct bandgap and outstanding in-plane anisotropic properties. BP is one of the few two-dimensional materials where it is possible to tune the bandgap over a wide energy range from the visible up to the infrared. In this article, we report the observation of a giant Stark effect in electrostatically gated few-layer BP. Using low-temperature scanning tunnelling microscopy, we observed that in few-layer BP, when electrons are injected, a monotonic reduction of the bandgap occurs. The injected electrons compensate the existing defect-induced holes and achieve up to 35.5% bandgap modulation in the light-doping regime. When probed by tunnelling spectroscopy, the local density of states in few-layer BP shows characteristic resonance features arising from layer-dependent sub-band structures due to quantum confinement effects. The demonstration of an electrical gate-controlled giant Stark effect in BP paves the way to designing electro-optic modulators and photodetector devices that can be operated in a wide electromagnetic spectral range.

Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices.

Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view toward high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations. The electron mobility of black phosphorus is significantly enhanced to 262 (377) cm2 V-1 s-1 by over 1 order of magnitude after potassium modification for two-terminal (four-terminal) measurements. Using lithography technique, a spatially controlled potassium doping technique is developed to establish high-performance complementary devices on a single black phosphorus nanosheet, for example, the p-n homojunction-based diode achieves a near-unity ideality factor of 1.007 with an on/off ratio of ∼104. Our findings coupled with the tunable nature of in situ modification scheme enable black phosphorus as a promising candidate for further complementary electronics.

Chemical Vapor Deposition of Large-Size Monolayer MoSe2 Crystals on Molten Glass.

We report the fast growth of high-quality millimeter-size monolayer MoSe2 crystals on molten glass using an ambient pressure CVD system. We found that the isotropic surface of molten glass suppresses nucleation events and greatly improves the growth of large crystalline domains. Triangular monolayer MoSe2 crystals with sizes reaching ∼2.5 mm, and with a room-temperature carrier mobility up to ∼95 cm2/(V·s), can be synthesized in 5 min. The method can also be used to synthesize millimeter-size monolayer MoS2 crystals. Our results demonstrate that "liquid-state" glass is a highly promising substrate for the low-cost growth of high-quality large-size 2D transition metal dichalcogenides (TMDs).

Chemical Stabilization of 1T' Phase Transition Metal Dichalcogenides with Giant Optical Kerr Nonlinearity.

The 2H-to-1T' phase transition in transition metal dichalcogenides (TMDs) has been exploited to phase-engineer TMDs for applications in which the metallicity of the 1T' phase is beneficial. However, phase-engineered 1T'-TMDs are metastable; thus, stabilization of the 1T' phase remains an important challenge to overcome before its properties can be exploited. Herein, we performed a systematic study of the 2H-to-1T' phase evolution by lithiation in ultrahigh vacuum. We discovered that by hydrogenating the intercalated Li to form lithium hydride (LiH), unprecedented long-term (>3 months) air stability of the 1T' phase can be achieved. Most importantly, this passivation method has wide applicability for other alkali metals and TMDs. Density functional theory calculations reveal that LiH is a good electron donor and stabilizes the 1T' phase against 2H conversion, aided by the formation of a greatly enhanced interlayer dipole-dipole interaction. Nonlinear optical studies reveal that air-stable 1T'-TMDs exhibit much stronger optical Kerr nonlinearity and higher optical transparency than the 2H phase, which is promising for nonlinear photonic applications.